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' New York State Museum Bulletin

Published by The University of the State of New York

No. 285 ALBANY, N. Y. December 1930

* S - 4

NEW YORK STATE MUSEUM
Charles C. Adams, Director

GEOLOGY OF THE CAPITAL DISTRICT

(ALBANY, COHOES, TROY AND SCHENECTADY

QUADRANGLES)

By Rudolf Ruedemann Ph.D.

State Paleontologist, New York State Museum

WITH A CHAPTER ON GLACIAL GEOLOGY

By John H. Cook

CONTENTS

PAGE

Preface g

Introduction 2

Topography 8

Three Peneplanes of Capital District ig

Drainage 21

Descriptive Geology 25

Structural Geology ; x^o

Historical Geology 7 x62

Glacial Geology by John H. Cook 181

Economic Geology ' Xgg

Points of Geologic Interest in the Cities of Albany, Troy and

Schenectady 204

Bibliography . 207

Index 2I^

Geologic Map and Sections A*. .In pocket at end,

ALBANY

THE UNIVERSITY OF THE STATE OF NEW YORK
1930

M2S9r-Je29-2500

\ ,

M259r-Je29-2500

THE UNIVERSITY OF THE STATE OF NEW YORK

Regents of the University
With years when terms expire

1934 Chester S. Lord M.A., LL.D., Chancellor - - Brooklyn

1932 James Byrne B.A., LL.B., LL.D., Vice Chancellor New York
1931 Thomas J. Mangan M.A., LL.D. ----- Binghamton

1933 William J. Wallin M.A. ------- Yonkers

1935 William Bondy M.A., LL.B., PhD., D.C.L. - New York

1941 Robert W. Higbie M.A., LL.D. ----- Jamaica

1938 Roland B. Woodward M.A. ------ Rochester

1937 Mrs Herbert Lee Pratt L.H.D. ----- New York

1939 Wm Leland Thompson B.A. ------ Troy

1936 John Lord O’Brian B.A., LL.B., LL.D. - - Buffalo

1940 Grant C. Madill M.D., LL.D. Ogdensburg

1942 George Hopkins Bond Ph.M., LL.B., LL.D. - Syracuse

President of the University and Commissioner of Education

Frank P. Graves Ph.D., Litt. D., L.H.D., LL.D.

Deputy Commissioner and Counsel

Ernest E. Cole LL.B., Pd.D., LL.D.

Assistant Commissioner for Higher and Professional Education

James Sullivan M.A., Ph.D., LL.D.

Assistant Commissioner for Secondary Education

George M. Wiley M.A., Pd.D., LL.D.

Assistant Commissioner for Elementary Education

J. Cayce Morrison M.A., Ph.D.

Assistant Commissioner for Vocational and Extension Education

Lewis A. Wilson D.Sc.

Assistant Commissioner for Finance

Alfred D. Simpson M.A., Ph.D.

Director of State Library

James I. Wyer M.L.S.,' Pd.D.

Director of Science and State Museum

Charles C. Adams M.S., Ph.D., D.Sc.

Directors of Divisions

Administration, Lloyd L. Cheney B.A., Pd.D.

Archives and History, Alexander C. Flick M.A., Litt.D., Ph.D.,
LL.D.

Attendance, Charles L. Mosher Ph.M.

Educational Research, Warren W. Coxe B.S., Ph.D.

Examinations and Inspections, Avery W. Skinner B.A., Pd.D.
Health and Physical Education, Frederick R. Rogers M.A., Ph.D.
Law, Irwin Esmond Ph.B., LL.B.

Library Extension, Frank L. Tolman Ph.B., Pd.D.

Motion Picture, James Wingate M.A., Pd.D.

School Buildings and Grounds, Joseph H. Hixson M.A.

Teacher Training, Herman J. Magee M.A.

Visual Instruction, Alfred W. Abrams Ph.B.

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New York State Museum Bulletin

Published by The University of the State of New York

No. 285 ALBANY, N. Y. December 1930

GEOLOGY OF THE CAPITAL DISTRICT
(ALBANY, COHOES, TROY AND SCHENECTADY
QUADRANGLES)

By Rudolf Ruedemann Ph.D.

State Paleontologist , New York State Museum

WITH A CHAPTER ON GLACIAL GEOLOGY

By John H. Cook

PREFACE

The writer undertook the mapping of the capital district of New
York for various reasons. For one, there had come requests for
detailed geologic maps of the district both for economic use in con-
nection with various engineering problems and for theoretical use
by students, the capital district, with its expanse from the heights
of the Rensselaer plateau to the summits of the Helderberg mountains
being a favorite field for excursions by students of geology. Another
reason that led the writer to the rather arduous task of mapping
such a large area is that it comprises the entire series of shale forma-
tions of the so-called Shale Belt of eastern New York from the
Lower Cambrian to the Indian Ladder beds of Middle Ordovician
age, which the writer believes he is, from his long study of these
formations, better prepared to distinguish than younger geologists
would be. He therefore felt it his duty to perform this service.

In order to make the work as practical and as accessible to the
greatest number of readers as possible, it has been written in popular
language with the exception of a few chapters which deal with
purely technical matters and have been denoted as technical chapters.

In order to show at once on the map where the rocks are near the
surface or entirely hidden by glacial and river deposits, the
demarcation of the areas of rock outcrops, shown on the map by
the lack of overprint, has been carried out in great detail and with
great care. This required more work than had been anticipated and

[3]

NEW YORK STATE MUSEUM

proved the cause of much delay in the final completion of the map,
but it is confidently believed that the result justifies the greater work,
the map showing at a glance where outcrops are to be expected and
where not. It seems that altogether too many maps have been made
in the glaciated areas of New York and other states as well, showing
simply the outlines of the formations without any indications of the
underlying evidence, sometimes boundaries being drawn across the
map by sheer main strength. Professor Cushing used to draw in
continuous lines boundaries directly observed, and in dotted lines
those only inferred. This method gave a fair clue to the relative
exactitude and positiveness of the boundaries drawn on the map.
A detailed overprint carries this further and practically enters on the
map all notes on observed outcrops.

The writer would like to say a final word on the correctness of
the map. He is fully aware that there are errors in this map, for
in areal mapping the geologist is always meeting local problems,
structural and tectonic in kind, which have to be solved one way
or another and the solutions entered on the map. There is often
not sufficient evidence exposed at the time to reach a positive conclu-
sion, yet the map requires a positive delimitation of the formations.
Later new exposures may be created by road or dam building or
other engineering works, which put another aspect on the local
structure recorded in the map.

It may be added here that outcrops come and go. Human activities
now often produce wonderful temporary outcrops and as often hide
or destroy others. As an illuminating instance may be mentioned
the bluestone quarries below Van Vranken avenue in Schenectady,
which for many years were actively operated and also regularly
visited by college professors and their classes (as by Professor
Charles S. Prosser) and in which the writer obtained his principal
collection of Ordovician eurypterids. These now have been filled in
and built over, so that every trace of them has disappeared, or is dis-
appearing. It is the same with sometimes highly illuminating out-
crops in road ditches, foundations of houses, sewer trenches etc.
There are thus recorded on our map by a star localities which have
furnished fossils where today all opportunity for collecting has van-
ished. On the other hand, new exposures produced by man may at
any time change boundary lines based only on inference without any
reproach to the mapping geologist.

The author has enjoyed, while engaged in this work, the personal
interest in the mapping of the capital district of the late Director,

GEOLOGY OF THE CAPITAL DISTRICT

Dr John M. Clarke, as well as of his successor, Dr Charles C. Adams.
Active help was given him by Winifred Goldring, who for three
months joined in the work of mapping the Helderbergs, being herself
engaged on the Berne quadrangle, and of filling in hitherto unob-
served areas on the Albany and Schenectady quadrangles. Clinton F.
Kilfoyle and Walter J. Schoonmaker of the Museum staff also
assisted in looking up outcrops on the Troy and Cohoes quadrangles
and Mr Kilfoyle made most of the pen drawings. Edwin Stein took
the photographs which accompany this paper with his usual care and
artistic skill, and made some of the drawings.

While the writer was primarily interested in the rock geology of
the region, the glacial geology has such a profound and unmistakable
influence upon the secondary surface characters of the country, as
well as upon the origin of the drainage, character of soil, and other
important features, more or less directly shown on a geologic map,
that he considers as a most valuable complement to the rock geology
of the district the brief survey of the glacial geology of the capital
district, written for this bulletin by Professor John H. Cook. The
glacial geology of the Schenectady and Cohoes quadrangles has
already been described by Professor James H. Stoller.

INTRODUCTION

The capital district of New York, comprising four quadrangles
(Schenectady, Cohoes, Albany and Troy, in their order from north-
west to southeast) covers an area of about 900 square miles (877.90
square miles to be exact). It is situated in the subtriangular inner
lowland formed between the Adirondack mountains in the north,
the Rensselaer plateau in the east and the Helderberg escarpment and
plateau in the south. Its geographic center is formed by the conflu-
ence of the Mohawk and Hudson rivers, toward which point the
greater part of the district can be said to slope and the drainage
is directed.

The topography of the district, which can be seen best at one
glance from the top of one of the towering buildings of Albany, as
for instance the Telephone Building or State Capitol, is given its
character by the straight north-south escarpment of the Rensselaer
plateau in the east, with the Taconic and Green mountains in the
farther distance, the distant peaks of the Adirondacks in the north,
the Helderberg escarpment in the southwest, with the overtowering
blue Catskill mountains in the far background and the trenches
of the Hudson and Mohawk rivers in the middle of the plain that is
inclosed on all sides by these mountains.

The picture as seen from the top of one of the buildings is not only

NEW YORK STATE MUSEUM

wonderfully charming and picturesque, revealing on no less than three
sides mountain ranges that reach above 4000 feet but it is hard to
match in the State also for geologic interest, for these three mountain
ranges seen in the blue distance reveal entirely different chapters in
the geologic history of the State. The capital district is the very
center where the three fundamental structures of the State approach
each other so closely that they can be seen together. The Adiron-
dacks represent the nucleus of the State, composed of granites and
gneisses, the rocks that form the very foundation of the visible
portion of the crust of the earth, and that date from the earliest
era of our geologic history, the Precambrian era. They have been
exposed through elevation of the whole region in relatively late
time, the middle and later ages of earth’s history, and the resulting
erosion of the once overlying masses of younger rocks, mostly shales
and limestones that were deposited over the plateau where it was
submerged, wholly or partly, under the sea. The mountain chains
in the east, as seen in the Rensselaer plateau, Taconic mountains and
Green mountains, are on the other hand the last remains of the
branches of the great Appalachian mountain system that parallels
the east coast of the continent from Alabama to New Foundland.
This gigantic mountain system, a series of folds of the crust produced
by a pressure that came from the ocean side, arose toward the end
of the Paleozoic era shortly after the great coal deposits of America
had been formed from Pennsylvania to Kansas. These mountains
consist along their highest axes, in the Green and Taconic mountains,
also of rocks that are altered into the crystalline condition as those
of the Adirondacks, and are, in parts at least, portions of the
fundamental complex of the crust pushed up during the folding.
The largest part of these ranges is, however, composed of much
younger rocks of early Paleozoic age (Cambrian to Ordovician
systems) that are now intensely folded, and through eons of
weathering have been eroded to their very roots. We shall see
that the history of this portion of the capital district is not only
quite complicated but also full of dramatic interest, revealing gigantic
movements of the earth crust.

It is entirely different with the Helderberg plateau and the Cats-
kill mountains in the southwest. These beautiful mountain districts,
while topographically fully as rugged and picturesque as the Taconic
mountains in the east and the Adirondacks in the north, breathe
placid peace throughout their entire geologic structure. They con-
sist of shales, sandstone and limestone of younger age (Devonian

GEOLOGY OF THE CAPITAL DISTRICT

age) than those in the east and north, that on the whole are still
nearly horizontal and very close to the position in which they were
deposited in the ancient seas. The Helderberg plateau consists of
the earlier Devonian rocks and the great mass of the Catskills rest-
ing on this plateau is composed of the latest Devonian rocks. All
these rocks once extended over the plains of the capital district
northward upon the Adirondack massif. They have been gradually
eroded and the escarpment of the Helderbergs has slowly wandered
away from the Adirondacks toward the southwest, getting higher
at the same time.

The lowland that one sees from the tall buildings of Albany or
from the Indian Ladder extending between these three bounding
mountain systems has been formed in the eons of time since the sea
receded from the surface of the entire region by the weathering
away of the Helderberg and Catskill rocks and Rensselaer rocks (all
of Devonian age) above it, the Helderberg and Catskill rocks reced-
ing southwestward, the Rensselaer rocks eastward.

The lowland of the capital district is technically known as an
“inner lowland” in distinction to coastal and river plain lowlands,
because it lies between a plateau of sedimentary rocks, the Helder-
bergs, and folded mountain masses, from which the plateau is back-
ing away by weathering. The bed rock of this lowland is composed
to unknown depths of shale and sandstone of early Paleozoic age
(ancient era of earth) and the larger part of its area is more or less
deeply buried under unconsolidated materials of glacial age, consist-
ing of “boulder clay,” gravel, sands and, at the lower levels, of
stratified or layered clay deposited in a body of water which flooded
the lowland at the end of the Glacial Period and which has been
named Lake Albany. As a result, the bed rock of this lowland is
exposed only in scattered places, as in the Cohoes gorge, the Nor-
manskill gorge, at French’s Mills etc., while the stream banks,
especially of the Hudson, consist of clay. The exposures show two
different structures. If we look at the shales and sandstones
exposed in the western portion, as at French’s Mills or, below Sche-
nectady, at Rexford and Aqueduct, we see that they lie perfectly
flat, as the Helderberg beds do, but, as we go eastward, they become
more and more disturbed until, at the Cohoes gorge and at the Nor-
manskill gorge at Albany, they are highly tilted (usually at angles of
70°) and intensely folded and crumpled. This condition continues
and is intensified as we go eastward, and as a result the surface of
the rock floor east of the river is very irregular and presents a rest-
less appearance (figure 41). The cause of this is the presence of

NEW YORK STATE MUSEUM

numerous hummocks and hills, caused by harder beds, grit and sand-
stone, that are thrown into steep folds, and by those portions of the
folds where these hard beds are present, having been protected from
erosion. Rysedorph and Olcott’s hills so well seen across the river
when one goes down State street, Albany, are typical examples of
such hummocks built up by protruding harder rocks.

The boundary line between the folded and unfolded regions of
the shales of the lowlands can be quite accurately drawn. It is
marked on the accompanying geologic map and passes near Ballston
lake, below Rexford and between Albany and Voorheesville. The
country east of it was all once highly folded and part of mountain
ranges that now are worn down to their roots and buried deeply
under glacial and postglacial deposits.

TOPOGRAPHY

Having obtained a general survey of the geologic structure of the
capital district, we are now better able to describe its topography and
drainage, its climatic, geographic and cultural features which are all
dependent on its geology.

Of the three mountain systems that are bounding the district, and
can be seen from the Capitol, only two actually extend into the dis-
trict, namely the Rensselaer plateau in the east and the Helderberg
mountains in the southwest.

The Rensselaer plateau rises from the lowland along a line
extending east of Raymertown past Poestenkill, Averill Park, East
Nassau to Brainard. The escarpment is everywhere distinct (figure
41) and mostly steep. The plateau itself, as seen best in the Grafton
Center region and about Stephentown is a wooded region with sub-
dued sculpture, the highest hills reaching just beyond the edge of
the sheet near Cranberry pond 1800 feet above sea-level. Seen from
a distance (figures 41 and 43) the top of the whole plateau is
remarkably level, which means that uniform weathering has reduced
the once highly mountainous region to a near-plane, a so-called pene-
plane. The entire district is underlain by a coarse sandstone, the
Rensselaer grit, and intercalated red and green shales, which together
produce an infertile and often acid soil full of grit boulders. The
district has, therefore, been very lately settled (in the first half of the
last century) and not being favorable to farming, has, after the lum-
bering operations ceased, again lost a large portion of its population
and is, in large part, going back into woodland. It was once the
home of the charcoal-burners for the district. The rather harsh
beauty of the country, however, with its dark woods and scattered

GEOLOGY OF THE CAPITAL DISTRICT

small lakes and ponds, is beginning to attract people who are seeking
summer homes not too far from the cities, and the future of the
region seems to lie in that direction. There is little doubt that some
of the finest woods in the district are now occupying the eastern
uplands. There are luxuriant growths of white oaks intermixed with
red, scarlet and dwarf chestnut oaks ( Quercus prinoides ) in spite of
the open, thin, acid soil that supports large fields of blue huckle-
berries. Dale (’93, p. 325) gives the following vivid description of
the plateau : “Outcrops on the plateau are generally confined to the
hilltops or edges ; great areas are covered with swamps, and the
ponds are numerous,” to which is added in a footnote : “Boulders
are enormously abundant on the plateau, and these almost all grit,
indicating a large amount of erosion in the northern part. The
boulders are so numerous that some of the roads, although nearly
level, are well-nigh impassable. The brook beds are full of them.
Stone walls 10 feet thick, of boulders collected to clear the land, are
frequent.”

In the northeastern part of the district the southern extremities of
the mountain ridges that extend east of the Hudson river through
Schuylerville quadrangle and beyond, come just within the area
north of the Hoosick river. These ridges are of little importance to
the capital district and it may suffice to say that they are also por-
tions of the Taconian fold system that are preserved because of
harder rocks in them, mainly cherty beds and limestones.

The Helderberg plateau, popularly known as the “Helderberg
mountains,” while geologically quite different from the Rensselaer
plateau is topographically very similar. Its most conspicuous fea-
ture is the escarpment, the “Helderberg cliff” that bounds it on the
northeast. Behind this cliff, which is caused by a series of hard
limestone beds with shale above and below, one sees from the low-
land about Albany, long, fairly rounded, well-wooded hills, as for
example Countryman’s hill. These hills reach up to and beyond
1600 feet in height. (Countryman’s hill is 1694 feet.) If one
ascends one of these hills and looks back over the plateau, one recog-
nizes at once that while the whole region is broken up by small val-
leys into a series of ridges and hills, the longest of which is the
Helderberg mountain, just along the edge of the sheet, the tops of
these ridges form a very distinct level sky line (figure 44), above
which farther south the Catskill mountains rise to 4000 feet. It is
easily seen that this sky line is the result of uniform weathering. It
represents an approach to a peneplane, that is, a base-level plain due
to continuous weathering down of a region composed of rocks of
fairly uniform hardness.

NEW YORK STATE MUSEUM

The Catskill mountains again show a uniform level of their high
peaks (figure 44). This interesting feature shows that there was
once a much higher peneplane extending over the whole region,
many eons or millions of years ago. This peneplane probably was
continuous with that now seen on top of the Adirondacks and on the
high mountains in the southwest of the State as, for example, in
Allegany State Park. It is believed that this peneplane was formed
when the area of the State had been reduced to near sea-level in the
Cretaceous time, or geologically speaking, in the middle age of the
earth and before the glacial period. Later in Tertiary time, there
followed an elevation of the whole region which produced the main
features of the topography and the principal stream valleys, as the
Hudson and the lower Mohawk river valleys, leaving these old pene-
planes behind as wonderful ruins of times that passed in the gray
and distant past of the earth.

The Helderberg mountains, to come back to this most lovely
region of the capital district, when seen from in front appear as a
solid plateau, only breached by a few creeks, but offer an entirely
different aspect when viewed from the interior of the region. The
views here given from Cass hill (figure 45) and Copeland hill (fig-
ure 46) show that back of the Helderberg cliff the country mostly
slopes downward toward the southwest. This is due to the fact that
the beds all dip down in that southwesterly direction and that the
weathering following the harder rock beds or strata will finally
expose the surface of these sloping harder beds. Likewise the view
from Cass hill shows a series of three hills (Copeland, Blodgett and
Bennett hills) all of like form with the steep slopes on the north-
east side, like the Helderberg cliff, and the gradual slopes on the
other side. These hills are composed of the later shales and flags of
Hamilton (Middle Devonian age), that have held out longer against
weathering and that form all the interior hills of the Helderbergs.
Such slopes that run with the dip of the rocks are known as “dip
slopes.”

The Helderberg region is more fertile than the Rensselaer plateau.
This is due to the presence of limestones and more easily weathering
shales or sandstones and besides there are broad and fertile val-
leys as that of the Oniskethau, breaching the ridges. The region
was therefore early occupied by Dutch settlers, brought there by the
patroons of Albany. Their descendants, who freed themselves from
the onerous land rents that had been paid for centuries to the
patroons, in the locally famous “Helderberg War” (1839) are
found in the valley farms of the region. Unfortunately the lure of

GEOLOGY OF THE CAPITAL DISTRICT

the cities has also extended to the rugged settlers of these regions,
and many farms and whole sections are now deserted and the woods
are reconquering large areas, once the homes of happy tillers of the
soil. The Helderberg region with its stately hills, the tops of which
offer magnificent panoramas, sweeping the country from the Cats-
kills to the Adirondacks ; its small, but mysterious lakes with hidden
outlets and inlets ; its fertile laughing valleys with attractive home-
like villages, as Clarksville ; its old-fashioned inhabitants, in part
still with the customs and beliefs of the first settlers — all these fea-
tures lend the region a charm, reminding one of parts of the Old
World. The region is not nearly so well known to the city people
of the capital district as it deserves, however, and there is no doubt
that in time the deserted farms of the region (often still with fine,
substantial houses standing), will be taken up by city dwellers look-
ing for summer homes. It would be better yet if they were in the
hands of immigrants from the hard-working farming people of
northern Europe, who could again make the region as productive as
similar ones still are in Scotland, Scandinavia and Germany.

The Helderberg plateau is gradually returning to the mag-
nificent woods that once covered the whole region. The gor-
geous fall coloring brings out the great variety of trees that cover
the slopes, and vary from white pine to elm, oak, bass wood etc.
The different belts of rocks, varying from the Helderberg limestones
to the quartzose rocks of the Oriskany sandstone and shales of the
Esopus and the Hamilton flags, also contribute to the variety of for-
est growths as well as of small plants.1 Thus the limestone ledges
support the cork or rock elm ( Ulmus Thomasi), a special form of
basswood ( Tilia neglecta), large stands of snow berries ( Symphori -
carpos albus), as especially along the top of the Indian Ladder cliff,
where also the June berry ( Amelanchier amabilis), the purple vir-
gin’s-bower (Clematis verticillaris) and the hairy honeysuckle ( Loni -
cera hirsuta ) are found, while below the cliff one may find those
mysterious and rare ferns that are the delight of nature lovers as,
for instance, the “walking fern”2 ( Caniptosorus rhizophyllus),
brittle fern ( Cystopteris fragilis), bladder fern (C. bulbifera), and
smaller ferns as Asplenium trichomanes, Cryptogramma Stelleri,
Pellaea atro purpurea, that grow only in the shady moist woods,
often covering the fallen limestone blocks with a rich velvet blanket.

1 1 am indebted to the State Botanist, Dr Homer D. House, for the infor-
mation on the distribution of the plants.

2 The walking fern is very partial to the weathered surface of the Coeymans
limestone. It is frequently found covering glacial erratics of this formation
far south of the parent ledge while the bed rock on which the erratic lies, even
when limestone, has not been invaded.

NEW YORK STATE MUSEUM

The belts of sandstone and gritty shales (as the Oriskany sandstone
and Esopus grit, see below p. 56) are readily recognized by the pre-
vailing cedar trees and the juniper bushes. Such a belt is distinctly
seen between Callanan’s quarry and South Bethlehem ; and the banks
of the gorges in the Esopus grit are covered with rich, dark green
mats of the yew ( Taxus canadensis) .

The topography of the plains of the capital district is fully as
interesting and the landscape, if properly understood, as fascinating
as that of the surrounding uplands. We must there distinguish
between two regions, as set forth before, according to the underlying
rock bottom. The western region, which extends within a few miles
of the Hudson river, is marked by great level areas. This is the
region where the rock bottom is not folded and hence probably
relatively flat and undisturbed, and also worn down to greater depths
and hence deeply covered by moraine and Albany lake clays. The
eastern region is that where the rocks of the rock bottom are greatly
folded, and the old rock surface is therefore very irregular, not so
deeply worn down nor covered by glacial deposits and therefore
sticks out all over in little hummocks, giving the region the appear-
ance of a restless moderately choppy sea (figures 49 and 50).

The topography of the western plain is, owing to the deep burial
of the rock bottoms, quite independent of that bottom, its structure
being the result of glacial and postglacial agencies. These are fully
discussed in the appended paper by Professor Cook ; we will mention,
therefore, only the most salient features of the district. The clay
plains rise close to the Hudson river to various elevations : 200 feet
at the southern border of the Albany quadrangle, 300 feet just
west of Albany, 320 feet in the southern portion and 360 feet in
the northern portion of the Cohoes quadrangle.

On this clay rest areas of sand hills, that were wandering sand
dunes before vegetation recovered the desert left by the glaciers
and Lake Albany. One such dune area, known locally as the
“Pinebush,” begins at the outskirts of Albany and extends north-
west toward Schenectady and Guilderland, crossing the New York
Central tracks and the state road for two miles just outside of
Schenectady. Another large area of sand dunes and wind-blown
sand extends north of the Mohawk from Crescent through Clifton
Park to within two miles of Round Lake. Still another large area
is found in the town of Stillwater extending from a mile north of
Willow Glen to within a mile of Saratoga lake and continuing east
of the lake. Other smaller areas of sand dunes are found north and
west of Schaghticoke.

GEOLOGY OF THE CAPITAL DISTRICT

Figure 45 gives a characteristic view of such dunes. While the
old lake bottom with its clay and loam beds makes very rich farm
land, as in the area between Albany and Voorheesville, the sand dune
regions are unproductive and mostly wooded. They carry a very
characteristic stunted forest growth of pitch pines, gray birches,
scrub oaks, alders, hazelnuts, poplars, a thick undergrowth of black
huckleberry bushes ( Gaylussacia baccata ), and other light-loving
plants. The open plains are covered with a new immigrant from the
west, Leptoloma cognatum, the “diffuse crab grass,” a most magnifi-
cently colored pinkish-brown grass, that I admired greatly in the
Great Plains of Oklahoma and other states and that, as Dr Homer
D. House, State Botanist, tells me, was not observed by him in the
Albany region before 1919 (see House, ’24 p. 70). These sandy
regions, however, with their rounded wooded hills do by no means
lack in charm, and they are decidedly beautiful in the fall, when
the dark pines contrast with and form a background for the gor-
geously colored deciduous trees. Truck farmers, mostly new immi-
grants, cultivate the scattered level stretches and add life to the
otherwise lonesome country.

It is interesting to note that, as Doctor House has pointed out,
these sandy dune regions once supported an entirely different and
rich forest and ground flora. Dr James Eights, in a series of articles
in the Albany Zodiac in 1835-36 (see also House, Report of the
State Botanist for 1924, N. Y. State Museum, Bulletin 266, p. 11)
reports that the old road to the fort at Schenectady led through a
forest so high and dense (probably mostly white pine) that the trees
closed above the road and shut out the sunlight. The ground was
so swampy that much of the road was corduroyed. He also cites a
number of plants as common that now have entirely disappeared
from the region (see House, op. cit.). It appears that reckless
cutting and still worse, series of forest fires, have destroyed the rich
humus that once covered the sandy regions, and thus brought about
chemical and especially also physical changes of the soil that have
led to its deterioration and acidity. A small area, Doctor House
states, north of Earners, in the midst of the sandy region, still
retains its old soil and fine stand of oaks and white pines. Originally
the sand dune regions were undoubtedly great gloomy forests of
prevailing white pines and oaks with little undergrowth.

The Lake Albany clay deposits form the level, rich farm land
extending on the west side of the Hudson to Albany and all the
way up to Schuylerville and westward to South Bethlehem, Feura
Bush, New Scotland, northward to the Normanskill, and up the

NEW YORK STATE MUSEUM

Normanskill to South Schenectady, thence up the Mohawk valley to
Rotterdam Junction and northward on the Schenectady quadrangle
to High Mills and east of the Clifton Park dune area beyond the
sheet. This clay plain is the fertile farming land of the capital dis-
trict. The fine homes, the sleek cattle and splendid orchards testify
to the prosperous condition of this farming population, and the
gigantic forests that once covered this rich land are still suggested
by fine growths of scattering American elms in front of the farm-
houses, by oaks, chestnuts, hickory and tulip trees and other stately
and now altogether too rare survivals of the primeval woods in small
patches of forests.

Between the broad smooth expanse of the Lake Albany clays and
the cliff front of the Helderbergs extends a zone, three to four miles
wide and well marked, between New Scotland and New Salem
and thence north to Altamont, that is more hilly, the hills composed of
glacial materials overlying a rock bench.

There are also two regions projecting from the lake deposits in the
northwest corner of the district that are underlain by solid rock.
One is the escarpment south of the Mohawk river, northwest of
South Schenectady and the other the Glenville hill west of Town
House Corner. In both of these areas the heavy sandstone beds
intercalated in the Schenectady formation (see p. 33) have preserved
these banks of preglacial drainage channels.

Farther west of the Hudson river there are two larger areas,
where the bed rock appears at the surface producing an irregular
topography. One of these is around the mouth of the Mohawk,
extending from Waterford through Cohoes and over Peebles, Van
Schaick and Green Islands to Watervliet. Here the much- tilted and
contorted Normanskill shales and sandstones (see p. 96) are exposed
in many small hillocks and ridges. These outcrops are below the
level of the clay plain.

The other is an interesting rock area extending from Glenmont,
south of Albany beyond Cedar hill (see map) and reaching a width
of a mile and a half. This region rises west of Cedar hill, above
the 200-foot contour and was therefore a prominent tract before the
deposition of the Albany clays. It owes its prominent character,
besides the intense folding of the rocks, to the indurated or hardened
character of the shales and hard sandstone beds and really belongs
topographically with the folded country on the east side of the river.
The induration of the slates has given it a flinty character and a
peculiar white weathering on the surface, readily seen on the surface
rocks just below Glenmont, where the state road crosses the West

GEOLOGY OF THE CAPITAL DISTRICT

Shore Railroad. It is interesting to note in this place that, as Doctor
House informs me, this small island of flinty rocks in the clay plains
is distinguished by a little flora of its own, the most notable members
of which are the fragrant sumac ( Rhus aromatica), the yellow
chestnut oak ( Quercus Muhlenbergii [acuminata]) , the big-flowered
chickweed ( Cerastium arvense) , the early scorpion grass ( Myosotis
virginica ) and a fern ally, the rock selaginella or festoon pine
( Selaginella rupestris), and the ferns, Woodsia ilvensis and Woodsia
obtusa.

Other plants that are found on these ledges and not on the sur-
rounding clay and sand are: Lonicera affine var. hypomcdeucum (L.
pubescens) , Viola adunca (subvestita) , Houstonia longifolia, the two
oaks, Quercus ilicifolia and Q. prinoides, that while common in the
sandplains between Albany and Schenectady, are here confined to
the outcrops of the ledge of chert; further, a small rose, Rosa Caro-
lina var. glandulosa Farwell ( R . serrulata Raf.), a sedge-grass Carex
Bicknellii Britton, and Arenaria stricta, Micheaux, the small white
flowers of which are readily seen near the ground.

East of the Hudson river the clay plain of Lake Albany forms but
a narrow strip, that in its widest part near the northern margin of the
capital district is but two and one-half miles wide and often not
more than a quarter of a mile wide. Beyond this extends the rocky
country, described before, covered by a mostly thin mantle of moraine
or till formed by the ice of the glacial period (figures 41 and 49).
This hilly moraine, till and rock country forms a belt, six and more
miles wide, between the clay plain in the west and the Rensselaer
plateau and the mountains of the Cambridge district. The hills have
as a rule a rock core, formed by small pitching anticlines of heavy
sandstone or indurated flinty shale. Their axes all run about N. 20° E.
with the prevailing strike of the folded rocks. The northern end
of the hills often shows more or less smoothed rock exposures. It
was the “stoss-side” of the protruding ledge. Behind it often a
ridge of moraine material has been heaped up by the glacier. Between
these sharply projecting rock hills one sees the evenly rounded
glacial hills, either kames or drumlins, that is, hills that were formed
at the end of the glacier or under it, and also small sand dunes.
These rounded glacial hills are usually farmed, often plowed, but
mostly used for pasturage, while the rocky hummocks are left
wooded.

This rocky belt rises gradually eastward from the 300-foot con-
tour to the 6oo-foot contour at the foot of the Rensselaer plateau.
It is therefore in reality a westward sloping upland, from which

NEW YORK STATE MUSEUM

the Rensselaer plateau rises abruptly to 1300, and in some places
to 1400 feet along the escarpment.

There are several larger hills protruding in this belt, that are topo-
graphical landmarks and as such deserve special notice. The north-
ernmost are Rice Mountain near Grant Hollow and Mount Rafin-
esque (popularly known as Bald Mountain) east of Lansingburg, Rice
mountain rising 500 feet above the plain to 925 feet and Mount Ra-
finesque nearly 900 feet to 1 197 feet. This latter picturesque mountain
stock (figure 42) so well seen from the State Education Building and
other high buildings of Albany to rise as a fine wooded mountain
chain just northeast of Troy, owes its origin to several causes, the
most important of which seems to be that hard and competent
rocks form here a cross-fold, extending east and west (see below
under Structural Geology). Farther south three prominent hills are
plainly seen as one goes down State street in Albany to rise from the
horizon just across the river. These are Olcott’s hill and Ryse-
dorph hill (popularly known also as Bald mountain and Pinnacle
hill) a triangulation station of the United States Geological Survey
and south of it Catamount hill (not named on map). This hill, I
was told by an old settler of the neighborhood, has received its name
from a cantonment of troops in the war of 1812, the word “canton-
ment” having been perverted into “catamount.” These hills owe
their prominence to the hard sandstone or grit, characteristic of a
geologic formation (the Normanskill shale) outcropping upon them,
and Rysedorph hill to the conglomerate bed that has received its
name from the hill.

South of Catamount hill runs a fine ridge north and south, extend-
ing south from the Rensselaer-East Greenbush road and known
as Teller hill and Grandview hill. This ridge also contains the in-
durated, flinty beds of the Normanskill shale, forming there an
anticline. Finally, in the southeast corner of the capital district,
just west of Tackawasick pond, there rises from the plain a wooded
ridge, Curtis mountain, known to local hunters as an excellent
hunting ground. This ridge is also a large syncline or fold that has
withstood weathering longer on account of the hard quartzite
beds it contains in folded condition,

GEOLOGY OF THE CAPITAL DISTRICT

1 7

Figure i Block diagram of capital district, to show the three peneplanes of the area. I-I Cretaceous peneplane.
1I-II Tertiary peneplane. III-III Incipient recent or Albany peneplane (inner lowland)

NEW YORK STATE MUSEUM

Figure z Schematic diagram to show the three peneplanes undissected, indicated in figure

GEOLOGY OF THE CAPITAL DISTRICT

THREE PENEPLANES OF CAPITAL DISTRICT

(Figures 1 and 2)

We have mentioned in the preceding pages the peneplanes of the
Helderbergs and of the Catskills. The peneplanes of the capital dis-
trict are such prominent and important features of the topography
that they require separate description.

If one looks out from the windows of the Capitol or any other of
the public buildings on Capitol hill, one can not fail to see, rising
beyond the houses of the city, a broad plain stretching south and west
to the Helderbergs, north to the Adirondacks and east to the Rens-
selaer plateau. Into this plain (figures 41 and 43) the deep valleys
of the Hudson and Mohawk rivers are sunk. The plain is about 200
feet above sea-level at Albany ; it rises westward slowly to 300 feet
and eastward to about 600 feet at the foot of the Rensselaer plateau.
This “inner lowland” of the Helderberg plateau has distinctly the
character of an incipient peneplane or erosion plane, for it is cut
across folded and unfolded beds alike, almost without regard to the
rock structure, as the appended sections B-B and C-C clearly show.

Still there project above the plain numerous hillocks, especially
east of the river, that owe their prominence to the existence of harder
rocks (mostly grit beds or chert beds) that are brought up by small
folds. Teller hill, Grandview hill, Rysedorph hill, all three south of
Rensselaer, are such projecting rock hills. Mount Rafinesque and
Rice mountain, north of Lansingburg, are larger mountains, project-
ing to 1300 feet and also caused by folded and harder beds, mostly
chert and grit beds of Norrnanskill age. These projecting hills and
mountains, composed of harder rocks, partake of the nature of the
so-called “monadnocks,” that is, of mountains that, like Mount
Monadnock in New Hampshire, owe their existence to their com-
position of harder rocks, and are erosion remnants. There are also
numerous other more gently rounded hills of glacial origin scat-
tered over the plain.

This lowest or Albany peneplane, as we may call it, is the youngest
of the region. It existed at the end of the Tertiary period, when
the glaciers advancing from the north buried the country under ice.
It originated from the uplift of the country in Tertiary time when the
rivers established new grade.

The Albany peneplane was not so smooth and level before glacial
time as it appears now. It was more dissected and irregular, because
of the great differences in rock structure and hardness, but the

NEW YORK STATE MUSEUM

mantle of drift that was deposited by the glaciers and still more the
mantle of laminated clay, laid down in the group of lakes known to
geologists as Lake Albany, have smoothed out and hidden many
irregularities of the former surface, while, on the other hand, some
new irregularities of the plain, in the form of sand dunes and drum-
lins, were formed. Considered as a whole, however, the inner low-
land was distinctly a “near-plane” in the wider sense, or a new level
that was being formed below the Helderberg peneplane, when the
glacial epoch began. While it may not be a peneplane in the strict
sense, it is undoubtedly an incipient peneplane that in the course of
time, if no new elevation occurs, will extend down the river and
spread in all directions.

The next higher peneplane can be distinctly recognized when one
looks from the Helderberg mountains backward toward the Catskills
(figures 44 and 46). The top of the Helderberg ridges appears then
as a level, more or less dissected plateau, that once must have been a
continuous plain. If one looks across the Albany peneplane towards
the Rensselaer grit plateau (popularly known as the Grafton and
Stephentown hills) one will see at once that these mountains again
form a distinctively level plateau (figures 41 and 43) which extends
north-south, and is of about the same height as the Helderbergs. The
Helderberg mountains rise to 1600 feet on Countryman hill, near
New Salem, and this level of 1600 to 1700 feet is maintained over
the plateau. The average height of the Rensselaer plateau is likewise
1600 to 1800 feet, the plateau rising eastward from 1400 feet at the
western margin to 2000 feet above the Little Hoosick valley, with
most of the plateau at about 1600 feet. It is therefore legitimate to
conclude that the Helderberg and Rensselaer plateaus belong to the
same, or are remnants of the same peneplane, that once extended
above the Albany peneplane across the Hudson river valley. By
comparison with the peneplanes known south of New York the
Helderberg peneplane can be correlated with the peneplane that was
uplifted in early Tertiary (Eocene) time, and that is known as the
Harrisburg peneplane.

The last and highest peneplane is the one we see represented by
the even tops of the Catskill mountains as seen from higher altitudes,
as for instance, the tops of the Helderbergs (figure 44). This pene-
plane lies now at an elevation of about 4000 feet. It was once a low
plain that extended all over the district, in fact, far and wide over
the East. It was elevated in early Cretaceous time and is known as
the Kittatinny peneplane. The tops of the Adirondack mountains

GEOLOGY OF THE CAPITAL DISTRICT

and the level stretches of the Taconic and Green mountains also
appear to be remnants of this ancient peneplane.

Summarizing, we can picture to ourselves the capital district as
composed of three stories of rock formation that once rose into the
sky above the district, and that were successively eroded away, leav-
ing only remnants. These are, from top to bottom, the Cretaceous
peneplane, 4000 feet high and extending from the top of the
Catskills to that of the Adirondacks; the early Tertiary peneplane,
extending from the top of the Helderbergs to that of the Rensselaer
plateau, about 1600 feet high; and the Albany or late Tertiary pene-
plane, about 100 to 600 feet high and extending from the foot of
the Helderbergs to that of the Rensselaer plateau and of the
Adirondacks.

DRAINAGE

The drainage system of the capital district is in its major features
entirely controlled by the general geologic structure, finding expres-
sion in the physiography just described; and on the other hand, the
minor physiographic features of the region are in their part largely
controlled by the drainage and by erosion in general.

The trunk stream of the district is the Hudson river, which crosses
the district in south-southwest direction from the northeastern
margin to the approximate center of the southern margin. The river
is sunk now in a valley, about 200 feet below the lowest terrace of
the clay plain and about a mile wide. The stream channel is one-
fourth to one-half of a mile wide. The head of the navigation is at
Troy and the tide reaches to the Troy dam, where the river is only
3.8 feet above sea level.

The principal tributary of the Hudson river and the other principal
stream of the district is the Mohawk river, which rising to the west
of the Adirondack plateau flows around it in the south and reaches
the Hudson river valley at Cohoes. The next important tributary of
the Hudson river in the district is the Hoosick river, which rises east
of the Taconic mountains and breaking through the Appalachian
ranges in southern Vermont reaches the Hudson river from the east
two miles above Mechanicville. An interesting southern tributary
of the Hoosick river in New York is the Tomhannock creek, rising
near the north end of the Rensselaer plateau and flowing through an
old lake bottom that has been revived as a lake in the Tomhannock
reservoir of the Troy water works. At Mechanicville empties the
Anthony kill which flows out of Ballston lake in a northeast direction,
then at East Line bends sharply southeast and flowing through Round

NEW YORK STATE MUSEUM

lake reaches the Hudson river at Mechanicville. The small creek
flows through a valley out of proportion to its size, and, as we shall
see presently, it has a most interesting geologic history which explains
that disproportion. The larger Mourning kill comes within a mile
of the Anthony kill near East Line, but then turns northward toward
Ballston, where it joins the Kayaderosseras creek, that in its turn
empties into Saratoga lake, located astride the north margin of the
district. Saratoga lake is drained by Fish kill that flows at Schuyler-
ville into the Hudson river.

The only noteworthy tributaries of the Mohawk are the Alplaus
kill on the north and the Lisha kill on the south. The Alplaus kill
(Alplaus is a perversion of the German “Aalplatz,” meaning a place
to catch eels, at the mouth of the creek) drains the country east of
the Glenville ridge.

Other tributaries on the west side of the Hudson river that we
shall have occasion to mention are the Patroons creek, emptying just
north of Albany; the Normanskill, emptying in the southern out-
skirts of Albany, with its branch the Vly creek (Vly creek is a
tautology, since vley is Dutch for a swampy creek), that
drains the New Salem region ; the Vlauman kill, reaching the Hudson
river at Cedar hill ; the Oniskethau and Sprayt kill, which drain the
Helderberg area of the capital district and uniting form Coeymans
creek, that empties at Coeymans.

On the east side should be mentioned south of the Hoosick river,
the Deep kill, that arises in Mount Rafinesque and forms a gorge
above Grant PIollow, in which was discovered a series of fossilifer-
ous shales (Deep kill graptolite shales) that received their name from
that creek; the Poestenkill coming from the Rensselaer plateau and
emptying at Troy; the Wynantskill, which drains a whole series of
lakes at the foot of the Rensselaer plateau, in the eastern rocky
plains : namely Burden lake, Crooked lake, Glass lake, Sand lake
(now Crystal lake), Reichard pond and Aries lake (popularly
known as Snyders lake).1 It empties within two miles of the
Poestenkill. The Moordener kill empties at Castleton and the Valatie
kill, flowing through Nassau pond, empties beyond the capital district
into Kinderhook creek, which just cuts the southeast corner of the
district, receiving the Tackawasick creek, flowing through the Tacka-
wasick pond, as a northern tributary.

There are also extinct lakes and rivers which existed when the ice
of the glacial period was receding and thereafter during unknown
intervals of time, until the lakes became filled up or drained. They

1 Some of these artificially enlarged by dams.

GEOLOGY OF THE CAPITAL DISTRICT

are found especially in the eastern hill region where they form ex-
cellent green agricultural oases between the rocky hills. The largest
is the old Tomhannock lake, already mentioned, now revived by a
dam. Another large lake bottom is seen west of the village of
P'oestenkill and half a dozen small lake basins now filled in are
recognizable in the region south of West Sand Lake. They are
marked on the map as alluvial bottoms. Others are seen west and
east of Nassau pond. An exceedingly well marked extinct lake or
valley extends south from Raymertown near the foot of the Rens-
selaer plateau past Clums corners into the Quaken kill valley and the
extinct Poestenkill lake.

A drainage feature which deserves special mention in the capital
district is the great number of small brooks which have eroded deep
ravines in the several hundred feet of soft sands and clays of the
Albany lake on both sides of the Hudson valley. Many of them
can be seen well on both sides of the train from Waterford to
Mechanicville or between Rensselaer and South Troy, as also north
of Stillwater, and about Castleton. The Normanskill valley above
the Kenwood rapids is also a deep erosion valley in the Albany clays.
These numerous deep ravines on both sides of the river constitute a
characteristic physiographic feature of that particular region.

In some places the ravines have reached rock bottom, as south
of Troy and between Rensselaer and Castleton. In such cases they
give valuable information as to the composition of the rocks of the
immediate neighborhood of the river as well as to the former river
courses.

While it is readily seen that the courses of the smaller brooks and
creeks are of postglacial origin and no longer connected with the
drainage that existed before the glaciers overran the country, the
master streams, notably the Hudson and Hoosic rivers, have in gen-
eral returned to their old valleys. The creeks have but for short
distances reached rock bottom and then by always accidentally strik-
ing irregularities of the old rock bottom ; for the most part they are
in the glacial moraine material and the postglacial clays and sands of
Lake Albany, following the surface irregularities in the rather unsys-
tematic fashion of a new drainage.

The present valley of the Hudson, as here considered, is the broad
depression on the bottom of which the river flows in a more or less
winding course and the sides of which are the steep clay banks
which rise 100 feet or more above the valley bottom. The present
valley lies within the old rock gorge, its bottom being coincident with

NEW YORK STATE MUSEUM

the middle portion of the floor of the latter. The present channel of
the river, however, in the greater part of its extent, is cut into the
floor of the old gorge, forming a shallow rock gorge representing the
erosive work of the river in the recent period. The present valley
bottom, threaded by the channel, has a width varying from three-
fourths of a mile to one and one-half miles.

The result of the fact that the Hudson river flows in the inner
gorge of a broader valley with rocky banks is that the tributaries, all
of which were not able to erode their beds to grade or to the level of
the Hudson river on account of their smaller eroding power, form
now so-called “hanging valleys,” that is, their valleys hang so far
above that of the Hudson river that they form waterfalls where they
descend from the upper level of the rocky banks of the river. The
writer has already pointed out in the description of the Schuylerville
quadrangle what important influence these hanging valleys had
through the water power that they furnish in the development of the
settlements. In the capital district the hanging valleys of the Anthony
kill (Mechanicville), Mohawk (Cohoes), Normanskill (Normans-
ville and Kenwood), Vlauman kill (Cedar Hill), Hoosick river
(Schaghticoke), Poestenkill (Troy), Wynantskill (South Troy),
Mill creek (Rensselaer), Moordener kill (Castleton), either still
furnish power to mills or did so formerly, thereby starting most of
the settlements mentioned.

To this must be added the fact that the Hudson river itself had
lost its channel in various places and thereby is induced to form rapids,
which have become valuable sources of power, as at Stillwater,
Mechanicville and Troy, and thereby have made these places centers
of industry. Troy and Waterford further owe their location to the
end of navigation in the river at this place, the river proper entering
here its estuary or its lower stretch, which lies so low that it is made
to feel the influence of the tides. Albany itself marks the site where
the old Indian trail that followed the Mohawk down to Schenectady
cut across, using the Normanskill valley to the broad expanse of the
Hudson, thus avoiding the turbulent and circuitous course of the
Mohawk from Schenectady to Cohoes. The old corduroy road from
Albany to Schenectady, whence first the Mohawk river and later the
canal were used for transportation, was one of the chief highways
of America opening the West, a fact that the “Gateway bridge” at
Schenectady is intended to memorialize. Both Albany and Sche-
nectady owe their origin to this close approach of the navigable por-
tion of the Mohawk to the navigable portion of the Hudson river.

GEOLOGY OF THE CAPITAL DISTRICT

DESCRIPTIVE GEOLOGY

(Technical chapter)

The rocks of Precambrian age, or of the fundamental crust of
the earth, where complete metamorphism of the strata has taken
place, are not exposed in the capital district and have not been reached
in wells, although they extend in the north, on the Saratoga quad-
rangle, within six and one-half miles of our map.

The overlying rocks are all sedimentary in origin, that is, were
formed under water, mostly marine.

The exposed rocks of the four quadrangles are of Cambrian, Ordo-
vician, Silurian and Devonian age, together with the unconsolidated
deposits of Quaternary age.

There are 27 geologic formations recognizable in the capital dis-
trict. These extend from the lowest Cambrian to the uppermost
Devonian. They are the following in ascending order :

A Lower Cambrian (Taconian) system

1 Nassau beds

2 Bomoseen grit

3 Diamond Rock quartzite

4 Troy shales and limestones

5 Schodack shales and limestones
B Ordovician system

6 Schaghticoke shale

7 Deep Kill shale

8 Normanskill shale

9 Tackawasick limestone and shale

10 Rysedorph Hill conglomerate

1 1 Snake Hill shale

12 Canajoharie shale

13 Schenectady beds

14 Indian Ladder beds
C Silurian system

15 Brayman shale

16 Rondout water lime

17 Manlius limestone
D Devonian system

18 Coeymans limestone

19 New Scotland beds

20 Becraft limestone

21 Oriskany sandstone

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22 Esopus grit

23 Schoharie grit

24 Onondaga limestone

25 Marcellus shale

26 Hamilton shale and flags

27 Rensselaer grit

In looking at the map we see these formations so distributed that
the youngest formation, the Rensselaer grit of Upper Devonian age,
occupies the eastern highland, the Rensselaer plateau ; the remainder
of the Devonian, together with the thin Silurian beds, forms the
Helderberg plateau. Between these two highlands the formations
are arranged in broad belts that in general run nearly north-south,
or more correctly, north-northeast to south-southwest. They are so
arranged that the oldest, the Lower Cambrian rocks, are in the east,
and the lower division of these, the Nassau beds, directly under the
youngest of the series, the Rensselaer grit, a fact of considerable
significance for the tectonic history of the region, that will be dis-
cussed in the chapter on tectonic geology.

The next belt is the upper division of the Lower Cambrian, the
Troy shales and limestone and associated formations. Then follows
the belt of Normanskill shale, that crosses the Hudson river, with
small patches of Deep Kill shale scattered along the Cambrian-
Ordovician boundary.

The next belt west of the Normanskill shale belt is that of the
Snake Hill shale. Beginning very broadly in the north, where it
extends from west of Saratoga lake to east of the Hudson river, it
contracts to a narrow band, where it dives under the Helderberg
plateau near Feura Bush.

The last belt is that of Schenectady beds which occupies the
western half of the Schenectady and Albany sheets, with a triangular
area of Canajoharie shale along the northern margin.

It would appear from this simple arrangement of the belts that
they formed a regular series or succession of formations, the lower
Cambrian at the bottom and the Schenectady beds at the top. This
is, however, not at all the case. On the contrary, the work of the
author, as set forth in the Geology of Saratoga Springs and Vicinity
(Cushing and Ruedemann, ’14) and other publications, has brought
out the fact that two entirely different sets of formations are piled
up here along side of each other. We have assumed that these were
formed in two different troughs, more or less separated from each

GEOLOGY OF THE CAPITAL DISTRICT

other, possibly by a longitudinal bar. We have designated one as the
eastern trough and the other as the western trough. The formations
of both troughs are now in close contact, principally owing to the
fact that the rocks of the eastern trough have been carried westward
by folding and overthrusting along numerous fault planes (see
chapter 4 on Structural Geology).

Systems

Western Trough

Eastern Trough

U pper Devonian

Rensselaer grit

IVTiHHIe Devonian . .

Hamilton shale and flags
Marcellus shale

Onondaga limestone ....

Schoharie grit

Lower Devonian

Esopus grit

Oriskany sandstone

Becraft limestone

New Scotland beds

Kalkberg limestone

Coeymans limestone ....

Silurian

Manlius limestone

Rondout waterlime

Ordovician Silurian interval
Upper Ordovician

Bray man shale

Indian Ladder beds

Middle Ordovician

Schenectady beds

Canajoharie shale

(Glens Falls limestone) . .

(Amsterdam limestone)..

Snake Hill shale
Tackawasick limestone
and shale

Rysedorph conglomerate
Magog shale

Lower Ordovician

Normanskill shale
(Bald Mountain lime-
stone)

Deep Kill shale
Schaghticoke shale

Ozarkian

(Little Falls dolomite) . .
(Theresa formation) ....

(Potsdam sandstone) ....

Lower Cambrian

Troy shales and lime-
stones

Diamond rock quartzite
Nassau beds

Schodack shale and lime-
stone

Bomoseen grit

Precambrian

Precambrian rocks

NEW YORK STATE MUSEUM

As a result of this division we must, from the beginning, separate
the formations into two series. A whole group of formations, which
we know, from the Saratoga and Glens Falls quadrangles, to underlie
the western trough, do not appear on the surface in the capital district.
They are buried there deep under the shales. Nevertheless, we will
add them to the series for the sake of completeness. The two series
beginning with the youngest formations, are shown in the preceding
table. Those not exposed in the capital district, but in adjoining
quadrangles and undoubtedly present here although underground,
are put in brackets. As a matter of fact, some have recently been
reached in deep wells.

The strange fact appears at once in this table that today there
is no formation common to the two sets or troughs. In the Cambrian
and Ordovician periods this is due to an alternating draining and
submerging of the two troughs, so that when one was submerged
the other was drained ; in the Silurian and Devonian it is largely
due to the erosion of the formations outside of the Helderbergs.

A Paleozoic Rocks of the Western Trough

There is no doubt that the Potsdam sandstone, the Theresa forma-
tion (with the Hoyt limestone member), the Little Falls dolomite,
the Amsterdam limestone, the Glens Falls limestone and the Cana-
joharie shale are all underlying the Schenectady beds in the western
trough, for they all are well developed in the Saratoga quadrangle
directly to the north of the Schenectady quadrangle, and their gen-
eral southwest dip would carry them beneath the Schenectady beds.
The Canajoharie beds are exposed at the northern margin of the
Schenectady quadrangle, in Ballston Spa, and extend undoubtedly
under the drift southwestward, as indicated on the map. It is not
necessary here to describe these formations, they have been fully
reported on in the Geology of Saratoga Springs and Vicinity by
Cushing and Ruedemann. It may suffice to state that the Potsdam
formation consists, just north of the capital district, of 50 to 150
feet of buff and white silicious sandstone, often with a conglomerate
at the base. This grades into the Theresa formation, which is 150
to 200 feet thick and consists of alternating beds of sandstone and
dark gray dolomite. A local, more calcareous phase of the upper
Theresa formation that is found west of Saratoga, is the Hoyt lime-
stone. It consists of alternating beds of black limestone and gray
dolomite, with some black oolites, and contains the famous Crypto-
zoon reef of the Lester State Park. The Little Falls dolomite is a
thick formation of 350 to 400 feet of massive beds of dark gray and

GEOLOGY OF THE CAPITAL DISTRICT

light gray dolomite. It is seen along the fault-scarp in Saratoga
Springs. On the Little Falls dolomite rest in this region 40 to 60
feet of a blue crystalline, quite fossiliferous limestone, known as
Amsterdam limestone and referred to the Black River stage of the
Ordovician system. It is poorly exposed on the Saratoga quad-
rangle, being shown at Rock City Falls. The Amsterdam limestone
is followed by 40 feet of alternating shale and limestone, the Glens
Falls limestone, of the age of the basal Trenton formation.
It is a weak formation, seen only in well sections in the Saratoga
region.

1 The Canajoharie shale. The Glens Falls limestone is followed
by a great formation of black shale, the Canajoharie shale. It is
of the same age as the lower Trenton limestone at Trenton Falls
and in the Mohawk valley. This formation may be 1000 feet thick
in this district; yet, on account of the softness and weakness of
the shales, it is mostly buried deeply under drift. It is, however,
well seen about Ballston Spa, as at the Iron Spring, and along Kaya-
derosseras creek, above the village. It enters the capital district at
Ballston Spa and, being buried under drift, forms the underlying
rock surface for an unknown distance south, probably as far as
Ballston lake, as indicated on the areal map.

These soft black carbonaceous, more or less calcareous, argil-
laceous shales contain hardly any intercalations of sandstones or
cherty beds as the shales of the other formations of the capital
district do, and they are therefore characterized by their uniform,
carbonaceous, fine-grained character. They form a broad belt in
the lower and middle Mohawk valley, being replaced westward by
the Trenton limestone, which is of the same age. Just west of the
Schenectady quadrangle they reach a thickness of more than 1200
feet in Adebahr hill, south of Rotterdam Junction. This great belt
of black shales then swings east and northeast around the foothills
of the Adirondacks and passes up into the Champlain valley, where
it is found near Ticonderoga and especially on the Vermont side.
The shale was considered in the older literature as of Utica age, until
the writer recognized its fauna as being of older age. (Ruedemann
’01, ’08, ’12, ’14, ’19.) At Canajoharie, which is the type locality
of the shale, it was found at the base intercalated with basal Trenton
limestone (Ruedemann, 1912, p. 21)1.

1 The fossils of all formations here described can be studied to great advan-
tage in the Hall of Paleontology (eastern hall) of the State Museum. All
more important formations are represented there in the high cases with their
characteristic and common fossils, as well as outcrop and paleogeographic
maps.

3°

NEW YORK STATE MUSEUM

The fauna is a very characteristic one. It consists of graptolites
and small individuals of brachiopods, mollusks, trilobites and ostra-
cods, all indicating an unfavorable condition for marine life, as is
also done by the black carbonaceous shale that contains much pyrite
and thus suggests conditions of foul water in the depths where the
shale was deposited. Nevertheless some layers contain a great
number of the small shells. The fauna consists of the following
species :

Sponges:

Graptolites:

Machaeridians:

Bryozoans:

Brachiopods:

Pelecypods:

Pteropods:

Gastropods:

Cyathodictya ? tubularis Ruedemann.

Sponge spicules

Corynoides calicularis Nicholson
Dicranograptus nicholsoni var. parvulus Rued.
Diplograptus amplexicaulis (Hall)

D. vespertinus Rued.

D. macer Rued.

Mesograptus mohawkensis Rued.

Climacograptus strictus Rued. (C. “putillus” auct.)
C. spiniferus Rued.

Glossograptus quadrimucronatus var. cornutus
Rued.

Lasiograptus (Thysanograptus) eucharis (Hall)
Lepidocoleus jamesi (H. & W.)

Spatiopora sp.

Prasopora simulatrix Ulrich
Leptobolus insignis Hall
Lingula curta Hall
Schizocrania filosa Hall

Dalmanella rogata Sardeson (D. “testudinaria”

auct.)

Rafinesquina alternata (Emmons) , small
Plectambonites sericeus (Sowb.) H. & C.
Prolobella? trentonensis (Hall)

Pterinea insueta (Emmons)

Whiteavesia sp.

Ctenodonta nuculiformis ? Hall
Ctenodonta sp. nov.

Clidophorus sp.

Hyolithes pinniformis Rued.

Clathrospira subconica (Hall)

Liospira cf. rotuloides (Hall)

GEOLOGY OF THE CAPITAL DISTRICT

Ceplialopods: Orthoceras hudsonicum Rued.

O. arcuolineatum Rued.

O. cf. amplicameratum Hall
Trilobites: Triarthrus becki Green

Isotelus sp.

Calymmene senaria Conrad var.

Ostracods: Primitiella unicornis Ulrich

Ulrichia? bivertex Ulrich

The characteristic fossils of the Canajoharie shale that do not
occur in the Utica shale are :

Corynoides calicularis

Diplograptus amplexicaulis

Diplogr. (Mesogr.) mohawkensis

Glossograptus quadrimucronatus mut. cornutus

Prolobella? trentonensis

Pterinea insueta

Ulrichia ? bivertex

Primitiella unicornis

On the other hand, many of the Canajoharie forms are found in
the contemporaneous Snake Hill shale of the eastern trough.

We have been able to distinguish five zones (Ruedemann, ’12,
T9, p. 126) in the Canajoharie shale of the lower Mohawk valley,
in ascending order as follows :

Zone of Mesograptus mohawkensis.

Zone of Diplograptus amplexicaulis, Corynoides calicularis, etc.

Zone of Glossograptus quadrimucronatus cornutus.

Zone of Lasiograptus eucharis.

Zone of Climacograptus spiniferus, Diplograptus vespertinus, etc.

The writer found early in his work some outcrops of black shale
of the characteristic appearance of the Canajoharie shale in the Snake
Hill belt of the capital district. One of these indicated on the map
is along the Alplaus creek about a mile and a quarter south-south-
east of Burnt Hills. This locality has afforded besides Corynoides
calicularis, Glossogr. quadrimucronatus mut. cornutus, Lasiograptus
eucharis, and Leptobolus insignis, the cephalopod Orthoceras hud-
sonicum that preserved the embryo shell (protoconch) (Ruedemann,
T2, p. 1 12) in this locality. It is probable that this small outcrop,
represents an inlier of Canajoharie shale in Schenectady beds, part

NEW YORK STATE MUSEUM

of a tilted block near the Ballston Lake fault that has become ex-
posed by erosion.

Another interesting exposure of black shale of Canajoharie ap-
pearance was found years ago by Doctor Clarke within sight of
James Hall’s grave in a road metal pit of the Rural Cemetery. It
furnished a very remarkable fauna that has been described by
Ruedemann (’oi, ’08) and consists of:

Mastigograptus circinalis Rued.

Corynoides calicularis Nicholson.

Glossograptus quadrimucronatus mut. cornutus Rued.

Lasiograptus eucharis (Hall.)

Climacograptus strictus Rued.

Eopolychaetus albaniensis Rued.

Pontobdellopsis cometa Rued.

Leptobolus insignis Hall.

Schizambon canadensis Ami.

Hormotoma cf. gracilis (Hall.)

Glossograptus quadrimucronatus mut. cornutus Rued, was described
from the splendid material of this locality (Ruedemann, ’12) as
well as the strange worms, Eopolychaetus and Pontobdellopsis.

The writer considered this locality and the belt in which it lies, first
as Utica shale (Ruedemann, ’01) and after the Snake Hill shales and
Canajoharie shales had been separated from the mass of the “Hudson
River shales’’ held this occurrence as due to the infolding of Canajo-
harie shale with the Snake Hill formation in the much disturbed
region (’12.) Closer study, however, of the structure of the capital
district and recognition of the fact that the Canajoharie and Snake
Hill shales belong to different troughs and that the Snake Hill
shale is underlain by the thick Normanskill shale, Rysedorph Hill
conglomerate and other terranes that have been pushed by over-
thrust over on the western trough, make it impossible to imagine
how a thin belt of the Canajoharie shale could appear so far east in
the Snake Hill rocks. We are therefore forced to the conclusion
that temporary connections existed between the two troughs or of
both troughs with a third basin, probably in the north that allowed
Glossograptus quadrimucronatus cornutus, a floating graptolite, to
enter the Snake Hill trough. It is in this connection of some signifi-
cance that the cemetery locality has furnished besides the graptolites
strange fossils that have not been observed in the Canajoharie shale, as
especially the worms, one of which (Pontobdellopsis cometa), how-

GEOLOGY OF THE CAPITAL DISTRICT

ever, has been collected in the Snake Hill shale below Mechanic-
ville. While the brachiopod Schizambon canadensis is known only
from Canada, a similar form has, however, been described as
Schizambon albaniensis (Ruedemann, ’ig, p. 105) from the Snake
Hill beds at Watervliet. It thus seems after all that this occurrence
has as close relations faunistically with the Snake Hill shale as it
has with the Canajoharie shale. We have separated the outcrop of
the Rural Cemetery on the map as a Canajoharie shale belt mainly
to emphasize the presence of this Canajoharie phase of the Snake
Hill shale.

2 Schenectady beds. The Canajoharie is overlain in the capital
district by the Schenectady beds. They appear in the farthest
southwest corner of the Saratoga quadrangle in the town of Galway
and thence extend in a broad belt southward and westward forming
the surface rock in the whole area between Schenectady and the
Helderberg escarpment, entering the Schoharie valley as far as
Schoharie village. In the capital district they form a belt six to
eight miles wide, along the western margin.

The Schenectady formation consists of about 2000 feet of grits
and sandstones with interbedded black and gray argillaceous shales,
the two forming a monotonous, uniformly alternating series through-
out this great thickness. The sandstone beds are quarried about
Schenectady and Aqueduct. In the latter place where the Mohawk
river in its postglacial course breaks through a ridge of these
harder beds an excellent section of a portion of the formation is
furnished. These gray, impure sandstones and gray to black argil-
laceous shales have until recently been generally correlated with the
“Hudson River,” Lorraine and Frankfort formations, mainly for
the reasons that they overlie black (Canajoharie) shales which were
identified with the Utica shale and that they are lithologically like
the Lorraine beds. Investigations by the writer (’12, ’14) have,
however, shown that this thick formation contains a fauna not
younger than Trenton and that the underlying black shale is not Utica
but early Trenton in age.

The Schenectady beds are overlain by the Indian Ladder beds.
The latter are of younger than Utica (of Eden) age. Provided
there is no hiatus between the Schenectady and the Indian Ladder
beds corresponding to the Utica shale, it is to be inferred that the
upper part at least of the Schenectady is of Utica age, although the
fauna does not give any support to this view. Indeed, Doctor Ray-
mond (’16) has suggested that the Schenectady beds are of Utica

NEW YORK STATE MUSEUM

and probably also of Frankfort age. The fossil evidence, however,
is in favor of the Trenton age of the formation and the Utica aspect
of a portion of the fauna is undoubtedly due to the shaly facies.
This evidence will be given later when the fauna is discussed. To
this may be added that the Schenectady formation rapidly dwindles
westward and that the Utica, as well as the Frankfort shales, do the
same eastward in the upper Mohawk valley.

The thickness of the formation has not been measured ; it is in-
ferred from the width of the belt and the general dip. There are,
however, continuous sections of more than 1000 feet, like that pub-
lished by Cumings (’oo, p. 45) on Waterstreet hill near Rotterdam,
to the west of the capital district; and in a well at Altamont the
drill iwent through 2880 feet of sandstone and shales before reaching
the Trenton limestone (Ruedemann, ’12, p. 38).

The cause of the astonishing thickness of the Schenectady shales
is to be sought in their deposition in a basin, formed by sinking
foreland in front of the rising Green Mountain folds to the east;
which basin was rapidly being filled with sediments. The shallow
water origin of most of the shales and sandstones of the Schenectady
beds is proven by the shrinkage cracks found in the thinner sand-
stones (as at the Bozen kill), the frequent layers of mud pebble
beds, cross bedding with plunge structure, very rapid change of
thickness of beds and other features.

The writer (’12, p. 41) has expressed the following views regard-
ing the causes of the structure of the Schenectady beds :

The constant alternation of more or less coarse sandstone with
shales is indicative of a frequent shifting of the conditions, presuma-
bly through currents, either reversal (tidal) or continuous currents.
There is sometimes clear evidence of absolutely regular or rhythmic
shifting. Such a place for instance was observed in an abandoned
quarry on the Bozen kill between Altamont and Delanson. The
base is here formed by a compact bed of sandstone some 15 feet
thick. This sandstone is abruptly followed by dark argillaceous shale
in which higher up thin sandstone layers appear, that become more
frequent until another thick sandstone bed is formed, like the basal
one. This in turn is cut off by a shale that gradually yields to sand.
The whole cycle is in this place repeated three times, shales and sand-
stones being each of equal thickness, the whole indicating a most
remarkable regularity of change of deposition which on account of
the very shallow character of the rocks of that locality may well
have been a condition due to reversal or tide currents.

P. G. Sheldon (’28) has just published a paper regarding the
sedimentation conditions in the Middle Portage rocks and has
described conditions exactly duplicated in the Schenectady beds, for

GEOLOGY OF THE CAPITAL DISTRICT

instance at the Bozen kill. He finds that these Portage sandstones
begin abruptly above the shale, as a massive sandstone with scat-
tered mud pebbles, that above this flat sedimentation prevails in the
middle and minute cross bedding and ripple marks at the top. This
succession is the result of a regularly diminishing current, which in
the first stage kept the sediment thoroughly churned, then in the
middle produced distinguishable channels and finally diminished
enough to produce ripples at the bottom. Sheldon sees the cause in
fluctuations in the effective strength of the transporting waters. If
fluctuations in the power of moving water alone is the cause, the
alternations in the Schenectady beds would indicate gradually
increasing currents from the shale to the sandstone.

The best outcrops of this formation in the capital district are along
the Mohawk below Schenectady, especially at Aqueduct and Rexford
Flats, and at French Mills on the upper Normanskill. In both these
localities the heavy sandstone beds, characteristic of the upper por-
tion of the formation, may be seen. At Aqueduct they are in a very
regular alternation with shale. At French Mills two beds each
eight feet thick are exposed. The formation, especially its gritty and
sandy beds, comes also to the surface over a large area on the Glen-
ville ridge, northwest of Schenectady, along the margin of the map.
This ridge is undoubtedly due to the competent character of the
grits and sandstones that prevail especially in the upper part of the
formation. The alternating shales and sandstones (called blue-stones)
have been quarried for many years between Schenectady and Aque-
duct, largely for crushed stone. Very heavy sandstone beds (15 feet
thick and more) are found in the upper portion of the formation,
west of Altamont.

The flora and fauna of the Schenectady beds consist of :

Plants:

Graptolites:

Crinoids:
Starfish
( Brittle Stars):

Sphenophycus latifolius (Hall)

Dictyonema multiramosum Rued.

Azygograptus sp. nov.

Mastigograptus sp. nov. cf. simplex Walcott
M. sp. nov.

Diplograptus vespertinus Rued.

Climacograptus spinifer Rued.

C. typicalis Hall

Lasiograptus (Thysanograptus) eucharis (Hall)
Joints

Taeniaster schohariae Rued.

NEW YORK STATE MUSEUM

Brachiopods:

IV orms :

Pelecypods:

Gastropods:

Conularids:

Cephalopods

Trilobites:

Ostracods:

Burypterids:

Lingula (Pseudolingula) rectilateralis Emmons
mut. major Rued.

Lingulasma elongatum Rued. (’16, p. 70)
Leptobolus insignis Hall
Dalmanella rogata Sardeson
Rafinesquina ulrichi James
Plectorthis plicatella Hall
Orbiculoidea sp.

Serpulites sp.

Saffordia ulrichi Rued.

Cyrtolites cf. ornatus Conrad

Conularia trentonensis Hall var. multicosta Rued.

Cyrtoceras sp. nov.

Spyroceras bilineatum {Hall)

Trocholites ammonius Conrad
Triarthrus becki {Green)

Isotelus gigas Dekay
Cryptolithus tesselatus Green
Primitia

Eurychilina cf. subrotunda Ulrich
Eurypterus pristinus Clarke and Rued.

E. megalops C. & R.

E. ? (Dolichopterus ?) stellatus C. & R.

Eusarcus triangulatus C. & R.

E. ? longiceps C. & R.

Dolichopterus frankfortensis C. & R.

D. latifrons C. & R.

Hughmilleria magna C. & R.

Pterygotus nasutus C. & R.

Stylonurus ? limbatus C. & R.

This fauna contains on one hand, elements of the Utica fauna, on
the other, Trenton biota, and finally a large element of its own.
The Utica elements are for the most part forms connected with the
shaly facies and therefore already appearing in the Canajoharie
shale. Such are Climacograptus typicalis, Lasiograptus eucharis,
Leptobolus insignis. The forms pointing to the Trenton age are:
Conularia trentonensis, Spyroceras bilineatum , Triarthrus becki (the
Utica form being T. eatoni), Cryptolithus tesselatus. The species
apparently restricted to the Schenectady beds are: Sphenophycus
latifolius, Dictyonema multiramosum, Taeniaster schohariae, Saf-
fordia ulrichi and especially the eurypterids.

GEOLOGY OF THE CAPITAL DISTRICT

The peculiar seaweed Sphenophycus latifolius was originally
described by Hall from the “Hudson River shale” (Schenectady
beds) at Schoharie. The writer has also found it as the most com-
mon fossil in the blue-stone quarries about Aqueduct and at French
Mills, and still in the highest beds of the formation above Altamont,
as well as in other localities. It is therefore the most reliable index
fossil of the Schenectady beds.

The brittle star was found only in a single specimen by the writer
below Schoharie village.

The most striking element of the fauna are the eurypterids. This
is the largest Ordovician eurypterid fauna that has as yet become
known. Indeed, before this fauna was discovered a few fragments,
a body ring and a leg, of a Utica form, and some fragments
from the Cincinnati region, which had been described as graptolites,
were the only Ordovician eurypterids known. Unfortunately the
principal locality is now wholly lost. This was the Dettbarn quarry
on the outskirts of Schenectady, between Van Vranken avenue and
the river. The quarries have been filled in and the district has been
built over. The eurypterids were found there by the writer in the
shale layers between the sandstone (blue-stone) banks, together with
the graptolites, trilobites and other fossils. Smaller collections of
less favorably preserved eurypterid material were also obtained on
Waterstreet hill near Rotterdam Junction, in the blue-stone quarries
about Duanesburg and near Delanson. It is therefore probable that
the seaweed Sphenophycus and the eurypterids, as well as some of
the graptolites, are well distributed through the whole thick forma-
tion.

It is quite apparent that the hundred-fold repetition of sandstone
or grit beds and shale together with the eurypterids, seaweeds and
scattered graptolites and other marine fossils indicate conditions of
deposition different from those usually found. We have already seen
that the beds were laid down in a basin or trough extending north-
south or more correctly north-northeast to south-southwest in the
direction of the later Green mountain folding, and that this basin
was rapidly sinking. The writer sees in the lithic and faunal condi-
tions evidence of currents that brought in the material probably from
the northeast ; in times when they were very strong the sandstones
were deposited ; when they were weak the shales were formed, the
black shales with the graptolites indicating the times of least motion
of the water. Others would consider these beds as the result of
rapidly changing depth of water and the moving up or down of the
shore line, and still others see in them delta deposits.

NEW YORK STATE MUSEUM

3 Indian Ladder beds. The Indian Ladder beds have their type
locality, the Black creek ravine at the Indian Ladder, just beyond
the edge of the capital district. They extend from there, rapidly
thinning, below the Helderberg cliff, as far as New Salem, where
they can still be recognized in the ravine above the village. They
are well exposed to the west of the Indian Ladder, below Haile’s
cave and will be fully described by Miss Goldring in the Guide of the
Indian Ladder region.

The writer (’12) separated this formation from the Schenectady
beds, after the discovery of a fauna in the Black creek ravine, that
is younger than Utica age and corresponds to that of the Southgate
member of the Eden shale about Cincinnati and in age to the Frank-
fort shale of central New York.

The type section is along the upper left branch of Black creek,
forming the fall and deep ravine at the Indian Ladder. The section
comprises here about 410 feet (aneroid measurement), of which the
lowest 100 feet are dark gray to black argillaceous shales with two
thick sandstone beds (each about four feet)1 while the next 100 feet
are of a character not met with in the Schenectady beds. They con-
sist of rapidly alternating gray shales and thin yellow rusty-looking,
somewhat calcareous sandstone layers, one-half to one inch or more
thick. The uppermost part of this portion becomes quite sandy.
Nearly 100 feet are there covered while some 120 feet at the top
consist of prevailingly heavy sandstone beds with intercalated dark
arenaceous and argillaceous shales, and an occasional limestone band.
The top is formed by a white hard sandstone bank three and one-
half feet thick and consisting largely of rounded sand grains. This
is separated by shale, one layer of which consists of pyrite, from an
underlying gray sandstone bed, also composed of rounded grains.
The sandstone beds of this upper part of the formation are extremely
irregular courses. In one case a bed was seen to run out within ten
feet from four feet to one-half a foot. In the excellent section
exposed near the first fault-line, about one mile southeast of the
Indian Ladder, a considerable thickness of dark gray shale is fol-
lowed by a ten-foot bed of solid sandstone, then 20 feet of alternat-
ing dark shale and thin beds of sandstone, the latter increasing
toward base, and a last seven-foot sandstone bed on top, upon which
the Brayman shale rests.

The Indian Ladder beds have an extremely barren aspect. Very
thorough search has furnished us a small graptolite faunule in the

1 In Bulletin 162, figure 5 is the lower thick-bedded sandstone with shale
alternations and figure 6 the overlying alternating shale and thin fossiliferous
limestone beds, the two figures having been confused by the editor.

GEOLOGY OF THE CAPITAL DISTRICT

shales of the lower 200 feet and another faunule in the thin cal-
careous sandstone intercalations of the second hundred feet. A few
bands of the latter proved to be covered with the remains of a
microfauna, especially small crinoid joints.

The shale has furnished:

Dictyonema arbusculum Ulrich
Diplograptus cf. nexus Rued.1
Dicranograptus nicholsoni Hopkinson.

The calcareous sandstone fauna consists of :

Cystids:

Crinoids:

Machaeridians:

Bryozoans:

Brachiopods:

Trilobites:

Calyx plates and columnals of cystid allied to
Cheirocrinus

Crinoid columnals (Heterocrinus)

Lepidocoleus jamesi (H. & W .)

Hallopora onealli (James) Ulrich
Arthrostylus tenuis Ulrich
Helopora sp. nov.

Rhinidictya cf. parallela (James)

Rafinesquina ulrichi (James)

Plectambonites centricarinatus Rued.

P. plicatellus (Ulrich)

Dalmanella multisecta (Meek)

Cryptolithus bellulus (Ulrich)

Acidaspis crossota Locke
Calymmene sp.

In the New Salem section the Indian Ladder beds are exposed in
the ravines leading from the village to the new state road. Here for
about 80 feet gray and black, partly sandy shales are observed.
Thirty feet below the base of the Manlius the yellowish-weathering
calcareous intercalations, so characteristic of the lower Indian Lad-
der beds in the Indian Ladder section, are observed through an
exposed interval of 15 feet; farther up blocks of the heavy top sand-
stones are seen in little disturbed position. Years ago the writer
collected in the shale of this locality Dicranograptus nicholsoni and
Clima co grap tus typicalis (variety with somewhat longer distal
spines). This is the only outcrop on the Albany quadrangle of the
Indian Ladder beds that is not doubtful. Small outcrops of dark
blue to olive-tinted argillaceous shales farther east, just under the
cliff, are lithologically noncommittal and have failed to furnish
fossils.

1 Diplograptus peosta cited by the writer in 1912 (p. Si) is a much later
(Maquoketa) form of the west. Diplograptus nexus occurs in the Whetstone
Gulf (lower Lorraine) formation of central New York.

NEW YORK STATE MUSEUM

The Indian Ladder beds with their restricted horizontal distribu-
tion, east and west, in spite of the great thickness that they attain
at the Indian Ladder, represent a puzzling formation, especially since
their fauna is nowhere else represented in eastern New York. It
is, however, of the same age as that of the Moose Creek member of
the Whetstone Gulf formation of central New York, corresponding
to the Southgate member of the Eden formation of Ohio. It is to
he inferred from the distribution of the rocks and the character of
the fauna that the Indian Ladder beds represent an independent
advance of the Eden sea from the south northward in one of the long
troughs developing in the Appalachian region. In Pennsylvania the
Martinsburg shale represents in part the Eden formation and it is
probable that this isolated occurrence of a formation, younger than
the Utica, has there its derivation. (Ruedemann, ’25, p. 152, fig. 8.)

4 Brayman shales. The extremely heavy top bed of the Indian
Ladder beds, a sandstone bank seven feet thick, is overlain by two
feet four inches of a greenish sandstone to coarse arenaceous shale,
thickly charged with iron pyrites, at the Indian Ladder. This bed is
soft and rots away so easily that it is exposed only below the falls
and at the caves. It has receded far back of the cliff and is usually
covered by talus material. A good exposure is, however, shown at
the first fault-line, about one mile southeast of the Indian Ladder,
where two feet four inches of very pyritiferous Brayman shale are
seen that is separated from the underlying heavy sandstone bed
(seven feet thick) by a disconformity plane, full of pyrite.

On the Albany quadrangle it has dwindled to about ten inches
about New Salem, where it is exposed in a small glen one-half mile
south of New Salem. It is not exposed again farther east at the
base of the cliff.

This thin bed of greenish sandy shale has been variously corre-
lated. Prosser and Rowe (’9 7) who first described it from the
Indian Ladder and New Salem region considered it as the attenu-
ated Clinton formation. They thus connected it with the so-called
Clinton shales of the neighborhood of Cobleskill. These shales
reach there 40 feet in thickness, are olive or grayish clay shales,
loaded with concretions of iron pyrites of all sizes, although gener-
ally not much larger than a man’s fist. This strange formation has
never furnished any fossils and its age has therefore remained uncer-
tain. Grabau (’06) proposed the name Brayman shale, from the vil-
lage of Braymansville on the Cobleskill, for the shales. While
Hartnagel, Clarke and others were inclined to consider the Brayman
shale of Salina age, Grabau would correlate it only with the lower

GEOLOGY OF THE CAPITAL DISTRICT

part of the lower cement bed at Rosendale. Ulrich and Ruedemann
independently reached the conclusion that it probably is a residual
bed or soil of the Ordovician representing the large hiatus between
the Indian Ladder beds and the Cobleskill beds of Niagaran age
(Ruedemann, ’12, p. 56).

This conclusion is based in part on the character of the shale, and
in part on its overlapping of various Ordovician formations (Frank-
fort shales in west, Schenectady beds in Schoharie region, Indian
Ladder beds farther east). The Brayman shale is therefore not
directly attachable to any of the Ordovician formations, but inde-
pendent of them. On the other hand, Grabau (op. cit. p. 127) has
argued that the Brayman shale is more sharply separated by its lithic
character and the nature of the contact from the overlying water-
lime than from the underlying sandstone. He would therefore draw
the Siluro-Champlainic boundary somewhere below in the sandstones
and consider the uppermost sandstone beds as equivalent to the
Binnewater sandstones of the Rondout cement region.

B Silurian and Devonian Rocks of Both Troughs

5 Rondout Waterlime. The Brayman shale is sharply separated
from the overlying waterlime. This latter bed, which was formerly
known as the “Salina waterlime,” and which was later correlated with
the Rondout waterlime horizon, is of varying, but small thickness.
It is exposed in but five places in the region, namely, at the Indian
Ladder just outside of the Albany quadrangle, where it is seen along
Bear Path under the cliff, especially under the waterfall and measures
three and three-fourths to four and three-fourths feet. It is again
seen in the small glen one-half mile south of New Salem (Prosser &
Rowe, ’99, p. 338) where the Brayman shale is exposed. It is there
six and one-half feet thick; it measures 12 feet in the South Albany
quarry ; and finally it is found in the large quarry at South Bethle-
hem. It is there about 12 feet thick.

In the Cobleskill region this formation has thickened to 60 feet,
the lowest six feet of which are mined for the manufacture of
cement at Howes Cave. In the capital district the bed contains no
cement, but consists of drab impure magnesian limestones, in three
or four layers with some shaly intercalations. As at Rondout the
surface (the uppermost in the South Bethlehem quarry) of some
beds is characterized by mud-crack structures, mostly of pentagonal
form. These indicate that the fine lime mud which formed the bed
was probably exposed at times (low tide) to the drying influence
of the sun.

NEW YORK STATE MUSEUM

No fossils have been observed in the capital district localities men-
tioned. Grabau has observed at Howes Cave fragments of Favosites
helderbergiae var. precedents which have passed up from the under-
lying Cobleskill limestone. Since the latter is of Silurian age, there
can be no doubt of the Silurian age of the Rondout waterlime what-
ever the age of the Brayman shale may be.

GEOLOGY OF THE CAPITAL DISTRICT

NEW YORK STATE MUSEUM

6 Manlius limestone. The Manlius was originally known as the
Tentaculite limestone, a name derived from the abundant occurrence
on the slabs of the little straight shells of Tentaculites gyracanthus,
a supposed pteropod. Later the formation, following the present
custom of deriving names from the most typical locality, was termed
the Manlius limestone, after Manlius near Syracuse.

In the capital district the Manlius is a very characteristic, easily
recognized formation in the lower part of the vertical Helderberg
cliff (figures 53, 71, 74, 76). It consists of thin-bedded, dark blue
limestone of fairly pure composition, in layers one to three inches
thick, the layers being especially thin in the lower part with alternat-
ing lighter and darker beds (ribbon-limestone of authors). The thin
limestone slabs are of remarkable hardness and resistance ; they
break with a ringing sound and weather with a characteristic light
color. This formation is, however, most easily recognized by the
immense numbers of the tentaculites upon certain surfaces, while
others are covered with the little brachiopod Spirifer vanuxemi, and
others again with the fairly large ostracod Lcpcrditia alta. It is on
account of this hardness of the rock that the Manlius forms such a
distinct vertical cliff, either jointly with the overlying Coeymans
limestone, as at the Indian Ladder, or often by itself as in localities
between New Salem and South Bethlehem, as, for example, on the
Clarksville road and above Feura Bush.

The best exposure in the Albany region is at the Indian Ladder,
where the whole thickness is shown in the cliff. The thickness is
there given by Prosser (’99, p. 30) at 3ij4 feet for the typical
Manlius limestone and 14^2 feet for the transitional beds from the
Manlius to the overlying Coeymans limestone. In a later paper (’07)
the same author has, however, given the formation a thickness of
54% feet at the Indian Ladder, with still a transition bed of two
feet above it.

Owing to displacements along fault-lines the Manlius comes to or
nearly to the top of the vertical cliff in two places south of the Indian
Ladder, and it can be traced fairly persistently along the foot of the
cliff.

Excellent exposures on the Albany quadrangle are furnished by
the small quarry near the state road above New Salem, where 25
feet of Manlius limestone are exposed ; in the new large quarry of
the Albany Crushed Stone Co. one and one-half miles southeast of
Feura Bush ; and in Callanan’s quarry at South Bethlehem. The
section in the small glen one-half a mile south of New Salem has
furnished Prosser 32*4 feet of typical Tentaculite limestone and

GEOLOGY OF THE CAPITAL DISTRICT

12^ feet of transitional layers above with Spirifer vanuxemi and
Lepcrditia alta. Darton (’94, p. 441) states that the average thick-
ness of 30 feet for the formation is maintained throughout Albany
county. We have measured 45 feet of Manlius in the section east
of New Salem, drawing the boundary line with the Coeymans along
a distinct, somewhat wavy line with a thin seam of shale above
where Manlius pebbles are seen in the Coeymans limestone.

The New Salem quarry exhibits a series of features that clearly
indicate the tide-flat conditions under which the Manlius limestone
was deposited. There are besides the thin bedding of the limestone
thin shaly films separating the limestones, mud cracks and faint
ripple marks, comminuted shells, parallel arranged Tentaculites-
tubes and piled-together masses of Leperditia shells, also mud pebbles
in the bottom beds. As many as three Stromatopora beds are seen ;
one eight to nine feet thick occurs in the true Manlius formation.
In the transition beds are three feet four inches of extremely thin-
bedded shaly material full of black grains, apparently phosphate of
lime. Flat coral stocks of Stromatoporas are also seen here at the
top of the transition beds.

The Stromatopora bed of the Manlius is also seen in the little
glen south of New Salem and on the road from Albany to Clarks-
ville, in the floor of an abandoned quarry about a mile southwest
of Stony hill, and again three-fourths of a mile farther west at the
foot of the cliff in the deep reentrant.

Owing to the intensive work, the exposures in the gigantic South
Bethlehem quarry are continually changing. The heavy Stromatopora
bed is probably always visible at the top of the Manlius limestone
and in the middle of the quarry also five to ten feet of Coeymans
limestone above it. Mr Hartnagel has measured in Callanan’s quarry
the following section :

Depth
in feet

Upper Manlius 15

Waterlime with Leperditia 4

Lower Manlius 36

Waterlime . 14

Hudson River Beds.

Sicberella cocymanensis ( galeate auct.) was found to appear not
until at least 20 feet above the Manlius. A fault in the upper Manlius
may cause a duplication of beds.

The fauna of the Manlius is very meager, although it has
afforded in other regions, as that of Jerusalem Hill in southern
Herkimer county, some very remarkable fossils, such as strange
crinoids and cystids. d he talus of the cliff in the capital district

NEW YORK STATE MUSEUM

will hardly furnish anything else but the bryozoan : Monotrypella
arbusculus Hall;

the brachiopod: Spirifer vanuxemi Hall.
the small pelecypods : Megambonia aviculoidea Hall and
Modiolopsis? dubia Hall.

the pteropod : Tentaculites gyracanthus {Eaton) Hall and
the ostracod: Leperditia alta ( Conrad ) Hall.

Of these Spirifer vanuxemi Hall, Tentaculites gyracanthus and
Leperditia alta can always be found.

To these must be added the Stromatoporas, which formed coral
reefs that can now be seen for long distances in the cliff, in section,
both in the Manlius and Coeymans limestones. They consist of
great horizontally connected subglobular masses, of concentric struc-
ture. They belong to an extinct class of organisms that probably
was related to the Hydrozoa. The latter today form similar coral
stocks, as in the genus Millepora, which comprises some of the most
important recent reef-builders. The Indian Ladder form has been
described as Syringostroma barretti by Girty (’94).

When one sees these reefs stretching through the Helderberg
cliff at various levels, one can not help connecting the peculiar thin-
bedded Manlius limestones with their tentaculites, ostracods and small
Spirifers and lamellibranchs, mud cracks and mud pebbles with these
reefs and see in the Manlius limestone principally lagoon deposits
on tide flats formed between and behind the coral reefs. The
transition beds contain alternating layers with the fauna of the
Manlius and with elements of the following Coeymans, thereby in-
dicating oscillating conditions of the sea. The Coeymans elements
found are especially the small brachiopods Stropheodonta varistriata
and Camarotoechia semiplicata.

Geologists of the First Geologic Survey, in the ’30’s and ’40’s of
the last century, distinguished the Lower and Upper Helderberg
limestones that were separated by a sandstone or grit bed, the
Oriskany sandstone. Under the leadership of James Hall the Upper
Helderberg beds were classed with the Devonian, the Lower with
the Silurian. Later Clarke in following the more refined demarca-
tion of the Silurian-Devonian boundary carried out in Europe,
brought the Lower Helderberg boundary limestones into the
Devonian because of their close faunal relationships with the
“Hercynian” of Europe, with the exception of the Manlius, and com-
prised the limestones below the Oriskany sandstone as the Helder-
bergian group. The Manlius was retained in the Silurian because its
small fauna shows no such relationship, but is rather Silurian in

GEOLOGY OF THE CAPITAL DISTRICT

aspect. The Manlius has been the object of argument as to its age
ever since. This is not the place to enter into a discussion of this
mooted question; it may suffice to state that while most authors
follow Clarke, some would also place the Manlius with the Devonian
and others put the division line between the Silurian and Devonian
within the Manlius. As stratigraphic methods become steadily more
refined, it is certain that the question will be finally answered satis-
factorily. So far as the Manlius of the eastern Helderberg cliffs
which may not entirely coincide with the typical Manlius of Onon-
daga county is concerned, it would seem that the observation of a
distinct irregular unconformity between the Manlius and Coeymans
at the Indian Ladder (see below), as well as about Catskill, with
Manlius pebbles in the base of the Coeymans as observed there by
Professor Chadwick, would indicate the presence of at least a local
unconformity between the Manlius and the Coeymans.

7 Coeymans limestone (figures 53 and 73). The Coeymans
limestone was known to the earlier geologists as the Lower
Pentamerus limestone or Pentamerus limestone in general from the
most common brachiopod Pentamerus galeatus (now Sieberella
coeymanensis) . Clarke and Schuchert in 1899 proposed the new
name from the village of Coeymans in Albany county. The Coey-
mans limestone is the principal cause of the Helderberg cliff. Its
massive character forms the cliff.

It is the most striking Helderberg formation through the thickness
and hardness of its beds; for these, combined with the vertical joint-
ing and the softer transition beds below, make the Pentamerus lime-
stone stand up in magnificent vertical cliffs over 50 feet high, and
usually projecting beyond the underlying Manlius and Rondout beds,
which are inclined to form caves and shelters ; as those about the
Indian Ladder.

The most massive beds are in the lower part while toward the top
the beds become more thin-bedded.

The Coeymans retains its thickness of about 50 feet1 over a
remarkably large area, from Schoharie past the Indian Ladder and
New Salem to Rondout, while eastward it decreases to 45 feet at
Becraft Mountain near Hudson. It also extends farther west than
the other Helderbergian formations, namely as far as the vicinity of
Manlius, Onondaga county.

1 Prosser gives 50 feet at the Countryman hill — New Salem sections; Grabau
about the same at Schoharie. Darton gives 65 feet but includes the Manlius-
Coeymans transition beds. Harris, on the other hand, gives the thickness as
32 feet and that of the Manlius as 63.7 feet, including the transition beds with
the latter.

NEW YORK STATE MUSEUM

The beds are usually several feet thick, of bluish-gray color,
weathering light gray and fairly regularly bedded, but there is, as
pointed out by Darton “also an irregular subbedding into flat, inter-
locking lenses and corrugations, the outlines of which are brought
out by weathering. Occasional shale partings occur and also
nodules and thin lenses of chert.” The rock itself is described by
Grabau as “mainly a rather coarse semicrystalline limestone com-
posed of fragments of shells, crinoids and corals. At intervals the
rock is a nearly typical shell limestone or coquina with the brachiopod
shells composing it largely in a perfect state of preservation. These
weather out in relief on the exposed edges of the rock and with care
may be collected from these surfaces.”

The fauna is a rather small one and consists almost entirely of
brachiopod shells which, entire or broken, largely compose the rock.
There are also a number of trilobites which the formation has in
common with the overlying New Scotland beds. The fossils are
hard to obtain unless the rock has been slightly burned.

By far the most common and diagnostic fossil which rightly gave
the formation its name is the Sieberella ( P entamerus ) galeata (Dal.)
H. & C. It received its name from the characteristic helmetlike
shape of the shells, and these stout shells are found everywhere in
the formation. The next common brachiopods are the Uncinulus
mutabilis (Hall), a subglobular form with many ribs and the long-
ranged Atrypa reticularis (Linn.) Dal. Besides these are recorded
from the Albany quadrangle by R. B. Rowe (p. 349) :

Strophonella punctulifera (Con.)

Stropheodonta (Brachyprion) varistriata (Con.)

Spirifer vanuxemi Hall.

S. perlamellosus Hall.

Rhynchonella semiplicata (Con.)

Meristella laevis (Vanuxem)

Orthis (Orthostrophia) strophomenoides Hall (?)

O. sp.

Anastrophia verneuili (Hall) ? and the coral

Favosites helderbergiae Hall.

The lower transition beds contain Spirifer vanuxemi and Stropheo-
donta varistriata as abundant fossils.

In the Schoharie region and in Herkimer county the Coeymans
limestone has furnished a number of beautiful crinoids and of strange
cystids, as Lepocrinites gebhardi with its carrotlike anchor and nut-
like head. These may also still turn up in the district. The small

GEOLOGY OF THE CAPITAL DISTRICT

crinoid Homocrinus sc Oparins was found in great numbers in Litch-
field, Herkimer county, by Doctor Clarke and the writer, together
with the peculiar starfish H allaster forbesi (Hall). There were
crinoid plantations growing in that region in Coeymans time, ap-
parently in more quiet water than prevailed farther east.

8 New Scotland beds (including Kalkberg limestone) . The New
Scotland beds are at once the least conspicuous and the most fossil-
iferous member of the Helderbergian series. They are not con-
spicuous, forming gentle slopes above the Coeymans cliff, because
they consist of thin-bedded, very impure shaly limestones and cal-
careous shales, varying in color from gray to gray-brown; they
weather readily and hence form soil-covered gentle slopes that are
often used for grazing and quite frequently used by farms, while the
broad back slope of the Coeymans, extending from west of Stony
hill to South Bethlehem is mostly wooded. Good outcrops are
therefore rare, and much sought after by collectors on account of
the splendid collecting that the New Scotland beds afford. It was
the stamping ground of the pioneer collectors of the Albany Survey ;
Hall was often in Clarksville and his assistants, Beecher, Clarke,
Simpson, Schuchert, the Van Deloos, Walcott and Whitfield, used
to walk out there Sundays from Albany and often return the same
day with their bags filled to capacity. Especially Bradford Allen’s
farm, two miles this side of Clarksville, on the Albany road, was
searched every year, the field there being strewn with weathered-out
fossils, silicified bryozoans, corals, trilobites and silicified brachio-
pods. G. B. Simpson told me that he gathered the largest portion of
the New Scotland material for volume 6 of the Paleontology of
New York on this farm. Also the Oniskethau creek below Slinger-
land’s Mill was famous among collectors ; this place as well as the
stone fences in the vicinity were a harvesting ground, especially for
trilobites. The creek and fences furnished the remarkable trilobites
Lichas pustulosus, Dalmanites pleuroptyx, Phacops logani etc., as
well as beautifully preserved gastropods of the genera Platyceras and
Strophostylus, bryozoans and brachiopods. At the sawmill at the
end of the section the trilobite Acidaspis tuberculatns is regularly
found. In later years the ground around the spring ( Voorheesville
water works) below the “Parrish house” (Kenny Parrish) on the
old road leading up from New Salem has been much frequented by
college classes in geology.

To these earlier enthusiastic and industrious collectors the forma-
tion was known as the “Delthyris shaly limestone,” from its most

NEW YORK STATE MUSEUM

common and characteristic fossils, the brachiopods Spirifer perlamel-
losus Hall and 5'. macropleura (Conrad) known also by the older
names Delthyris perlamellosus and D. macropleura. Before, the
formation was also known as “lower shaly limestone” and “Catskill
shaly limestone,” names that were applied by the geologists of the
first Survey. Clarke and Schuchert (’99) proposed the name “New
Scotland beds,” from the town of New Scotland in which Clarks-
ville and the other mentioned fossil localities are located. The village
of New Scotland is on Schenectady beds.

The shale, while resting flat in the northern and middle Helder-
berg region of the Albany quadrangle, is very soft and readily
weathered. Where, however, it has been folded, as in the southern
portion of the quadrangle, south of South Bethlehem, it is traversed
by slaty cleavage and much harder. It also possesses a distinct
slaty fracture cleavage and greater hardness along the fault south of
the Indian Ladder.

Above New Salem, in about the middle of the formation along the
new road, layers of fossil-bearing lime concretions are seen.

The thickness of the New Scotland beds averages about 100 feet
according to Darton; Prosser measured 120 feet in the Countryman
hill section, beginning a little northwest of New Salem and 127
feet in the Clarksville and Oniskethau creek section. Miss Goldring
and myself found 105 feet for the formation below the Parrish
house where the contact with the overlying Becraft limestone is
exposed. As in the measurements of the Manlius and Coeymans
limestones, there is not only slight variation from locality to locality,
but the differences also result from the uncertainty of the boundaries
and the presence of transition beds.

In the Schoharie region Grabau found 115 feet and at Becraft
mountain 70 to 75 feet, while at Kingston the thickness is estimated
at 100 feet. It is therefore safe to say that, as Darton concluded,
the thickness averages about 100 feet.

The transition beds between the Coeymans and New Scotland
beds are so strongly marked by parallel seams of black flint and a
mixed fauna at Catskill, Greene county, that they have been separated
by Chadwick as “Kalkberg limestone.” (Kalkberg, meaning lime-
stone mountain, is the local Dutch name for the Helderberg ridge.)

In the capital district the Kalkberg is not so distinctly set off from
the adjoining formations, but yet recognizable. At the Indian Lad-
der it was pointed out to Miss Goldring and the writer by Professor
Chadwick that the formation is there 20 feet thick, the beds charac-

GEOLOGY OF THE CAPITAL DISTRICT

terized by being a little heavier, not weathering so yellow and the
fossils being siliceous, with some chert. The thick stems of the
crinoid Mariacrinus stoloniferus and the brachiopods Bilobites,
Spirifer perlamellosus and 5'. cyclopterus are common in the bed, also
S. coeymanensis occurs.

Farther up in the New Scotland formation heavier beds are found
that contain only the small brachiopod species of Lingula and
Orbiculoidea.

South of Callanan’s quarry, near the edge of the Albany quad-
rangle, Miss Goldring and the writer found the Kalkberg formation
well recognizable, represented by firmer beds than those farther
north in the Helderbergs and containing chert. Also the uppermost
bed of the Coeymans is here filled with chert. The Kalkberg is
here 20 to 25 feet thick and while readily recognized it grades into the
Coeymans below and the typical New Scotland above so that the
boundary lines are hard to draw. We have mapped it with the New
Scotland formation because it belongs topographically with it.

Owing to variations in hardness the Kalkberg often forms one or
two local subterraces, as above New Salem ; another subterrace ap-
pears in the higher New Scotland where cherts and more silicious
admixture produce somewhat harder beds.

The fauna is too large to be listed fully here. It is interesting to
know, however, that according to a survey I made for this purpose,
there are cited in the volumes of the Paleontology (volumes 3, 4
and 7) and Director’s reports from the New Scotland beds 1 of
Clarksville the following numbers of species of each class :

Calcareous algae (Ischadites, Receptaculites) 2

Sponges 1

Corals 10

Bryozoans 71

Brachiopods 62

Lamellibranchs 9

Gastropods 21

Conularids 1

Trilobites 7

Cephalopods and ostracods 0

There are altogether 184 species recorded as occuring in the New
Scotland beds of that region. The two outstanding classes in this
fauna are the bryozoans and brachiopods ; the mollusks are only well
represented by the gastropods ; the trilobites are prominent as a faunal
element, not so much by variety of species as by number of indi-
viduals, but they are far surpassed by the bryozoans and brachiopods.

1 Some cited merely as Lower Helderberg beds of Clarksville. The lists
from the Indian Ladder would much increase this number.

NEW YORK STATE MUSEUM

Prosser and Rowe ('99, p. 338, 349) have listed 26 species from
the New Salem section and 43 forms from the New Scotland beds
of Clarksville but they did not make any effort to collect from the
bryozoan beds. I will merely cite here the species they have recorded
as common or abundant:

Clarksville (listed by Rowe) :

Corals: Streptelasma strictum Hall
Brachiopods: Spirifer macropleurus ( Conrad )

S. cyclopterus Hall

Leptaena rhomboidalis ( Wile kens )

Stropheodonta (Leptostrophia) becki Hall
Strophonella punctulifera ( Conrad )

Trilobites: Dalmanites pleuroptyx {Green)

New Salem section (below Parrish House) (listed by Prosser) :
Bryosoans: Fenestella sp.

Brachiopods: Stropheodonta (Leptostrophia) becki Hall
Spirifer perlamellosus Hall
Leptaena rhomboidalis ( Wilckens )

Trematospira globosa Hall
Spirifer cyclopterus Hall
S. macropleurus {Conrad)

Strophonella punctulifera {Conrad)
g Becraft limestone. The Becraft limestone was formerly known
partly as Scutella or Encrinal limestone and partly as Upper Penta-
merus limestone. The name “Becraft limestone” was introduced by
N. H. Darton (’94) with the sanction of James Hall. It is derived
from the well-known Devonian outlier Becraft mountain, just out-
side of Hudson, Columbia county.

GEOLOGY OF THE CAPITAL DISTRICT

16 57

12.32.

410

A13 425

a!2- Onondaga ■ ,

A,0EsopUS 12.1'

At Manilas 34'

A* Schenectady & Indian Ladder Beds 57'

A1 Schenectady BedLs Covered 300'

Sea.. Level

Scale t" = 150' '

Figure 5 Section of Countryman hill, near Salem. (From Prosser & Rowe).
Shows the two cliffs produced by the Upper and Lower Helderberg

limestones. , , | ,, |

NEW YORK STATE MUSEUM

It is the uppermost member of the Helderbergian (Lower Helder-
berg) limestones and in the earlier correlations formed the top of the
Silurian, while now it is the top member of the Helderbergian division
of the Lower Devonian.

It is a heavy bedded, light gray, coarsely crystalline limestone and
largely composed of fossils, mostly brachiopods and crinoids. The
formation is not very thick in the capital district, only the lower part
of the whole Becraft, as it is exposed farther south, as about Catskill,
being present. Darton found its thickness to average 15 feet but
states that at some points it appears to be slightly less. Prosser and
Rowe measured 13 feet in the Countryman hill section and 20 feet
near Clarksville. Miss Goldring and the writer found a thickness of
but 12 feet a mile northeast of the hamlet of Oniskethau, and only
about nine feet along the new Indian Ladder road, but 27 feet two
and one-fourth miles south-southeast of New Salem. It seems
thus that the formation varies considerably between 12 and 27 feet
in thickness in the capital district. It shows much greater thick-
ness farther south; at Becraft mountain it measures 45 feet.

In spite of its small thickness the formation is quite prominently
exposed forming a distinct flat in many places of the Helderberg
region in the capital district. Just outside of the latter it is now well
exposed by the new road, leading uphill from the Indian Ladder,
where it shows some shaly intercalations. The new state road from
New Salem to the Indian Ladder crosses it one-quarter of a mile
from the edge of the sheet and about one mile from the Indian Lad-
der, and it runs along the west side of the road for a mile and a
quarter on this side of that crossing. Along the old road leading
around Countryman hill it is well exposed at the Parrish house, which
stands on it, showing there just below the house the contact with the
subjacent New Scotland beds. Back of the house, where the joint
system of the formation is well exposed (also well seen along Indian
Ladder road), the old “Beaverdam road,” the first road that led from
Schoharie to Albany is still recognizable. It took advantage of the
bare rock surface of the Becraft flat.

A good contact of the Becraft and New Scotland beds is also seen
two and a quarter miles south-southeast of New Salem, where the
road leading south of New Salem climbs the escarpment. The
Becraft is also shown in typical development full of scutellas along
the new state road from Albany to Clarksville, a mile and a quarter
this side of Clarksville before one reaches the crossroads connecting
with the Feura Bush-Indian Fields road and at this crossroad the
contact with the superjacent Oriskany sandstone is exposed.

GEOLOGY OF THE CAPITAL DISTRICT

The new New Salem-Wolf hill state road gives fair collecting in
the New Scotland beds at the left in the first woods of the New
Scotland plateau and then along the road in successive outcrops of
the Becraft, Oriskany, Esopus and Onondaga formations (the latter
in large quarries).

The Becraft is covered by drift south of Oniskethau, but again is
well exposed along the road leading southwest into the Helderbergs
from South Bethlehem.

Although the Becraft limestone is composed of shells and shell
fragments, its fauna is not very large. The most conspicuous fossil,
from which it received its name “Scutella limestone,” from a fancied
resemblance of the fossil to the sea urchin Scutella, is the basal
portion of a large crinoid, Aspidocrinus scutelliformis Hall. These
fossils are solid, from one to two inches in diameter, usually flatly
bowl-shaped plates with a small central circular depression. They
were considered by Hall and later authors as the base of the calyx
of a large crinoid. Miss Goldring (’23) has found them to be the
basal expansions of crinoid columns, the columns themselves being
as yet unknown. The scutellas are found everywhere in the Becraft
limestone and form its best index fossil, although they appear in
the upper part of the New Scotland limestone. The shields are
rendered crystalline, like all echinoid remains, by secondary infiltra-
tion, often of pinkish or glistening white color and therefore readily
seen ; they also stand out in relief on the weathered surfaces.

In the lower part of the Becraft limestone large crinoid columns
or their scattered joints are common, and this fact gave the rock the
name of “Encrinal limestone.” Its last name of “Upper Pentamerus
limestone” it received from the brachiopod Sieberella (formerly
Pentamerus ) pseudogalcatus (Hall). This is also helmet-shaped,
as the Pentamerus of the Coeymans limestone, but bears no ribs on
the middle. It predominates especially in the upper portion of the
Becraft limestone.

Prosser (’99, p. 341) cites the following fossils from the Becraft

limestone at the Parrish house:

Crinoids: Aspidocrinus scutelliformis Hall (abundant)

Corals: Lichenalia torta Hall (rare)

Streptelasma strictum Hall. (r)

Favosites sphaericus Hall (r)

Brachiopods: Spirifer concinnus Hall (a)

Sieberella pseudogaleata Hall (a)

Atrypa reticularis (Linn.) Dal (a)

NEW YORK STATE MUSEUM

Wilsonia ventricosa (Hall) (r)

Uncinulus nobilis (Hall) (common)

U. campbellanus (Hall) (r)

Schizophoria (formerly Orthis) multistriata

Hall (c)

Rhipidomella (formerly Orthis) oblata Hall. . . . (r)

Spirifer cyclopterus Hall (?) (r)

Leptaena rhomboidalis (Wilckens) (r)

Orthothetes cf. woolworthana (Hall) (r)

From Clarksville Rowe records (’99, p. 351) :

Crinoids: Aspidocrinus scutelliformis Hall (aa)

Brachiopods: Stropheodonta becki Hall (rr)

Leptaena rhomboidalis (Wilckens) (rr)

Spirifer concinnus Hall (rr)

Strophonella punctulifera (Conrad) (a)

Atrypa reticularis (Linn.) Dal (a)

Orthis (Rhipidomella) discus Hall (rr)

O. (R.) oblata Hall (r)

O. (Dalmanella) planoconvexa Hall ( ?) (rr)

Orthothetes woolworthana (Hall) (rr)

10 Oriskany sandstone. The Orislcany sandstone in the capital
district averages only one to two feet, yet it is one of the best known
formations among collectors of fossils and geologists, partly on
account of its remarkable fauna of heavy shells and partly on account
of its important position at the base of the upper Helderberg forma-
tion or Oriskanian in the Helderbergs. In America, formerly, it was
even the base of the Devonian. It is also topographically important,
because it is itself extremely hard and resistant and, being followed
by soft shales, it forms a distinct broad platform in many parts of
the Helderbergs, altogether out of proportion to its thickness.

The formation was first called the Oriskany sandstone by Hall
and Vanuxem (’39) after the Oriskany Falls in Oneida county.
While it is very thin in the capital district, it thickens considerably
southward along the Hudson and extends far to the south, north
and southwest.

At its type locality, the Oriskany Falls, the formation consists of
20 feet of nearly pure, white fossiliferous siliceous sandstone. In
the Helderbergs it is a very dark, bluish-gray, hard, quartzitic sand-
stone with a strong admixture of calcareous matter which increases
southward but is variable in the Flelderbergs. It is this lime which
is dissolved out in the exposed rock and leaves behind a brown porous

GEOLOGY OF THE CAPITAL DISTRICT

sandstone. While it is very difficult to distinguish the fossils in the
fresh rock or to extract them, they are shown in the decayed rock
as beautifully preserved external and internal molds. It is for this
reason that in the days of widespread paleontologic enthusiasm in
New York State the wonderful collections of Oriskany fossils were
mostly obtained in old stone fences especially around Schoharie and
in the Helderbergs of Albany county. A splendid collection, now
on exhibition in the State Museum, was later obtained in weathered
joint cracks at Glenerie near Kingston in Ulster county.

Darton (’94, p. 439) found the Oriskany sandstone to vary in
Albany county from one to four feet and to average about three
feet over the greater part of the area. He also found that for
several miles south from Callanan’s corner it appears to be absent,
the Esopus shales and Becraft limestone appearing to be in direct
contact in several places. Prosser and Rowe (’99, p. 336) measured
two feet in the Countryman hill section and one foot in the Clarks-
ville section. We found one and one-half feet along the new Indian
Ladder road near the edge of the Albany quadrangle and three feet
one inch in a ledge that crosses the Oniskethau creek one and one-
half miles below Clarksville.

As already pointed out by Darton, the Oriskany sandstone is much
more exposed than one should expect from the thickness of the bed.
It is now very well shown along the new Indian Ladder road at the
bottom of a road metal quarry in the Esopus shale about one and
one-quarter miles this side of the Indian Ladder. The Oriskany, 18
inches thick, is here a very dark rock, obviously very siliceous, and
with many well-rounded sand grains on the surface. Its contact
with the underlying Becraft is sharp and irregular and a “welded”
contact, the two formations being so tightly adhering that they can
be broken out in one piece of rock. The sharp irregular contact and
the great differences in rock composition and faunas between the
two formations indicate a marked disconformity. The Port Ewen
formation, well exposed in the Kingston region and southward, is
missing here in this interval. Its fauna is a mixture of New Scot-
land elements and prenuncial Oriskany forms. The Port Ewen
formation is therefore grouped with the Oriskany sandstone. It is
also present again farther west at Howe’s Cave and Schoharie.

The Oriskany continues on the Becraft along the road in many
places as a thin layer of a few inches that remained from weathering.
The contact with the overlying Esopus shale is also sharp ; yet the
lower beds of the Esopus are flinty and still quite similar to the
Oriskany. The top of the Oriskany in most outcrops is marked by
the curving bushes of Taonurus cauda galli (see below, p. 59).

NEW YORK STATE MUSEUM

Another good outcrop of the Oriskany is back of the barn of the
Parrish house on the old Countryman hill road and north of that
house for a considerable distance in the road itself. The rock is
here two feet thick. Along the New Salem-Wolf hill state road it
is shown on the left side, before the road cut in the Esopus is reached.
A very well exposed ledge crosses the Oniskethau creek, one and
one-half miles below Clarksville, and the contact between the Becraft
limestone and the Oriskany sandstone is shown at the last four
corners before one reaches Clarksville.

The fauna of the Oriskany is especially notable by the large size
and thick shelled character of the forms, denoting turbulent water
conditions in the sea of that region, evidently along an advancing
shore line. The most characteristic and common of these are large
brachiopods, namely: Spirifer arenosus and N. murchisoni, Hip-
parionyx proximus, Rhipidomella musculosa, Leptostrophia mag-
nified, Pletliorhyncha barrandei, Camarotoechia oblata and Rens-
selaeria ovoides. These are associated with two large lamellibranchs,
viz. Pterinea textilis var. arenaria and P. gebhardi; and large gastro-
pods, Strophostylus expansus and Platyceras nodosum.

Prosser (’99, p. 341) collected at the Parrish House:

Brachiopods: Spirifer arenosus ( Conrad ) (a)

S. arrectus Hall (a)

S. pyxidatus Hall (r)

Rensselaeria ovoides {Eaton) (c)

Eatonia peculiaris {Conrad) (c)

Meristella lata Hall (r)

Leptocoelia flabellites {Conrad) (r)

Orthis (Rhipidomella) musculosa Hall (c)

Hipparionyx proximus {Vanuxem) (r)

Orbiculoidea ampla {Hall) (r)

Orthis sp (r)

Stropheodonta cf. magniventra Hall (r)

Gastropods: Platyostoma ventricosa Conrad (r)

Platyceras nodosum Conrad (r)

11 Esopus grit. The Esopus grit was known to the earlier geolo-
gists as the cauda galli or cocktail grit. It received its name from
the abundant markings on the bedding planes resembling a rooster’s
tail, already noticed on the top surface of the Oriskany sandstone.
Darton (’94) introduced the name “Esopus grit” (Esopus slates)
after the excellent exposures along Esopus creek below Saugerties in
Ulster county.

GEOLOGY OF THE CAPITAL DISTRICT

The Esopus grit (figures 54 and 77) is a blackish, gritty or sandy
shale of very uniform character, weathering to a dark brown color.
It is remarkably barren of organic remains, the cocktaillike mark-
ings that abound on the bedding planes being the only signs of life
in the formation. These were named Spirophyton ( Taonurus )
cauda galli and considered as impressions of “fucoids” or seaweeds ;
they are essentially bundles of sigmoid furrows rising in a spiral
curve around a central tube. They have more recently been con-
sidered as inorganic wave marks (Grabau, ’06, p. 168) and finally
been shown by Sarle to be produced by mud-swallowing worms, that
move in a spiral about the central tube. The State Museum has on
exhibition two specimens of Taonurus that actually show the worms
in place at the outer edge of the markings. These are from the
Hamilton shale of Western New York.

The lower eight feet of the Esopus grit in the road metal pit along
the new Indian Ladder road are highly siliceous or flinty and filled
with Taonurus-markings, indicating close relations of the Esopus
grit with the Oriskany sandstone, of which in part it may be a facies.
The middle portion is more argillaceous, the upper part becomes
again strongly siliceous, and the last five or six feet are a heavy
sandstone, well shown in the Clarksville-Oniskethau section. This
sandstone passes gradually into the Schoharie grit, showing also
close connection between the Esopus grit and Schoharie grit.
Prosser and Rowe drew the line in the Oniskethau valley, where the
Schoharie fossils appear. Southeast of Blodgett hill, near the south-
ern edge of the Albany quadrangle the Schoharie grit is reduced to
two feet or less and the Esopus appears to be in places in direct
contact with the Onondaga limestone. It also is so below Daniel
O’Connell’s home above the Indian Ladder road.

Darton (’94, p. 438) found an average thickness of 100 feet in
the Helderberg mountains ; Prosser and Rowe (’99, p. 348) measured
121 feet in the Clarksville and Countryman hill sections; Miss Gold-
ring and the writer found 120 feet above the new Indian Ladder
road just below the O’Connell house, and 105 feet on the south-
eastern slope of Countryman hill, while above the Parrish house
there are only about 100 feet of Esopus shale. The Esopus seems
thus to vary in thickness between 100 and 120 feet on the Albany
quadrangle. Southward this formation becomes much thicker; at
Becraft mountain and at Rondout it is about 300 feet, including the
Schoharie and at Port Jervis about 700 feet. It thence extends to
New Jersey and Pennsylvania. In the other direction toward Scho-

NEW YORK STATE MUSEUM

harie it loses in thickness and disappears not far west of Otsego
county.

In the landscape of the Helderberg mountains the Esopus shale
forms a very characteristic gentle slope between the terraces of the
Oriskany sandstone and the Onondaga limestone that widens con-
siderably southward from Countryman hill and is, as a rule, given
up to grazing. Toward the southern edge of the sheet where the
Helderberg formations become flexed into anticlines, the Esopus
shale becomes harder and develops more strongly a slaty cleavage
already apparent at Clarksville ; as a result it stands out in very
sharp ridges of barren aspect, as seen on the geologic map two miles
south and southwest of South Bethlehem. This condition extends
thence southward.

The best outcrops of this formation in the capital district are along
the new Indian Ladder road, the Wolf hill road and in the gorge
below Clarksville, in a road metal pit along the road a mile southeast
of Callanan Corner and along the roads leading south from Callanan
Corner and southwest of South Bethlehem near the edge of the map.
The Taonurus-markings are especially well seen in the small inlier of
Esopus shale in Onondaga limestone at Clarksville along the creek
(see map) and along the road this side of Clarksville.

12 Schoharie grit. The Schoharie grit was named so by Van-
uxem in 1840. Its chief distinction is the great wealth of fossils.
It is largely only a local formation found principally in the Scho-
harie valley, in Albany and Otsego counties and in the Hudson river
valley, and it is only six to seven feet thick in the Schoharie valley.
Yet this bed has furnished 123 species of fossils, the great majority
large and striking forms and restricted to the Schoharie grit !

The Schoharie grit, when fresh, is a dark bluish gray, impure
siliceous limestone which weathers to a dark buff, porous sandstone.
In the capital district it is found best exposed about Clarksville
between the Esopus and Onondaga formations and again near the
edge of the quadrangle south of South Bethlehem. In some places
the Onondaga and Esopus are in direct contact. This variable
occurrence of the Schoharie grit is obviously due to the fact that it
is probably no more than a sandy facies of the basal Onondaga lime-
stone. This is clearly shown by the fact that the Schoharie merges
into the overlying Onondaga, as already observed by Darton. There
are known to us two large boulders where the Onondaga limestone
and Schoharie grit are directly alternating. One of these, reproduced
in figure 55, lies by the road, one and a quarter miles south of Keefer
Corner opposite the house of Isaac Spanier. Here two layers of

GEOLOGY OF THE CAPITAL DISTRICT

Schoharie grit, seven and five inches thick are separated by 1 1 inches
of Onondaga limestone, which again in the middle has a thin band
of Schoharie grit two inches thick. Another similar block lies in front
of the N. Blair farm south of the Albany quadrangle and west of
Indian Fields just opposite the great Hannacroix waterfall. On
the upper Oniskethau creek between Countryman hill and Wolf hill
Miss Goldring and the writer observed several large boulders of
Schoharie grit with an intercalated six-inch band of Onondaga lime-
stone, the numerous fossils (corals and cephalopods) passing freely
across the welded contacts. These boulders are undoubtedly of local
origin and prove the actual alternation of Onondaga limestone with
Schoharie grit in some part of the Helderberg region.

The northernmost outcrop of the Schoharie grit in the Albany
quadrangle is at the base of the Onondaga cliff south and west of the
Parrish house where Prosser and Rowe measured two feet one inch.
It is next seen below the old road leading from New Salem over the
southern slope of Countryman hill to the new Wolf hill road. There
22 inches of Schoharie grit are seen at the foot of the Onondaga
cliff.

In the section along the new Wolf hill road the Schoharie grit is
well exposed with a thickness of about three feet resting on similar
sandy Esopus grit. The next outcrops are those about Clarksville
where the erosion of the Onondaga limestone has left the Schoharie
grit well exposed at the foot of the upper gorge and the top of the
lower gorge. Prosser and Rowe measured here three feet. Miss
Goldring and the writer found on top of the gorge (south side)
two feet seven inches of typical Schoharie grit and below 12 inches
of gritty shale layers weathering like Schoharie grit and transitional
to the Esopus shale. The contact with the Onondaga is here sharp,
the bottom layer of the Onondaga being soft and weathered out. The
upper two feet of the Schoharie grit are very fossiliferous, the corals
filling the upper eight inches. A good outcrop of three feet of Scho-
harie grit was found in the falls of a southern tributary of Oniske-
thau creek three-fourths of a mile east of Oniskethau hamlet. One
and one-fourth miles east-southeast of this locality the Schoharie
grit is exposed in the road. The greatest thickness of the Schoharie
grit occurs near the Callanan Corner-Coeymans road, three-fourths
of a mile south of Callanan Corner on the slope in the woods to the
right. Here six to eight feet of Schoharie grit were found and the
Schoharie and Onondaga are seen to be interfingering in places and
welded in others, with the lower Onondaga somewhat sandy. Pro-
fessor G. H. Chadwick (abstract of Geological Society meeting, ’27)

NEW YORK STATE MUSEUM

on the other hand, has found in the Catskill region disconformities
at the top and bottom of the Schoharie member indicated by
glauconite.

Finally, there are outcrops near the southern edge of the sheet
west of the South Bethlehem-Coeymans road, the Schoharie measur-
ing there two and one-half feet. Schoharie grit appears also half a
mile to the east of this road at the foot of the steep Esopus cliff as
a result of folding.

These occurrences would suggest a fairly continuous outcropping
of the Schoharie grit at the base of the Onondaga although it may
be absent west of Callanan Corner and in places north of Clarks-
ville. Darton (’94, p. 438) states that to the north and west of
Clarksville there are a few exposures of the base of the Onondaga
limestone, in which the grit is seen to be absent.

While thus the Schoharie grit varies in the capital district from
nothing to eight feet and also at Schoharie reaches not more than
five or six feet according to Grabau (’06, p. 180), some 150 to 200
feet of strata at Becraft mountain have been referred to the Scho-
harie grit, although in rock aspect they are more similar to the
Esopus grit, since some of the characteristic Schoharie fossils have
been found in them.

The fauna is the most remarkable feature of this formation. Thin
as the formation is, it usually abounds with fossils. The whole
fauna has been listed by Grabau (op. cit. p. 325). He enumerates
123 species, namely, bryozoans, 2; brachiopods, 33; pelecypods, 14;
gastropods, 12 ; pteropods, 2 ; cephalopods, 44; trilobites, 16. Grabau
lists no corals but the fauna of the Schoharie grit in Albany county
is largely composed of corals and cephalopods. Prosser and Rowe
(sp. cit. p. 352) cite Zaphrentis and Streptelasma sp. as abundant in
the Clarksville section. The largest biota of this fauna is the
cephalopods, which prevail so much in individuals and species, as
well as size of the fossils that the Schoharie grit is a distinct
cephalopod facies. To this must be added that there appear a num-
ber of species that are rare in general, as seven species of Gom-
phoceras, two of Gyroceras and no less than nine species of the
aberrant Trochoceras whose shells are coiled in gastropod fashion
and which is known practically only from this formation. To these
may be added 16 species of trilobites, among them such monstrous
and rare forms as Lichas ( Terataspis ) grandis and Conolichas
hispidus. No wonder the Schoharie grit has been the stamping
ground of collectors from all over the world, especially in the Scho-
harie valley, and is yet as far as the increasing rarity of stone fences
and of favorable outcrops does not discourage or stop the pursuit.

GEOLOGY OF THE CAPITAL DISTRICT 63

Rowe (’99, p. 352) gives the following list of fossils from the
Clarksville section :

Corals: Zaphrentis sp (a)

Streptelasma sp (c)

Brachiopods: Strophonella ampla {Hall) (r)

Atrypa reticularis {Linn.) Dal (aa)

Pentamerella arata {Conrad) (a)

Meristella (Pentagonia) unisulcata {Conrad) . . (rr)

M. nasuta {Conrad) (aa)

Centronella glans-fagea Hall (r)

Orthis (Rhipidomella) peloris Hall {?) (r)

O. (R) alsus Hall (r)

O. (Schizophoria) propinqua Hall ( ?) (rr)

Spirifer raricostatus {Conrad) (r)

S. duodenaria Hall (rr)

S. fimbriatus {Conrad) (rr)

Orthotetes pandora {Billings) (rr)

Chonetes hemisphericus Hall (r)

Cyrtina hamiltonensis Hall (rr)

Stropheodonta perplana {Conrad) (rr)

S. inaequiradiata Hall (rr)

S. demissa {Conrad) (r)

Coelospira Camilla Hall (r)

Amphigenia elongata {V anuxem) (rr)

Pelecypods: Cypricardinia planulata {Conrad) (r)

Conocardium cuneus {Conrad) (c)

Cephalopods: Orthoceras zeus Hall ( ?) (rr)

Orthoceras sp (c)

Cyrtoceras cf. eugenium Hall (rr)

Trilobites: Phacops cristata Hall (r)

Dalmanites anchiops {Green) (r)

13 Onondaga limestone. The other great cliff of the Helderbergs
seen from the Albany plain above the lower one of the Manlius-
Coeymans limestones is that of the Onondaga limestone. It forms
a gray band, more interrupted than the lower, fairly half way up to
the top of the Helderbergs. The conspicuous summer home of
Daniel O’Connell, which can be seen above the new Indian Ladder
road from the Albany plain, stands upon the platform formed by the
Onondaga limestone at the edge of the cliff.

NEW YORK STATE MUSEUM

The Onondaga limestone which has a very wide distribution, far
surpassing that of the other Helderberg formations (see below)
was at first known as Onondaga (Hall), Corniferous (Eaton) and
Seneca (Vanuxem) limestone in western New York, the names
being applied to different divisions of the formation by the geolo-
gists of the first survey. The name “Onondaga limestone” proposed
by Hall in 1839 includes now also the cherty division (Corniferous)
and the purer upper limestone (Seneca) (figures 55, 75, 77).

The Onondaga limestone is a moderately pure, massively bedded,
light blue-gray limestone containing lenses of chert in parallel layers,
especially in the lower part of the formation. The distribution of
the chert is very irregular and it is abundant in some localities and
sparse in others. According to Prosser and Rowe (’99) the upper
nine feet are entirely free of chert; below this are 15 feet in which
chert is very abundant. In the lower part of the formation chert
was encountered but in rather small quantities. In the town of New
Scotland quarry, on both sides of the New Salem-Wolf hill state
road, five courses of chert, each four to six inches thick are seen.

The Onondaga limestone is, according to Prosser and Rowe, 100
feet thick in the Countryman hill section and 85 feet in the Clarks-
ville and Oniskethau creek section. About Cobleskill Prosser meas-
ured 95 feet.

This thick formation of pure limestone is quarried in many
places, as at Cobleskill. It furnishes excellent road metal and is
therefore quarried along the Wolf hill road, as mentioned before.

The rock is traversed everywhere by a very perfect system of
intersecting joint fissures. These help to produce the cliff by the
breaking away of rock along the vertical joints. Weathering out by
solution in the relatively pure limestone into broad and deep fis-
sures, they have produced in places an underground drainage, as
about Thompsons lake and many small “sinks,” that are depressions
in which the drainage of a greater or lesser area disappears. Such
phenomena of the underground drainage of limestone regions which
are exhibited on a gigantic scale in Kentucky where the Mammoth
cave is a part of the system, and in the Karst region of the Dal-
matian Alps are known as “Karst phenomena.” The caves and
springs at the foot of the Indian Ladder are further instances of
such Karst phenomena in the Lower Helderberg limestones. In the
broad Onondaga terrace at the foot of Bennett, Copeland and Blod-
gett hill many such sinks are seen, especially near the base of the
Marcellus-Hamilton hills, forming a conspicuous and characteristic
feature of this formation, as stated by Darton (’94, p. 437).

GEOLOGY OF THE CAPITAL DISTRICT

Owing to the contrast in resistance to weathering between the
compact Onondaga formation and the overlying Marcellus shale, the
latter has been widely eroded away from the Onondaga limestone
and the former forms now a continuous terrace along the Helder-
bergs above the cliff. This terrace is not very wide on the slope of
Countryman hill where the O’Connell house stands on it, but
becomes more than a mile wide south of Countryman hill and forms
the broad stretch of good farming land, on which the village of
Clarksville and the hamlet of Oniskethau stand. The map also shows
distinctly how the roads follow this terrace, often running for miles
on the bare rock, as for example the Clarksville-Oniskethau road
and Oniskethau-Callanan Corner road at the foot of Copeland hill.

The best outcrops of the formation are those at the town quarry
of New Salem and around Clarksville, especially in the gorge of the
Oniskethau creek above the village and in Ingraham’s quarry.

The fauna is characterized by the corals ; not so much in species
as in individuals. Much of the Onondaga limestone was undoubtedly
formed by coral reefs. Such reef rock filled with corals is well
shown at the boat landing of Thompsons lake and in the cliffs south
of it. The State Museum contains a restoration of a portion of such
a reef, built from large coral stocks obtained about LeRoy south of
Rochester. These coral stocks show the size to which the corals
grew. The abundance of the corals and the purity of the limestone
indicate that the Onondaga sea offered very congenial conditions for
coral growth and marine life in general in this region. Grabau (’06,
p. 328) extracted a list of 57 species for the Onondaga limestone of
the Schoharie region. Of these species are : corals, 5 ; bryozoans, 3 ;
brachiopods, 27 ; pelecypods, 1 ; gastropods, 3 ; pteropods, 1 ; cepha-
lopods, 7 ; trilobites, 10. While numerically the brachiopod species
prevail, in individuals the corals are the most prominent element of
the fauna. They are species of Favosites, Zaphrentis and Cyatho-
phyllum. Among the brachiopods very large forms as Stropheo-
donta hemispheric a, Spirifer divaricatus and the index fossil of the
Onondaga, Amphigcnia clongata, testify to the favorable life condi-
tions. The pelecypods, which, as a rule, prefer muddy bottoms, are
little represented. Among the gastropods we find again large and
strikingly spinose forms as Platyceras dumosumi, which is repre-
sented in the case of restorations of Helderberg life in the State
Museum. The cephalopods show, in distinction to the prevailingly
straight form (Orthoceras) of the Schoharie grit, curved (Cyrto-
ceras) or involute forms (Gyroceras) ; and also the trilobites have
afforded peculiarly spinose ( Conolichas eriopis, Ceratolichas gryps,

NEW YORK STATE MUSEUM

C. dragon ) forms and the largest known representative of the genus
Dalmanites (D. myrmecophorus) , all facts which point to an
extremely rich invertebrate life. Besides, remains of fish have also
been obtained in the Onondaga limestone.

Rowe (’99, p. 352) cites the following 16 forms from the Onon-
daga limestone of the Clarksville and Oniskethau creek section :

Corals: Zaphrentis gigantea ( LeSueur ) (rr)

Z. corniculum ( LeSueur ) (rr)

Bryozoans: Fenestella biseriata Hall (rr)

Brachiopods: Meristella unisulcata ( Conrad ) (r)

Leptaena rhomboidalis ( Wilckens ) (r)

Atrypa reticularis ( Linne ) Dalman (aa)

A. spinosa Hall (aa)

Pentamerella arata ( Conrad ) (c)

Stropheodonta concava Hall (r)

S. textilis Hall (rr)

Spirifer duodenarius Hall (a)

S. macra Hall (?) (rr)

Gastropods: Platyceras dumosum Conrad (c)

Cephalopods: Cyrtoceras sp (rr)

Trilobites: Dalmanites (Coronura) aspectans Conrad. . . (rr)

Phacops cristata var. pipa Hall (rr)

It appears from this list that the fauna of the Onondaga limestone
in the capital district is not very rich. It will be shown, however, in
Miss Goldring’s guide to the Indian Ladder region, that close by in
the Thompsons lake region a very rich fauna, especially also of
genera of corals, stocks of Edriophyllum, etc., not mentioned either
by Grabau or Prosser and Rowe, flourished.

14 Marcellus beds. The Onondaga limestone in the capital dis-
trict is abruptly followed by dark shales — the Marcellus shales. In
western New York the boundary is less marked owing to the pres-
ence of calcareous beds in the Marcellus. Chadwick (abstract for
Geological Society meeting, ’27) has found a very distinct erosion
surface at the top of the Onondaga limestone, in the Catskill region,
which, in his view “appears to dispose finally of the theory of ‘con-
temporaneous overlap’,” by the Marcellus black shale.

The type locality of the Marcellus beds (Hall, ’39) is at Mar-
cellus in Onondaga county. It is typically represented there as black
shale, (Marcellus black shale,) with some calcareous intercalations
and an upper division of gray shale (Cardiff shale of Clarke and
Luther, ’04).

GEOLOGY OF THE CAPITAL DISTRICT

At Schoharie Grabau (’06, p. 206) found about 180 feet of black
fissile shales which split up into thin leaves and become more or less
rusty on exposure. They are there poorly exposed since they have
weathered so much that they form the gentler slopes in the hillsides
above the Onondaga terrace and are mostly covered by soil. The
same is true in the capital district, where the Marcellus shales form
good pasture land on the lower slopes of the hills above the Onon-
daga, but lack outcrops.

As a result, neither Darton nor Prosser and Rowe were able to
establish the boundary with the overlying Hamilton flags and shales
and the thickness of the formation. Darton did not use the term
“Marcellus” and distinguished 600 feet of “Hamilton black shales”
that are overlain by the Hamilton flags and shales. He describes
this formation as consisting “in greater part of shales, hard above
and softer below with occasional thin, intercalated beds of flaggy
sandstones among its upper members. Its basal beds are in some
places so dark that they have been mistaken for coal, and many
attempts have been made to work them for coal.” Also Prosser
and Rowe (’99, p. 335) in the Countryman hill section did not
undertake the separation of the Marcellus and Hamilton in the 425
feet of rock that they found above the Onondaga limestone because
they found the slope covered with soil. They mention, however, the
gradual change in the lithologic characters from the Marcellus to the
Hamilton in the Helderberg region and the fact that the Marcellus
shales have a greater thickness than in central and western New
York. Prosser (’98, p. 56) has measured 170 feet up the hill to the
south of the New Salem road.

In the Clarksville and Oniskethau section they ascribe 300 feet to
the Marcellus. They measured their section in a gully in the rear of
the house of Elias Mathias (Clarksville). They found there the
lower. 100 feet covered, after that about 80 feet of black argillaceous
shales, then 30 feet of shales of this character interspersed fre-
quently with layers of slightly calcareous dark sandstone above
which are 85 feet of dark, argillaceous shales. Above this the shales
suddenly become more arenaceous in character.

Miss Goldring, who in mapping the Berne sheet, had to establish
the exact boundary, and the writer made a thorough search for the
Marcellus-Hamilton boundary in the capital district. In a general
way it was found that the four larger hills of the region, namely
Countryman hill, Bennett hill, Copeland hill and Blodgett hill, show
a more or less distinct shoulder, usually about half way up, which is
due to a marked stiffening of the beds by the prevalence of sandy
flags. We decided to draw the line in that neighborhood, just below

NEW YORK STATE MUSEUM

the shoulder, especially since above that line undoubted Hamilton
fossils appeared. We were fortunate enough to find a continuous
section through the Marcellus from the Onondaga contact to the
Hamilton contact on the upper Oniskethau creek, north of Wolf hill,
crossing the boundary of the Albany and Berne quadrangles.

The Marcellus consists in that section of 170 feet (aneroid meas-
urement) of black fissile carbonaceous shales which end abruptly
with an earthy, pyritiferous soft black shale against the heavy sand-
stone beds, forming a waterfall and alternating with gray blockv
shale of the Hamilton. There are but few sandy beds in the Mar-
cellus in the lower five feet and the upper half, the rest is all black
fissile shale. In one horizon of the upper part, about 35 to 40 feet
below the top, a course of large calcareous concretions, two to four
feet in diameter and one to two feet thick appears in the beds. The
lowest somewhat sandy beds were quite fossiliferous, Liorhynchus
limitaris (Vanuxem) and L. mysia Hall being noted especially.

Another good section from the Marcellus into the Hamilton has
been opened along the state road from Keefer Corner to Indian
Fields. It is here seen that while the fissile black shale, typical of the ,
Marcellus, ends rather abruptly, dark argillaceous shales, with an
increasing amount of intercalated sandy flags, continue still for some
distance, these beds lithologically partaking somewhat of a transitional
character. It is these beds which Darton united with his Hamilton
black shales. The fauna in these beds, though very meager, is dis-
tinctly Hamilton in character. These lower dark Hamilton shales
with intercalated thin sandstone beds are also well exposed in road
metal pits along the road leading east from Keefer Corner. Here
also the shoulder formed by the lowest Hamilton is well displayed.
Going up the abandoned road that passes Koong hill on the east,
one soon reaches the typical Hamilton with large specimens of
Spirifer granulosus and can well observe the gradual change from
fissile dark shale to gray shale, that breaks more blocky on weath-
ering.

The Marcellus itself is well exposed this side of Keefer Corner
along the Albany road, down to the Onondaga flat. The thickness
amounts there to about 200 feet.

A third good exposure of the Marcellus-Hamilton boundary has
been produced by the new cut-off in the Clarksville-Dormansville
road, one and a half miles south of Clarksville.

Restricting the Marcellus shale to 170 to 200 feet in the capital
district, we draw the line where Prosser and Rowe found the inter-

GEOLOGY OF THE CAPITAL DISTRICT 69

spersion of sandstone layers to begin, namely at 180 feet from the
base and exclude the upper 120 feet of their Marcellus.

A good Marcellus fauna was found along the road one-fourth of
a mile northeast from Lawson lake, with abundant Styliolina fissur-
ella, Hall, (minute needlelike pteropod shells) and small lamelli-
branchs ( Lunulicardium marcellcnse Vanuxem).

Rowe (’99, p. 353) cites from the Marcellus of the capital district
(collected from gorge at foot of Bennett hill) :

Chonetes mucronatus Hall (a)

Glyptocardia speciosa Hall (a)

Coleolus tenuicinctus Hall (r)

Goniatites (Parodiceras) discoideus Conrad (c)

The finding of the Parodiceras discoideus, a goniatite (coiled
cephalopod) in the Clarksville region is of some interest so far as it
indicates the continuation of the fauna of the Agoniatite limestone
into the capital district. In the Schoharie region and west of it the
Marcellus shale contains calcareous intercalations (Cherry Valley
and Agoniatites limestones) that carry a striking fauna of large
cephalopods not found anywhere else. A remarkable slab with that
fauna from the neighborhood of Syracuse is on exhibition in the
State Museum. The writer once, in connection with Doctor Clarke’s
work on the Marcellus shale (’03), tried to trace these limestones
eastward but found them to disappear. This goniatite would suggest
a continuation of at least some elements of the fauna in this direction,
unless the occurrence is due to postmortem drifting of the shells,
cephalopod shells, owing to their gas-filled air-chambers, being liable
to be carried far out of their life zones.

15 Hamilton beds. The Hamilton beds are the highest formation
in the Helderbergs of the capital district and form there the tops of
the highest hills (figures 45, 46, 52), as also of the “Helderberg
mountain” proper, in the southwest corner of the quadrangle. Only
a part of the thick Hamilton is preserved there, the remainder having
been eroded away, and there is no doubt that also the thick upper
Devonian formations, the Sherburne flags, Oneonta shales, and the
great mass of the Catskill beds, once spread thousands of feet thick
over the Helderberg region and far beyond, and that all have been
carried off as waste by the rivers.

The Hamilton beds (name proposed in 1840 by Vanuxem) com-
prise in the Albany quadrangle a great series of thin-bedded sand-
stones with intercalated beds of dark often bluish to greenish shales.

NEW YORK STATE MUSEUM

As we have already seen, the lowest 200 feet have on the whole
darker colored shales and less sandstone than the remainder.

Prosser (’99, p. 243) has calculated the total thickness of the
Hamilton in the town of Berne directly adjoining the Albany quad-
rangle on the west as between 1415 and 1720 feet. Darton (’94, p.
434) estimated the Hamilton flags and shales at 700 feet and the
Hamilton black shales at 600 feet; subtracting 170 feet for the Mar-
cellus from these 1300 feet leaves 1130 feet for the Hamilton. Of
this great thickness of the Hamilton formation, reaching possibly
1700 feet, probably not much more than 600 feet are present in the
highest ridge on the Albany quadrangle, the Helderberg mountain,
which continues northward into Wolf hill and Countryman hill.
Prosser found in the Clarksville section to the top of Wolf hill 300
feet of Marcellus and 490 feet of Hamilton shales. Assigning about
170 feet to the Marcellus, there would be about 620 feet of Hamilton
in that section, as we define it.

The lowest 100 to 130 feet of these are still dark to black argil-
laceous shales with intercalations of beds of dark slightly calcareous
sandstone. The shales are, however, sandy enough to break blocky,
a feature which becomes more distinct as one goes upward in the
section. The dark to blackish color persists for 200 feet more, the
shales being, however, more distinctly arenaceous and weathering to
a brownish color. At the same time the sandstone intercalations
increase steadily and the fossils become more abundant. The latter
appear in large numbers about 300 feet above the base, where the
shales have become greenish and bluish. The sandstones are not
evenly distributed through the formation and vary greatly in thick-
ness. Much of the sandstone is dark gray, moderately fine grained
and splits readily along the bedding planes into slabs one-half inch to
three inches thick. These sandstones have given rise to the “flag-
stone” industry that flourished for many years and to some extent
still persists, in the region west of Albany county and south to King-
ston. The thickness of the beds of flagstones is exceedingly variable.
They often reach 10 to 15 feet. The sandstones and the shale inter-
calations are in the upper part divided in about equal proportions,
and the heavy sandstone courses give rise to conspicuous outcrops
and to a series of minor terraces.

As Darton has pointed out (’94, p. 434), the sandstones and shales
change into each other horizontally in a very irregular manner. This
fact as well as the cross-bedding observed at times, and the preval-
ence of brachiopods and lamellibranchs in the fauna (see below)

GEOLOGY OF THE CAPITAL DISTRICT

7 1

indicate shallow muddy water with frequent changes in direction of
currents. In western New York the Hamilton beds are more cal-
careous, the formation consisting of calcareous shales and limestones ;
eastward it becomes more arenaceous, until along the Hudson river
arenaceous shales and sandstones prevail. This change in lithologic
character has given rise to changes of name (Cornwall shale, Hart-
nagel; Mount Marion, Grabau ; Ashokan shale, Chadwick).

The fauna of the Hamilton beds is exceedingly rich and it may
with more detailed study permit the division of the formation into
life zones. Grabau (’06, p. 329-31) has enumerated 123 species
from the Hamilton of the Schoharie region; in central New York
the fauna is still larger. Of these are: worm-trails, 1; brachiopods,
27 ; pelecypods, 76 ; gastropods, 9 ; pteropods, 3 ; cephalopods, 2 ;
trilobites, 4. The Hamilton is therefore a typical pelecypod or
lamellibranch facies. It has furnished the multitude of mussels so
beautifully illustrated by Hall in volume V of the Paleontology, with
their striking species of Aviculopecten, Liopteria, Modiomorpha,
Goniophora, Palaeoneilo, Grammysia, Sphenotus and Orthonota. I
have heard members of the old Survey, as R. P. Whitfield and
G. B. Simpson, tell with enthusiasm of their lamellibranch hunting
expeditions into the Hamilton in preparation of volume V. Many
of the figured specimens are exhibited in the Hamilton cases in the
State Museum. The brachiopods, which prevail in the limestone for-
mations, are the next in abundance, but attain only one-third the
number of the lamellibranchs.

Of fossil localities on the Albany quadrangle may be noted the
top of Copeland hill with Spirifer granulosus in slightly calcareous
layers ; a ravine on the eastern slope of Koong hill, where Spirifer
granulosus, S. mucronatus, Chonetes coronatus, Anibocoelia urn-
bonata, species of Grammysia, etc., occur. On the Keefer Corner-
Indian Fields road, one-quarter mile from the southern edge of the
quadrangle, a ledge on the side of the road held numerous fossils
in the lowest layers, among them species of Pleurotomaria and
Palaeoneilo. The top of the Helderberg mountain, where the road
crosses it, held calcareous layers in the heavy sandstone beds, full
of fossils, especially brachiopods as Spirifer mucronatus, Chonetes
coronatus, Orthothetes chemungensis var. arctostriatus, etc. The road
leading on the west side of the Helderberg mountain from Cass hill
to Dormansville passes for a good part of its length over Hamilton
ledges where Hamilton fossils are visible, sometimes finely preserved.
Especially at a waterfall in about the middle of the road, three miles
north of Dormansville, fossils were abundant, among them a

NEW YORK STATE MUSEUM

Conularia, Lingula punctata, Tropidoleptus carinatus, Chonetes
coronatus, Modiomorpha mytiloides. Rowe (’99, p. 353-54) collected

in gullies of Wolf hill the following forms:

1 Found about 200 feet above base of Hamilton (that is about
300 feet above) :

Brachiopods: Lingula punctata Hall (?) (rr)

Chonetes deflecta Hall (c)

Newberria claypolii (Hall) ? (rr)

Pentamerella pavilionensis (Hall) ? (rr)

Camarotoechia congregata (Conrad) (rr)

2 Found over 400 feet (that is about 500 feet) above base of
Hamilton :

Brachiopods: Spirifer acuminatus (Conrad) (a)

S. mucronatus (Conrad) (c)

Tropidoleptus carinatus (Conrad) (rr)

Athyris spiriferoides (Eaton) (rr)

Chonetes deflecta Hall (c)

Strophalosia cf. truncata (Hall) (r)

Pelecypods: Pterinea flabella (Co nrad) (r)

Nyassa arguta Hall (aa)

Leptodesma rogersi Hall (rr)

Actinopteria subdecussata Hall (rr)

Liopteria dekayi Hall (rr)

L. bigsbyi Hall (rr)

Palaeoneilo maxima (Conrad) (rr)

P. constricta (Conrad) (r)

Modiomorpha concentrica (Conrad) (rr)

Pteropods: Tentaculites bellulus Hall (?) (rr)

C Paleozoic Rocks of the Eastern Trough

The Paleozoic rocks that have been distinguished in the eastern
trough are in descending order :

Devonian Rensselaer grit

r Snake Hill shale

Middle Ordovician < Tackawasik limestone and shale
L Rysedorph Hill conglomerate
r Normanskill shale
Bald Mountain limestone
| Deep Kill shale
Schaghticoke shale

Lower Ordovician

GEOLOGY OF THE CAPITAL DISTRICT

'Schodack shale and limestone
Troy shales and limestones
Lower Cambrian . Diamond rock quartzite
(Taconian) Bomoseen grit

Nassau beds

The Lower Cambrian rocks presumably rest, as everywhere else,
on the Precambrian foundation of the known crust, probably gneisses,
schists and injected plutonic rocks, as granite, syenite etc. They
have nowhere yet been seen at the base of the eastern trough; but
since we know them for the western trough, from the southern
spurs of the Adirondacks near Saratoga, it is legitimate to assume
that like rocks underlie the eastern trough.

C1 Lower Cambrian rocks (Taconian). The Lower Cambrian
rocks of the capital district are a section of a belt of Lower Cambrian
rocks that extends from Canada through eastern New York, New
Jersey, to Pennsylvania and beyond. They are a great mass of slates,
quartzites and brecciated limestones that was first termed the Georgia
group by Hitchcock (’61) from Georgia, Vermont. In 1891 Wal-
cott proposed the term “Georgian group” for the Lower Cambrian.
More recently, on finding that term preoccupied, the term “Wau-
coban” was proposed by the same author. Still the Lower Cambrian
is currently known as the Georgian beds.

There is still another name, however, with a distinct right to
adoption. That is the name “Taconian.” Emmons in 1842 proposed
the term “Taconic system,” from the Taconic mountains in eastern
New York, for the rocks older than the Potsdam that he was con-
vinced he had discovered in the slate belt of eastern New York.
The acrimonious discussion that followed ended with the complete
suppression of Emmons’ term for the Cambrian of America. Lap-
worth (’91) has pointed out that this term has the right of priority
for the Lower Cambrian and Schuchert (’18) has independently
arrived at the same conclusion and now uses the term “Taconian”
for the Lower Cambrian (’19, ’24). Since the Taconic mountains,
just east of the capital district, as well as the capital district itself,
were the chief fields of Emmons’ studies, it seems quite appropriate
that the term should be used here.

The character of the Taconian rocks of the capital district has
been very carefully described by Dale (’04) both as to macroscopic
and microscopic characters. The reader is referred to this work,
as well as to his paper on the New York- Vermont Slate Belt (’93)
for details of the composition of the rocks.

NEW YORK STATE MUSEUM

The Lower Cambrian formations form a belt of rocks directly
east of the great overthrust fault, being part of “Logans fault” (see
below). They begin near the north edge as a narrow strip between
the Snake hill beds and the Normanskill shale. The belt widens and
unites with another belt coming from the east, on the north side of the
Rensselaer grit plateau about Raymertown. At the southern edge
of the capital district it has attained a width of n miles. It contains
two areas of Ordovician rocks ; one of these is about nine square
miles, including Mount Rafinesque (locally known as Bald mountain)
and Rice mountain, two conspicuous hills that rise about 1000 feet
above the plain (Mount Rafinesque 1107 feet high, and Rice Moun-
tain 925 feet high). Another smaller area, that covers about two
square miles is situated in the town of North Greenbush, west and
south of Aries lake (locally Snyder’s lake). The structure of these
two areas is quite complex and will be described in the chapter on
the tectonics of the region. There is also resting on the Lower
Cambrian a small outlier of half a square mile of the Upper Devonian
Rensselaer grit south of North Nassau, that is a residual patch left
by the erosion of the Rensselaer grit plateau. And another larger
separated area just projects with its northern point into the capital
district at East Nassau.

By far the most prevailing rock of the whole belt is a dark
greenish-gray siliceous shale or slate. It is, so to say, the ground-
mass in which all the rocks, quartzites, red and purple shales, lime-
stones and sandstones are distributed (figure 6).

The folded structure of these rocks, combined with their unequal
hardness, has through the unequal operation of erosion upon these
different materials, produced a very irregular topography, with many
rock hills running in the general direction of the prevailing strike
(N.N.E.). As has been already mentioned in the chapter on topog-
raphy, these rock hills are accompanied by numerous glacial hills,
usually of smoother outline, and often rock hills and glacial hills are
combined.

As Dale has pointed out (’04, p. 14) there are certain rocks of
the Lower Cambrian that have marked characteristics peculiar to
the Lower Cambrian in the capital district. The most important of
these are a metamorphic olive grit, usually weathered a light brick
red, a calcareous sandstone and an associated limestone breccia.
The latter “may be taken as an almost infallible indication of Cam-
brian age.” There is further a limestone conglomerate of peculiar
character, and several kinds of quartzose beds and quartzites, be-
sides the red and purple shales.

GEOLOGY OF THE CAPITAL DISTRICT

Figure 6 Columnar section of the Lower Cambrian series exposed
at Troy, worked out by A. F. Foerste (see Dale. ’94, p. 26). A,
red and green shale, in places with small quartzite beds ; B,
light blue dolomitic limestone intercalated as fine layers and
sometimes forming “brecciated pebbles” in the shale ; C, shale
with or without limestone beds ; D and E, quartz sandstone more
or less calcareous, sometimes replaced by sandy shale ; F, light
blue dolomitic limestone

The greenish-gray, red and purple Cambrian shales, as well as
those of the Ordovician, have farther north been changed by the
regional metamorphism that has affected the rocks east and northeast
of the capital district, into the well-known roofing slates that have
created an important industry in Washington county and the adjoin-
ing parts of Vermont. In our district the rocks were close to the
western limit of the folded region and therefore subjected to much
less intense compression and very little metamorphism. While they
are distinctly harder and more resistant than the shales of the western
trough, and in distinction to them possess a well-defined cleavage,
thereby splitting slaty, the latter is nowhere of such a character as
to produce a roofing slate. Very often several cleavage systems
or partings divide the rock into sticklike fragments, a fact which
leads to a quicker decay of the rock into a clayey subsoil and soil
and contributes considerably to the improvement of the land. (See
chapter on economic geology.)

NEW YORK STATE MUSEUM

The greenish-gray shale is, according to Dale (’04, p. 16), under
the microscope seen to be “a very fine-grained aggregate of mus-
covite and chlorite scales, angular quartz grains, rarely plagioclase
grains, with brownish dots which are probably limonite.” The
muscovite (white or potash mica) as the matrix of the shale is of
great importance for the soil, since it furnishes potash. The green
color of the shale is due to the chlorite. When there is a strong
admixture of chlorite, the shale becomes very green.

The reddish shales derive their color from the hematite or red
iron ore, that is a constituent in varying amounts, thereby producing
different intensities of color. The color is especially deep red in the
belt west of Burden lake, exposed both along the road and on top
of the ridge. It is purplish in many other places, as notably in the
gorge of the Poestenkill, above Troy. The purple color is due to a
mixture of limonite and chlorite. Finally, there are also black and
dark gray shales, which derive their color from the carbon.

In the Lower Cambrian of the capital district there is seen none,
or very little of the deep bluish black shale such as the graptolite
shales of the Ordovician are. Such black shale as has been found,
has never furnished any trace of graptolites or any other fossils.

The “olive grit,” which weathers brick red, is an important rock
in the slate belt of Washington county, where it covers large areas,
and apparently underlies the roofing slate (Dale, ’99, p. 180). It
becomes less frequent farther south, where it is still found near the
western edge of the Cambrian belt, as far south as North Green-
bush. It is a typical graywacke, and is described by Dale (’99, p.
179) as follows:

A greenish, usually olive-colored, very rarely purplish, more or
less massive grit, generally somewhat calcareous, and almost always
spangled with very minute scales of hematite or graphite. Under the
microscope it is seen to consist mainly of more or less angular grains
of quartz, with a considerable number of plagioclase grains, rarely
one of microcline, in a cement of sericite with some calcite and small
areas of secondary quartz.

As outcrops in our district are cited (Dale, ’04, p. 15) :

One-half mile east of Lake Ida, in Troy, and also north of its
eastern end ; one-half mile southwest of Wvnantskill ; at the mill
dam in Raymertown ; at Brunswick Center ; in Lansingburg, at Oak-
wood Cemetery, on the north side of the outlet of the pond, where it
contains organic impressions and is in contact with the Ordovician
shale ; and at a point a mile south of Grant Hollow.

GEOLOGY OF THE CAPITAL DISTRICT

The southernmost outcrop seen by the writer is along Mill creek,
a mile east of Teller Hill. Also this is close to the Cambrian-
Ordovician boundary.

The most characteristic rock of the Cambrian of the region is the
calcareous sandstone with associated limestone breccia. As described
by Dale (’04, p. 15) :

This rock usually consists of roundish quartz grains held together
by a cement of crystalline and granular calcite or of dolomite. On
the weathered surface these grains stand out in relief and are slightly
opalescent .... This sandstone very often includes beds of bluish
fossiliferous limestone from one-half to one inch thick, which are
generally brecciated, probably because of their greater rigidity under
lateral compression than the intervening sandstone.

The most picturesque outcrop of this brecciated limestone is a
vertical wall of the rock, two feet thick, standing up on the left of the
road leading from the Albany-West Sand Lake highway to Aries
lake, one-quarter of a mile from the main road. Figures 56 and 57
are pictures of this most interesting place. Dale (’96, p. 569; ’04,
p. 15) has given a sketch of a portion showing several small beds
of limestone broken up and pushed across one another.

The calcareous sandstone is further described by Dale as “fre-
quently associated with (either passing horizontally into or under-
lain at no great interval by) a quartzite in which the cement is
either very slightly calcareous or sericitic. Both sandstone and
quartzite are apt to be traversed by a network of veins and veinlets
of quartz, which, owing to the rapid weathering of the CaCO3 of
the cement, project on its surface. This sandstone crops out in
Oakwood Cemetery in Lansingburg, and continues north-northeast
for a mile to a hillock, known locally as ‘Diamond Rock’,1 * on account
of its abundance of quartz crystals ; these occur in association with
such veins.”

A very common constituent of the shale beds, especially the red
shale which regularly alternates with it, are quartzose beds weather-
ing rusty brown, from one-half to two inches thick. The cement of
these beds is described by Dale as sometimes pure silicious, or partly
silicious and partly calcareous or sericitic, and sometimes entirely
dolomitic. We shall see that the red and green shales with alternat-

1 The glimmering quartz crystals of Diamond Rock have given origin to a
beautiful Indian legend, told by Sylvester. According to this legend, they

represent the petrified tears of a Mohican mother who waited on this rock for

20 years for the return of her son, who had gone to Canada to recover from
the Algonquins the bones of his brother, to sec'ure rest for him in the other
world. The legend states the Indian fulfilled his mission, but the mother’s
tears are on the rock to this day.

NEW YORK STATE MUSEUM

ing thin quartzite bands, form a definite member of the series. There
are in these red and green shales also greenish coarse and fine
quartzite beds, which owe their greenish color to an abundance of
admixed chlorite or chlorite schist fragments. This latter quartzite
is remarkable for the fact that it frequently bears the fossil Oldhamia
occidens.

Dale (’04, p. 17) has fully set forth the difficulty, or rather the
impossibility, of determining exactly the thickness of these beds, “be-
cause they consist so largely of closely folded and easily weathering
shale and because there are so few deep cuts across them.” Dale
and his efficient assistant Prindle have, however, worked out a num-
ber of detailed sections, from which they were able to construe a
stratigraphic series and arrive at an estimate of the thickness of the
formation.

Dale (’99, p. 178) has estimated the thickness of the Lower Cam-
brian at two places, on Mount Hebron and east of North Granville,
in the slate belt of Washington county, and found about 1400 feet;
the measurements of Pumpelly, Wolff and Dale (’94, p. 190) in
the Green mountains in Massachusetts have given 800 to 900 feet for
the Lower Cambrian quartzite. Dale, adding to this the Lower
Cambrian part of the overlying Stockbridge limestone in Vermont
Valley, which measures 470 feet, arrives at 1270 to 1370 feet for
the Lower Cambrian in that region. His table of the divisions in
Rensselaer county, copied below gives a maximum thickness of 1225
feet. As we do not know the thickness of the basal member, as
pointed out by Dale, the maximum of 1400 feet may be easily ex-
ceeded. “At any rate from 335 to 1400 feet of it are exposed.” We
have not made any efforts to secure new measurements in the capital
district, since it was obvious that the conditions were not favorable
to finding reliable guide beds, the quartzite being repeated and the
beds being too similar to each other to be clearly identified in different
outcrops.

The following is the table published by Dale (’04, p. 29) showing
the Lower Cambrian series as exposed in Rensselaer county. We
have added in the first column the names proposed by us for the
formations in 1914 (p. 69).

GEOLOGY OF THE CAPITAL DISTRICT

The Lower Cambric series as exposed in Rensselaer county and part of
Columbia county, N. Y.

NAME OF FOR-
MATION

SERIAL

LETTER

DESCRIPTION OF STRATA

FAUNA

ESTI-

MATED

THICK-

NESS

IN FEET

a 20-200

Schodack
shale and
limestone

limestone, in varying alternations
with black or greenish shale and
calcareous guartz sandstone.
Some of the limestone beds brec-
ciated within the sandstone or
shale and forming brecciation
pebbles, in places, however, beach
pebbles.

T roy shale

Greenish, reddish, purplish shale,
in places with small beds of more
or less calcareous quartzite.

At Troy, in upper part a 2j foot
bed of calcareous sandstone.

Oldhamia, annelid

trails

Hyolithes and Hyo-
lithellus

25?-IOO +

Granular quartzite, in places a cal-
careous sandstone.

10-40

rock quart-
zite

Bomoseen

grit

Olive grit, metamorphic, usually
weathering reddish; absent at
south.

18-50

Greenish, or reddish and greenish,
shale with small quartzite or grit
beds

Massive greenish quartzite, in
places very coarse.

Reddish and greenish shale with
small beds of quartzite or grit
(rarely up to five feet thick).

Massive greenish quartzite, in
places very coarse.

Reddish and greenish shale with
small beds of quartzite or grit,
from 1 to 12 and, rarely, 24 inches
thick.

Casts of impressions,
Oldhamia b

65-535

10-50

30-80

8—40

50-80

Nassau beds

Casts of impressions,
Oldhamia

a Usually 50. b Oldhamia occurs in A, C or E, and quite possibly in all three.
Minimum, 286. Maximum, 1225 +.

A comparison of the two series of divisions, published by Dale
for the slate belt of Washington county and Vermont and that for
Rensselaer county, shows considerable differences, the most import-
ant of which are the much greater development of the Bomoseen
grit in the north, and the absence of the “Black patch grit,” Cam-
brian roofing slates and the “Ferruginous quartzite and sandstone”
in the capital district. We have on the Schuylerville quadrangle (’14
p. 66) been able to distinguish only three units, the Schodack
shales and limestones, Eddy Hill grit (the Black patch grit) and the
Bomoseen grit, and mapped only the Schodack shales and limestones
and the Bomoseen grit. In the capital district the following mem-
bers can be distinguished in descending order :

NEW YORK STATE MUSEUM

1 6 Schodack shale and limestone. This is the Cambrian black
shale of Dale and typically his division I to which we have added
the neutral greenish shale J, that is usually associated with it. The
formation is characterized by the thin-bedded limestones, and the
beds of brecciation pebbles, as well as by carrying the Olenellus
fauna in these pebbles and thin-bedded limestone. Its typical
locality comprises the fine exposures two miles south of Schodack
Landing, N. Y., in the cliffs above the tracks of the New York Cen-
tral Railroad and the belt of these rocks in the town of Schodack,
N. Y. The pebble beds are shown there to great advantage. It is
these beds that were described as intra-formational conglomerate.
They are also well exposed in the old quarry in Beman Park above
Troy, where once a stone crusher was in operation and where S. F.
Ford, a Troy jeweler, made his collections of Lower Cambrian fos-
sils with incredible patience and perseverance, proving for the first
time by comparison of these fossils with the Bohemian and Canadian
material the actual pre-Potsdam age of the beds.

The often large rounded limestone pebbles which fill the rock are,
as Foerste has shown (Dale, ’96, p. 569) not beach pebbles, but
brecciation pebbles, produced by the separation of thin limestone
beds by successive plication and cleavage, as shown in the diagram.
Still there are also true beach pebbles in the formation, as noted by
Dale.

The Schodack shale and limestone has furnished nearly all the
known faunas of the Lower Cambrian of the capital district, with
the exception of the Oldhamias. Walcott, in his monumental Cam-
brian Brachiopoda (’12), has brought together lists of all fossil
localities that have furnished material to the National Museum.
These are by far the most complete lists, owing to Walcott’s long
specialization in Cambrian research. We are here citing these
localities from the capital district for the benefit of local collectors.
{op. cit., p. 162, 188, 200, 212, 266, 277). Walcott’s locality num-
bers are in parenthesis.

1 (2 b) Lower Cambrian limestone just north of Beman Park, in
the northeastern part of the city of Troy; Troy quadrangle (U. S.
G. S.) ; Rensselaer county, N. Y. (H. E. Dickhaut, 1899)

Micromitra (Paterina) labra- Obollella crassa

dorica

Bicia gamma Botsfordia caelata

B, Whiteavesi (type locality) Billingsella salemensis

GEOLOGY OF THE CAPITAL DISTRICT

2 {2d) Arenaceous limestone in the knobs just east of Beman
Park and southwest of Brunswick, near Troy etc. (H. F. Dick-
haut, ’99)

Obolella crassa

3 (2 7) Even-bedded and conglomerate limestones on the ridge
in the eastern suburb of Troy etc. (Cooper Curtice, ’83)

Obolella crassa
Bicia gamma
Botsfordia caelata
Acrothele nitida (type loc.)
Archaeocyathus rarus {Ford)
A. rensselaericus {Ford)
Scenella retusa {Ford)
Stenotheca rugosa {Hall)
Platyceras primaevum Billings
Hyolithellus micans Billings
Hyolithes americanus Billings

H. communis Billings
H. communis emmonsi Ford
H. iinpar Ford
H. sp.

Microdiscus lobatus {Hall)
M. speciosus Ford
Elliptocephala asaphoides
Emmons

Olenoides fordi Walcott
Solenopleura nana Ford

4 (44a) Limestone on Valatie kill, near the line between Nassau
and Schodack townships, near line between Troy and Kinderhook
quadrangles etc. (C. D. Walcott, ’87)

Acrotreta sagittalis taconica
Microdiscus connexus Walcott

5 (72) (Same horizon as 72a) Limestone 5 miles (8 km) east of
Albany, 1 mile southwest of Wynantskill, (C. D. Walcott and T. N.
Dale, ’93)

Obolus prindlei

6 (338 K) Limestone two to five miles southwest of Wynantskill,
Rensselaer county (L. M. Prindle, ’93)

Obolus prindlei

7 (33811) Western belt of conglomeratic limestone, Rensselaer
county, N. Y.

Yorkia washingtonensis
Microdiscus lobatus {Hall)

^ (33%) (Hall, ’47, p. 290) Calcareous beds, two miles north-
east of Troy
Obolella crassa

9 (367) Conglomerate and limestone, Troy
Lingulella schucherti (type locality)

Microdiscus schucherti

Protypus hitchcocki (Whitfield)

These species may be from different localities.

10 (367*) (Hall, ’47, p. 290). Shales near Troy
Botsfordia caelata (type locality)

NEW YORK STATE MUSEUM

These localities are marked on Dale’s map (’04) by a red circle
and they have been identified on our map by stars.

The fauna consists almost entirely of small and primitive forms,
but it is to be emphasized in this connection that, barring some scat-
tered and mostly doubtful Precambrian fossils, this is the oldest
fauna as yet known. It consists for the most part of small primitive
brachiopods, of the genera Obolus, Lingulella and Acrotreta, some
very rare primitive sponges (Archaeocyathus), and corallike forms;
of primitive gastropods of simple cap-shape (Scenella, Stenotheca,
Platyceras), supposed pteropods (Hyolithes) and small and primitive
trilobites as Microdiscus (now Goniodiscus), Olenoides, Solen-
opleura.

The most common species are Obolella crassa and Botsfordia
caelata, (formerly Obolella), whose interior structure was made out
by Ford from Troy material; Hyolithellus micans, Goniodiscus
lobatus and parts of the somewhat larger trilobite Elliptocephala
asaphoides. These forms may yet be obtained in Beman Park with
sufficient assiduity, as well as in localities northeast of Troy. Some
of the old Troy localities are not any more accessible; on the other
hand, some good new outcrops have appeared, as the ones on the
north and east sides of the campus of the Rensselaer Polytechnic
Institute, where for instance, the brachiopods (Obolella) can be col-
lected back of the dining hall.

In Vermont and Pennsylvania the Lower Cambrian has afforded
stately trilobites, as Olenellns thompsoni, similar to forms observed
in other parts of the world in Lower Cambrian beds. From these
the division is internationally known as the Olenellus beds.

17 Troy shales and limestones. The Troy shale is closely associ-
ated with the Schodack beds, which it underlies. It consists of 25
to 100 feet of colored shales with small beds of calcareous quartzite.
The shale has furnished Oldhamia occidens Walcott, a calcareous
alga ; a calcareous sandstone, in the upper part, Hyolithes and Hyoli-
thellus. These beds are well exposed at Troy, at the dam in the
Poestenkill below Mount Ida lake, and in the gorge of the Poesten-
kill, there with Oldhamia. Below the Poestenkill dam the shale is
overlying the overthrust fault. The belt continues east of Rensse-
laer, where Hyolithellus was found halfway between Defreestville
and Best (coll. C. F. Kilfoyle).

18 Diamond Rock quartzite (figure 58). This name was pro-
posed by Ruedemann (’14, p. 70) for division G of Dale’s Rensse-
laer county series. It is 10 to 40 feet thick, composed of granular
quartzite and associated calcareous sandstone and well exposed in

GEOLOGY OF THE CAPITAL DISTRICT

Oakwood cemetery and the “Diamond Rock” in Lansingburg
(North Troy), from which it takes its name. It has not afforded
any fossils to our knowledge.

19 Bomoseen grit. This name was proposed by Ruedemann
(’14, p. 69) for Dale’s “olive grit.” This formation of olive-colored,
brick-red-weathering grit, which is a prominent member of the
Lower Cambrian series in southern Vermont and Washington
county of New York, and there reaches a thickness of 200 feet, is
but little exposed in the capital district, and always, in the western
portion of the belt, in association with the Troy and Schodack beds.

The formation seems to be quite barren of fossils. We have not
seen any in the rock and the only record of a fossil we can find is
that of Obolella crassa in Walcott (’12, p. 188).

2 ya Reddish sandstone about one mile (1.6 km.) east of Lansing-
burg, north of Troy, Cohoes quadrangle (U. S. G. S.), Rensselaer
County, N. Y. (Curtice, ’83).

20 Nassau beds (figure 59). This name was proposed by Ruede-
mann (’14, p. 70) for divisions A to E of Dale’s series in Rensse-
laer county. In the capital district the Bomoseen grit is underlain
by the lowest division, the Nassau beds, which consist of a series
of reddish and greenish shales, alternating with small beds of quartz-
ite, mostly one to two inches thick. There are three groups of these
alternating reddish and greenish shales and quartzite, the uppermost
of which is more than 500 feet thick in places. These three groups
are separated by two massive beds of greenish quartzite that reach
40 to 50 feet in thickness. The intercalated small quartzite beds of
probably all three sections contain Oldhamia occidens. The entire
group is 150 to 800 feet thick.

With the exception of two localities of Oldhamia in the Troy
beds (one in the gorge of the Poestenkill, about two miles east of
Troy, and the other in the Moordener kill, one and one-half miles
above Schodack Depot), the others are in the Nassau beds. Dale
has entered these occurrences on his map (’04), one on the upper
reaches of the Valatie kill, a mile south of Burden lake, another one
and one-half miles farther down the kill at a sawmill dam, and a
third at the left of the Albany- Pittsfield state road, a mile east of
Nassau village. We found a fourth locality in the Nassau beds,
also in small quartzite beds, on the slope east of the road halfway
between Nassau village and Nassau pond. This locality showed
fairly good collecting and furnished some specimens that added
materially to our knowledge of the problematic fossil by exhibiting

NEW YORK STATE MUSEUM

the bases of the tufts of filaments. The writer has published a sepa-
rate paper on this occurrence (Ruedemann, ’29) and referred the
fossils to the calcareous algae. Unfortunately the hillside has been
taken up for cottage building and the locality may be soon destroyed.

Atfeal distribution of Lower Cambrian formations. Dale had
neither attempted to map his divisions of the Lower Cambrian sepa-
rately nor suggested an areal arrangement of the same. He gave,
however, the principal outcrops of the characteristic rocks of the divi-
sions, namely “sandstone and limestone breccia,” “typical red and
green shale with small quartzite beds,” and “olive grit” by symbols.
We have also found it impracticable to separate the four higher divi-
sions, the Schodack, Troy, Diamond Rock and Bomoseen beds, be-
cause they are too much involved with each other by folding and the
great majority of the outcrops exhibit only the greenish gray shales
that are common to the Schodack and Troy beds. The four higher
groups form distinctly the western division of the Lower Cambrian
beds, while the Nassau beds form the eastern division. We have
therefore mapped these two groups separately. The Nassau beds are
readily recognized by the frequent bands of alternating red shale
and small quartzite beds.

In general, it is quite obvious that the Lower Cambrian formations
are arranged in ascending order from east to west, the lowest
division, the Nassau beds, being farthest east. These are followed
by outcrops of Bomoseen grit in the northern part of the capital dis-
trict, as about Raymertown, south of Haynersville and as far south
as Wynantskill. At the other hand, the Bomoseen grit is again
exposed east of Rice mountain, and especially frequently and typi-
cally along the west edge of the Cambrian belt in the narrow strip
west of Mount Rafinesque and Rice mountain from Speigletown
northeast to Melrose, and also east of Troy along the Poestenkill,
above the Troy beds. We also found the Bomoseen grit well
exposed a mile south of Dale’s localities, in abandoned quarries south
of the Wynantskill, between South Troy and Albia, and less than
half a mile from the overthrust line, and still much farther south,
east of Grand View hill (Greenbush) on the upper Mill creek. It
is thus apparent that the readily recognizable Bomoseen grit appears
in at least four (possibly five) different belts, and in three of them
far away from its normal place, next to the Nassau beds. These
Bomoseen grit belts indicate the repeated alternation or interming-
ling of the Lower Cambrian in the western belt of the Cambrian area
due to folding and overthrusting.

GEOLOGY OF THE CAPITAL DISTRICT 85

The middle and upper Cambrian rocks are lacking in the eastern
trough, presumably by nondeposition.

C 2 Ordovician rocks of the eastern trough. Hudson River
shale. Mather (’40) in the First District Report of the New York
Survey, designated the great mass of shale in the Hudson valley
the “Hudson River shale,” and considered it to be younger than the
Utica. This name and this correlation were maintained, until it was
found that the Hudson River shale contains a great variety of
formations of different ages, practically all older than Utica. The
name has no more stratigraphic meaning, but it is still used by some
for the entire terrane of shales in the Hudson River valley, especially
when the age of the formation in question has not been established.

21 Schaghticoke shale. The name “Schaghticoke shale” was
proposed by Ruedemann (’03) for a formation that is typically
exposed in the bed and the banks of the Hoosic river at Schaghti-
coke, Rensselaer county, N. Y. It is characterized by the graptolites
Dictyonema flabelliforme var. acadicum Matthew, and Staurograp-
tus dichotomies, Emmons var. apertus Rued., which have been
described with their growth-stages, from material obtained at
Schaghticoke, in Memoir 7 of the New York State Museum.
Besides these two graptolites there were also found Clonograptus cf.
mile si Hall, a form from northern Vermont described by Hall, large
spicules of the sponge Protospongia and the minute primitive
brachiopod Acrotreta bisecta Matthew, and A. cf. belti (Davidson)
Matthew ; species known from the Dictyonema beds of Cape Breton,
N. S. and Navy island, St John, N. S., respectively.

The rock at Schaghticoke has a most characteristic appearance.
It is composed of very fine bedded, black and dull greenish to olive
siliceous and argillaceous slates with intercalations of thin gray to
white limestone beds (figures 60 and 64). The latter, consisting of
hard gray, very fine grained limestone, are but six inches thick.

The Dictyonema flabelliforme zone or Dictyonema-bed is known
in America from the lower St Lawrence region, Cape Breton island
and the St John basin (N. S.). It is widely spread in Europe, in
Great Britain, Scandinavia, Belgium, Bohemia, Esthonia and other
countries, thus constituting one of the most important guide-horizons.
It was generally considered as marking the top of the Cambrian, but
was at the time of the publication of the writer’s paper placed at the
base of the Ordovician by European, especially Scandinavian,
authors. In New York it rests on the Lower Cambrian from which
it is separated by a great hiatus. It is followed by the lithologically
identical Deep Kill shale, thus giving no conclusive evidence as to
its stratigraphic position. While it is currently placed at the base of

NEW YORK STATE MUSEUM

the Ordovician in Europe and in this country, it is still to be remem-
bered that in Great Britain, where the Cambrian was first recognized
and defined, this zone is still held as being in the Cambrian. The cur-
rent view in this country is perhaps best expressed in the chart (table
i) of Bassler’s Bibliographic Index (’15, plate 1), where the
Schaghticoke shale is placed at the base of the Canadian (Beekman-
town) and directly overlying the Ozarkian. In eastern Europe, the
Dictyonema shale introduces an extensive Ordovician transgression,
and it seems to do the same in the northern part of the Appalachian
geosyncline.

In mapping the Schuylerville quadrangle, an outcrop of the shale
with its characteristic fauna was found in a cut of the Hudson Val-
ley Railroad, about a mile north of Schuylerville, and thence traced
across the Hudson river. The rock there consists for the most part
of light greenish gray, glazed argillaceous shale that weathers to a
light drab, with intercalations of coarser, more or less sandy mud
shale and small streaks of black shale containing the graptolites. It
there also contains three and one-half feet of coarse grit with black
calcareous and argillaceous pebbles and large, scattered, rounded sand
grains. One part of the formation is characterized by a number of
calcareous sandstone beds one-eighth foot to one foot thick which
weather into a characteristic chestnut brown sandy crust.

It is thus seen that the rock has changed considerably in lithic
aspect north of its type locality. It has not been observed again in
the capital district outside of Schaghticoke, on the Cohoes quad-
rangle. It is, however, undoubtedly present in many other places
in the slate belt of the district, but owing to its small thickness,
hidden in the great mass of Normanskill shales.

We find at Schaghticoke a minimum thickness of 30 feet, but
the thickness is most probably considerably more.

The Dictyonemas and Staurograpti are not found mingled in the
same beds at Schaghticoke and it is quite obvious that they belong
to different horizons. We have therefore distinguished the two
zones as:

b Zone of Staurograptus dichotomus.

a Zone of Dictyonema flabelliforme.

22 Deep Kill shale. In 1902 the writer described as the Deep
Kill shale the graptolite shales of Beekmantown age which he had
discovered along Deep kill in Rensselaer county, N. Y., exposed
in a continuous series of rocks. This splendid outcrop begins a
quarter of a mile above the hamlet of Grant Hollow in the creek
bed, and extends to the dam of the reservoir of the Troy water-

GEOLOGY OF THE CAPITAL DISTRICT

works in the Deep Kill gorge. It has been very fully described in
New York State Museum Bulletin 52 (also Volume 55, Report of
the New York State Museum for 1901, p. 546-605, 1903), because
it is the only complete section through the Beekmantown graptolite
shale known as yet south of that at Point Levis, near Quebec.

The occurrence is an inlier in the Lower Cambrian rocks, which
surround it on at least three sides and on the north and south
overhang the ravine, in which the Deep Kill shales are exposed.
The exposure of the rock at Schaghticoke is of the same type. It
is also in the gorge of a river and surrounded by Lower Cambrian
on higher levels. For the tectonic significance of this feature see
chapter on structural geology.

It was estimated by the writer that the rocks of this section must
have attained a total thickness of 200 to 300 feet. Dale (’04, p. 33),
who has recorded some other outcrops of Beekmantown shale in the
capital district, roughly estimated the thickness in these localities at
50 feet, but considers it a possibility that some of the green shales
without banded quartzites and without fossils belong to this forma-
tion, and therefore, he holds his estimate to be a minimum.

The Deep Kill shale is most characteristically represented by
finely banded quartzite beds that in places are very calcareous and
are associated with greenish and grayish shales, resembling the
lower Cambrian shales. Along the Deep kill we have the following
succession of rocks (the letters refer to the figure) :

b Limestones (more or less silicious) with shaly intercalations 4' o"

c Sandy shales and grits 2' 8"

d Greenish siliceous shale and black graptolite shale o' 8"

Graptolite bed 1

e Thin-bedded shales, grits and limestones 1' 8"

f Greenish silicious shale and black graptolite shale 1' 9"

Graptolite bed 2

g Greenish silicious shale

h Thin-bedded, dark gray limestone

i Greenish silicious beds and black graptolite shale

Graptolite bed 3

j Greenish silicious beds and sandy shales

(two thin seams of bluish black shale with graptolites)

k Dark gray thin-bedded limestone layers

I Greenish silicious beds and black graptolite shale

Graptolite bed 4

m Thin-bedded limestone with shale partings

n Covered

o (Quarry) Two to three-foot banks of hard, fine-grained thin-
bedded layers (banded greenish gray and lighter). Many tenuous,
graptolitiferous partings of black shale

Graptolite bed 5

q Covered (distance of 825')

2 9

14 3
2'

5' 5"

5 9
4”

I 6'

8' 9"

(ioo'T)

NEW YORK STATE MUSEUM

r Exposure at north side of dam, 135 feet long, mostly greenish
gray quartzite, with some brecciated layers and some thin bands

of gray limestone (70'+)

Graptolite bed 6 (s') and graptolite bed 7 (2')

Worth noting in this section is the appearance of a breccia and
coarse-grained sandy shale in c, the uneven surface of the lime-
stone layers in h, and the still more undulating or interlocking sur-
faces in k, and limestone breccia in l. Still more important is the
distinct alternation of calcareous beds and silicious and graptolite
shales, indicating at least five cycles of deposition between b and o,
either due to oscillations in the depth of the trough, or to changes
in currents.

The writer (’03) divided the Deep Kill graptolite shales as exposed
at the type locality, into three main zones, namely,

a Tetragraptus zone, comprising graptolite beds 1 and 2
b Zone of Didymograptus bifidus and Phyllograptus anna. Grap-
tolite beds 3, 4 and 5.

c Zone of Diplograptus dentatus and Cryptograptus antennarius,
Graptolite beds 6 and 7.

Later (’19, p. 119), the writer found it advisable to divide each
of the zones into two subzones, since the graptolite faunas of the
two or more graptolite beds of each zone show differences in their
faunal composition that correspond to those recognized in other re-
gions, notably Great Britain and Sweden. Furthermore, another
zone below the deepest Deep Kill zone exposed at the Deep kill
is indicated by an occurrence, discovered by L. M. Prindle on the
road between Defreestville and West Sand Lake (Dale, ’04, p. 30).
This contains forms of the Clonograptus zone of Quebec and Europe.
We have accordingly distinguished the following subzones in ascend-
ing order. (’19, p. 121) :

I. Zone of Clonograptus flexilis and Tetragraptus j Tetragraptus

II. Zone of Phyllograptus typus and Tetragr. J beds

quadri-brachiatus

III. Zone of Didymograptus

a Subzone of D. nitidus, D. patulus

b Subzone of D. extensus, Goniogr. thureaui J beds
IV. Zone of Didymograptus bifidus

a Subzone of Goniogr. geometricus, Phyllogr. anna
b Subzone of Didymogr. similis, Phyllogr. typus
V. Zone of Diplograptus dentatus

a Subzone of Climacogr. pungens, Didymogr. forcipiformis
b Subzone of Phyllogr. angustifolius, Retiogr. tentaculatus
c Subzone of Desmogr. and Trigonogr. ensiformis

GEOLOGY OF THE CAPITAL DISTRICT

The first zone, that of Clonograptus flexilis and Tetragraptus, is
represented only by a faunule that was obtained by Prindle in a
small road metal pit between Defreestville and West Sand Lake
(marked on map as fossil locality) about four and one-half miles
east of Albany. The outcrop consists of light greenish and darker
silicious slate with interbedded yellowish weathering, thin (one inch
thick) quartzite layers, the beds resembling very much those of
Schaghticoke and the Deep Kill. The following fossils were found

in this locality:

Dictyonema murrayi Hall c

Clonograptus cf. flexilis Hall cc

Tetragraptus quadribrachiatus Hall c

T. serra Brongniart c

We placed (’04, p. 426) this faunule as the Clonograptus zone at
the base of the Deep Kill zones. It has since been found by Ray-
mond, (’04, p. 523) to form the base of the Point Levis series in
Quebec, that corresponds to our Deep Kill series.

The locality on the West Sand Lake road has on more recent
visits not afforded any more fossils. It is, however, undoubted that
the zone is present in other localities and will appear in new out-
crops. The Deep Kill beds cross the eastern slate belt of the capital
district, for the writer has found them at Rensselaer and again
south of the capital district at Stuyvesant Landing, in the railroad
cut just below the station and there with the characteristic alterna-
tion of dark green and black shales with whitish calcareous and
silicious beds.

The second zone, that of Phyllograptus typus and Tetragraptus
quadribrachiatus, has not been directly recognized in our section.
It is the second zone of the Tetragraptus bed at Point Levis, but the
zone is undoubtedly present in the Ordovician shales of the capital
district, as is evinced by the frequent occurrence of the Tetragrapti
in our first and second graptolite beds of the Deep Kill section,
which we, in the earlier papers (’03, ’04), called the Tetragraptus
beds — or zone on account of these Tetragrapti. Since the true Tetra-
graptus beds at Point Levis are below this zone, we have termed
the first two zones at the Deep kill the Didymograptus beds.

The lowest zone at the Deep kill (graptolite bed 1) is the zone
of Didymograptus nitidus and D. patulus.

The fauna of this zone at the Deep kill is the following :

Callograptus salteri Hall r

Bryograptus lapworthi Rued c

NEW YORK STATE MUSEUM

Dichograptus octobrachiatus Hall rr

Tetragraptus fruticosus Hall c

T. serra Brongniart r

Didymograptus nitidus Hall c

D. patulus Hall cc

Phyllograptus ilicifolius Hall r

P. angustifolius Hall rr

The next zone, that of Didymograptus extensus and Goniograptus
thureaui (graptolite bed 2) contains:

Dictyonema furciferum Rued r

Dendrograptus flexuosus Hall c

D. fluitans Rued r

Callograptus salteri Hall c

C. cf. diffusus Hall r

Bryograptus lapworthi Rued cc

B. pusillus Rued rr

Goniograptus thureaui McCoy cc

G. geometricus Rued r

G. perflexilis Rued cc

Loganograptus logani Hall (?) cc

Dichograptus octobrachiatus Hall cc

Tetragraptus quadribrachiatus Hall cc

T. amii Ellcs & Wood c

T. fruticosus Hall cc

T. serra Brongniart c

T. similis Hall cc

T. taraxacum Rued r

T. pygmaeus Rued c

Didymograptus extensus Hall cc

D. nitidus Hall c

D. patulus Hall cc

D. nicholsoni var. planus E. & W r

D. filiformis Tullberg r

Phyllograptus ilicifolius Hall cc

P. angustifolius Hall r

P. anna Hall (in uppermost layers) . r

Temnograptus noveboracensis Rued c

Other fossils :

Dawsonia monodon Gurley c

D. tridens Gurley c

Caryocaris curvilatus Gurley c

GEOLOGY OF THE CAPITAL DISTRICT

Graptolite bed 2 is covered on every bedding plane with a multitude
of beautifully preserved graptolites. As this list shows it also produces
a great variety of forms, among them the most beautiful Deep Kill
graptolites, the many-branched regular Goniograptus forms and the
stately four-branched species of Tetragraptus, notably T. fruticosus,
one of the most striking graptolites known. It will be noted that
there are no less than seven species of Tetragraptus present in that
bed, and five of Didymograptus. In number of individuals, however,
the Didymograpti prevail by far. No less than nine species of this
bed were new to science, and have not been found in any other
locality. Some large magnificent slabs from this horizon are on
exhibition in the State Museum. Since the rock with the graptolites
is a very hard black slate, large surfaces can be obtained in this
locality with the proper tools (large chisels and bars). The Museum
has sent collections of graptolites, mainly from this ledge to rep-
resent the Deep Kill fauna, to all parts of the world in exchange for
other graptolite faunas.

The Dawsonias are doubtful organisms. Similar bodies lately, have
been considered by Manck (’26) as identical with the gonangia or
reproductive sacs of Diplograptids after they have separated from
the colony and burst open to discharge the spawn (described by
Ruedemann, ’97). Caryocafis curirilatus is a small crustacean
peculiar to the graptolite beds in Great Britain and in eastern and
western North America. The small list of associates of these grapto-
lites is completed by worm-tubes ( Serpulites interrogans Rued.)
found in these graptolite beds at the Deep kill (Ruedemann, T6,

p. 86).

The zone of Didymograptus extensus and Goniograptus thureaui
is undoubtedly present in more localities than have been recorded so
far. We have found Loganograptus logani and Tetragraptus quad-
ribrachiatus in a road metal pit in Rensselaer (corner High street
and Third avenue) formerly considered by us as belonging to the
Normanskill. The rock consists of black, gray and greenish as well
as some reddish shale and in part contains silicious bands as at the
Deep kill, and in another a two-foot bed of black chert. It is possi-
ble that in this locality, with its much contorted beds both Deep Kill
and Normanskill shales are intermixed.

Beautiful specimens of Caryocaris curvilatus were collected in a
road metal pit one-quarter of a mile south of Aries lake (Snyders
lake), where the road reaches the top of the hill.

NEW YORK STATE MUSEUM

Goniograptus thureaui and other Deep Kill fossils of this zone
were also collected in typical Deep Kill rocks south of the capital
district at Stuyvesant Landing.

The zone is also present on the southern slope of Mount Rafinesque
and southeast of Tomhannock.

The fauna found in the two Didymograptus zones has a world-
wide distribution. It is known from Europe, Asia, America and
Australia. Goniograptus thureaui, for example, was first described
in Australia.

b Zone of Didymograptus bifidus and Phyllograptus anna. The

first subzone of this horizon is that of Goniograptus geometricus

and Phyllograptus anna. It is found in graptolite beds 3 and 4 of

the section. The fauna consists of :

Dictyonema furciferum Rued r

Dendrograptus flexuosus Hall r

Ptilograptus geinitzianus Hall rr

P. tenuissimus Hall rr

Goniograptus thureaui McCoy c

G. geometricus Rued cc

G. perflexilis Rued r

Dichograptus octobrachiatus Hall r

Tetragraptus quadribrachiatus Hall r

T. fruticosus Hall cc

T. clarkii Rued c

T. pendens Elies r

T. similis Hall c

T. pygmaeus Rued r

T. lentus Rued r

Didymograptus similis Hall r

D. acutidens Lapworth rr

D. gracilis Tornquist c

D. ellesae Rued c

D. tornquisti Rued r

D. bifidus Hall cc

Phyllograptus typus Hall c

P. angustifolius Hall c

P. anna Hall cc

Sigmagraptus praecursor Rued rr

It will be noted that this fauna is still very close to that of the
underlying Didymograptus beds. There are still three species of
Goniograptus, seven of Tetragraptus, six of Didymograptus and
three of Phyllograptus. The relative abundance of the species has,

GEOLOGY OF THE CAPITAL DISTRICT

however, greatly changed, the delicate Goniograptus geometricus
being now the most common form; among the Tetragrapti two new
species, T. clarkii and pendens have appeared ; among the Didymo-
grapti the leading species of the preceding horizon, D. extensus,
nitidus and patulus have entirely disappeared; D. bifidus appears
now in great number and serves as a guide fossil for the horizon ;
among the Phyllograpti, P. typus appears for the first time in the
section and the diminutive P. anna is the most common form.

The second subzone of the zone of Didymograptus bifidus and
Phyllograptus anna is that of Didymograptus similis and Phyl-
lograptus typus. It is found in graptolite bed 5. The fauna con-

sists of :

Callograptus salteri Hall r

Didymograptus similis Hall c

D. bifidus Hall cc

D. nanus Lapworth r

D. caduceus Salter c

Phyllograptus typus Hall cc

P. ilicifolius Hall r

P. anna Hall c

The fauna of this subzone is a rather small one, as represented in
graptolite bed 5. The most common graptolites are Didymograptus
bifidus and Phyllograptus typus. The latter and Didymograptus
similis are the most characteristic forms.

c The last zone of the Deep Kill section we termed in 1903 that of
Diplograptus dentatus and Cryptograptus antennarius.

We have in 1919 divided it into three subzones, namely:
a Subzone of Climacogr. pungens, Didymogr. forcipiformis
b Subzone of Phyllogr. angustifolius, Retiogr. tentaculatus
c Subzone of Desmograptus and Trigonogr. ensiformis

The first of these subzones is known to us only from the Ashhill
quarry at Mount Merino near Hudson, and concerns us here no
further, although it is to be assumed that it is also present in the
capital district and even in the Deep Kill section, and may be dis-
covered there some day.

The subzone of Phyllograptus angustifolius and Retiograptus
tentaculatus is represented by graptolite bed 6. This has furnished :

Phyllograptus angustifolius Hall c

P. anna Hall c

Diplograptus dentatus Brgt r

Trigonograptus ensiformis Hall r

Retiograptus tentaculatus Hall r

NEW YORK STATE MUSEUM

This faunule is interesting mainly, as that of the Ashhill quarry,
by its mixture of distinct elements of the earlier period, when only
graptolites without axes (order Axonolipa) existed, with those of
the later era, when the graptolites with axes (Axonophora) pre-
vailed. They are here represented for the first time in the Deep
Kill section by the genera Diplograptus, Trigonograptus and
Retiograptus.

Finally there is the last subzone of the Deep Kill series, that with
Desmograptus and Trigonograptus ensiformis. This, found in

graptolite bed 7, has afforded :

Dictyonema rectilineatum Rued r

Desmograptus cancellatus Hopkinson c

D. intricatus Rued c

D. succulentus Rued c

C. cf. diffusus Hall r

Ptilograptus plumosus Hall rr

Loganograptus logani Hall rr

Dichograptus octobrachiatus Hall rr

Tetragraptus quadribrachiatus Hall rr

Didymograptus caduceus Salter mut. nana Rued c

D. incertus Rued rr

Strophograptus trichomanes Rued c

Diplograptus dentatus Brgt cc

D. inutilis Hall r

D. longicaudatus Rued rr

D. laxus Rued c

Glossograptus hystrix Rued r

G. echinatus Rued rr

Trigonograptus ensiformis Hall cc

Climacograptus ? antennarius Hall cc

C. pungens Rued r

Retiograptus tentaculatus Hall r

To these graptolites may be added two strange forms of brachio-
pods which the writer collected in this horizon. One is a gigantic
Lingula, about two inches long, and identical or closely related to
L. quebecensis Billings, a similarly large form that is known from
the graptolite shales of Quebec. The other form, also of enormous
size for brachiopods, is semicircular, four inches wide and more
than two inches long, with very tenuous, chitinous, phosphatic shell.
Clarke (’07, p. 606) has described this shell as Eunoa accola. It is
possible that these brachiopods, with their large, flat, tenuous shells,
led a planktonic or swimming life like the graptolites.

GEOLOGY OF THE CAPITAL DISTRICT

The graptolite fauna of this zone is characterized by the wonder-
ful mixture of dendroid forms of the genera Dictyonema, Desmo-
graptus and Ptilograptus, on one hand, with a multitude of true
graptolites (Graptoloidea) on the other; and among these, again, of
the older forms without axes, Dichograptus, Loganograptus, Tetra-
graptus, Didymograptus, with the later and more advanced types
with axes, of the genera Diplograptus, Glossograptus, Trigono-
graptus, Climacograptus, Retiograptus.

The appearance of this new class of graptolites, the Axonophora,
that characterizes the faunas of the later Ordovician and Silurian
in the last Deep Kill zone, has seemed to the writer to indicate an
important break between that zone and the preceding zones. It is
for this reason that he has correlated this zone (with its three sub-
zones) with the Lower Chazy rather than with the Beekmantown,
with which the preceding undoubtedly must be correlated.

23 Bald Mountain limestone. The Bald Mountain limestone has
been described by the writer (’14, p. 75) from the fine quarries at
the foot of Bald mountain in Washington county (Schuylerville
quadrangle), where the overthrust of the Lower Cambrian on the
Ordovician is wonderfully exposed. It there contains a Beekman-
town fauna and is of considerable thickness, as much as 70 feet or
more south of the Bald mountain quarries, and as tests have shown,
is in these quarries of greater purity than any other limestones in
the State.

The Bald mountain limestone disappears about three and one-half
miles south of Middle Falls and five and one-half miles south of
the Bald mountain quarries, nor has it been traced northward. This
would appear to give it a purely local development, in place of the
Beekmantown graptolite shales, which, it is true, have not been
found on the Schuylerville quadrangle. Since, however, the short
belt of the limestone is exposed only just below the great overthrust
line and bounded by overthrust planes above and below, thus appear-
ing as a great wedge carried along, it may well be present in the
capital district, hidden under the overthrust Cambrian rocks, and it
may come to the surface at any place, especially near the great over-
thrust plane. A similar wedge of Trenton limestone, is, as we shall
see presently, present in the capital district in the southeast corner
of the Troy quadrangle.

As a matter of fact, there is exposed on Rysedorph hill, east of
Greenbush, just north of the conglomerate cliff, a ledge of white
limestone that has the appearance of the Bald Mountain limestone
and does not seem to be referable to any formation in the district.

NEW YORK STATE MUSEUM

It has as yet not furnished any fossils that would solve the riddle
of its age.

That the Bald Mountain limestone continues through the eastern
slate belt and may form a portion of the Wappinger limestone
(also known as the Neelytown, Newburgh or Barnegat limestone)
on the Poughkeepsie and Newburgh quadrangles, is strongly sug-
gested by the identification by Ulrich in the Bald Mountain limestone
(Ruedemann, 14, p. 77) as Eccyliopterus planidorsalis and E. plani-
basalis Ulrich MS. of gastropods, years ago announced by Whitfield
as “Maclurea magna” from the limestone southwest of Newburgh
(Holzwasser, ’26, p. 42).

24 Normanskill shale. The name “Normanskill shale” was used
by Ruedemann in 1901 for beds typically exposed at the Normans-
kill at the southern outskirts of Albany, at Kenwood (figure 48).

This formation contains a large and cosmopolitan graptolite
fauna. Hall described in volume 1 of the Paleontology of New
York (1843) the more common forms of the fauna from the “black
glazed slates on the Normanskill, near Albany,” under the heading
“ Utica slate and Hudson river group,” accompanied by three
beautiful steel-engraved plates. He added 11 species from the
“ Hudson river group near Albany,” in the appendix to volume 3
of the Paleontology (’59) together with figures of supposed repro-
ductive vesicles (ibid. p. 507).

The neighborhood of Albany has thereby become classic ground
for the largest and best known graptolite fauna of America, that of
the Normanskill shale. While the old locality, which was the
foundation for a mill just above the Kenwood bridge, as well as
the mill itself, has long ago disappeared, new outcrops are continu-
ally opened in the neighborhood of Albany, especially across the
river. The richest ground for Normanskill graptolites was found
for a time when the West Shore Railroad was built in 1883 in the
cut just below Glenmont (a railroad station), one and one-half miles
south of Kenwood. This locality, which to the old collectors was
known as Van Wies Point (a promontory in the river) or “ The
Abbey ” (a near-by inn) furnished magnificent large slabs with
splendidly preserved fossils, among them the complete compound
colonies of Diplograptus, never found anywhere before or since in
such perfection (described by Ruedemann, ’95, plate 4, from
material lent by Hall, in connection with other material the writer
had obtained at Dolgeville, N. Y.). A part of this splendid material
is now on exhibition in the State Museum.

GEOLOGY OF THE CAPITAL DISTRICT

Small collections can still be obtained at the old localities, in the
cut of the Delaware and Hudson Railroad at Kenwood and in that
of the West Shore Railroad at Glenmont. For larger collections one
has to go across the river and outside of the capital district.

The belt of Normanskill rocks crosses the district diagonally from
the northeast corner to a little east of the southwest corner, where
it dives under the Helderberg series of formations. For a long
distance the belt runs along the Hudson river, crossing it in the south-
ern part of Albany. Independent areas of Normanskill beds are
formed in the Mount Rafinesque — Rice mountain outlier northeast
of Troy and in a large area north of the Rensselaer plateau and
east of the Lower Cambrian belt. A smaller outlier, that also con-
tains Deep Kill shale, occurs west and southwest of Aries lake
(Snyders lake).

Lithologically the Normanskill shale is a varied formation ; the
great mass of probably 2000 feet consists of mostly dark gray to
black argillaceous shales, but also red and green shales and heavy
beds of chert and grit. The latter two are especially characteristic
of the formation so that it can be recognized by them when fossils
are not available.

The chert, formed by the induration of black to dark green shale,
occurs in beds varying from two feet in thickness to ten and more.
Dale (’99, p. 186) calls it “a siliceous and feldspathic slate,” formed
probably from “a feldspathic mud, with quartz fragments and
muscovite scales.” Our finding of graptolites on the Schuylerville
quadrangle in the chert would also indicate the origin of the chert
beds from mud similar to that forming the shale. The chert has a
peculiar way of weathering white or light gray and has therefore
been distinguished as the “white-weathering chert,” or “white beds”
by Dale (’99, p. 185). The white color may be due to a kaolinization
of an originally feldspathic mud (Dale, ’99, p. 186), or to the loss
of carbon on kaolinization (Dale, ’04, p. 36). The white-weathering
cherty beds do not form in the capital district such prominent out-
crops or even ridges as they do on the Schuylerville quadrangle to
the north, for instance on Willard mountain. Still they are well
exposed in several localities, as below Glenmont on both sides of the
state road before it crosses the railroad. The white ledges are seen
there everywhere projecting through the sod and they can be seen as
cliffs in the woods to the west of the road. They are also well ex-
posed in the long cut of the Boston and Albany Railroad below
Grandview Hill, south of Greenbush (now Rensselaer) and they
form the top of that hill.

NEW YORK STATE MUSEUM

An outlier of this rock occurs also just north of Waterford and
another smaller one, in a small but prominent hill, just west of the
Delaware and Hudson tracks at Watervliet, where the peculiar ap-
pearance of the rock has led to fruitless mining operations.

Another most characteristic and typical rock of the Normanskill
formation is the grit. It is usually associated with the cherty beds. It
has been very carefully described by Dale (’99, p. 187) as “the Hud-
son grit.” This Normanskill grit is, according to Dale, easily
recognized.

It is coarse, grayish, sandy looking. Fresh fracture surfaces are
very dark and show glistening glassy quartz grains and very fre-
quently minute, pale, greenish, slaty particles. Under the micro-
scope it consists of angular grains of quartz, orthoclase, plagioclase,
and scales of muscovite, probably clastic. The cement contains not.
a little carbonaceous matter, secondary calcite and pyrite. . . . The
marked features are the heterogeneity of the fragments, their irregu-
lar size, angular outline, and usually the absence of any arrangement
in them.

A further peculiarity of the Hudson grits is that they contain
particles of various fragmental rocks, showing that they were derived
from the erosion not only of older granites and gneisses, but of sedi-
mentary rocks of Ordovician or Pre-Ordovician age ; the particles
of clastic rocks were found to consist of shale, micaceous quartzite,
calcareous quartzite, limestone or dolomite, shale and flint. The
most abundant were found to be quartzite, slate and shale.

We will have occasion to return to the significance of the feldspar-
content (orthoclase and plagioclase), as well as of the particles of
various fragmental rocks in the grit.

The grit beds are ever present in the Normanskill shale, ranging
in thickness from two feet to 30 feet, and in many localities, especially
where erosion is deep and drift cover heavy, they are the only rocks of
the formation appearing on the surface, as in some ravines on the
west side of the river. The grit is, or was, quarried in many places
in the Hudson valley, especially farther south. In the capital district,
where the nearby Helderbergs furnish excellent road metal, it is only
of local importance. There is a large quarry in the grit at Kenwood
on the south side of the Normanskill creek.

Besides the black and gray shales with interbedded grit and white-
weathering chert, there are also masses of reddish, purplish and
greenish shales with small quartzite bands, often disturbingly similar
to the Cambrian rocks. These shales, which are not protected by the
grits and cherts do not appear so often, however, on the surface in
the capital district. They are best shown on the top of the great
cross-fold of Mount Rafinesque northeast of Troy.

GEOLOGY OF THE CAPITAL DISTRICT

The shales with limestone and the limestone conglomerate, both
with Trenton faunas, which Dale included in the Hudson shales, are
here separated (see p. 104) and placed on top of the Normanskill
formation. Dale (’04, p. 37) gave the following divisions of the
Hudson formation as exposed in Rensselaer county :

Descriptions of strata Fauna

1 Black shale with arenaceous lime- Diplograpt'us amplexi-

stone (Ruedemann’s stations 24- caulis
26)

2 Black and gray shale with inter- Normanskill graptolite

bedded grit . . . fauna

3 Similar shale with limestone and Trenton fauna in lime-

limestone conglomerate stone and cement of

conglomerate

4 Black, silicious, white-weathering, cherty-looking shale

5 Reddish, purplish, greenish shale with small quartzite bands.

Estimated
thickness in
feet

1200-2500?

Of these groups of rocks, No. 1 is our Snake Hill formation,
No. 3 is the Tackawasick shale and limestone and the Rysedorph
Hill conglomerate.

We have presented evidence (’14, p. 89) from the Schuylerville
quadrangle which makes it probable that the grit is nearest the base
of the formation and the white-weathering chert above.

Another question which can not be satisfactorily answered as yet
is that of the thickness of the Normanskill formation. Dale (’99),
in his table (facing p. 178) of Cambrian and Silurian formations of
the slate belt of eastern New York and western Vermont, assigns
to the Hudson grits 500 feet ; to the Hudson white beds 400 feet
or less ; to the Hudson shales 50 + feet ; to Hudson red and green
slate 100 -)- feet. We had an opportunity to make some estimates on
the west side of Willard mountain on the Schuylerville quadrangle
(Ruedemann. '14, p. 91), as follows: grit, 500 ± feet; white beds,
400 ± feet; shale, 100 ± feet. The capital district has not furnished
any further evidence on the thickness of the formation. From both
Dale’s and our own estimate we would consider 1000 feet as a mini-
mum for the Normanskill shale, with a possibility that it goes to
double this thickness.

The fauna of the Normanskill shale, as brought together in the
capital district, mainly at Glenmont, consists of 56 species, as
follows :

P'tilograptus poctai Rued rr (Gl.)

Dictyonema spiniferum Rued rr (Gl.)

Odontocaulis hepaticus Rued r (Gl.)

Desmograptus tenuiramosus Rued rr (Gl.)

IOO

NEW YORK STATE MUSEUM

Thamnograptus capillaris ( Emmons ) c (K. etc.)

Didymograptus sagitticaulis Gurley cc (K. etc.)

D. serratulus (Hall) c (K., Lans. etc.)

D. subtenuis (Hall) cc (K. etc.)

Azygograptus ? simplex Rued c (K., Gl., Lans.)

Leptograptus flaccidus mut. trentonensis

Rued cc (Gl.)

L. flaccidus var. spinifer E. & W. mut. tren-
tonensis Rued c (Gl.)

Syndyograptus pecten Rued rr (Gl.)

Amphigraptus divergens (Hall) rr (K., Gl.)

A. multi fasciatus (Hall) rr (K.)

Nemagraptus gracilis (Hall) cc (K., Gl. etc.)

N. gracilis var. succularis (Hall) c (K., Gl.)

N. gracilis var. distans Rued r (Gl.)

N. gracilis var. approximate Rued r (K., Gl.)

N. exilis Lapworth c (Gl.)

N. exilis var. linearis Rued c (K., Sp.)

Dicellograptus mensurans Rued r (K.)

D. divaricatus (Hall) c (K., Gl.)

D. divaricatus var. rectus Rued r (K., Sp.)

D. divaricatus var. bicurvatus Rued c (Gl., K.)

D. divaricatus var. salopiensis Elies & Wood r (K.)

D. intortus Lapworth rr (Sp.)

D. gurleyi Lapworth cc (Gl)

D. sextans (Hall) cc (Poest.,Troy, K., Gl.,

Tomhannock etc.)

D. sextans var. exilis Elies & Wood

D. sextans var. tortus Rued

Dicranograptus nicholsoni Hopkinson var.

parvangulus Gurley

D. nicholsoni var. diapason Gurley

D. ramose Hall

D. spinifer E. & W

D. spinifer var. geniculatus Rued

D. furcatus (Hall)

D. furcatus var. exilis Rued

D. contortus Rued

Corynoides curtus Lapworth

C. gracilis Hopkinson

r (Gl.)
c (K.)

cc (Gl.)
c (Gl.)

c (K., Gl., Cas., Mt
O.)
r (Gl.)
r (Gl.)
cc (K., Gl.)
r (K.)

c (K., Mt O.)
cc (Gl., K., Troy, Cas.)
cc (Lans.)

GEOLOGY OF THE CAPITAL DISTRICT

IOI

C. gracilis rnut. perungulatus Rued cc (Gl., Sp.)

Diplograptus incisus Lapworth cc (Gl., K. etc.)

D. acutus Lapworth cc (Gl., K. etc.)

D. angustifolius H all c (Gl., K., Lans. etc.)

D. (Glyptograptus) euglyphus Lapworth.. c (Gl., Sp.)

D. euglyphus var. pygmaeus Rued cc (Lans.)

Glossograptus ciliatus Emmons c (K., Gl. etc.)

G. whitfieldi (Hall) cc (K„ Gl. etc.)

Cryptograptus tricornis ( Carruthers ) cc (K., Gl. etc.)

Climacograptus parvus Hall cc (K., Gl., Cas., Mt O.,

Poest.)

C. modestus Rued cc (Lans.)

C. scharenbergi Lapworth c (Gl.)

C. bicornis Hall cc (K., G. etc.)

Retiograptus geinitzianus (Hall) r (K., Gl. etc.)

Lasiograptus mucronatus (Hall) cc (K., G. etc.)

L. bimucronatus (Hall) c

We have added the principal graptolitiferous localities of the
capital district in parentheses, K. meaning Kenwood ; Gl., Glenmont ;
Lans., Lansingburg ; Cas., Castleton ; Poest., Poestenkill at Spring
street, Troy; Mt O., Mount Olympus in Troy; Sp., Speigletown.
All of these localities are denoted by stars on the geologic map.

There is no doubt that the Normanskill formation covers a long
interval of time and is composed of a number of subzones. This is
suggested not only by its great thickness of over 1000 feet, but also
by the fact that the graptolite faunules of the different localities
show considerable differences. We have so far been unable to find a
continuous section and therefore can only surmise, and have only indi-
rect evidence to offer as to the succession of the faunas. There are
distinguishable at least two, possibly three, different associations of
forms. The most important of these is the typical Normanskill
fauna of Kenwood and Glenwood, which is also by far the richest.
This fauna is usually found associated with the Normanskill grit and
the white-weathering chert, and is most probably the lowest of the
faunas. Lapworth in 1887 distinguished two subfaunas in the grapto-
lite beds of the St Lawrence shale of this age, namely a lower one,
with Coenograptus gracilis , his Coenograptus zone of Griffin cove
and the Marsouin river, and a higher one, apparently destitute of
Coenograptus gracilis, the Cove Fields and Orleans subfauna; the
former he correlated with the Middle Llandeilo of Great Britain,

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the latter with the highest Llandeilo or lowest Caradoc beds of
England. It is evident that the typical Normanskill graptolite fauna,
which contains Nemagraptus ( Coenograptus ) gracilis, corresponds
to the first subzone.

From the upper zone Lapworth cites:

Diplograptus foliaceus Murchison var.

D. amplexicaulis ? Hall
D. truncatus ( ?) Lapworth
D. euglyphus Lapworth (?)

Corynoides calycularis Nicholson
Dicellograptus sp.

Dicranograptus tardiusculus (?) Lapworth
Dicranograptus ramosus var. spinosus Lapworth
Climacograptus bicornis Hall
C. two sp.

C. scharenbergi Lapworth
Cryptograptus tricornis Carruthers.

Most of these species are Normanskill forms, especially so the
positively identified species, yet the most characteristic Normanskill
forms are lacking. Gurley (’96) distinguished the two zones as the
Upper and Lower Dicellograptus zones in Canada. Lie gave a large
list of graptolites from Magog, Quebec (near the Vermont line) as
characterizing this zone. A smaller list of this fauna had already
been given by G. M. Dawson (’94), and a larger one with figures
was published in 1902 by C. H. Richardson. These three lists show
rather strong discrepancies, especially Gurley’s, which differs from
the others by citing a considerable number of new species (manu-
script names). Professor Richardson was kind enough to allow me
to select typical material from his large collection now in Syracuse
University. Inspection of this shows that the graptolites are strongly
distorted or deformed by being stretched in one direction and com-
pressed in that at right angle, in the manner described for the
material from the Hoosic tunnel by the writer (’08, pi. 25, p. 7- 9).
This deformation is undoubtedly responsible for Gurley’s new
species.1

The writer (’08, p. 29) has united the Cove Fields faunas, the
Upper Dicellograptus fauna and that from Magog under the term
“Magog shale,” but erroneously also referred the beds at Watervliet,
Troy (Rushers quarry), Sandy hill and Van Schaick island to this
zone and termed it from the guiding fossil of the last named localities

1 The Magog fauna will be revised in another publication.

GEOLOGY OF THE CAPITAL DISTRICT

103

the zone of Diplograptus amplexicaulis. Later studies have proved
that these beds belong to a later zone, that we unite now with the
Snake Hill beds. In recognition of this fact, we have ('19, p. 122,
130) designated these later beds as Magog shale (or zone of Cryp-
tograptus tricornis insectiformis) and the upper division of the Nor-
manskill shale as zone of Corynoides gracilis. From an inspection
of Professor Richardson’s material we have been convinced that the
term “Magog shale” can be properly applied only to the upper
division of the Normanskill.

This is distinguished from the lower zone by the reduction in
species and individuals of the genera Dicellograptus, Dicranograptus
and Didymograptus and the prevalence of Diplograptidae, especially
the genera Diplograptus and Climacograptus. Also two species of
Corynoides, C. calicularis and gracilis cover whole bedding planes.
In the capital district it is C. gracilis that prevails. A typical locality
of the upper horizon was found by the writer at the north end of
Lansingburg, at the power house of the traction company. It
afforded besides the Normanskill species: Didymograptus serratulus,
Asygograptus ? simplex, Dicranograptus ramosus, Climacograptus
parvus, C, modestus, C. bicornis and Diplograptus acutus, the follow-
ing peculiar elements of its own : Diplograptus amplexicaulis var.
pertenuis, Diplograptus euglyphus var. pygmaeus, Climacograptus
eximius and Corynoides gracilis.

No other fossils but a few minute brachiopods with chitinous
shells occur in the Normanskill shale with the graptolites. These
are Paterula amii Schuchert, Schizotreta papilliformis Rued, and
Leptobolus walcotti Rued. Only the latter is seen more frequently.
In a quarry near Catskill, however, the writer discovered a fauna
of eurypterids associated with the graptolites. This is the oldest
eurypterid fauna known. It was described by Clarke and Ruedemann
in the Eurypterids of New York.1 No trace of these strange asso-
ciates of the Normanskill graptolites has as yet been found in the
capital district.

The correlation of the great mass of Normanskill rocks has been
the subject of considerable doubt. As mentioned before, it was
originally with the “Hudson river beds” placed above the Utica and
correlated with the Lorraine. Lapworth’s correlation of the
Coenograptus zone of Canada with that of Great Britain suggested
a greater age than Utica for the formation ; also Dale’s work in the

1 The writer (’12, p. 41 1) has given Professor G. H. Chadwick credit for
having discovered this eurypterid fauna, but is informed by Professor Chad-
wick that he directed my attention only to the graptolite fauna, not being aware
of the eurypterids, and that these were found by myself.

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slate belt (’99, table p. 178) led to the inference that the Hudson
shales, cherts and grits may be replaced westward by limestone, that
represents Trenton, Chazy and Beekmantown. The discovery of
the Rysedorph Hill conglomerate (see below), apparently inter-
calated in the Normanskill and carrying Trenton fossils as well as
the finding of the Normanskill below the zone with Diplograptus
amplexicaulis, led the writer (’01) to the conclusion that the Nor-
manskill shale could not be younger than middle Trenton and that
it corresponds to a part of the middle or lower Trenton limestone
(’01, p. 551). Later the discovery of Normanskill graptolites in
association with other fossils in Virginia led to the assignment of
the Normanskill to still older periods ; it was first placed by Ulrich
(Ti, p. 512) below the Lowville and above the Chazy and then by
Raymond (T6) correlated with the Upper Chazy. If the typical
Normanskill corresponds to the Upper Chazy, the upper Norman-
skill zone (Magog shale) may be of Lowville and Leray age. It
thus closes the upper gap to the Snake Hill beds of Trenton age, and
the Normanskill closes the gap in the Chazy above the uppermost
Deep Kill zone which we considered of lower and middle Chazy age.

25 Rysedorph conglomerate. Two of the most interesting rocks
of the capital district are a conglomerate and a fault breccia. The
conglomerate was fully described by the writer in 1901 and termed
the Rysedorph conglomerate, from its exposure on Rysedorph hill,
a prominent eminence two miles southeast of Rensselaer (figure 61).
The hill is not known locally under the name given it on the
topographic map, but is called the Pinnacle or Sugar Loaf hill. It
is a triangulation station with a bench mark and can be recommended
to the geologists not only as a fine collecting ground for Rysedorph
fossils, but also for its magnificent view, which sweeps the country
to the Adirondacks in the north, the Green mountains in the east,
the Catskills in the south and the Helderbergs in the west, thereby
affording a most complete survey of the topography of the capital
district.

The Rysedorph conglomerate has a wide distribution within the
Normanskill shale belt in the capital district; but it also extends
into the Schuylerville quadrangle, where the writer has described it
from the base of Bald mountain (’14, p. 80) ; and it is found at
Schodack Landing and may be identical with the Burden con-
glomerate described by Grabau from Becraft mountain near Hudson.

The typical outcrop on top of Rysedorph hill is a vertical
ledge ; the main bed is two and one-half feet thick. It is
distinctly underlain by black and green shales on the west side. This

GEOLOGY OF THE CAPITAL DISTRICT

105

condition led Emmons (’55, pt II, p. 72), in his endeavor to establish
the Taconic system, to cite this hill as one of his critical localities.
As his section indicates, Emmons believed he had the “Calciferous
sandstone” (Beekmantown), resting uncomformably on the “green
Taconic slates,” thereby proving the primordial age of the latter.
The writer has fully described the later history and interpretations
of this interesting locality, (’01, p. 4 ff.). It may here be mentioned
that Hall (’47, p. 35) disputed the Beekmantown age of the rock
which Emmons had based on a cephalopod, and declared the mass
to be “the Trenton limestone thrust through the Hudson River
slates.” Walcott (’88, p. 319) had also studied the outcrop and
considered it a block of Trenton conglomerate caught on the line
of the great fault which passes through the hill and which separates
the Cambrian and Ordovician strata. The writer has in the past
20 years taken many geologists, both from this country and from
Europe, to the well-known locality and all have returned with inter-
esting fossils and facts from this historic point.

A study of the conglomerate by the writer was carried out with
a wagonload of pebbles, most of which being composed of intensely
hard siliceous limestone which broke through the fossils, had to be
baked in the kitchen range and dumped into cold water, to assure
breaking along the fossils. The material proved fully worthy of the
work spent on it. There were found seven kinds of pebbles which
furnished an amazingly rich and strange fauna. The writer (’01)
described 84 species from this small locality, a prodigious number
for Paleozoic outcrops ; and 25 of these were new, among them six
new trilobites. Later collecting has added still new forms. These
will be published later in a revision of the fauna.

The most interesting facts obtained were that the faunas of the
pebbles ranged from the Lower Cambrian to the Trenton, that the
Chazy is represented in the pebbles, which is only known on the
surface in northern New York and Vermont, and that the
Mohawkian fauna contains Atlantic elements hitherto known only
from Europe, but which since have been found at Quebec, in Penn-
sylvania, Virginia and Alabama in the identical forms first described
from Rysedorph hill. It may be added that, with the exception of
the Lower Cambrian limestone, none of the groups of pebbles with
their faunas can be referred to ledges of rock in eastern New York
or the neighboring parts of Vermont and Massachusetts, which
means, in our view, that they came from rocks in the east and north-
east which are now so metamorphosed (as the Stockbridge limestone
and marble etc.) that the faunas are unrecognizable, just as the
shales of the slate belt are metamorphosed farther eastward into

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NEW YORK STATE MUSEUM

schists (the Berkshire schist). This small ledge thus presents us,
like a page from a lost work, with a glance into hidden treasures that
may never become fully revealed to science.

The following are the groups of pebbles from the Rysedorph hill
conglomerate and their faunas :

1 Gray limestone of Lower Cambrian age

Hyolithellus micans Billings

2 Gray and reddish sandstone

No fossils

3 Black crystalline limestone (Chazy limestone)

Bolboporites americanus Billings

Paleocystites tenuiradiatus (Hall)

4 Lowville limestone

Phvtopsis tubulosa Hall. Tetradium cellulosum. Hall

5 Black compact limestone

The pebbles of this group are considered the most valuable and
interesting portion of the Rysedorph Hill conglomerate. Unfortu-
nately they are rare and mostly small ; they are intensely black when
fresh, but very soft and of brownish tint when weathered. It was
these pebbles that furnished the rare brachiopods, gastropods and
trilobites. Altogether, 45 species were listed by the writer from
these pebbles, as follows:

Corals: Streptelasma corniculum Hall c

Graptolites: Diplograptus foliaceus Murcli r

Climacograptus scharenbergi Lapworth r

Bryozoans: Corynotrypa (Stomatopora) inflata (Hall) c

Stictopora cf. elegantula Hall r

Callopora multitabulata Ulrich cc

Brachiopods : Siphonotreta minnesotensis Hall & Clarke rr

Crania trentonensis Hall r

Rafinesquina alternata (Emmons) c

Leptaena rhomboidalis Wilckens c

Plectambonites sericeus (Sowerby) c

P. pisum Rued cc

Christiania trentonensis Rued c

Orthis tricenaria Hall c

Platystrophia biforata (Schlotheim) c

Dalmanella testudinaria (Dalman) c

Pclecypods: Whitella ventricosa (Hall) rr

Ctenodonta sp. ind rr

C. cf. astartaeformis Salter r

GEOLOGY OF THE CAPITAL DISTRICT

10 /

Gastropods: Sinuites cancellatus {Hall) r

Conradella compressa {Co nr ad) r

Carinaropsis carinata Hall r

Lophospira bicincta {Hall) r

Liospira americana {Billings) rr

Eccyliopterus spiralis Rued rr

Holopea paludiniformis Hall rr

Conularids: Conularia cf. trentonensis Hall rr

Cephalopods: Zitteloceras hallianum d’Orbigny rr

Trilobites: Tretaspis reticulata Rued cc

T. diademata Rued rr

Ampyx (Lonchodomas) hastatus Rued cc

Remopleurides linguatus Rued cc

Isotelus maximus Locke c

Illaenus americanus Billings c

Cyphaspis matutina Rued r

Bronteus lunatus Billings rr

Calymmene senaria Conrad rr

Pterygometopus callicephalus {Hall) c

Ceraurus pleurexanthemus {Green) c

Cybele sp .. rr

Sphaerocoryphe major Rued r

Ostracods: Isochilina armata Walcott var. pygmaea Rued... r

Primitia mundula Miller var. jonesi Rued r

Aparchites minutissimus Hall var. robustus Rued c

Bythocypris cylindrica Hall r

The most important and interesting forms of this association are
the brachiopods Plectambonites pisum and Christiania trentonensis,
and the trilobites Tretaspis reticulata, T. diademata, Ampyx hastatus,
Bronteus hastatus and Sphaerocoryphe major, because they all belong
to extremely rare genera or species. Representatives of the genus
Tretaspis were before known only from Great Britain.

The brachiopod Plectambonites pisum, a small, almost globular
shell, is so common in these beds that it makes an excellent index
fossil. It has also been found in other outcrops of the Rysedorph
Hill conglomerate (see below), and in association with Christiania
trentonensis and Tretaspis reticulata has been traced into Virginia
(Bassler, ’09) and Alabama (Butts, ’26) and Quebec (Raymond,
’13). The formation in which they occur is the Chambersburg
limestone, a thick formation that comprises the uppermost division of
the Chazy (the Blount), and the Black River group of New York
(including the Lowville, Watertown and Amsterdam limestones). It

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NEW YORK STATE MUSEUM

is therefore, from the general aspect of the fauna, correct to corre-
late these black pebbles with the Black River group, probably more
especially the upper part, the Watertown or Amsterdam limestones.

6 Reddish gray compact limestone

These pebbles are composed of very hard, compact, fine-grained,
dark gray limestone, that weathers into a reddish gray rock. It is
most remarkable for its ostracods, which are the most common fos-
sils, appearing with their tiny, black, glossy shells in wonderful dis-
tinctness. Besides these some trilobites of the rare genera Ampyx
and Remopleurides also were found in these pebbles. The fauna

is the following:

Brachiopods: Rafinesquina alternata ( Conrad ) r

Dalmanella testudinaria ( Dalman ) r

Triplecia nucleus Hall r

Protozyga exigua Hall c

Gastropods: Carinaropsis carinata Hall r

Trilobites: Gerasaphes ulrichana Clarke rr

Ampyx hastatus Rued r

Remopleurides linguatus Rued r

R. tumidulus Rued rr

PterygOmetopus callicephalus {Green) r

Ostracods: Leperditia resplendens Rued c

Isochilina armata Walcott var. pygmaea Rued... r
Schinidtella crassimarginata Ulrich, var. ventrila-

biata Rued cc

Eurychilina reticulata Ulrich c

E. bulbifera Rued c

E ( ?) solida Rued rr

E. subradiata Ulrich var. rensselaerica Rued c

Bythocypris cylindrica {Hall) cc

The pebbles of this group are by their fauna and lithologic transi-
tion in some pebbles closely connected with those of the next group.

7 Gray crystalline limestone, which often changes into a veritable
shell rock. This is by far the most common group of pebbles on
Rysedorph Hill. Most of the pebbles are made up of shells of
Plectambonites sericea and Rafinesquina alternata or parts of the

trilobite Isotelus gigas. The fauna is the following:

Bryozoans: Prasopora simulatrix Ulrich var. orientalis Ulrich, r

Brachiopods: Rafinesquina alternata {Conrad) cc

R. deltoidea {Conrad) r

Leptaena rhomboidalis Wilckens r

GEOLOGY OF THE CAPITAL DISTRICT 109

Plectambonites ruedemanni Raymond cc

(in original list cited as P. sericeus jasper
James )

P. pisum Rued r

Triplecia nucleus Hall c

Orthis tricenaria Conrad c

Plectorthis plicatella Hall c

Dalmanella testudinaria ( Dalman ) c

D. subaequata Conrad var. pervetus Conrad c

Dinorthis pectinella ( Emmons ) r

Parastrophia hemiplicata Hall r

Protozyga exigua Hall c

Zygospira recurvirostris Hall c

Pelecypods: Modiolopsis cf. aviculoides Hall r

Gastropods: Conradella compressa Conrad r

Carinaropsis carinata Hall c

Lophospira bicincta ( Hall ) c

L. perangulata (Hall) c

Liospira subtilistriata (Hall) cc

Clathrospira subconica Hall c

Trochonema umbilicatum (Hall) c

Cyrtospira attenuata Rued rr

Hyolithids: Hyolithus rhine Rued rr

Cephalopods: Cyrtoceras subannulatum Hall rr

Spyroceras bilineatum (Hall) rr

S. cf. annellus (Conrad) r

Trilobites: Remopleurides linguatus Rued rr

Isotelus maximus Locke cc

Illaenus americanus Billings c

Thaleops ovata Conrad r

Pterygometopus eboraceus Clarke r

P. callicephalus (Hall) c

Dalmanites achates Billings c

Ceraurus pleurexanthemus Green c

Ostracods: Leperditia fabulites Conrad c

L. resplendens Rued cc

Eurychilina bulbifera Rued r

E. obliqua Rued rr

E. subradiata Ulrich var. rensselaerica Rued c

E. dianthus Rued c

Primitia mundula Miller var. jonesi Rued r

NEW YORK STATE MUSEUM

Bollia cornucopiae Rued rr

Macronotella ulrichi Rued c

M. fragaria Rued rr

Bythocypris cylindrica (Hall) c

The pebble groups 6 and 7 belong to adjoining beds and their
faunas have also the principal forms in common. This is the most
common and principal fauna of the Rysedorph conglomerate. It is
a lower Trenton fauna. As this is the youngest fauna obtained in
the Rysedorph conglomerate, the latter must be of younger than
lower Trenton age.

The Rysedorph conglomerate is exposed in a number of other
localities in the capital district. It appears in a five-foot bed at the
upper falls in a ravine just east of Papskanee island and thence
south in a series of outcrops on top of the Van Denburg ridge.
Another interesting outcrop is on Papskanee island on the shore of
the Hudson river. Here it forms a hill and cliff on the river bank,
on which the clubhouse of the Papskanee Boat Club stands. The
writer has picked up there Ordovician brachiopods, as Plectambonites
scriceus, alongside of recent fresh water gastropods at the edge of
the water. An excellent exposure of the conglomerate is seen in the
big cut of the Boston and Albany Railroad on the hillside south of
Rensselaer. Here it is involved with Normanskill shale, grit and
chert.

A fine series of outcrops of the Rysedorph conglomerate is ex-
posed in the lower Moordener kill near Castleton. Dale (’04, p. 34)
describes five different outcrops of conglomerate from the Moor-
dener kill from Prindle’s observations, the fifth being 50 feet thick,
and the third 12 feet thick.

We consider all these outcrops as belonging to the same bed,
repeated by folding and doubled in places upon itself. The matrix
and pebbles, as well as the fossils, are the same in all outcrops. The
first outcrop is below the lower falls, about 200 feet upstream from
an outcrop with Normanskill graptolites.

Another conglomerate bed, five feet thick, forms the top of the
lower falls, containing boulders two feet in diameter (composed of
the brownish sandy calcareous matrix of the Rysedorph conglomerate
and squeezed off the main body). The conglomerate here contains
also white and brown quartz pebbles and black chert pebbles. Two
hundred paces farther up the conglomerate appears again, 12 feet
thick, another is below the upper falls and 500 feet above the upper
falls is a fifth outcrop. The conglomerate is here folded in with

GEOLOGY OF THE CAPITAL DISTRICT

III

Normanskill shale, grit beds and white-weathering chert beds com-
posed of alternating limestone (one inch thick) and shale, suggesting
Deep Kill. At the lower falls the conglomerate is part of an over-
turned anticline.

Also farther up the Moordener kill, half a mile above the Schodack
depot, is an outcrop of a breccia or conglomerate containing pebbles
of black chert and limestone with crinoid stems and bryozoans. This
conglomerate is closely associated with Normanskill grit.

Two further outcrops of brecciated conglomerate are found in the
Vlockie kill, the next creek south of the Moordener kill, one of these
six and one-half feet thick, and both closely associated with the
black white-weathering Normanskill chert and black Normanskill
graptolite shale.

The Moordener kill conglomerate (see Ruedemann, ’oi, p. 544)
contains Lowville limestone boulders with “bird’s-eyes” ( Phytopsis
tubulosa) and Tctradimn cellulosum, and still larger boulders (two
and one-half feet in diameter) of dark gray Trenton limestone. The

latter contained (Ruedemann, ’01) :

Streptelasma corniculum Hall r

Callopora cf. ampla Ulrich c

Plectambonites ruedemanni Raymond cc

Strophomena incurvata ( Shepard ) c

Rhynchotrema increbescens Hall r

Conradella compressa {Hall) r

Pterygometopus callicephalus Hall r

Isotelus cf. gigas Dekay c

Macronotella ulrichi Rued r

Bollia sp.

Also pebbles of dull black, very fine-grained limestone were found

which contained (Ruedemann, ’01) :

Callopora ampla Ulrich c

C. multitabulata Ulrich c

Dalmanella testudinaria ( Dalman ) c

Platystrophia biforata ( Schlothcim ) c

Plectambonites pisum Rued cc

Christiania trentonensis Rued r

Eccyliopterus sp. nov r

Ceraurus pleurexanthemus Hall
Conularia trentonensis Hall

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NEW YORK STATE MUSEUM

This black limestone is quite obviously identical with that of
Rysedorph Hill containing the Black River — Chambersburg fauna.

An interesting feature of the Moordener conglomerate is that it
furnishes a number of fossils in the matrix, namely : Pachydictya
sp., Stromato cerium sp., Rafinesquina alternata, Strophomena incur-
vata, Plectambonites ruedemanni , P. pisum, Pterygometopus calli-
cephalus. An outcrop south of the capital district, back of the vil-
lage inn at Schodack Landing, has also afforded fossils in the matrix,
namely: Strcptelasma corniculum, Plectambonites ruedemanni, P.
pisum and Ortliis triccnaria. The matrix in the Rysedorph cliff,
which is more sandy than in the outcrops farther south, contains only
comminuted fragments of Rafinesquina Plectambonites etc. Even
if we assume that some of these fossils were broken off pebbles,
the number and preservation of those at the Moordener kill mark
them as probable elements of the fauna of the matrix.

Northward of Rysedorph hill the conglomerate is very little ex-
posed. An excellent exposure was, however, found as far north as
Bald mountain, northeast of Schuylerville, where it forms the north-
ern point of the wedge of Bald Mountain limestone, and lies between
the Snake Hill shale and Lower Cambrian, separated from both by
overthrust planes. Several geologists whom I took to this outcrop,
declared it to be a breccia and not a conglomerate. The blocks are
indeed very angular, suggesting a crush breccia of one kind of rock
to these visitors. More careful search by the writer (’14, p. 80), has
furnished, however, a variety of pebbles from Lower Cambrian to
Trenton age and the following fossils:

Lingula sp.

Siphonotreta cf. minnesotensis Hall & Clarke.

Rafinesquina sp.

Plectambonites pisum Rued.

Ceraurus cf. pleurexanthemus Green

Bythocypris cylindrica (Hall).

Isochilina armata Walcott var. pygmaea Rued.

The matrix has also furnished specimens of Plectambonites pisum.
There is, from the facts here given, no doubt in our mind that at
this northern locality, there is an outcrop of the Rysedorph con-
glomerate.

The origin of this strange rock has been the subject of animated
discussion, whenever it has been studied by geologists. The writer
(’01, p. 109) has fully discussed the earlier views and will here but

GEOLOGY OF THE CAPITAL DISTRICT 113

briefly mention them. Walcott, in his well known paper on intra-
formational conglomerates (’93, p. 191 ), suggested that the sea bed
was raised in ridges or domes above the sea-level, and thus subjected
to the action of seashore ice, and the aerial agents of erosion. It
was the writer’s opinion that the erosion of anticlinal ridges would
be best suited to furnish the variety of materials of different ages,
such as is found in the Rysedorph conglomerate. Others have sug-
gested flood-plain deposits and others glacial beds or sea-ice trans-
portation. To the writer, the presence of fossils in the calcareous
matrix is of decisive importance in proving the submarine origin
of the conglomerate either along a shore swept by currents of an
advancing sea that deposited the coarse material derived from prom-
ontories and rivers, or on the flanks of an anticline that was being
eroded. The extension of the conglomerate in a north-south direc-
tion, as well as the crude assortment of the material, shown by strings
of pebbles, especially on Rysedorph Hill, and the fact that in some
places the pebbles are still angular and appear to belong to a con-
tinuous bed broken up and at once recemented, all these observa-
tions suggest the deposition of the bed in the sea and the derivation
of the material from exposures along an anticline. There are certain
features in the conglomerate which suggest to us a derivation of
much of the material of the pebbles from rocks outcropping farther
north. These are especially the rare Chazy and the more common
pebbles of typical Lowville limestone. There is no Lowville lime-
stone known in the East at all, and west of the Rysedorph conglomer-
ate not until the upper Mohawk valley is reached.

In the first paper (’01) dealing with this conglomerate, we placed
it within the Normanskill shale, seeing in the Trenton fauna of the
conglomerate evidence of the Trenton age of the Normanskill shale.
With the recognition of the fact that the typical Normanskill shale is
older than the Trenton, it became necessary to assume that the
Rysedorph conglomerate either is intercalated in the upper division
of the Normanskill (Magog shale) of Black River and perhaps
earliest Trenton age or rests entirely on the series. The relative
position of the conglomerate to the shales gives no indication of its
age, except that, as at the Moordener kill, it is undoubtedly inter-
folded with Normanskill shale, which yet must be considerably older.
We are now placing the Rysedorph conglomerate at the top of the
whole Normanskill shale and below the Snake Hill shale, correlating
it with the lower Trenton.

26 The Poestenkill fault breccia. A rock that is similar to the
Rysedorph conglomerate and that occurs in the same region is the

NEW YORK STATE MUSEUM

1 14

fault breccia found below the plane of the great overthrust separat-
ing the overlying Cambrian from the subjacent Ordovician. This
fault breccia has been very fully described by the writer (’12, p. 83)
from the Schuylerville quadrangle, where it is splendidly shown in
the quarries at Bald mountain, resting upon the Bald mountain lime-
stone. It reaches there 30 feet in thickness in one place and is
composed of black soft mud, carrying a variety of small pebbles.
It is a typical mylonite, that is, a rock produced by the grinding up
of rocks (mostly shales in this case), along the fault plane. Where
great masses of Trenton limestone have been worked into the
mylonite, it becomes similar to the Rysedorph conglomerate and
may even contain fossils. As an illustration of this we have drawn
in the diagram of the Bald mountain quarry (’12) accompanying
the geologic map of the Saratoga-Schuylerville quadrangles, a large
block in the quarry as Rysedorph conglomerate which later turned
out to be composed of mylonite.

The capital district furnishes excellent exposures of the fault
breccia on the campus of the Rensselaer Polytechnic Institute (figure
64), where it is exposed in a small cliff back of the fence close to
the north side entrance on Sage avenue, and especially in the ravine <(
of the Poestenkill below the fall, as well as along Congress street,
Troy, below Ida Park. The fault breccia on the campus is overlain
by green Lower Cambrian slate and underlain by gray and black
Snake Hill shale, showing in a road metal pit on the other side of
the street. The breccia, a coarse mylonite, is largely composed of
black Normanskill chert, Normanskill grit and Bald mountain lime-
stone. It will be noted that the composition of this fault breccia is
entirely different from that of the Rysedorph conglomerate. The
breccia at Congress street is almost entirely composed of Normans-
kill grit, some boulders showing fine “mud-flow” structure and many
well-rounded by strong abrasion. The outcrop in the bed of the
Poestenkill (figures 26, 62 and 63), after which we name the rock, is
the most instructive. It is 150 feet wide, largely composed of Nor-
manskill grit, some of the blocks being ten feet in diameter and
mostly well rounded. It rests on Normanskill grit and is overlain
by Lower Cambrian green slate.

The principal difference between the Rysedorph conglomerate and
the Poestenkill fault breccia is that the former is composed of rocks
foreign to the capital district while the Poestenkill fault breccia con-
sists of the rocks of the immediately adjoining formations, mostly
the Lower Cambrian and Normanskill. Furthermore, the Rysedorph
conglomerate appears to be continuous over a large area and of

GEOLOGY OF THE CAPITAL DISTRICT 115

fairly uniform thickness, while the Poestenkill fault breccia is prob-
ably discontinuous and of very irregular thickness, swelling up
locally, as at the Poestenkill and disappearing in other places.

It has lately been pointed out by Cornelius (’27) that polymikt
tectonic breccias never have any large extension, and this quite
clearly also is true of the Poestenkill fault breccia. Although the
fault itself may pass through a very large area and be of great length,
the breccia has accumulated only in certain favorable localities, while
in others the contact is free of all brecciated and ground-up material.

27 Tackawasick limestone and shale. Along the southern edge
of the Rensselaer grit in the capital district there appears a narrow
belt of calcareous shale with Trenton fossils. This belt appears
entirely out of place both in its location as well as in its character.
It is situated between Lower Cambrian shale on one side and Rens-
selaer grit on the other and it is a limestone where all other forma-
tions are represented mainly by shales and quartzites (figure 7).

W E

Figure 7 Diagram section by Dale (U. S. Geol. Surv. Bui. 2 '2'' across the
western edge of the Rensselaer plateau and the second ridge east of
Tackawasick pond, in Nassau, showing the surface relations and the
probable structural relations of the Lower Cambrian quartzite and shale
(Cl), the Tackawasick limestone (Ot) and the Rensselaer grit (Dr).
Dotted beds (Cl), quartzite; lined beds red and green shale with small
quartzite beds

We are aware of only three outcrops of this formation in the
capital district. The principal one is one-half of a mile east of the
north end of Tackawasick pond, on top of the ridge paralleling the
road on the east. An old quarry marks the outcrop. The Trenton
outcrop, altogether 70 feet wide, with an easterly dip of 50°-55°,
consists of thin-bedded shaly gray limestone, the beds about one inch
thick with interbedded one-fourth inch dolomitic layers, and some
20 feet of interbedded greenish argillite. There is also a limestone
bed two to three feet thick. Toward the east is a swampy and

Il6 NEW YORK STATE MUSEUM

wooded land and the contact with the Rensselaer grit is not shown,
nor is a direct contact observable with the greenish gray and red
Cambrian shale which, however, is close by on the west. There is
another smaller outcrop three-quarters of a mile farther north,
one south of Pike hill, and similar gray calcareous shale is seen also
farther south.

Dale (’90, p. 311), in his excellent paper on the Rensselaer Grit
Plateau in New York, has carefully described these occurrences of
Trenton limestone. He reports that Dr A. F. Foerste in 1890 found
Trenton fossils at the locality south of Hoags Corners (east of
Tackawasick pond), on what is known as the Coonradt farm,
namely: “Monticulipora (under old interpretation Lycoperdon), a
Murchisonia, a Calymene, an Orthis of O. plicatella type, and
crinoid stems.” The writer could find only the Monticulipora, which
is not rare and the crinoid stems. The bryozoan has been deter-
mined by Doctor Ulrich as a Prasopora suggesting Eden age.

Dale concluded that the disconnected occurrences of the limestone
are “parts of a narrow limestone belt, anticlinal in structure, under-
lying the grit and belonging either to the upper part of the Stock-
bridge limestone, and thus of Trenton age, or else belonging to the
Berkshire schist horizon, and then of Hudson River age.” In his
later publication (’09, p. 35) he connects this belt with the outcrops
of limestone about Chatham (on the next quadrangle south of the
Troy quadrangle, that is, the Kinderhook quadrangle) from which
Bishop (’86 and ’90) and Foerste have reported the occurrence of
Trenton fossils.

The belt of Trenton limestone in the capital district has no con-
nection whatever with the other Trenton rocks of the belt, either
the Rysedorph conglomerate or the Snake Hill beds (see p. 130). It
is entirely isolated, as is well brought out by the diagram, furnished
by Dale and Prindle. In the south, however, it connects with the
“Hudson schist,” a broad belt of metamorphosed shales and grits,
possibly of Normanskill and Snake Hill ages. Likewise the Trenton
area north of Chatham is connected eastward with the Hudson
schist, and separated westward by the Lower Cambrian rocks from
the Normanskill and other Ordovician rocks.

It is likewise worth noting that the gray limestone of this belt is
not clearly recognizable as a constituent of the Rysedorph con-
glomerate ; we believe, because it is younger than the Rysedorph
conglomerate. Nor is it clearly referable to the Stockbridge lime-
stone, although by its connection with the Hudson schist it might
seem to have relation to it, for the Stockbridge limestone is not only

GEOLOGY OF THE CAPITAL DISTRICT

II 7

a thicker formation, but also undoubtedly older and rather to be
correlated with the Bald Mountain limestone.

There are, however, outcrops of thin belts of similar limestone,
farther south, as James O. Kimball (’90) finds such thin belts of
limestone intercalated with argillaceous shales and continuous with
calcareous grits overlying conformably the “Hudson River shales”
at Burden, Columbia county, and they may continue intermittently
as far as the Poughkeepsie quadrangle.

We propose to term this isolated limestone formation of Trenton
age the “Tackawasick limestone and shale,” to make it amenable to
correlation and discussion as a unit.

28 Snake Hill beds. This formation was first distinguished by
the writer from the “Hudson River formation” in the neighborhood
of Albany (’01) and referred to partly as middle Trenton shale and
partly as Utica shale and later correlated with the Magog shale of
Canada. Mainly on account of the large and distinctive faunas
obtained around Albany, Green Island and Cohoes (figure 67), and
especially at Snake hill on the shore of Saratoga lake, these beds
have more recently (’12) been considered as a separate formation
by the writer and named the “Snake Hill beds” from the most fos-
siliferous outcrop.

Lithologically, the formation is similar to the Normanskill beds
but it lacks the strong development of the grits and white- weathering
chert beds as distinct divisions, although both are present in thinner
intercalations. Besides, it possesses a conglomerate with characters
peculiar to itself. The preponderating portions of the formation,
however, are dark gray to black, bluish and greenish gray argillaceous
shales which are difficult of separation from the Normanskill shales,
save by the inclosed faunas.

The argillaceous shales prevail so much in the Snake Hill forma-
tion that we have not observed in the capital district any thick grit
beds.

Black, carbonaceous, graptolitiferous bands or seams are more fre-
quently found than in the Normanskill shale, but they contain a much
impoverished graptolite fauna as compared with that of the Nor-
manskill formation. On the other hand, small lamellibranchs,
gastropods, brachiopods and trilobites are frequently seen in the
shale, while but only traces of such have been observed as yet in the
Normanskill shale of New York.

The dark shales not infrequently contain thin, sandy bands and
still oftener intercalations of sandy limestones and also gray crystal-

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NEW YORK STATE MUSEUM

line limestone, reaching half a foot in thickness. These bands fre-
quently contain a faunule of brachiopods, crinoid joints etc., and they
have furnished the great number of fossils, other than graptolites,
recorded by the writer in New York State Museum Bulletin 42.
Frequently concretions of both limestone and clay are found scattered
or more or less obscurely arranged in layers. Lines of such project-
ing concretions are well seen traversing the gorge at Cohoes.

Owing to the extreme pliability of the argillaceous shales and the
lack of strengthening intercalations of grits etc., the Snake Hill beds
are, as a rule, intricately contorted and crumpled and cut by cleavage
planes and smoothed slip planes until they have the character of the
shales which were termed by the geologists of the first survey
“glazed” and “semimetamorphic” shales. These shales so designated
were Snake Hill shales of the Hudson valley.

There seems to be a gradual change in lithologic characters south-
ward from the Saratoga and Schuylerville quadrangles, whence the
formation was first fully described. It is obvious that also in the
capital district the bluish gray, argillaceous, often sandy and slightly
micaceous shales greatly prevail. Still occasional grit beds, several
feet thick are seen, but more characteristic of the formation are thin
(two to three inches thick) layers of cross-bedded reddish and pink
micaceous sandstones, that weather yellow and are sometimes associ-
ated with rusty-weathering shale. These beds are especially seen in
the uppermost division of the thick formation south of Ballston. On
the surface the grit beds are most liable to appear, because of their
greater resistance, although but widely scattered in the shales.

The thickness of the formation is obviously great. As it is much
folded and crumpled almost throughout the belt, it is hard to get
estimates. There is, however, a continuous outcrop of Snake Hill
shales exposed along Anthony kill from the little hamlet of East Line
to Round lake. The distance is three miles and the dip ii° E.
200 S. Disregarding the slight divergence of the section from the
dip direction and the grade of the creek (only 60 feet in the whole
distance), the thickness of the section appears to be above 3000 feet.
Extending this rate of thickness to the whole width, we would obtain
a still greater thickness, but it is obvious that the folded portion
east of the section should be discounted. There remains still another
mile from East Line to the Schenectady beds, which may add another
1000 feet. We therefore consider 3000 as a minimum measurement.

The Snake Hill shales form the broad belt of shales between the
Normanskill and Wappinger limestone at the Hudson river bank and

GEOLOGY OF THE CAPITAL DISTRICT Iig

the Skunnemunk mountains, a fact which in itself already indicates
a considerable thickness. Ries (’95, p. 401), and more recently
Holzwasser (’26, p. 65), have computed a thickness of 1500 to 2000
feet for these shales in Orange county, mainly by comparison with
the Trenton limestone. Although the belt is much folded, we con-
sider this a minimum figure in view of the width of the belt, which
is over 20 miles.

The fauna of the Snake Hill beds is a fairly large one, and the beds
have afforded a number of strange fossils not found elsewhere. The
principal localities that have furnished fossils north of the capital
district are : Snake hill on the east shore of Saratoga Lake and the
shales along the shore, especially north of Snake hill (Ruedemann,
’14, p. 96f¥). In the capital district are a number of localities that
at times have afforded excellent opportunities for collecting, but are
not any more accessible. Others still available are the following:
Waterford (Ruedemann, ’01, p. 514) ; Block Island, Cohoes {ibid,
p. 516) ; Hudson Light and Power Co., two miles below Mechanic-
ville {ibid, p. 519) ; North shore of Green Island {ibid, p. 525) ;
East shore of Green Island {ibid, p. 526) ; Railroad cut at Menands
{ibid, p. 527) ; Black rock cut on New York Central at North Albany
(Beecher, ’89, p. 502) ; Foundations for penitentiary, Albany (Ruede-
mann, ’01, p. 530) ; Watervliet arsenal (Whitfield, ’75) ; Fitzgerald’s
quarry, Port Schuyler (Ruedemann, ’01, p. 534) ; Brothers quarry,
South Troy, {ibid, p. 536). The writer was also able to collect very
fine material when the ground was graded for the Delaware and Hud-
son shops at Colonie, south of Watervliet and for the felt mill in
North Albany. Such temporary collecting fields may be opened at
any time by building operations in the neighborhood of Albany.

The combined list of fossils obtained at these localities with the
identifications brought up to date is as follows :

Graptolitcs: Dicranograptus nicholsoni Hopkinson

Corynoides gracilis Hopkinson
C. calicularis Nicholson

C. curtus comma Rued.

Diplograptus (Glyptograptus) amplexicaulis {Hall)

D. amplexicaulis var. pertenuis Rued.

Climacograptus typicalis Hall
C. spiniferus Rued.

C. caudatus Lapworth
C. strictus Rued, (putillus auct .)

Cryptograptus tricornis insectiformis Rued.

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NEW YORK STATE MUSEUM

Cystoids:

Machaeridia:

Crinoids:

Worms:

Bryosoans:

Brachiopods:

Pclecypods:

Lasiograptus eucharis (Hall)

Glossograptus quadrimucronatus mut. pertenuis Rued
Dawsonia campanulata Nicholson
Edrioaster saratogensis Rued.

Lepidocoleus jamesi Hall & Whitfield
Turrilepas (?) filosus Rued.

(Pollicipes) siluricus Rued.

Glyptocrinus sp. cf. decadactylus Hall, (joints)
Heterocrinus ( ?) gracilis Hall
Cremacrinus sp.

Carabocrinus cf. radiatus Billings (plates)
cf. Schizocrinus nodosus Hall (joints)
Pontobdellopsis cometa Rued.

Serpulites magnus Rued. (’16, p. 88)

Paleschara ulrichi Rued.

Pachydictya acuta Hall
Prasopora sp.

Escharopora cf. angularis Ulrich
Leptobolus cf. insignis Hall
Lingula curta Conrad
Trematis terminalis ( Emmons )

T. punctostriata Hall var. minor Rued. (’19, p. 103)
Schizambon albaniensis Rued. (’19, p. 105)

Pholidops sp. aff. subtruncata Hall
Schizocrania filosa (Hall)

Plectorthis cf. whitfieldi (Winchell)

P. plicatella Hall (probably var. trentonensis Foerste)
Dalmanella rogata Sardeson
Plectambonites sericeus (Sowerby)

Rafinesquina alternata (Emmons)

R. deltoidea (Conrad)

Plaesiomys retrorsa auct.

Clitambonites americanus (Whitfield)

Rhynchotrema increbescens (Hall)

Platystrophia sp.

Parastrophia hemiplicata Hall
Triplecia nucleus (Hall)

Zygospira recurvirostris (Hall)

Colpomya faba (Emmons)

Clionychia undata (Emmons)

Whiteavesia cincta Rued.

W. cumingsi Rued.

GEOLOGY OF THE CAPITAL DISTRICT

121

Gastropods:

Pteropods
{ supposed ) :
Cephalopods:

Crustaceans
( mostly trilo-
bites and
ostracods) :

Orthodesma ? subcarinatum Rued.
Whitella elongata Rued.

Clidophorus ventricosus Rued.

C. foerstei Rued.

Ctenodonta levata {Hall)

C. declivis Rued.

C. prosseri Rued.

C. recta Rued.

C. radiata Rued.

C. subcuneata Rued.

Lyrodesma schucherti Rued.

Solenomya ? insperata Rued.

Cuneamya acutifrons Ulrich
Archinacella orbiculata {Hall)

A. patelliformis {Hall)

Sinuites cancellatus {Hall)

Tetranota bidorsata {Hall)

Kokenospira rara Rued. (’19, p. 106)
Cyrtolites cf. retrorsus Ulrich & Schofield
Cyclonema montrealense Billings
C. cushingi Rued.

Clathrospira subconica Hall
Liospira americana Billings
(Pleurotomaria lenticularis auct.)
Lophospira bicincta {Hall)

L. uniangulata Hall var. abbreviata Hall
Cyclora cf. minuta Hall
Cyclospira bisulcata {Emmons)

Pterotheca cf. canaliculata {Hall)

Conularia trentonensis Hall
Spyroceras bilineatum {Hall)

S. subannulatum {D’Orbigny)

Endoceras proteiforme Hall
Eoharpes ottawaensis Billings
Trinucleus concentricus {Eaton)
Cryptolithus tesselatus Green
Proetus undulostriatus {Hall)

Calymmene senaria Conrad
Bronteus sp. nov.

Isotelus gigas Dekay

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NEW YORK STATE MUSEUM

Pterygometopus callicephalus (Hall)

Ceratocephala (Acidaspis) trentonensis Hall
Ctenobolbina ciliata ( Emmons )

C. ciliata var. cornuta Rued.

C. subrotunda Rued.

Technophorus cancellatus Rued.

No one seeing the great masses of barren shales of the Snake
Hill beds would expect to find a fauna of almost a hundred species
in them. It is true that, aside from the graptolites which are more
widely distributed, the fossils are mostly found only in restricted
layers or in small areas or “nests.” It is further notable that the
fauna consists everywhere of small forms, or small individuals of
larger species. It is a pronounced “microfauna” like that of the
Utica shale, and the cause of this is quite clearly to be sought in
the unfavorable conditions produced by the rapid deposition in a
relatively narrow basin of great quantities of mud, argillaceous and
sandy. Under these conditions it is no wonder that this fauna, right
under the feet of the most active geologic state survey of the United
states remained practically unnoticed for 70 years.

The most common graptolites are Dicranograptus nicholsoni,
Diplograptus ample xicaulis and its variety pertenuis, Climacograptus
spiniferus and the species of Corynoidcs. It is, however, to be noted
that few of these are found associated, but practically each is in
certain localities present to the exclusion of others. Thus Dicrano-
graptus nicholsoni is extremely common north of Snake hill, Diplo-
graptus amplcxicaulis var. pertenuis was found in great number at
the site of the Watervliet arsenal, G lossograptus quadrimucronatus
pertenuis on Van Schaick island, Corynoidcs curtus comma at
Mechanicville, etc.

The Snake hill beds have in common with the Canajoharie shale
the occurrence of Diplograptus amplcxicaulis and Corynoides cali-
cularis, but otherwise bear in both the graptolite and nongraptolitic
biota a more distinctly easterly, Atlantic aspect. Here belong the
shale on Van Schaick island with Cryptograptus tricornis insecti-
formis and the shale of Mechanicville with Climacograptus caudatus
and Corynoidcs curtus comma. There is no doubt in our mind that
these occurrences represent a zone that is older than any of the
Canajoharie shale zones and that is equivalent or directly follows
upon the shale exposed at Magog, for Climacograptus caudatus is
found in Sweden only in the lowest of the three subzones of Dicran-o-
graptus clingani and it is also in Great Britain restricted to the zone

GEOLOGY OF THE CAPITAL DISTRICT

123

of Dicranograptus clingani. Not only do Climacograplus caudatus
and Cryptograptus tricornis insectiformis indicate a low horizon and
nearness to the Normanskill horizons, but also the outcrops where
these fossils occur are close to the Normanskill belt. We have dis-
tinguished this earlier zone of the Snake Hill beds as the zone of
Cryptograptus tricornis insectiformis and Climacograptus caudatus
(Ruedemann, ’19, p. 124).

In the large nongraptolitic portion of the fauna, the brachiopods,
especially Dalmanella rogata and Plectambonites sericeus, and the
pelecypods are the most commonly found. As the list shows, a large
proportion of the pelecypods proved to be new species.

The fauna is undoubtedly a Trenton one and proves the early
Trenton age of the Snake Hill beds (Ruedemann, ’14, p. 99). It
roughly corresponds to the lower, and perhaps part of the middle
Trenton. It contains, however, a large independent biota of its own.
The writer has described 26 new forms from this fauna ; three others
( Archinacella orbiculata, Proetus undulostriatus and Triarthrus
becki ) are also restricted to or peculiar to this formation. The well-
known fossil Triarthrus becki, which is currently credited to the
Utica shale, was described by Green in 1832 from the “glazed
shales” at Waterford, and is restricted to the Snake Hill and Cana-
joharie beds. The Utica form is the Triarthrus eatoni Hall. Be-
sides, it has furnished such unique fossils as : (Pollicipes) siluricus,
Edrioaster saratogensis, Kokcnospira rara, Eoharpcs ottawaensis,
Bronteus sp. nov., and Technophorus cancellatus. This strange
aspect of the Trenton fauna, quite different from that of the Trenton
limestone, is undoubtedly due partly to the different facies and partly
to the different marine connections, the Snake Hill fauna having
lived in the Levis trough (see p. 163) that was more or less separated
from the interior Trenton sea.

The possible occurrence of a thin shale intercalation with a Cana-
joharie shale fauna in the Snake Hill beds has been dealt with on
page 31.

29 Rensselaer grit (figures 68-70). The only post-Ordovician
formation that is found in the capital district resting upon the deposits
of the eastern trough is the Rensselaer grit. Only the western margin,
about two and one-half miles wide, of the Rensselaer grit area, that
reaches a width of nine miles, extends into the capital district.

The Rensselaer grit has been fully described by T. Nelson Dale in
1893 in his paper on The Rensselaer Grit Plateau in New York, and
again in 1904 (Dale, p. 39). Dale also proposed the name Rensselaer
grit (’93) for the formation.

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NEW YORK STATE MUSEUM

Since the Rensselaer grit plateau with its sharp escarpment on the
west and north sides is a striking topographic feature and the ex-
tremely hard grit projects everywhere in cliffs on the hilltops, the
rock formation was early noted. Eaton (’30, p. 73) noticed this
great mass, called it “the greywacke of Rensselaer” and stated :
“This coarse grey rock forms the basis of more than half the county.
It is perfectly insulated, and lies upon the argillite like a huge turtle
upon the beach ; its back forming the middle and elevated part of the
county.” It appears from Eaton’s further notes that he considered
this mass as resting unconformably on the “argillite” (shales).
Mather (’43, p. 384) stated later, however, that while it appeared
from Eaton’s statements that the graywacke of Rensselaer was
“superimposed on the slate rocks unconformably his inference is,
“It may be so situated, but I have seen no evidence that would lead
to that conclusion.” Also, other authors failed to separate this great
mass that Eaton had recognized. Emmons (’43, ’55) included it in
his Taconic formation; Logan and Hall placed it in the “Quebec
group,” and Walcott in the Lower Cambrian or Georgian (’88, pi.
III).

It was Dale (’93) who clearly recognized that the mass of Rens-
selaer grit rests uncomformably in the east on Berkshire schist and
in the west on “Hudson River shale and limestone” and Cambrian
rocks, the terrane forming a broad, much folded syncline.

As contacts between the Rensselaer grit and the subjacent forma-
tions are hard to observe, owing to the fact that they are usually
buried under the talus slope, Dale (’04, p. 41) has carefully described
two contacts, both in the capital district. One of these is a half
mile north of Hoag Corners, in Nassau, about 400 feet east of the
road to Alps. Here the red and green shale and Rensselaer grit
are separated by an interval of only 150 feet from the typical red
Cambrian shale with small quartzites. The other contact is in the
town of Brunswick, where the road from Eagle Mills toward Davitt
pond crosses the geologic boundary. Here a direct contact is ob-
servable, with a one-foot bed of roundish quartz grains in a cement
of chlorite on the boundary.

Dale (’04, p. 43) describes the formation as being about 1400 feet
thick and consisting of “dark green metamorphic grit with inter-
bedded reddish and greenish shale or slate and conglomerate, con-
taining pebbles of quartzite, marble, black silicious shale, grit, phyllite,
all of Lower Cambrian age, some of them possibly of Ordovician
age; also pebbles of gneiss and granite of pre-Cambrian origin.” To

GEOLOGY OF THE CAPITAL DISTRICT

125

this may be added the following petrographic notes by the same
author (Dale, ’04, p. 39) :

Its petrographic characteristics, in brief, are as follows : A dark
green, tough, generally thick-bedded, often calcareous, crystalline,
granular rock, with visible quartz and feldspar grains, and traversed
by veins of quartz, in places of epidote and calcite. This rock alter-
nates with beds of purplish, reddish or greenish slate or shale. . . .
In some places the grit contains beds of conglomerate up to four
feet in thickness, with pebbles of quartz, orthoclase, plagioclase,
microcline, granitoid gneiss or granite (with the same feldspars), fine
grained gneiss, and rarely chloritized diabase or gabbro, together
with pebbles of the following sedimentary rocks : Quartzite (white,
black or red), greenish phyllite, siliceous shale and fine grit ....
granular and crystalline limestone, and cryptocrystalline quartz . . .
the diameter of these pebbles does not usually exceed an inch, but
the quartzite sometimes attains two inches, the limestone four, and
the gneiss in one case measured 12 by 8 by 3.1

We have little to add to this excellent description. There are
several belts of red and green shale or slate exposed in the capital
district, some reaching a thickness of almost 50 feet. The red slate
is well exposed in the Foestenkill fall at Barberville, as well as along
the north trending road just east of Davitt pond. It also appears in
a road metal pit by the side of the state road at Quackenkill. A dull
purple slate in this locality is, or has been used for making paint.
The conglomerate, with its greenish groundmass and partly rounded,
partly angular pebbles of reddish brown, purplish and white quart-
zite, cream-colored, reddish brown and deep red feldspars, forms
a beautiful “pudding-stone” (figures by Dale, ’93, pi. C). It is well
exposed in the abandoned quarry south of East Nassau, in the
southeast corner of the map, where also the red shale is well shown,
and in less prominent development on the roadside a quarter of a
mile below the hamlet of Quackenkill. The State Museum contains
a magnificent block of this rock, which on its polished surface
brings out the full beauty of the colored minerals.

The Rensselaer grit itself is shown in picturesque clififs to the
north of the Grafton road along the Quackenkill, and appears almost
everywhere in the plateau either along the roads, or as low, rounded
rocks in the fields and woods.

1 East of Quackenkill, near the road to Grafton, we also fo'und pebbles of
white-weathering Normanskill chert, up to three inches in diameter, in the
conglomerate.

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NEW YORK STATE MUSEUM

The rocks of the Rensselaer grit formation are distinctly meta-
morphosed, that is, changed considerably from their original mineral
constitution. It is especially the groundmass or cement that con-
tains minerals formed secondarily by crystallization under the in-
fluence of pressure and heat (regional metamorphism). These min-
erals are especially chlorite (giving the green color to the ground-
mass of the conglomerate), sericite, mica (muscovite), feldspar
grains, epidote, secondary quartz and calcite.

Barrell, following a suggestion by Gilbert, has considered it prob-
able that the strong metamorphism of the Taconic region is due to
injected masses of granite that have not yet been exposed by erosion.
Also the Ordovician and Cambrian rocks are strongly metamor-
phosed, south and east of the capital district, into schists (Hudson
schists and Berkshire schists).

The Rensselaer grit no doubt once covered a larger area. This
is indicated not only by its abrupt termination by erosion at the edge
of the plateau, but also by outliers, one of which is situated south-
west of the plateau at North Nassau. Others are beyond our map;
one at Austerlitz (east-northeast of Hudson) is 12 miles south of
the plateau. The origin and age of the Rensselaer grit are still in
doubt. No fossils, except faint worm-trails (Dale, ’04, p. 38) were
found in the formation. Hence its correlation is entirely a matter
01 conjecture.

Eaton thought that the eastern portion of the terrane, which he
termed the “Millstone grit and grey rubble,” might be equivalent
to the Shawang'unk grit, a suggestion that was cited and not contra-
dicted by Mather (’43, p. 382). Dale recognized that the Rensselaer
grit, resting unconformably on folded Cambrian and Ordovician
rocks, must be younger than Ordovician in age, assuming that it was
the Taconic revolution at the end of the Ordovician that folded the
rocks. Since it is itself folded, “to the post-Devonian or Carbonif-
erous movement, which folded both Devonian and Silurian beds at
Becraft mountain in Columbia county, must be assigned the folding
and the metamorphism of the Silurian grit of the Rensselaer
plateau.” He assigned the grit to the Silurian, correlating it with
the Oneida conglomerate and Medina. This important conclusion
is best stated in his own words (’04, p. 53) :

The geographical relations of the Rensselaer grit to the Silurian
formations west of the Hudson river are shown on the Lower
Hudson, the Hudson-Mohawk, and the central sheets of Merrill’s
geologic map of New York, It will be noticed that the northern edge

GEOLOGY OF THE CAPITAL DISTRICT

127

of the Rensselaer plateau is in nearly the same latitude as the bound-
ary between the Silurian (Oneida-Medina) and the Ordovician
(Hudson) in Herkimer county, and that its southern part is in line
with the southern continuation of the same boundary along the Kitta-
tinny mountain. The plateau thus lies at the apex of the angle formed
by the receding shore line of Silurian and Devonian time, as indicated
by the outcrops. The west-northwest and east-northeast strikes at the
north end of the plateau and the east-northeast one in the Hudson
shale on Mount Rafinesque are either related to the general move-
ment which resulted in the general east-west course of the boundary
between the Ordovician and Silurian across the State of New York,
or else are due to transverse folding. For all these reasons it may
be assumed that the grit mass now forming the plateau was near
the end of the Silurian bay ; but in the Taconic range, in the northern
half of Rutland county, Vt., about 57 miles north-northeast of the
northern edge of the plateau, lies another mass of grit and conglom-
erate, also containing pebbles of Cambrian quartzite and overlying
the Hudson schist, but only about 500 feet in thickness, and covering
not quite four square miles. The bay of Silurian time may thus
possibly have sent an arm up the Champlain valley.

Hartnagel (’07, p. 51), in his study of the formations of the
Skunnemunk mountain region, came to the conclusion that the
Rensselaer grit must be younger than the Oneida conglomerate and
that the sea did not cover the region “after the Green mountain
uplift until later Upper Siluric or Devonic time.” He bases his
conclusion on the following arguments : ( 1 ) The extensive gap by

nondeposition between the eastern terminus of the Oneida conglom-
erate in Herkimer county, and the Rensselaer grit plateau; (2)
the long time interval which must be postulated to account for the
Taconic folding and the erosion that preceded the deposition of the
grit; (3) the gradual transgression northward of arenaceous sedi-
ments over the eroded folds, the Shawangunk grit being a more
southerly and hence earlier representative of such transgression.
(Clarke, ’08, p. 159, from report submitted by this writer ).

In preparation of his great memoir on the Devonian of New York
and Eastern North America, Doctor Clarke became interested in
the Rensselaer grit problem, and asked the writer in 1906 to make
a cursory study of the Rensselaer grit for evidence as to its age.
The writer was as little successful in finding fossils other than worm-
trails as his predecessors in the field had been. Some supposed
plant remains turned out to be of inorganic origin. No beds younger
than the Trenton were found underlying the Rensselaer grit, nor
were there any traces of outliers found bridging the gap between the
Austerlitz outlier and Becraft mountain, the well-known Devonian

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outlier near Hudson, Columbia county. The crucial locality for
the correlation of the Rensselaer grit, however, was seen on top
of the Austerlitz outlier; for here the writer found the Rensselaer
grit on the mountain height, high above the Becraft Silurian and
Devonian outlier only nine miles away and down in the Hudson
valley, and across the river the mounting heights of the Catskills,
only 30 miles away, and composed of Upper Devonian. It is obvious
at this locality that not any of the Silurian, Lower and Middle
Devonian formations exposed in the Becraft outlier could
grade in this short distance into the thick Rensselaer grit mass, while
on the other hand, the conclusion is forced upon the viewer of the
situation, that the Rensselaer grit must have reached across and over
these buried lower formations to the Catskill formation. Doctor
Clarke published the writer’s conclusion (’09, p. 159) as follows:

The region of the Rensselaer grit has recently been carefully
searched for fossils but though this evidence still fails and its absence
can not be explained by secondary changes in the rocks, the strati-
graphic considerations indicate the propriety of assigning a distinctly
later than Medina age to this formation.

Near the edge of this plateau no beds of later than Trenton age
have been observed and there are apparently no outliers to bridge
the gap between the later Siluric and early Devonic outliers of
Becraft mountain, Mount Bob and the southernmost outliers of
Rensselaer grit in the town of Austerlitz, Columbia county. This
last-named outlier is of especial interest as it lies but 20 miles north-
east of Becraft mountain and is a considerable distance south of the
main Rensselaer grit plateau. For these reasons it has been closely
studied but found to be in no way lithologically different from the
grit of Rensselaer county at the north containing the same alterna-
tions of grit with red and greenish slates.

From the presence of only the closing stage of the Upper Siluric
at Becraft mountain and in the Helderberg near Albany, (Country-
man hill) — the two places where the deposits of the Siluro-
Devonic basin of New York approach nearest to the Rensselaer grit
plateau — it may be properly inferred that the Upper Siluric sea of
New York did not extend into the present area of the Rensselaer
grit plateau at any time except possibly in the latest (Manlius) stage
of that period. In regard to the latter, the problem is the same as in
regard to the Helderberg limestones in general which are exposed
at Becraft mountain and of which the Rensselaer grit might be
conceived as representing the littoral facies. In favor of this view
it may be said that both formations rest on the same basis (Cambric
and Lower Siluric slate) and that on account of the rising of the
Taconic mountains in early Siluric time, there may have existed a
littoral facies of the Helderberg rocks to the east. But this view is
strongly opposed by the fact that the Helderberg rocks do not show

GEOLOGY OF THE CAPITAL DISTRICT I2g

any indications of approach to a littoral region at Becraft mountain,
but retain the same lithologic characters over a vast area. There
would hence have to be assumed an extremely abrupt and improb-
able change in facies in the short distance of 20 miles from Becraft
mountain to the outlier at Austerlitz. A somewhat different case
is presented by the Oriskany sandstone, Esopus grit and Scho-
harie grit which in some places, as at Whiteport and Kingston,
contain conglomerate beds. It is altogether probable that the ma-
terial of these conglomerates was derived from the south and the
Oriskany sandstone is too thin a layer (30 feet) at Becraft moun-
tain, to be correlated with the thick mass of the Rensselaer grit
(1400 feet). It is, however, possible that the Esopus and Scho-
harie grits which at Becraft mountain have a combined thickness of
300 feet and are similarly barren in fossils, once continued north-
eastward into the Rensselaer grit trough. It must further be con-
sidered that the Rensselaer grit plateau represents a deposit in a
long submeridional Appalachian trough. Its pebbles of coarse and
fine gneiss came from a short distance and the numerous Lower
Cambric pebbles probably came from places north of the plateau.
Its deposits suggest those of an embayment receiving its materials
from the north. The entire absence of the fossils occurring in the
nearby Becraft mountain formations favors this conception of
estuarine conditions.

The evidence compels us to grant that the Rensselaer grit is of
later than Siluric age; there is some good reason for regarding it an
eastern deposit contemporary with the early Devonic, but the alter-
native proposition stands open, that its estuarine character and
great thickness suggest identity with the Catskill beds which stand
sheer on the other side of the Hudson river in heights of several
thousand feet and only 30 miles away from the outlier at Austerlitz.

The fact that the generally barren Catskill beds with their fresh-
water pelecypods ( Amnigenia ( Archanodon ) catskillensis) , late
eurypterids ( Stylonurus excelsior ) and plants are undoubtedly
fresh-water or brackish delta or estuarine deposits, that grade west
and southward into marine beds, while northeast of them we find
the still more barren Rensselaer grit, extending in a rather narrow
belt far north (see Dale’s exposure in Vermont and his suggestion
that the Rensselaer grit extended into the Champlain Valley), to-
gether with the coarseness of the grit, its frequent plunge structure
and oblique bedding, and the occurrence of conglomerate, inter-
bedded in the grit in layers or only in nests and streaks — all these
facts lead to the conclusion that the Rensselaer grit was deposited in
a narrow north-south running trough, probably emptying into the
Catskill bay and that the deposits are largely river and delta deposits.

The occurrence of fresh large feldspars in the conglomerate, as
well as a variety of minerals in the grit, according to Dale (’04, p.

1 3°

NEW YORK STATE MUSEUM

39), microscopic grains of quartz, orthoclase, plagioclase, and micro-
cline feldspar, biotite, garnet, tourmaline, zircon, magnetite, ilmen-
ite and epidote, all of which indicate an origin from plutonic rocks
such as granite, that are found in the Adirondacks and Green •
mountains, clearly points to a northern derivation of the com-
ponents of the grit. The freshness and the angularity of many
>f the feldspars further indicate a not very long or rapid trans-
portation1, and the irregularity of bedding in many of the grit
beds suggests current action. Likewise the red shales indicate
oxidation by exposure to air of the muds and hence shallow waters, j
All these facts mean to us that the Rensselaer grit is the product
of a large river flowing from the north into the Catskill embayment.

STRUCTURAL GEOLOGY

The capital district in its structural geology is distinctly a segment 1
of the Hudson valley-Lake Champlain depression, that extends from
north to south between the Green mountain-Taconic folds in the 3
east and the Adirondacks and Helderbergs in the west. It there-
fore shares its principal structural features with the whole physio-
graphic unit. ^

Cushing and Ruedemann (’14) have fully described the struc-
tural geology of the Saratoga and Schuylerville quadrangles. The
present chapter is largely only an application of the results obtained j
there to the southerly adjoining capital district.

In the structural history of the district we have to distinguish
between three periods of folding and two of faulting, which formed
the last phases of the two last periods of folding.

The first period of folding was Precambrian in age. It produced
several long barriers, running in north-northeast to south-southwest
direction across the district, and forming two or more troughs.
Two of these troughs we have positively recognized and designated
as the eastern and western troughs. They are characterized by their
entirely different geologic series of formations, as we have fully set
forth in the preceding chapter. The eastern trough is the one which

1 Large, angular feldspars in sedimentary beds have been attributed to several
causes. W. von Leszinski (’13, p. 501), has argued that they indicate periods
of cool climate, because in another climate they would not remain undecom-
posed. He cites the arkoses of the Rotliegende, Lower Devonian arkoses of
the Ardennes, and Lower Lias and Cretaceous rocks as instances. On the
other hand, T. C. Chamberlin has repeatedly pointed to the preservation of
feldspar in sediments as proving a lack of vegetation in Precambrian time and
finally it is usually considered as explainable by close vicinity of disintegrating
granitic rocks.

GEOLOGY OF THE CAPITAL DISTRICT

*3*

Figure 8 Diagram of successive events in geologic history of capital district, showing the eastern and western
troughs of Cambrian-Ordovician age with the Precambrian barrier and their deposits, the hiatuses of
nondeposition, the Silurian and Devonian deposits an d their probable extension and the time of the orogenic
revolutions

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NEW YORK STATE MUSEUM

contains the Lower Cambrian beds and the long series of graptolite
shales, the Schaghticoke, Deep Kill and Normanskill shales and the
Snake Hill beds. Ulrich and Schuchert (’oi) have termed this the
Levis trough, from Point Levis in Canada, where the graptolite
shales and other rocks of the trough are well exposed. It is
bounded on the east by the Green mountain barrier, and on the west
by the Quebec barrier. The latter separates it from the Chazy basin
and its southern continuation which we have termed the western or
Lower Mohawk trough (’14, p. 140).

The western trough (figure 8) contains the “normal series” of
beds, namely: the Potsdam sandstone, Theresa formation, Little
Falls limestone, Beekmantown and Chazy beds farther north, the
Amsterdam limestone, Glens Falls limestone, Canajoharie shale,
Schenectady shale, Indian Ladder beds and the Helderberg series of
Silurian and Devonian formations. A minor barrier seems to have
separated this trough in the west, at least at certain times, from the
series of formations found in the upper Mohawk valley.

The Green mountain and Quebec barriers, delimiting the Lower
Cambrian sedimentation, must have been present at the beginning
of Lower Cambrian time and arisen, probably as low folds, in
Precambrian time. They are prenuncial in their direction and
location of the much greater folding in Ordovician and Carbonifer-
ous time. They arose in a geosyncline, or broader trough, ( Schu-
chert’s eastern proterozoic geosyncline) that extended in later Pre-
cambrian time from the northern Atlantic (or its ancestor Poseidon),
beyond Newfoundland, in a southwest direction to the present site
of the Gulf of Mexico. To the east of it were still broad “border-
lands of the continent” (Nova Scotis in the north, Appalachis in the
south), which furnished the material for the great thicknesses of
formations in the eastern trough.

These two troughs persisted through Cambrian and Ordovician
time according to the record they have left in the sediments and
fossils. They were, however, more or less independent from each
other, so that one could be drained while the other was inundated ;
and a study of the diagram (figure 37) shows that they were
drained in fairly regular alternation (see chapter on Historical
Geology, p. 163, for details).

The second folding that affected the rocks of the capital district
was the Taconic folding, named after the Taconic mountains on the
New York-Massachusetts boundary line. This folding took place at

GEOLOGY OF THE CAPITAL DISTRICT

1 33

the end of the Ordovician period according to general assumption.
It was believed to have extended over such a wide area in eastern
North America that Dana termed it the Taconic Revolution. It has
more recently been claimed by Clark (’21) that the Taconic folding,
at the close of the Ordovician, was localized in eastern and north-
eastern New York State. In this region, however, we have evidence
of a very extensive folding first, followed by equally profound and
widespread overthrust faulting.

The rocks of the eastern trough are everywhere intensely folded ;
those of the western trough are only faulted, or but slightly folded,
as in the Helderbergs (see p. 1 5 1 ) by a later post-Devonian

revolution.

Being for the most part incompetent shales, the rocks are mostly
closely folded, the folds turned over or bent over westward, the
packed folds producing the so-called isoclinal folding, where all
beds, the anticlines and synclines being deeply worn off, seem to
incline in the same direction, in our shale belt toward the east ; and
all striking in the general north-northeast direction (N. 20° E.).
Where, however, harder and thicker beds are present, as the Cam-
brian quartzites and grits of the Normanskill shale, the anticlines
and synclines are less compressed ; broad symmetric folds are found,
and often well shown. Dale (figures 10-15) has given excellent
diagrams of a number of synclines from the Cambrian belt of the
capital district that permit the making out of the succession of the
beds, and we have inserted them here. The Snake Hill shales, which
are much less competent than either the Cambrian or Normanskill
beds, are uniformly thrown into a mass of closely packed, small,
closed folds that are asymmetric and uniformly overturned or
inverted to the west, so that on the surface and in sections where
the tops of the anticlines are eroded away, the entire mass has an
isoclinal structure, most beds dipping to the east with varying
angles, averaging about 70°. This condition is, for instance, well
seen in the Cohoes gorge. In places these shales are so contorted
that they have the appearance of having yielded to the pushing by
simply crumpling up. Open folds, however, occur here also, when
heavier beds are present, as at Snake hill (figured by Mather, ’43,
pi. 11, figs. 10-12).

The folding dies out gradually towards the west (figure 7 and sec-
tion BB). While Albany stands on steeply inclined and intensely

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NEW YORK STATE MUSEUM

in folder )

GEOLOGY OF THE CAPITAL DISTRICT

135

Figure 11

Figure 13

(See page 136 for explanation)

136

NEW YORK STATE MUSEUM

W €1 loofeet E

Figure 15

Figures 10-15 Series of folds observed by Dale, of Lower Cambrain rocks on
Troy quadrangle (U. S. Geol. Surv. Bui. 242). Figure 10 Diagram section
showing the general structure of the ridge between Tackawasick creek and
pond and the Rensselaer plateau, in Nassau. Dotted beds quartzite; lined beds,
shales. Height, about 200 feet. Figure 11 Diagram section through the
southern part of Curtis mountain (Dusenbery ridge) in Nassau. Height,
about 400 feet. Figure 12 Diagram section two miles east of Defreestville,
in North Greenbush, showing two interpretations of the relations of the
greenish shale to the Lower Cambrian fossiliferous limestone (Cl). Figure
13 Diagram section near Speigletown in Lansingburg, showing the general
relations of the olive grit ( G ) to the Lower Cambrian sandstone (Cl) and
the Ordovician shale (Oh). Figure 14 Diagram section two miles south-
west of West Sand Lake, in East Greenbush, showing the relation of the
Lower Cambrian limestone (Cl) and gray shale. Figure 15 Diagram sec-
tion by Foerste, slightly modified by Dale, showing the probable general
relations of the Lower Cambrian fossiliferous limestone (Cl) at Troy to
the red and green shale (lined beds) and to the Ordovician shale (Oh).

folded beds, the shales along the Vly below Voorheesville are for the
most part in flat position, but there are still fault-lines and small
anticlines and synclines but a few feet high seen at the upper rapids
below the mill. An excellent section from the folded into the
unfolded region was formerly displayed along the canal and the
Mohawk river between Cohoes and Rexford (figures 16-24). The
damming of the river for the barge canal has unfortunately sub-
merged many of the best outcrops. Here could be seen the close,

GEOLOGY OF THE CAPITAL DISTRICT

137

crumpled folds in the eastern section, with occasional broader folds
where harder beds were involved, and the gradual opening of the
folds westward, until they disappeared rather abruptly near the bound-
ary of the Snake Hill and Schenectady beds, where evidence of over-
thrust fault-lines becomes visible (figure 16). West of this zone the
Schenectady beds are undisturbed. It can therefore be stated as a
general proposition that the rocks of the eastern trough are completely
folded, while those of the western trough are in their natural position.
In the Saratoga region Cushing and Ruedemann found that the rocks
of the western trough were much disturbed by normal faults, as the
ones at Saratoga, along which the springs come to the surface. If
there are such faults in the capital district, where blocks through the
action of gravity have sunk down along more or less vertical fault
planes, they are buried under the glacial drift and not recognizable.
Small normal faults were, however, observed in the Helderbergs
(see p. 159).

At the end of the Taconic folding, or rather as a special phase
of it, extensive overthrusting took place. We have recognized two
major thrust planes in the capital district, both of which were already
fully described by the writer from the Saratoga-Schuylerville regions
in 1914 (p. 109 ff.) (see figure 9).

One of these separates the intensely crumpled sediments
of the eastern trough from the undisturbed formations of the
western trough, or comes to the surface along the Snake hill-
Schenectady boundary. This fault, which is probably a nearly hori-
zontal thrust fault, is of the character of a “scission” fault or “char-
riage.” The eastern formations have been pushed westward over
this plane for an unknown, but probably considerable distance. It
is only by this movement that the deposits of the two different
troughs could come in direct contact, as they do along the line. A
considerable portion of the crumpling of the shales may be due also
to this overthrust movement. The barrier which once separated the
two troughs has been completely overridden.

This overthrust plane has nowhere been directly observed, not
even in the section along the Mohawk river, where it would be most
liable to appear. In its place appear a number of small overthrust
planes. It is therefore our conviction that the overthrust is dis-
solved into a multitude of smaller overthrusts. We had already
found clear evidence of this structure on the Schuylerville quadrangle

138

NEW YORK STATE MUSEUM

GEOLOGY OF THE CAPITAL DISTRICT

139

Figure 17

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

(See page 140 for explanation)

140

NEW YORK STATE MUSEUM

Figure 24

Figures 17-24 Sketches of structures along Mohawk between Ctohoes and
Schenectady, by Mather and Ruedemann. Figure 17 Section one and one-
half miles northwest of Cohoes Falls (Mather). Figure 18 Section from
the Island one-half mile west of Vischer’s Ferry (Mather). Figure 19
Section one-half mile northwest of Vischer’s Ferry (Mather). Figure 20
Two miles from Alexanders Bridge (Rexford), by Mather. Figure 21
Two miles west of Vischer’s Ferry (Mather). Figures 22-24 Sections
north and south of Mohawk river and in railroad cut, three miles northwest
of Niskayuna (Ruedemann). The folds are flatter where competent beds
(sandstone) prevail, and closely folded where shale predominates.

(Ruedemann, ’14, p. 103). In a good east-west section through the
Snake Hill shale along the Batten kill at Clark Mills, a whole series
of such faults, about 10 to 20 feet distant from each other, were
observed in the north wall and traced across the river bed. They all
rise toward the west at angles varying from 20° to 45 0 and many are
made conspicuous by calcite veins. The throw is always small, but
the upthrow side is always pushed a little to the west.

While the throw of each of these overthrust faults is small,
their accumulative effect, going from west to east, owing to their
great number and uniform direction of throw, must be quite large.
If we assume a throw of six inches for each fault and that they are
20 feet apart, we obtain for the belt measured from the foot of Wil-
lard mountain (on the Schuylerville quadrangle) normal to the strike,
with a width of ten miles, a compound throw of 1320 feet. The
effect of this accumulative throw would be to bring progressively
older beds to the surface as one goes east. It is therefore possible
that the position of the Normanskill belts to the east of the Snake
Hill belts is due largely to this effect of the small overthrust faults
which might be termed “multiple overthrusts.”

Likewise the rather indistinct boundary of the Snake Hill and
Schenectady beds is probably caused by the presence of numerous
small overthrust planes at the boundary instead of one large one.

GEOLOGY OF THE CAPITAL DISTRICT I4I

We have cited (Ruedemann, ’14, p. 103) instances on the Sara-
toga quadrangle where the slickensides upon the thrust planes, and
especially the direction of the slickenside scales, leave no doubt that
the upthrow side had moved from east to west upon that plane.
Some of these overthrust faults have clearly resulted from overturned
folds (fold thrusts). The upper leg is seen in such cases to have
been pushed westward beyond the lower. Some instructive exam-
ples of these were seen about Saratoga lake, especially on Snake
hill. Most of these small faults ran with the general strike (north-
northeast direction) of the beds or are strike faults; there were
observed, however, some which cut the beds obliquely, as one at Vic-
tory Mills, striking N. 6o° E. These deviations from the general
north-northeast direction are probably connected with local irregu-
larities in the general trend of the folds.

The multiple overthrust structure appears to be on a small scale,
what the Germans have called “Schuppenstruktur,” the separate
“Schuppen” being pushed one over the other like scales. It is an
imbricated structure, produced by many small overthrust faults
that has the total effect of a general overthrust. This structure has
recently been termed “shingle block.”

We ascribe to this structure the rather indefinite boundary line
between the Schenectady and Snake Hill beds on one hand, and the
Snake Hall and Normanskill on the other.

While our first observations on this progressive mode of over-
thrust were made on the Schuylerville and Saratoga quadrangles,
the capital district also furnishes evidence that supports it. There is
an overthrust plane that is nearly horizontal exposed on the west
shore of Saratoga lake, a little north of the edge of the capital dis-
trict. In the cliffs on the southwest shore of the same lake (on the
Schenectady quadrangle) many such overthrust faults were observed,
in one place four, each above the preceding. They all dip southeast,
mostly at an angle of about 250 (figure 25). Another place where
the small overthrusts were well seen, is the Brothers quarry in South
Troy. Here they appeared in part as mere slickensided slip planes
between the harder beds, and in part as slight excessive movement
of the upper legs of the overturned anticlines.

A distinct belt of faults extends from Ballston Spa to Ballston
lake. The Saratoga fault has been considered by Cushing and Ruede-
mann (T4) to continue through Ballston Spa, producing there the
springs, inclusive of the well-known iron spring. This is a normal
or gravity fault, one of the step faults of the Saratoga region, by
which the country has sunk down in steps to the east of the Adiron-

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Figure 25 Four small overthrust faults in Snake Hill shale in cliff on south-
west shore of Saratoga lake.

dack massif. These faults are characteristic of the unfolded region to
the west of the folded belt. On the other hand, the overthrust line
separating the rocks of the eastern trough, with the Snake Hill on top,
from those of the western trough, with the Canajoharie shale on top,
was drawn by us to pass a mile east of Ballston Spa. A temporary
outcrop in the village later showed us that the Snake Hill beds come
into the village, and the boundary line should run farther west, as
now continued on the map of the capital district. In that case the
Saratoga normal fault and the Canajoharie-Snake Hill overthrust
boundary come together at Ballston Spa ; that is, the much younger
Saratoga fault intersects the older overthrust line. A series of small
faults can be seen south of Ballston Spa in the capital district, in
evident continuation of the Saratoga fault. Two such small faults,
striking N. 50° E., are found in the bed of the Mourning kill under
the bridge of the Delaware and Hudson Railroad (Schenectady
branch), one and one-half miles south of Ballston Spa. Another
distinct fault line is seen a quarter of a mile east, where the Mourning
kill turns north. All these faults are in the Snake Hill beds, possi-
bly of small throw and normal faults. Another distinct fault line is
seen 250 feet west of Ballston lake, in Forest Park, where the grit
beds of the Snake hill stand vertical. Farther north it is seen that
the beds on the east side are dragged and dip east, the rock having
dropped on the east side of the fault. This fault was known to
Emmons, who claimed that it had a great length and importance
and was the cause of Ballston lake. Stoller (Ti, p. 10) has also
noted the fault line on the west side of the lake and inferred that “a
preglacial stream heading to the north followed the course of the
present Ballston channel, finding its bed in the line of vertical out-

GEOLOGY OF THE CAPITAL DISTRICT

143

crops of rock, and joined the Mohawk near Schenectady.” He con-
cluded that in glacial times the valley made by this creek was scoured
out and enlarged by ice erosion and thus the Ballston channel pro-
duced. It is our opinion that the entire depression extending from
Ballston southwest to Schenectady, and occupied by the Mourning
kill in the north, Ballston lake and the Anthony kill in the middle
and the Alplaus creek in the south, and furnishing an even grade
for the Schenectady branch of the Delaware and Hudson Railroad,
is caused by this zone of weakness, where the Saratoga fault has
been divided into a “horsetail,” or a number of secondary faults,
which finally die out southward. The Schenectady-Snake Hill over-
thrust line, which is older than this group of normal faults, diverges
from them at Ballston Lake.

Logan’s Line

While the Schenectady-Snake Hill and the Snake Hill-Normans-
kill overthrust lines are obscure, the overthrust which brings the
Lower Cambrian beds on top of the Ordovician east of the Hudson
river is very distinct and sharply defined. This overthrust is sup-
posed to be a segment of a more or less interrupted overthrust line
that extends from Canada through Vermont and New York south,
perhaps to the southern Appalachians. This line has become known
as “Logan’s line” after the former director of the Canadian Survey,
Sir William Logan, who first pointed to its long extension and
structural importance. While the continuity of this line is still doubt-
ful and it is certain that it is of Paleozoic age, and long ago became
inactive, after every earthquake in the East it is still revived by the
press and even by geologists as the seat of the disturbance. After
an earthquake the first question newspaper men ask geologists, at
least in eastern New York, is, “Is it Logan’s line?” It is not, and
never will be.

The Cambrian overthrust line, where the overthrust plane now
comes to the surface, passes from the northeast corner of the State,
from Easton to Schaghticoke, Grant Hollow, Lansingburg, Troy,
where it crosses the Rensselaer Polytechnic Institute campus, De-
freestville and Schodack Depot and Schodack Center. We have
traced it through the eastern part of the Schuylerville quadrangle,
where it is wonderfully exposed. The foremost locality there is
Bald mountain, where quarries in the Bald Mountain limestone
expose this Ordovician limestone at the base, with the Lower Cam-
brian (Schodack shale and limestone) above forming the mountain.
Along the thrust plane a mass of ground-up material (mylonite), in
one place 30 feet thick, is seen. That is the fault breccia ; here, how-

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ever, since much of the material was shale, pulverized into a black
powder with many rock fragments floating in it. In the capital dis-
trict, the fault breccia is splendidly exposed at the Rensselaer Poly-
technic Institute campus and in the Poestenkill. It has been
described on page 113 as the Poestenkill breccia.

The question of the extent of this overthrust in New York has
been a mooted matter. It was the writer’s early contention that it
is a major overthrust (’01, ’09, p. 191), while Dale (’04, p. 293)
would rather consider it as of local development only. We have
fully discussed this problem before (’14, p. 109) in relation to the
exposures on the Schuylerville quadrangle, and especially in regard
to Bald mountain. In 1913 the writer took the late Professor Roth-
pletz of Munich, a leading authority on the alpine “Decken” or
“charriage” structures, to Bald mountain and was assured that the
exposure had all the earmarks of an overthrust of the first order of
magnitude. We have in the former paper pointed out that the
Snake Hill beds and to the south of them the Normanskill beds, pass
successively under the Lower Cambrian overthrust plane, thereby
indicating the great width of movement of the overthrust mass. The
same observations can be made in Troy, as readily seen on the map,
where Normanskill, Snake Hill and again Normanskill pass under the 1
Cambrian rocks.

Another exposure of crucial importance in this connection is that
at Grant hollow, where the Deep Kill section described by the writer
is found at the bottom of the gorge, while the hills both north and
south of the gorge are composed of fossiliferous Lower Cambrian.
This occurrence is further of great interest because it connects the
Ordovician shale belt, west of the overthrust line, with the large
Mount Rafinesque-Rice mountain “outlier.” If the Georgian rocks
overlie the Beekmantown graptolite shale at Grant hollow, it is
probable that this outlier is really a “fenster,” or a portion of the
Ordovician rocks underlying here the Cambrian mass that is exposed
by erosion (see p. I45ff).

The exposure at Schaghticoke is also very instructive. There the
Schaghticoke shale is exposed at the bottom of the river and in the
river bank, but the hills to the north and south of the gorge, in the
general strike of the rocks, consist of Cambrian beds. These oldest
graptolite shales here lie clearly under the Cambrian.

An exceedingly fine exposure of the Cambrian-Ordovician over-
thrust is afforded in the gorge of the Poestenkill (figure 26), where
a mass of fault breccia, more than 50 feet thick, and containing
Normanskill grit blocks 20 feet in diameter, separates the overlying

GEOLOGY OF THE CAPITAL DISTRICT

145

Cambrian rocks from the subjacent Normanskill beds (figures 62,
63 and 65).

There is considerable and quite conclusive evidence that the thrust
plane is irregular in its hade, through folding ; for while the thrust
plane is very slightly inclined at Bald mountain and the Moses kill,
it is steep east of Willard mountain and in the neighborhood of Troy.
Also the sinuous form of the fault line near the southern margin of
the map in Schodack is due to the unevenness of the plane through
later folding. That these irregularities of the line are due to folding
of a character transversal to the general northeast strike of the beds
is indicated by the fact that where the hade is steep, the Cambrian
rocks descend deeper than where it is flat, these deeper appearances
of the Cambrian corresponding to depressions or synclines.

W E

Figure 26 Section of the Poestenkill at the fall in Troy, showing the position
of Logan’s line (7) as seen on north wall overlain by the Cambrian red,
purple and green slate with intercalated beds of sandstone (1-4), the one at
1 fossiliferous (Hyolithes, Hyolithellus) ; 5 is the mylonite (fault-breccia)
bed; 6 the Normanskill shale with interbedded Normanskill grit.

There is considerable evidence extant of folding of the entire
region long after the Green mountain or Taconic revolution, mark-
ing the Silurian-Ordovician boundary, and which is considered
responsible for the principal folding and overthrusting of this region.
Such later folding, probably of Carboniferous age, is shown by the
folded condition of the Rensselaer grit (see p. 148), and by the rem-
nants of the folded and overthrust Devonian limestones still found
farther down along the Hudson river, as at the Vlightberg at Kings-
ton and Canoehill at Saugerties.

A problem that is closely connected with the extent of the great
eastern overthrust is whether the “outliers” in the Cambrian east
of the river are regular outliers, that is, masses of Ordovician rocks

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normally resting upon the Cambrian and left by erosion of the con-
tinuous Ordovician cover, or “fensters” (windows), that is, expos-
ures of the Ordovician, buried by overthrusting under the Cambrian
and exposed by the erosion of the Cambrian. There are two such
areas, the large one, already mentioned, of the Mount Rafinesque
and Rice Mountain stocks, and a smaller one, west and south of
Lake Aries (Snyder’s lake). We have failed to find convincing
evidence for either possibility in the structural conditions, owing to
the complexity of the structures and the lack of sufficient outcrops.
It is apparently an important fact in the understanding of both out-
liers, that they are more or less connected with cross folds ; that is,
while the general strike of the folds is N. 20° E., there are found in
these areas east-west striking folds. The largest of them is that
which gives Mount Rafinesque, east of Lansingburg, its form and
direction. The strike of the rocks (E. N. E. to W. S.W.) is also
on the map indicated by the east-west strike of the Beekmantown
belt on the south slope of Mount Rafinesque. Also the Snyder’s
lake outlier is connected with a cross fold that just south of
Wynantskill has thrown the Beekmantown beds, as well as the
Lower Cambrian beds, into east-west strikes. Another cross fold is
south of Albany, forming the ridge south of The Abbey (Glenmont),
where the state road crosses the West Shore Railroad. Here the Nor-
manskill beds (mostly white- weathering chert) strike east and west.
Traces of this cross fold can still be noted across the river.

Whether these cross folds are due to local obstacles that threw
the folds of the Taconian revolution into a secondary direction, as
happens in folding, or are the result of the last folding of Car-
boniferous time, we do not know. If they are caused in the first
manner, it is probable that the “outliers” are due to the projection
upward of the Ordovician stocks into the Cambrian and are
“fensters” ; in the second case, they were folded long after the over-
thrusting and are merely erosion remnants, or true outliers.
E. Kayser (’21, p. 238, footnote) has pointed out that in the Hartz
mountains as in other mountain ranges local influences have produced
oblique stresses and torsions of the rocks to such an extent that in
places the strike has been turned by 90°. It is easily understood that
such closely folded, incompetent beds as the shales of the eastern
belt, would be readily turned aside by local obstacles, and this would
therefore seem to be the most acceptable explanation of the cross
folds in the belt.

There should be mentioned here one fact that appears to have a
direct bearing on the question of these outliers. That is their

GEOLOGY OF THE CAPITAL DISTRICT

147

position in the upper part of the Lower Cambrian. We have
shown before that in the Lower Cambrian of the capital district
at least two belts could be discerned, one of the older divisions
(Nassau beds) to the east, and one of the younger formations
to the west. These have been marked on the map by different
colors. It so happens that both of the outliers in question are
found in the belt of the younger Lower Cambrian formations.
It is obvious that this fact does not militate against their being
outliers, while, on the other hand, if they were “fensters,” they
would have had to pierce both the lower and upper divisions, or
the entire lower Cambrian, a rather improbable performance.

A fact of the greatest significance in regard to the structural
relations between the Lower Cambrian and Ordovician near the
overthrust line and in the direct continuation of the Mount
Rafinesque-Mount Rice outlier or fenster, was observed by the
writer when in 1903 the tunnel for the Troy waterworks was
drilled from the Tomhannock reservoir west paralleling the Tom-
hannock-Melrose road on the south. The writer had occasion to
study the tunnel in connection with some engineering problems
and found that while the surface rock was greenish gray Lower
Cambrian shale (and has been mapped as such by Dale), the rock
in the bottom of the shafts was fossiliferous Normanskill shale.
In shaft 1 (at A on map) the writer found at a depth of about
64 feet in the tunnels both east and west of the shaft black shale
with large concretions, the shale containing Normanskill grapto-
lites ( Climacograptus parvus, Corynoides curtus etc.) ; west of the
shaft the fossils were found in two places 50 and 108 feet from
the shaft. Also shaft 4 (at D on map) furnished at a depth of
50 feet black Normanskill shale with graptolites ( Diplograptus sp.
Climacograptus parvus, Dicellograptus sextans, Glossogr. whit -
fieldi ) ; and shaft 2 (at B on map) contained rocks of the litho-
logic character of the Schaghticoke and Deep kill shales, but af-
forded no fossils. Shaft 3 (at C on map) and the tunnels leading
from it were drilled in greenish gray shale probably of Lower
Cambrian age.

We have marked the site of the shafts on the map by the
symbols A, B, C and D, a mile northeast of Melrose. The picture
one obtains from the distribution and character of the rocks in
the shafts and tunnel is that the Ordovician rocks continue from
the outlier northward below the Cambrian surface rocks except
perhaps for a narrow tongue of Lower Cambrian rocks, at shaft
3, pressed in between the “outlier” in the east and the belt of

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Normanskill shale in the west. This observation, as well as that
of the position of the Deep Kill shale at Grant hollow, are cer-
tainly very suggestive of a partial overriding, at least, of the Ordovi-
cian rocks of the outlier by Cambrian rocks.

The last folding is that which is typically displayed in the
Rensselaer grit plateau. We have already seen that the Rensselaer
grit is probably of late Devonian age. It is strongly folded, and
this folding must be of later than Devonian age. There is little
doubt that it is a manifestation of the late Carboniferous to
Permian Appalachian revolution that folded the Appalachian sys-
tem and whose influence is widely felt through New England and
lower Canada, as well as in the Taconic and Green mountains. It
has long been recognized that the Appalachian folding is markedly
displayed in the much disturbed Lower Devonian rocks of the
Hudson valley, as about Kingston, Catskill and, in lesser degree, the
Becraft mountain. Weaker manifestations of the same force are
seen in the capital district in slight folds and small faults in the
Helderbergs (see p. 151). No doubt the Cambrian and Ordovician
rocks, already strongly folded by the Taconic revolution, again felt
the compressing and lifting force of the Appalachian revolution, but
the effects are hard to recognize. We have already attributed to this
cause the folding of the great overthrust plane and possibly the cross
folds observed in the capital district.

The structure of the Rensselaer grit plateau has been carefully
worked out by Dale (’93, p. 324), from whom we quote here
freely. After showing that the Greylock mass, the Taconic range
proper and the connecting East and Potter mountains are syncli-
noria, that is, compound synclines, composed of many smaller
synclines, and the Berlin-Lebanon valley an anticline, formed of
Stockbridge limestone (fig. 27), the grit plateau is described as a
broad compound syncline. It is shown from the strikes that a syncline
occurs a little west of the east edge of the plateau, that seems to con-
tinue northward into the schists. “In the hill of Grafton Center is an
anticline, and at least one anticline occurs also in the slates and shales
between Pittstown Corners and Hoosick Falls. Therefore at least one
anticline probably runs through the center of the plateau.” These
localities are just beyond the eastern margin of the capital district
map.

At one locality only (loc. 19 1, Bowman pond) were horizontal
strata found, but others probably exist. It is quite probable that
several gentle folds occur between the central anticline and the
west edge. In the southwest corner conflicting pressures have

NEW YORK STATE MUSEUM

150

operated [as shown by the confused strikes]. At the northeast
end there are also abrupt changes in the strike.

The structure of the west edge of the plateau, as shown in the
general section, was taken from between Barberville and Poesten-
kill, at the falls and in the gorge of the Poestenkill, and on Snake
hill, loc. 202. The river at Barberville flows south for a space
along the west side of a small anticline of grit and purple slate,
and then making a sudden easterly turn, cuts through the top of
the anticline [figure 68], flows into the adjoining syncline and then
plunges down some 70 feet, cutting off the east flank of a low
anticline, the layers of which dip at a small angle east [figure 28].

Figure 28 Section through the anticline at Poestenkill falls (see figure 68).
Height between water levels about 150 feet. From Dale (U. S. Geol. Surv.
13th Ann. Rep’t, 1891-92, pt 2).

Figure 29 Syncline in Poestenkill gorge. Length, 150 feet. From Dale (U. S.

Geol. Surv. 13th Ann. Rep’t, 1891-92, pt 2).

About 1000 feet west of Poestenkill falls, the grits and

slates dip 150 E. and then 70° to 750 W., forming another anti-
cline, which is closely followed by a sharp syncline, possibly accom-
panied by more folding [figure 37]. . . . The structure of the
west edge of the plateau consists therefore plainly of at least two
synclines and two anticlines, i.e., of several folds. Such folds have
also been shown to exist east of Tackawasick pond (PI. XCIX,
G.), and the topography about Quacken kill points to a like struc-
ture [figure 68].

The general structure of the plateau consists therefore of a well
marked syncline along its east side, a compound syncline along its

GEOLOGY OF THE CAPITAL DISTRICT 151

west side, and certainly one and probably several folds in the
intervening area. It is a synclinorium six to nine miles wide and
about 20 miles long, mainly of hard dense rocks with softer rocks
underlying it on all sides. This synclinal structure is apparent
in its narrower southwest portion.

We have little to add to Dale’s exhaustive description of the
structure, but wish to mention that more recent quarrying opera-
tions have in one case, the East Nassau quarry, (figures 69 and 70)
exposed a fine recumbent fold and in another quarry, directly at the
western margin of the grit plateau, at Poestenkill, beds that are
practically flat, dipping but slightly east.

This last observation, which brings out a strong difference in
dip with the adjoining Cambrian rocks, suggests the possibility
of slipping along the boundary line, amounting in places to a fault.
This would seem especially true of the southwestern edge, where
the belt of Tackawasick limestone and shale appears from below
the Rensselaer grit. It is hardly possible to assume there any
other structure than faults on both sides of the limestone, making
it a wedge brought out along a fault-movement. Dale’s figure
(copied here in figure 7) also suggests the same condition, and he has
furthermore (’93, p. 314, 327) mentioned the possibility of a
fault along the foot of the west side, which, however, is not great
enough to bring up anything older than the Berkshire schist into
contact with the grit.

Actual faults in the Rensselaer grit can be seen in the above-
mentioned East Nassau quarry. One, an overthrust fault, of small
throw, cuts the recumbent fold. Besides these, there are several
normal faults of small throw seen in the quarry wall. In fact,
the fold and faults and slipping along bedding planes and joints
have broken up the rock into a mass of blocks.

Helderberg Folds and Faults

(Figures 71-77)

The Appalachian folding and thrusting which has affected the Rens-
selaer grit plateau and the Helderberg rocks of the middle Hudson
valley, is but feebly displayed in the southernmost part of the Helder-
berg rocks of the capital district. It has already been well described
from that region by Darton (’94, p. 447). He writes:

As the formations of the Helderberg mountains are brought down
to the general country level, they extend to the east and south into a
flexed region. The first features noticeable are a series of gentle

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NEW YORK STATE MUSEUM

undulations which broaden the outcrop areas of the limestones and
indent their edges into a series of en echelon offsets. These undula-
tions enter the Helderberg area in succession from west to east, as
it extends southward, along axes striking south ten degrees west,
approximately, and pitching slightly in the same direction, which is
diagonal to the general inclination of the monocline. In figures
4 and 5 [our figures 30 and 32] I have attempted to illustrate the
nature of these features in the limestone area, for they are an inter-
esting example of the beginning of the series of flexures and they
explain the singular distribution of the Helderberg rocks in this
portion of Albany county.

Figure 30

GEOLOGY OF THE CAPITAL DISTRICT

153

Figure 31

Figure 33

Figures 30-33 Figure 30 Diagram of a portion of Albany county to illustrate
the undulations at the edge of the folded region, from New Salem southward.
The length of the stems of the dip marks is inversely proportional to the
amount of dip. A-A, section is given in figure 31; B, section in figure 32;
C, section in figure 33. Figures from N. H. Darton (47th Rep’t N. Y. State
Mus., 1894). The anticlinal and synclinal lines in figure 30 have been added
by the author.

It will be seen in these figures that the undulations increase in
steepness to the eastward and finally become a succession of steep
parallel folds which are of true Appalachian type.

One of the most noteworthy details of structure in southern
Albany county is an overthrust of small amount, but with most
interesting features. It is among the gentle flexures near the northern
edge of the disturbed area in the Helderberg rocks. Its general rela-
tions are represented in the following section :

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NEW YORK STATE MUSEUM

Figures 34-36 Figure 34 Cross section of overthrust west of South Bethle-
hem. Exposure on south bank of Sprayt creek. Looking north (reversed).
Figure 36 Same overthrust, cross section seen on north bank. Looking
north. Figure 35 /-//, Hypothetical sections to illustrate stages of develop-
ment of the overthrust. All figures from N. H. Darton (47th Rep’t N. Y.
State Mus., 1894).

GEOLOGY OF THE CAPITAL DISTRICT

I5S

The characteristics of this overthrust are an “underturned” flexure
in the thin-bedded underlying limestones, also involving the soft slate
of the Hudson river formation, and a fault which offsets the flexure
and traverses the hard, massive overlying beds of Pentamerus lime-
stone. The overthrust is exposed only on Sprayt creek, which it
crosses at an old mill about three-quarters of a mile west-southwest
of the village. Its trend is north and south, but it does not appear to
extend for any great distance. The principal features of the ex-
posure at the mill are shown in plate 6, in which the inclosed wedge of
slate is shown in the lower left-hand corner, the flat arch of the
inclosing limestones in the middle of the view, mainly far to the
right. The massive overlying series is the Pentamerus bed.

The relations of the mill and their interpretation are further
illustrated in the following figures, in which the features above the
broken-line portion of the sections are exposed in the bed and banks
of the creek.

I discovered these overthrusts in the autumn of 1892 and sent a
brief account of their relations to the Geological Society of America.
[Published in the Bulletin, 4:436-39.] In 1893 I again visited the
locality and on careful reexamination, under much more favorable
conditions, found that the features were somewhat more complicated
than I had first supposed.

It is unfortunate that the exposures are not more complete, but
sufficient is seen, I believe, to substantiate the interpretation given in
the figure. Only the upper portion of the “underturned” fold is
exposed in the limestone, but the greater part of the fault plane is
visible on the south bank of the creek above the dam. The enfolded
slate is seen to be excessively crumpled and its original bedding planes
obliterated, but the lower limestones bend over the arch with but
little fracture. There has been considerable slipping along the contact
of the slate, and the portion of the limestone which is folded under is
considerably broken and contorted. At several points, as shown in
the figure, fragments of the limestones have been torn off and are
more or less surrounded by the slate.

In the north bank of the creek, under the mill, the exposure is less
extensive, but the general relations are similar to those on the south
side. The principal features in this exposure are shown in the follow-
ing figure.

The mechanism of the overthrust is, I think, not difficult to under-
stand, and I have represented the hypothesis of its development in
the diagram in the above figure, I, being the first stage, II, the second
stage and the present conditions the third stage. The broken line on
I indicates the plane of weakness, the arrow the direction of thrust.
The fault, sheared diagonally through the massive beds of Penta-
merus limestone but the softer, thin-bedded underlying limestones in
moving forward with the thrust were buckled downward and back-
ward under the soft shales, as indicated by the arrows in II before
they were also fractured. The lower limestones were also con-
siderably broken and cross-faulted, as shown in the figures. The

NEW YORK STATE MUSEUM

156

amount of displacement of the overthrust is about 100 feet. The
force was exerted from the eastward and almost horizontally in
direction, unless the present low angle between fault line and axial
planes is due to subsequent tilting.

This interesting little overthrust is, on a small scale, a duplication
of the greater overthrusts described by Davis (’84) from Catskill;
by Van Ingen and Clark (’03) from the Vlightberg at Rondout; and
by Chadwick from Canoe hill at Saugerties (To). Chadwick, in
his paper (p. 160) infers that these “instances must at least apper-
tain to the same set of movements, the same rift, extending along the
entire eastern edge of the folded Appalachians as a constant and
normal feature.”

There is no doubt that small overthrusts are more frequent in the
southern part of the capital district in connection with the folding
than can be observed on the surface. For instance, two small over-
thrusts are well exposed in Callanan’s quarry in South Bethlehem.
Both fault planes dip eastward, the eastern portion being pushed
over the western. The larger and more distinct one (figure 76) is
seen in the western part of the quarry. It strikes about N. 50° E.
and the hade or amount of movement is about 25 feet; the other,
farther east, has led only to a slip of a few feet.

Two very distinct overthrust planes are now seen in the face of
the South Albany quarry. These follow in the middle, where they
are exposed in their strike, a low anticline. On the sides they are
seen to rise westward and cut across the formations. Robert Jones,
consulting geologist, advises that the quarries along the entire eastern
Helderberg front exhibit these small overthrust planes striking as a
rule true north io° east and rising to the west. He finds that they
appear to be mostly developed on the intersection of the low east-west
folds with the regular north-south folds, these intersections being as
a rule the sites of quarries.

Other small folds in the Helderbergs have been observed by
Prosser at Clarksville (figure 75). He states (’99, p. 343) :

Along the base of Bennett hill immediately south of the village
are seen the northernmost traces of those flexures which are so
apparent in these formations farther south (Appalachia 1884, 3: 20-
33, plate). They consist of two slight folds and a small overthrust.
The overthrust is in the gorge through the Onondaga above the
village and may be plainly seen on its eastern side. There is a layer
of Schoharie grit with Onondaga limestone dipping under it, eight
or ten feet of the limestone being exposed, while above the Schoharie
lies the regular thickness of Onondaga. A number of fissures filled
with calcite, made no doubt when the overthrust occurred, maj^ be

GEOLOGY OF THE CAPITAL DISTRICT

157

seen in the gorge. One of the folds consisting of a broad, low anti-
cline, is very evident in the sides of the gorge through the Esopus
shales below the village. The other fold is between the two gorges
east of the home of Mr W. H. Rowe.

A further effect of these structures is the inlier of Esopus in the
Onondaga limestone just south of Clarksville. The last and northern-
most fold, a low anticline, is seen in the town of New Scotland
quarry east of Wolf Hill. A little to the south of the capital district,
as in the “High Cliff” near Coxsackie, the folds have already become
so sharp that the beds approach in places a vertical position and the
folds are of the type of closed folds, perhaps in connection with
strike faults.

Three Stories of Folding in Capital District

In summarizing the orogenic revolutions of the past in the capital
district, it can be stated that we have here distinctly three stories of
folded rocks one above the other and each separated from the preced-
ing by a distinct plane of unconformity and erosion. The oldest is
that of the Precambrian rocks now deeply buried here but exposed
in the Adirondacks to the north and the Highlands to the south.
Its folding runs in NE-SW direction. Upon this first story rests
the second, that of the Taconic folding, seen in the Cambrian-
Ordovician rocks. It strikes N. 20° E. As the Precambrian rocks
were stiffened by their folded conditions, they were little affected by
the later folding. This second story is again cut off by a great
plane of unconformity and erosion that is now seen at the base of
the Helderberg cliff. Upon this rests the third story of folding, that
of the Appalachian revolution, shown in the Helderberg and the
Rensselaer plateaus. This folding probably also had but little effect
upon the already closely folded underlying rocks. It strikes nearly
north and south (see figure 30).

In other words, we have here the remains of three worn-down
mountain systems, each erected upon the deeply eroded roots of the
preceding, and each running in a somewhat different direction.

Cleavage

Connected with the folding of the shale belt of the capital district
is the cleavage found everywhere in the rocks. Cleavage, or the
parting of the rocks into thin plates, independent of the bedding,
results from “a rearrangement of the particles of a deposit by pres-
sure and a simultaneous arrangement of any new crystalline par-

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NEW YORK STATE MUSEUM

tides formed during that pressure. This arrangement of old and
new particles is related to the directions of pressure and of resist-
ance” (Dale, ’99, p. 205).

As the cleavage is much more strongly developed in the shales
than the bedding, it is often difficult to recognize the position of the
beds, unless quartzite layers or differently colored beds or sandy
streaks indicate the direction of the beds. As a rule, the cleavage
dips toward the east, under various angles, indicating a pressure
from that direction as is also indicated by the folds that are over-
turned to the west. Where shale alternates with heavy grit beds, as
in the Rensselaer grit, only the shale possesses cleavage, the grit
having been folded by the same compressive force that spent its
energy in cleaving the shale.

A remarkable vertical fracture cleavage in the Coeymans limestone
has been developed along the small fault, south of the Indian Ladder
(see p. 160).

Strike and Dip

The folded and overthrust rocks of the eastern trough show a
general strike to north-northeast (N. 20° E.), and, of course, a great
variety of dips. As the folding dies out toward the west, the dip
becomes more regular, and finally along the western margin of the
capital district it can be considered as fairly steady.

It was found by Cumings (’00, p. 462) that the rocks west of
the capital district dip south at the rate of 140 feet a mile. Farther
east, approaching the Helderbergs in Albany county, the dip gradu-
ally changes to the southwestward, changing the east-west direction
of the Helderberg escarpment, west of Albany, to a southeast direc-
tion east of Altamont. This southwest dip (amounting to i° to 2°)
is also found in the Schenectady beds of the district. Darton (’94,
p. 446) found the dip in the Helderbergs, west of the capital district,
on the Berne sheet, to be not more than 100 feet to a mile. About
Thompson’s lake and Indian Ladder it is reduced to an amount not
over 35 feet a mile ; it is, however, somewhat variable in that region
by reason of the slight faults described below (p. 159). Darton
shows that the dip, which averages 112 feet a mile, S. io° W. in
direction, “carries the outcropping edges of the (Coeymans) forma-
tion gradually downward along the face of the mountain, from an
altitude of 1100 feet above tide south of Altamont to about 1000
feet at Indian Ladder and 660 feet a mile south of New Salem.
To the southward, about Clarksville, the rate of dip gradually

GEOLOGY OF THE CAPITAL DISTRICT

159

decreases to 60 feet a mile, and its direction changes to due west.
As the formations of the Helderberg mountains are brought down
to the general country level, they extend to the east and south into
a flexed region.”

We have seen that the structural elements of the capital region
are a system of folds in the east of three different ages, Pre-
cambrian, late Ordovician and late Carboniferous. Both the late
Ordovician and the Carboniferous foldings of the region led to
extensive overthrusts, by which portions of the folded regions were
carried westward over unknown but possibly considerable distances.
The Ordovician system of folds, produced by the Taconic revolu-
tion, may not extend far beyond the New York slate belt. It also
produced, however, the two great overthrusts which ( i ) brought the
formations of the eastern trough (Snake Hill-Normanskill beds)
into contact with those of the western trough, the Canajoharie and
Schenectady formations along the overthrust line, running from
Ballston Spa to the Helderbergs, west of Feura Bush, and (2)
pushed the Lower Cambrian beds over the Normanskill and Snake
Hill beds along “Logan’s line” east of the Hudson river. The last
folding was that of the Appalachian revolution. Its effect is mainly
seen in the strong folding of the Rensselaer grit, the gentle folds of
the eastern Helderberg plateau and the final overthrusting of the
Helderberg rocks, but feebly displayed in the capital district, and well
shown in the middle Hudson region, from Saugerties to Rondout.

Normal Faults of Western Trough

We finally have as a last manifestation of the unrest of the crust
in this region the normal or gravity faults in the western or other-
wise undisturbed belt. We have already described the Saratoga fault,
which enters the capital district at Ballston Spa. There are un-
doubtedly others in the belt of the Schenectady formation, but the
monotony and thickness of the formation, as well as the scarcity of
exposures, serve to hide them effectually.

Into this group, however, fall several normal faults that we have
observed in the Helderbergs. Several of these escaped notice until
the new state road to the Indian Ladder exposed them.

The first of these (no. 1 of map) is about one and one-half miles
from the Indian Ladder not more than one-quarter of a mile from
the edge of the capital district. This fault runs in a little ravine. It
is distinctly seen at the edge of the cliff, where on the east side of
the fault the top of the Coeymans is at 1155 feet, while at the west it

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NEW YORK STATE MUSEUM

is at 1095 feet. There is thus a drop of 55 to 60 feet, the western
side having been dropped. The fault runs about N. 30°-40° E.
(magnetic). The fault line can be seen in the cliff, where about a
decade ago a long section of the cliff broke off along a joint plane,
producing a bare exposure and a long talus slope or rock slide, now
visible from the roads in the plain. An interesting feature of this
fault is the strong vertical cleavage that has developed in the Coey-
mans limestone and New Scotland beds along the fault and that is
especially well seen in small cliffs in the woods a little ways back
of the edge of the escarpment and to the east of the ravine.

Another small disturbance that is visible directly from the road, is
situated three-quarters of a mile from the preceding locality in the
direction towards New Salem. Here a block of Becraft limestone,
about 90 feet wide, and bounded by two faults, running in northeast
direction, has dropped 20 feet into the New Scotland beds on either
side. At the edge of the cliff, where there is a reentrant distinctly
visible from the plain and situated under Daniel O’Connell’s house,
one can also see the New Scotland dropped 20 feet into the Coey-
mans.

A third fault, already mapped by Darton, produces an offset in the
Helderberg cliff one and one-quarter miles southeast of Feura Bush
and only a quarter mile north of the South Albany Railroad quarry.
The fault itself is expressed by a deep wooded ravine leading up
through the cliff, in which sink holes and small vertical outcrops of
Coeymans and Manlius are found, indicating the drag along the fault.
The contact was not observed and the drop not established. This
fault strikes about N. 30° E.

A small fault, with a drop of about 20 feet, is directly visible in
the east end of the quarry, the eastern side having dropped there.
To the right of it a low syncline, followed by an anticline, was ex-
cellently exposed in the summer of 1927.

Another zone of disturbance is located in the depression south of
the quarry, where the road from Feura Bush leads onto the plateau.
This road runs along, or just to the west of the bottom of a syncline,
for in the depression to the east of the road the New Scotland beds
are present, while the Coeymans to the east and west dips steeply
toward the trough of the syncline (at 21 °, resp. ii°). In the bed of
the Oniskethau creek, a quarter of a mile to the southwest, a great
mass of very large upper Manlius boulders (the thick-bedded, fine-
grained limestone) is exposed, indicating that here the top of the
Manlius in the anticline, adjoining the syncline on the west, has been
cut into by the creek.

GEOLOGY OF THE CAPITAL DISTRICT l6l

A series of small structural disturbances is exposed about Clarks-
ville. There is an elongated outlier of Onondaga limestone, half a
mile east of Clarksville, forming a ridge. The eastern boundary of
this has the appearance of a fault-scarp. A very fine overthrust
plane (figure 78) is now exposed at the south end of this outlier in
the north bank of the state road. The Esopus shale is here pushed
over Onondaga limestone in a westerly rising plane. The same fault
is well exposed on the south bank of the Oniskethau creek, where it
brings the Onondaga and Esopus into lateral contact.

Another small overthrust has been described and figured by Pros-
ser (’99, p. 343), in connection with small folds (see p. 156). It
is exposed in the bed of the Oniskethau creek south of the village,
just below the bridge.

The age of these small faults is not known. They may be con-
temporaneous with the Carboniferous folding of the Helderbergs,
but are more probably of much younger age and connected with
adjustments that took place in Mesozoic time to the east and west of
the Appalachian fold system, as shown by the sunken fault blocks
in the Champlain basin and the Connecticut valley.

There is no doubt that faulting on a small scale takes place to
this day. This is shown by the observation by Woodworth (’07) of
series of small step faults, each with a throw of about a few inches,
in the Snake Hill and Normanskill rocks of South Troy (Brothers
quarry), Defreestville (along road), Rensselaer, and other localities
in the Hudson Valley. As these small faults appear in glaciated rock
surfaces, they must be of postglacial age. It is the opinion of Wood-
worth that these small faults indicate a continuation of the ancient
pressure that elevated the Appalachian system; because (in the
Brothers quarry) “the situation of the postglacial faults along the
eastern border of the sandstone core of the overturned syncline, in
the plane of the reversed dip of the stratification, is precisely where
overthrust planes would be expected to arise in mountain building
from a continuation of the ancient pressure.”

Nevertheless Professor John H. Cook has suggested to me that
some at least of the postglacial faults are connected with the post-
glacial differential elevation of the country. Such a fault, with a
throw of about one foot, was discovered by him in the lower reaches
of the Oniskethau in the Oriskany sandstone, about two miles east
of Clarksville. The fault forms a step of about a foot in the stream
bed, so recent that it has not even been channeled by the stream.
Smaller postglacial faults have been found by him just outside of

NEW YORK STATE MUSEUM

l62

John Boyd Thacher Park, three-quarters of a mile west of the
Indian Ladder, also in the Oriskany. It is believed by Professor
Cook that there are numerous such small postglacial faults which if
studied in detail might give important clues to the postglacial doming
of the country.

Volcanic Rocks

Although one might expect that a great amount of volcanic activity
would have developed in connection with the widespread folding and
elevation and the overthrusting of the country, thus far no volcanic
rocks have been found in the capital district.

There occurs, however, only a few miles from the eastern margin of
the capital district, between Babcock pond and Kantsville, an erup-
tive rock described by Wolff as “a surface volcanic flow” (Dale, ’93,
p. 327). And further, the Northumberland volcanic plug, popularly
known as the “Schuylerville volcano,” is an outcrop of volcanic rock
not very far north of the capital district. It is therefore quite pos-
sible that volcanic rocks occur in the capital district and may be
exposed some day through building or engineering operations.

HISTORICAL GEOLOGY

The geological history of the capital district is a very complex one
as the region has been part of a very unstable area, that existed from
Precambrian time.

There are at present no Precambrian rocks exposed in the capital
district, but we have not far to go for the granites and gneisses of
the Adirondacks, which come down to the northern outskirts of
Saratoga Springs. Dale (’04, p. 57) has suggested that the Pre-
cambrian rocks come to the surface in the Rensselaer grit plateau
and recommended a minute exploration of the plateau for a Pre-
cambrian mass.

There is no doubt that the Precambrian granites and gneisses
underlie our district at a depth of 4000 to 5000 feet (counting the
thicknesses of the formations of the eastern trough at Albany). Re-
garding these Precambrian rocks of the Saratoga region, Cushing
(’14, p. 135) has stated:

Our direct knowledge of the events of Precambrian time in the
region commences with the deposition of the Grenville series. These
rocks are very widespread and very thick, with great amounts of
shales and limestones and a lesser amount of sandstone. They must
have been deposited on some floor of older rocks which has since
been entirely destroyed by igneous action, or else yet remains to be
discovered. Judging by their extent and thickness the series was

GEOLOGY OF THE CAPITAL DISTRICT 163

probably deposited under marine conditions, but, lacking fossils,
there can be no certainty in the matter.

Following the deposit of the Grenville sediments the region was
repeatedly invaded from beneath by great masses of igneous rock.
The earliest and most widespread of these invasions was that of the
Laurentian granite. Subsequently came invasions of anorthosite,
syenite, granite and gabbro. These broke up the Grenville rocks into
groups of fragments, apparently ate away and digested much of the
basal portion of the sediments and caused the complete disappearance
of their old floor of deposit.

Then followed a very long period of erosion of the region during
which it was above sea level. A great thickness of rock was worn
away from the surface, bringing to daylight the tops of the great
igneous masses which originally solidified much below the surface.
The final effect of the long erosion period was to have reduced the
entire region to one of low altitude and small relief.

In the Adirondacks, or in fact wherever they are known, the P're-
cambrian rocks are intensely folded. It was generally held that
these folds are irregular in direction and hence of no structural
significance. The writer (’22) has shown that the folds are all
arranged in orderly fashion, and that this order is connected with
the original form of the continent, the folds having arranged them-
selves parallel to the outline of the continent, and the compressing
force having acted from the heavier bottom of the nearest ocean.
Thus in the Adirondacks the Precambrian folds strike in northeast
direction and the same is undoubtedly true of the folding deep under
the capital district. Recent researches by Schuchert (’23) indicate
that in the last division of the Precambrian era, in the Proterozoic
time, distinct geosynclines can be made out in North America. One
of these long depressions, which became submerged and sank as they
were filled with sediments from the neighboring mountain ranges,
and which finally were themselves folded again into long mountain
ranges, extended the whole length of the continent inside of the
borderland from Newfoundland or even beyond to Alabama. The
capital district formed just a small sector of this great Precambrian
geosyncline.

The first indication of mountain ranges that appeared in this
geosyncline were the bars or ridges that separated the troughs which
we find in early Cambrian time. The western basin, comprising the
Champlain-Hudson trough, has been called the “Chazy basin,” the
eastern the Levis basin. There were others still beyond the latter,
which do not concern us here.

These basins were sometimes inundated partly or wholly from the
northern Atlantic and sometimes the sea came in from the south, and

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NEW YORK STATE MUSEUM

Figure 3 7 Diagram of emergences and submergences in the eastern and
western troughs of the Appalachian geosyncline in capital district. The
lined intervals are those of emergences and the zigzag line indicates the
shifting of the alternate movement from one trough to the other.

GEOLOGY OF THE CAPITAL DISTRICT 165

sometimes the sea spread beyond them into the interior of the
continent.

We have represented in figure 3 7 the events going on in the two
troughs, during Cambrian and Ordovician times, where the shaded
periods represent emergences and the unshaded the submergences.
It is seen at once that frequent oscillations took place in both basins
and that the invasions of the sea and withdrawals did not take place
simultaneously in both basins, but at very different, times and ap-
parently independently of each other. The most interesting feature
that the diagram clearly brings out is that there was a regular
alternation of the sea in the two basins, indicating an east-west
shifting of the seas in the troughs, such as has been observed in more
complete development, by Ulrich (’ll, p. 547) in the Ordovician seas
of the Appalachian valley troughs in east Tennessee.

Cambrian and Ozarkian History

The Lower and Middle Cambrian time finds the western trough
entirely drained of the sea, while at the same time a great mass of
sediments was deposited to the east, the Lower Cambrian rocks in
the Levis trough, and the middle Cambrian or Acadian beds in still
more easterly troughs, and possibly also to a limited extent in the
Levis trough. This invasion came from the north. It brought with
it a fauna of trilobites, brachiopods and pteropods, and a flora
abounding in the calcareous alga Oldhamia. The sea was, for the
most part, quite shallow, as is indicated by the oblique sedimentation
and plunge structure in the quartzite beds and the conglomerates.
The beds deposited were alternately sandy, clayey, and calcareous
organic, the clayey beds predominating in the capital district and
especially in the upper divisions of the Lower Cambrian. The abund-
ant red and purple beds may indicate subtropical conditions on the
land or exposure and thorough oxidation of the muds in flats.
At the close of Lower Cambrian time the sea retreated northward
and a crustal movement folded these sediments. The new land sur-
face was exposed to atmospheric erosion during the long intervals
of Middle and Upper Cambrian time and considerably leveled. At
the close or shortly before the close of the Cambrian time, the basin
became again submerged and the Schaghticoke graptolite shales were
deposited.

Meanwhile the western trough remained dry until Ozarkian
time, when the Potsdam sandstone was deposited. This is an ac-
cumulation of coarse quartzose sands and gravels. The accumula-

NEW YORK STATE MUSEUM

1 66

tion began first on the northeast, in Clinton county, and extended
itself progressively to the west and to the south. Only the upper
portion of the formation is found in the Saratoga region and enters
more or less into the capital district.

This upper portion contains marine fossils and must have been
laid down in shallow marine waters. The climate was arid and
the land a desert without any vegetation. The land to the west and
south had strong relief, and vigorous currents transported the coarse
sands and gravels into the basin.

The sands of the Potsdam sandstone are succeeded in the Saratoga
region by the alternating sands and dolomites of the Theresa forma-
tion without any sign of a break between them. Erosion had lowered
the bordering lands and the Potsdam sea extended around and over
the Adirondack plateau in the north and south. As a result less
and less sand was brought down from the heights and dolomite
began to be deposited. The sands steadily diminish in frequence
and thickness, and thus the Theresa formation grades upward into
the Little Falls dolomite. Both these formations are marine, but in
both of them fossils are very rare, especially in the dolomite. The
great reefs of the calcareous alga Cryptozoon which occur at many
horizons in the neighborhood of Saratoga, especially at the “Crypto-
zoon Park” seem to indicate the likelihood of a congenial climate
and abundant life.

The Hoyt limestone is a local upper phase of the Theresa forma-
tion about Saratoga. It seems to represent a more offshore phase
of the formation, and fossils are much more abundant than in the
ordinary Theresa or the Little Falls formation. There is especially
an abundant fauna of trilobites.

These three formations are of extreme upper Cambrian age, or
belong to the era separated as Ozarkian by Ulrich, and are the only
Cambrian (or Ozarkian) deposits that were laid down in the Chazy
or Champlain trough. Following their deposit mild uplift occurred
and the troughs came above sea level, existed as land for a time, and
were somewhat eroded. This erosion gently beveled off the surface
instead of deeply cutting into it, which suggests that the land was of
low altitude.

Ordovician History

The uplift just mentioned forms for the geologist the dividing
line between the New York Cambrian formations and those classed
as of Ordovician age. No one has any clear idea in regard to the
length of elapsed time which this uplift represents. Eventually the

GEOLOGY OF THE CAPITAL DISTRICT

167

western trough became again depressed and occupied by marine
waters, and in these, on all four sides of the Adirondack region,
the various dolomite and limestone formations of the Beekmantown
group were laid down. These are thickest and most complete in the
Champlain trough, which sagged more and more to the east of the
Adirondacks, and for a longer time, than on the other three sides
of the Adirondacks. But the deposits of the Beekmantown of the
northern Champlain trough do not occur in the southern continuation,
in the Saratoga region and in the capital district. Apparently the
Beekmantown submergence fell just short of covering this district.
It is barely possible that the formation was thinly deposited and
subsequently entirely worn away.

It was entirely different in the eastern or Levis trough. Here
the sea spread in Beekmantown time from north as far as the capital
district and beyond, for an unknown distance. It deposited the
Schaghticoke shale, at the base of the Ordovician according to many
authors (others still place it at the top of the Cambrian, especially
in Great Britain), and the Deep Kill shales. These thick masses
of shales and grit carry no other faunas but graptolites and but rarely
stragglers from other classes. The writer has recently discussed
(’25, p. 78) very fully the conditions under which graptolite shales
were formed, and in agreement with Lapworth and Marr (’25) in
England, arrived at the conclusion that they were deposited in the
dead grounds, or as Marr expressed it, in the “poisonous” waters
of depths where lack of circulation does not provide sufficient oxygen
to permit life. The graptolites which were planktonic or pseudo-
planktonic (attached to floating seaweeds) in habit, dropped into
these depths from the higher regions after death, or when they were
torn from the seaweeds by storms. They were brought into the
trough from the open ocean, which was their home and it seems
that the rich graptolite zones of the Beekmantown and Normans-
kill would require channels with exits at both ends, to allow strong
surface currents to bring in the graptolite faunas. In the case of
the Normanskill shale there is little doubt that the Levis basin ex-
tended the full length of the Appalachian geosyncline and that the
sea could freely sweep through it.

It appears that the conditions were at least once congenial for
organic bottom life in the eastern trough in late Beekmantown
time. That was when the Bald Mountain limestone was deposited
north of the capital district. We do not know for a certainty whether
this extended as far south as Albany, but similar limestone appears
igain farther south, as on the Poughkeepsie quadrangle.

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The graptolite-bearing marine invasions continued through Chazy
time (uppermost Deep Kill zone and Normanskill shale), the sea
withdrawing for shorter intervals, as between the Deep Kill and
Normanskill invasions, and possibly between the lower and upper
Normanskill invasions, the latter probably of Black River
age. The Rysedorph conglomerate indicates a period of
great erosion or working up of various rock formations
by an advancing sea with strong currents, for some of
the pebbles, as those of Chazy and Lowville limestone, must have
been brought considerable distances from the north. This happened
in early Trenton time; then followed throughout the rest of Trenton
time the Snake Hill invasion, which deposited a great mass of shale
with some grit, probably the full length of the eastern or Levis
channel, for the Snake Hill shale can be traced from Vermont at
least, but probably from the St Lawrence river through New York
and farther south it merges into the Martinsburg shale of Pennsyl-
vania. The eastern trough must have been rapidly sinking, to allow
the accumulation of 3000 feet of shale and grits. While the fauna
consists largely of graptolites, brought in from the ocean by the
currents sweeping through the trough, there was also enough cir-
culation on the bottom to allow a fauna other than graptolites to
exist, for the most part consisting of small forms and appearing
'mpoverished, as if overwhelmed by too great accumulation of mud.
It is for this reason that the mud-loving pelecypods or lamelli-
branchs prevail in the Snake Hill fauna.

In this time, however, there were also places in the Levis channel
where better conditions existed and calcareous Trenton beds could
be formed, as is shown by the Tackawasick limestone and shale.
This may have formed in protected regions of the eastern part of
the trough, unless the limestone has not been pushed over by over-
thrusting from a still more easterly situated basin ; for it is not
without significance that the Tackawasick limestone has nowhere
been seen in the western portion of the basin and that it is nowhere
in contact with the Snake Hill shale, but appears between the Lower
Cambrian and the Devonian Rensselaer grit, separated from both
by thrust planes.

The Snake Hill closes the Ordovician series and the Eastern basin
was apparently completely drained during Utica and Lorraine time.'

Returning to the Western or Chazy trough, we have already seen
that the Beekmantown sea advancing from north, just missed reach-
ing the Saratoga and capital districts. Also the Chazy fell short

GEOLOGY OF THE CAPITAL DISTRICT 169

of advancing into this region. In Black River time the Amsterdam
limestone was deposited in the Saratoga region and it undoubtedly
also extended into the capital district. This is a pure limestone with
an abundance of life, indicating favorable conditions, due to the
absence of a great influx of mud and sand, which means that the
neighboring country had a low altitude.

There came a slight uplift of the region above sea-level and then
the Trenton sea invaded the western trough through its full length.
Its first deposit is the Glens Falls limestone in the Saratoga region.
There is no doubt that this limestone extends into the capital district
and is now deeply buried there under the Schenectady beds. Con-
ditions were at first favorable and the water clear, but the Glens
Falls limestone shows in its middle and upper parts much intercala-
tion of blackish shale, some of it containing graptolites and indicat-
ing the beginning of an influx of mud. It is followed by the
Canajoharie shale of Trenton age. The sea that deposited this great
mass of black shale, containing graptolites and small cephalopods and
lamellibranchs that could exist under the unfavorable conditions,
extended all through the Champlain basin, down through the whole
Chazy channel, and it also spread westward beyond the trough over
the southern slopes of the Adirondack plateau. Toward the west
the Canajoharie shale is replaced by the Trenton limestone, which
indicates the clear marine conditions farther out in the shallow
epicontinental Trenton sea.

The Canajoharie shale has its greatest thickness, over 1000 feet, in
exposures in the Amsterdam quadrangle, directly west of the capital
district. This great thickness is undoubtedly continued eastward
into the capital district. It was the result of the continuous sinking
of the Chazy trough and the influx of much fine detritus, probably
from the north.

The Canajoharie shale grades upward into the still thicker Sche-
nectady beds, also mainly of Trenton age, a great mass of mostly
grayish and more or less sandy shale, alternating with sandstone
beds, many of the latter of considerable thickness, especially toward
the top. The formation, more than 2000 feet thick, shows a per-
sistent hundredfold alternation of shales and sandstones, as along the
Schoharie creek below Esperance and in the neighborhood of Alta-
mont and Delanson, as well as at Schenectady. The rocks are for
the most part barren, but they have furnished in some localities sea-
weeds, marine brachiopods, pelecypods, trilobites and eurypterids.
It seems, therefore, that these beds were formed in a fast sinking

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NEW YORK STATE MUSEUM

basin that was rapidly filled with sediment. Shifting currents de-
posited sands along the coast in times of greater velocity and muds
in such of lesser velocity. The formation is not known to extend far
north or west and it disappears under the Helderbergs in the south.
We therefore do not know whence the invasion came or how far it
extended. There is no doubt that owing to a long interval of
emergence, the greater part of the Schenectady beds was eroded
again, at least in the north. The Schenectady is a distinctly clastic
shore formation that may pass westward and northward into upper
Canajoharie shale and finally into Trenton limestone; or in other
words, the same Trenton sea may have deposited Schenectady beds
in the capital district, black shales in the near north and west and
Trenton limestone farther away. This deposition may have con-
tinued even into early Utica time. The principal portion of Utica
time is, however, not represented in either the eastern or western
basin, and the true Utica shale is found only in the middle and
upper Mohawk valley. If there was any coarser shore deposit of
the Utica other than the upper Schenectady, it has been entirely
eroded away.

The last Ordovician formation of the western trough is the Indian
Ladder beds. This formation, consisting of shales and alternating
thin sandstone slabs, in the lower part calcareous, is exposed only in
a narrow belt under the Helderbergs, extending from Altamont to
New Salem. It reaches, however, considerable thickness in the
neighborhood of the Indian Ladder. The formation was evidently
deposited in a narrow trough that sagged rather rapidly in the middle
and that extended for an unknown distance from north to south.
It is connected by its fauna, a pronounced microfauna indicating
unfavorable life conditions, more closely with the Eden shale of
Cincinnati and the middle division of the Martinsburg shale in
Pennsylvania and more remotely with the Frankfort shale in New
York. It was therefore undoubtedly formed by an invasion advanc-
ing from the south in the western trough, to an unknown distance
north beyond the Indian Ladder. Whatever there was of it north
of the Indian Ladder has long ago been carried off to the ocean, for
there followed an exceedingly long interval of emergence in both
the eastern and western basins, comprising all the upper Ordovician
time, as well as the Ordovician-Silurian intersystemic interval of
general emergence and the earlier Silurian time.

It was in this long interval that the Taconic revolution took place,
which first threw the rocks of the eastern trough into a system of

GEOLOGY OF THE CAPITAL DISTRICT 171

complicated folds and then overthrust the folded mass successively
in a number of plates westward, so that finally the Snake Hill beds
of the eastern trough came to rest against the Schenectady beds of
the western trough and the Lower Cambrian beds came to rest, in
part at least, upon rocks of Ordovician age, notably the Norman-
skill and Snake Hill formations. This revolution took place at the
end of the Ordovician era, or in the Ordovician-Silurian interval of
continental emergence. Then followed again a long interval of
exposure to the atmosphere and intense erosion of the elevated
region. As a result it was reduced to a peneplane, when the sea in
Silurian time advanced again. Not only were both troughs com-
pletely obliterated and filled up by the Cambrian and Ordovician
formations, but the material was after the folding and thrusting so
far eroded that a broad belt of Normanskill shale came to the surface
from under the heavy cover of Snake Hill beds that had been totally
carried away, and the great cover of Normanskill beds and Snake
Hill beds, at least 4000 feet thick that once covered the Cambrian
beds, had been eroded away, with the exception of a few outliers,
exposing the very oldest fossiliferous formations that rest upon the
Precambrian rocks in the capital district. The Devonian Rensselaer
grit rests even on the lower division of the Lower Cambrian, the
Nassau beds, so that it may well be deposited in places even on
Precambrian rocks, as Dale suspects.

As a further result of the folding, overthrusting and great erosion,
the Silurian and Devonian rocks of the Helderbergs rest partly on the
Schenectady beds and Indian Ladder beds of the western trough,
partly on the Snake Hill and Normanskill rocks of the eastern
trough. The contact of the Helderberg formations especially with
the Normanskill rocks is a very unconformable one, that is, the
Helderberg rocks rest more or less undisturbed and horizontally on
highly folded and tilted beds, as is seen for instance on the Spray t
kill (figure 72). It is evident that during the Silurian and Devonian
invasions of the sea, the old Levis and Chazy troughs had entirely
ceased to function as depressions that received sediments, and the
Silurian and Devonian invasions extended more or less far east over
them. Becraft mountain, a small outlier of Silurian and Devonian
rocks east of Hudson, affords the best evidence of the distance to
which the Helderberg rocks extended eastward, some farther, some
not so far. Still farther east, at the margin of the capital district,
the Upper Devonian Rensselaer grit rests directly upon Lower Cam-
brian rocks, thereby proving that either the Helderberg rocks never

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extended thus fai , or that whatever thin sheets may have reached
there had been eroded again before a new longitudinal trough was
formed, in which the Rensselaer grit came to rest.

Silurian History

The long interval of emergence and erosion that followed the 1
small Indian Ladder invasion was finally terminated by a sea that
came in from the southeast, where the Atlantic ocean, or its pre- ■
decessor, the Poseidon, had closely approached to the present coast
line. The thin bed of pyritiferous Brayman shale, may, as we have
pointed out before, be a residual soil of the long era of weathering, ‘
reworked and redeposited by the advancing shallow Salina sea.’

1 he following Rondout waterlime deposited after another emergence,
is clearly a marine sediment, formed by chemical deposition in a
shallow epicontinental sea that extended from the Atlantic to Michi-
gan and in a narrower embayment southward into Virginia. The
greater thickness and development of the Salina formations east-
ward and especially westward seem to indicate that there was a
barriei in the capital district and its neighborhood, which frequently
interrupted the ingress of the sea, from the southwest, about where
New Jersey is today. As a result of this very incomplete connec-
tion with the ocean, the Salina beds are very unfossiliferous and
great deposits of salt and gypsum have formed in the shifting salt
pans from western New York to Michigan. The climate was evi-
dently an arid one, so that this more or less land-locked sea received
but irregular drainage.

d he next or Manlius sea, of similar extent, had, however, free
connection with the ocean and a marine fauna of corals, pteropods,
brachiopods, pelecypods and tnlobites flourished in a broad expanse
of sea that spread westward to Michigan and southward in a narrow |
trough to Tennessee. How far this, as well as all the following
Helderberg formations, extended, we do not know. There is, how-
ever, no doubt that they reached not far up onto the southern
slopes of the Adirondack massif. They have weathered back over
the broad inner lowland to the present escarpment (also called
cuesta) of the Helderbergs, the “Helderberg Cliff” exposing the
Ordovician rocks at the bottom.

In the capital district the Manlius sea was extremely shallow.
We have described before the evidence of tide flat conditions seen
in the New Salem quarry and elsewhere. The thin-bedded Manlius
limestones with their tentaculites, ostracods, small spirifers and
lamellibranchs, mud cracks and mud pebbles, and their association

GEOLOGY OF THE CAPITAL DISTRICT

173

with the Stromatopora beds, suggest that these limestones are prin-
cipally lagoon deposits on tide flats, formed between and behind the
coral reefs.

Devonian History

The Manlius sea in the capital district seems to have changed grad-
ually into the Coeymans sea, as is indicated by the transition beds,
although locally there is an unconformable contact with pebbles, as
at the Indian Ladder, caused by local elevation or stronger erosion
by currents. It is thus seen that the boundary between the Silurian
and Devonian systems is not so distinctly marked as we would expect
to find it.

The Coeymans sea was not greatly different in general outline
from the Manlius. In New York it extended westward from the
Helderbergs not quite so far as did the Manlius sea, and eastward
it had about the same extent. The sea in the Helderberg portion of
the capital district was deeper than before and produced a fairly
pure limestone, containing principally brachiopods. Farther west,
in Herkimer county, plantations of crinoids and cystids are found,
suggesting quiet waters.

The Coeymans beds are again connected by transition beds with
the overlying New Scotland beds, proving a gradual change of con-
ditions. The New Scotland sea lacked the westward extension of
the Coeymans and Manlius seas, but it extended southward in the
Appalachian region and it found a passage eastward across the
Taconic region into a narrow area that extended to the St Law-
rence country and beyond the Newfoundland region to the Atlantic.
The condition had changed in the capital district in that there was
a much greater influx of mud, so that the New Scotland beds are
impure shaly limestones and calcareous shales. On the other hand,
a much richer fauna than before flourished in this sea, a fauna that
consists of 184 species in the capital district, comprising sponges,
corals, bryozoans (71 species), brachiopods (62 species), lamelli-
branchs, gastropods and trilobites. It is a fauna of the littoral
region, but not of the tide flats, the preponderant bryozoans indi-
cating deeper and quieter waters.

The Becraft limestone is so well set off from the subjacent New
Scotland beds that there may have taken place a brief elevation of
the region above sea-level, or at least a shifting of barriers and
currents, that produced a mud-free clear sea in which a limestone,
largely composed of crinoid stems and plates and brachiopods, could
form. This sea formed but a narrow arm in New York, but it

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extended far down to Virginia and across the southern Taconic
region into an eastern trough that led, as in New Scotland time, to
the lower St Lawrence (Gaspe) country and Newfoundland.

The Oriskany-Esopus beds are separated from the Becraft lime-
stone by a break, during which the Port Ewen, Connelley and
Glenerie beds were deposited farther south in the Kingston region.
It is therefore probable that the sea withdrew during that time from
the capital district and the country to the west of it. The Oriskany
sandstone is characterized by its thick-shelled fossils and sandy
limestone, changing to pure quartz-rock at Oriskany; there is no
doubt that the turbulent sea near the northern shore line deposited
these beds. The Oriskany sea, that like all the preceding seas
had an oceanic connection in New Jersey, spread westward in a
narrow embayment into Ontario and like the preceding seas over the
Taconic region into Massachusetts and thence northward into the
Gaspe country, where thick calcareous beds (Grand Greve beds)
were deposited. The broad access of the northern Atlantic in the
Gaspe region and in Nova Scotia brought in the North Atlantic
fauna with European relations (Clarke’s Coblenzian invasion), that
furnishes the typical Oriskany brachiopods, in contrast to the pre-
ceding faunas that had southern Atlantic characters. The thick mass
of the blackish, gritty or sandy Esopus shale is but a different
facies of the upper Oriskany beds, or later Oriskany sea. These
barren beds, containing only the spiral worm trails, known as
Taonurus cauda galli, indicate such an influx of mud, that organic
life was almost impossible. These conditions did not extend far
west beyond the capital district (to Otsego county), but southward
to Pennsylvania.

The Schoharie grit is but a local development or sandy facies of
the lower Onondaga limestone, indicating a great influx of sandy
material in the region from Albany county to Otsego county. In
spite of this sandy admixture to the calcareous mud, the formation
has furnished a large fauna (of 123 species), indicating congenial
conditions, especially for brachiopods (33 species), cephalopods (44
species) and trilobites (16 species). It is a distinct cephalopod
facies, many of which, as the Trochoceras and Gyroceras forms
were undoubtedly bottom-crawlers. It was altogether the rich
benthonic life of the zone below the tides. This cephalopod facies
of the Schoharie grit marked only a restricted area in the great
Onondaga sea, that spread far to the west to the Great Lakes
region, sending a broad arm north to Hudson bay, and another

GEOLOGY OF THE CAPITAL DISTRICT

175

south to the Gulf of Mexico, as well as a narrow blind arm through
the old eastern trough to the St Lawrence region. The short Scho-
harie grit episode was followed by the open Onondaga sea, deposit-
ing pure lime and harboring widely spread coral reefs, that give
evidence of very dear warm water and generally congenial condi-
tions, reflected in brachiopods, large cephalopods and trilobites.

The Onondaga limestone is abruptly followed in the capital district
by nearly 200 feet of black fissile shales, the Marcellus beds with a
characteristic diminutive fauna. This fauna came from the south-
east, having wandered into this region from the southern Atlantic
by way of the Appalachian interior sea. Going west from here one
finds that the beds become more and more calcareous, and that at
least the lower 50 feet correspond to the upper Onondaga of western
New York. The Marcellus is therefore, in part at least, a muddy
facies of the Onondaga sea. Also the upper Marcellus contains in
the west a calcareous intercalation known as the Spafford limestone.
This, as well as an earlier smaller calcareous intercalation, beginning
just west of the capital district and known as the Cherry Valley
limestone, contains a Hamilton fauna. There is still another upper
division of the Marcellus beds present westward from Schoharie
county that we do not have in the capital district, namely the Cardiff
shale. The sea, when these muds were being deposited along the
eastern and northeastern shore lines, was already beginning to spread
far to the west, even beyond the Onondaga sea. The source of the
black muds must be sought in the higher lands, bordering the sea in
the east and north.

The Marcellus sea became by transitional stages, as shown in the
limestone intercalations with Hamilton faunas, enlarged into the
Hamilton sea, which spread from its entrance at the St Lawrence
and New Jersey regions across the continent with arms extending
to the Gulf of Mexico and north through the Mackenzie region to
the Arctic ocean. In New York this sea deposited several thousand
feet of shales and sandstones teeming with life, especially brachio-
pods and lamellibranchs, adapted to the muddy sediments. In the
east the faunas entered from the Atlantic, carrying the character-
istic Atlantic brachiopod Tropidoleptus carinatus, that is found as
far south as South Africa, and the Falkland Islands. In the western
portions of the great inland sea, Arctic and Pacific faunas are found.
Even if deposition of the beds took place much faster than that of
the limestones, the great thickness of the formation and the wide
extent of the sea indicate that it must have persisted over a long
period of time.

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NEW YORK STATE MUSEUM

While it is true that the Hamilton beds are the highest that we
find now in the capital district, there is not the least doubt that the
Devonian beds, that overlie the Hamilton beds in the eastern belt of
New York and south of the capital district, once extended entirely
over the district to the southern slopes of the Adirondack plateau.
They have been entirely eroded away. These formations are the
Sherburne sandstone, the Ithaca beds, the Oneonta sandstone and
the great mass of the Catskill beds. These several thousands of feet
of shales and sandstones indicate at least two floods and emergences
of the country. First it appears that there was a withdrawal of the
sea in the northeast, for in western New York there are a number
of formations, the Genesee beds (with the Tully limestone, Genesee
black shale, Gennudewa limestone and West River shale that do not
reach eastern New York) and in southeastern New York are the
Bellvale flags of the corresponding age. Then the Portage sea ad-
vanced from the west, depositing in western and central New York
the Cashaqua shale and in eastern central and eastern New York
the Sherburne sandstone. In Otsego and Schoharie counties the
fossils of this formation are a modified Hamilton fauna, that still
lingered from earlier times, but in Albany county, down to Greene
and Ulster counties, we find only barren flagstones bearing occa-
sionally a few species of plants. It is quite obvious from this obser-
vation that a broad bay, the Albany bay, had been formed in the
northeast corner of the Portage sea, where a river, most probably
coming down from the north, emptied and brought into the bay
the sands and the plant fragments now found in the eastern Sher-
burne rocks. These conditions continued while in western New
York the peculiar foreign Naples fauna flourished, and farther
east lived the Ithaca fauna, still a derivative of the Hamilton fauna.
This Naples-Ithaca sea deposited in the northeast corner, the Albany
bay, Ithaca beds, that are reddish and greenish shales and sandstones,
instead of the bluish and grayish marine shales of the west. These
reddish shales are again barren and both by this fact as by their
color denote their derivation from a near-by land and their deposi-
tion in a brackish bay. The Ithaca beds are followed by more than
500 feet of Oneonta beds between the Helderbergs and the Catskills.
These are “red and green shales, reddish sandstones and coarse
grained grayish to greenish gray sandstones” (Prosser, ’99, p.
313). They are unfossiliferous, except for an occasional specimen
of the fern Archaeopteris and the fresh-water clam Archanodon
( Amnigenia ) catskillensis. These beds are also correlated with marine

GEOLOGY OF THE CAPITAL DISTRICT

1 77

beds holding the Naples fauna, of Portage age. It was in this time
that on land to the east and north of the bay, the most ancient
forests grew, that we see reproduced in the Gilboa group in the
State Museum. Such forests may have grown above the shore lines
in the northern part of the capital district or only a short distance
beyond it. The northeastern Albany bay was now more sharply
separated from the sea than before, probably by a bar projecting
southward from the coast line in the north such as Clarke (’04,
plate B) has described. And upon the Oneonta beds are piled the
thousands of feet of Catskill rocks, shales and sandstones, that are
of the same age as the Upper Devonian Chemung rocks of western
and central New York, with a profuse organic life that strongly con-
trasts with the barrenness of the Catskill beds. At this time heavy
land drainage had changed the Albany bay into a large fresh-water
or brackish lagoon or estuary. As we have already described in an-
other chapter, a great river coming from the north into this bay
deposited the Rensselaer grit along the edge of the capital district
in a sinking trough at the same time that farther down in the bay the
Catskill beds were formed.

This was the end of the marine Paleozoic deposition of which we
have a direct record in this part of New York. In southwestern
New York and in Pennsylvania a great series of formations of
Carbonic age, both of the Mississippian group and the Pennsylvanian
group are still found. The rich coal beds of Pennsylvania were
formed in this time. There is no doubt that a large portion of these
formations, also, once extended into our district, and that for all
we know luxuriant swamp forests of the coal period may have
flourished here as well as in Pennsylvania, for, if we consider that
the capital district was exposed to the gradational work of wind
and weather ever since the Carboniferous period, that is, for 300
millions of years as geologic time is figured now, it is readily seen
that an enormous amount of material above the Catskill beds must
have been removed in this long time.

Toward the end of the Carbonic era the Appalachian revolution
began, which again folded eastern New York, throwing the Rens-
selaer grit into the series of anticlines and synclines that we find
now composing the plateau. This folding died out rapidly toward
the west. Its last vestiges are the small folds in the Helderbergs,
south of Clarksville, described in a former chapter.

And then began the great process of removal of the pile of rocks
which from the top of the Catskills to the base of the Cambrian

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amounted to over a mile of rock, and at the beginning probably to
a mile and a half. Considering that this mass was folded in the
eastern portion of the capital district and raised into mountain
ranges, it is not too much to say that there were possibly as much as
two miles of rock above the site of Albany that have been carried
off to the sea since Paleozoic time. The process began in the north
on the slope of the rising Adirondack plateau and worked backward
and southward in a series of terraces and escarpments, until now
everything of Silurian and Devonian age is eroded away north of
the Helderberg escarpment, and the older Ordovician and the very
oldest Cambrian rocks have come to the surface. Above the reced-
ing Helderberg cliff the enormous pile of rock that we see rising
farther south in terraces to the top of the Catskills has already been
worn away. It is due to this far-reaching erosion that the capital
district furnishes a section from the Lower Cambrian to the Upper
Devonion rocks.

Cushing and Ruedemann (’14, p. 142 ff.) held, in regard to the
Saratoga district, that the Silurian and Devonian seas did not reach
it, and that the preservation of the Ordovician rocks in the western
trough demonstrates that the region remained near sea-level and as a
result was exposed to but little erosion; further that “it is probable
that during oscillations which depressed the western trough, con-
tinental deposits accumulated in it and were subsequently worn away
during the intervening periods of greater altitude.” It was also
(p. 143) suggested that “much of the overthrusting is of later date
(than closing stage of the Paleozoic) and possibly very much later.”
In the light of the information gathered in the capital district, it
appears necessary to qualify these statements, since it is quite cer-
tain that the Silurian and Devonian rocks extended into the Saratoga
district from the Helderbergs and that continental deposits in the
eastern trough are represented only by the Rensselaer grit. The
fact that the overthrust planes pass under the Helderberg rocks with-
out producing any far-reaching disturbances in these overlying beds,
seems to us to demonstrate that the overthrusting must have taken
place before the deposition of the latter. Even if the slight folding
in the southeastern portion of the Helderbergs in the capital district
and Kingston region is attributed to the influence of the large over-
thrusts in the shale belt, it would make the latter not older than the
Appalachian revolution. If a direct connection between these over-
thrusts of the Devonian Helderberg rocks and those in the slate belt
can be established, it will mean either contemporaneity of the two
and late Carboniferous age for both, or that the overthrusting in

GEOLOGY OF THE CAPITAL DISTRICT

179

the Devonian rocks is a posthumous revival of the older overthrust-
ing activity.

In our opinion, the unconformable relationship of the late
Devonian Rensselaer grit to the underlying Cambrian-Ordovician
thrust masses must indicate that at least a part of the overthrusting
took place before the deposition of the Rensselaer grit. On the other
hand, if the Tackawasick limestone and shale is separated from the
Rensselaer grit by an overthrust, as seems to be inferred from the
structural relations, thrusting has still taken place after the deposi-
tion of the Rensselaer grit, and there is no saying when that may
have been.

Mesozoic History

For the Mesozoic history of the capital district we have only nega-
tive data. There is no trace of deposits of this long era here. It
would therefore seem to follow that the region must have been a
land area. During the early part of Mesozoic time, in the Triassic
period, however, certain troughs along the east margin of the
Appalachian region subsided and received a large thickness of con-
tinental deposits. If such later troughs had been formed in the
capital district, the Helderberg region would preserve a record in
some sagging of the beds. The Helderberg rocks, however, exhibit
fairly regular strike, with the exception of minor faults and folds.
Cushing and Ruedemann (’14, p. 144) have argued that the great
normal faults of the Champlain basin and the Saratoga region are
the result of repeated dislocations that began with the sagging of
the western trough in early Paleozoic time and the tendency of the
Adirondaclcs on the west to rise, and may have well continued into
Mesozoic time, for “the faults of the eastern Adirondack region
are normal with nearly vertical fault planes, and these certain
Mesozoic faults are of similar type” (as for instance those delimit-
ing and transecting the Connecticut Triassic basin). It is quite
possible that the Saratoga fault, which enters the capital district
and passes along Ballston lake, is of Mesozoic age, and likewise the
small faults found in the Helderberg cliff.

Cessation of the continental deposits of early Mesozoic (Triassic)
age in the troughs to the east of the Appalachian folds was probably
brought about by renewed uplift. Then followed a long period of
erosion, the final result of which was a rather thorough wearing
down of the region to a comparatively low plain, a so-called pene-
plane. A peneplane of late Mesozoic (Cretaceous) age was pro-
duced quite generally throughout the Appalachian region and eastern

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NEW YORK STATE MUSEUM

Canada, and it is quite reasonable to assume that it was also pro-
duced here.

In reconstructing in the mind the events of this Mesozoic era, we
can not help being aroused by the thought of the strange world that
during this long era (that began 600 million years and ended 200
million years before our time) existed at the beginning perhaps two
miles above the present site and level of Albany; of the strange and
gigantic reptiles, the tracks of which are still found in continental
deposits of the Connecticut valley, that once wandered about in
equally weird forests and swamps high above our present city; and
of the 40 million years of time, of which we have no record here
and during which the country gradually sank to near sea-level.

Cenozoic History

The Cenozoic history of the capital district is the same as that of
the Saratoga region, which has been described by Cushing and
Ruedemann (’14, p. 145) as follows:

At the close of the Mesozoic the region was again uplifted. The
low altitude peneplane which had been produced over the Adiron-
dack region was elevated some 1500 feet or more, and rapid erosion
of its surface began. Stream valleys were cut down and broadened.
It is the depth of the valley cutting below the old peneplane level
which enables us to estimate the amount of the uplift. The divides
between the valleys, however, have been but little worn down during
the time that has passed since the uplift. These divides rise now to
uniform levels, the level of the old peneplane. An observer, stand-
ing upon one of these divide summits and looking abroad to the
others, receives the impression of standing upon the surface of a
plain and has merely to imagine the valleys refilled with material in
order to picture the plain as it was at the time of the uplift.

This old peneplane surface is readily made out over most of the
Adirondack region. But in the extreme east it seems to fail and
the divide summits rise to very discordant levels instead of being
uniform. This we take to mean that here renewed slipping along
the old faults occurred as a phase of the uplift; that the Champlain
trough displayed anew its tendency to sag relative to the district
to the west; that it was uplifted much less than the Adirondacks ;
and that the difference in amount was made possible by additional
faulting, the easterly slices being thrown down relative to those west
of them. The old fault scarps had been peneplaned along with the
rest of the region. These further movements renewed them, and
their prominence today is in part due to this late movement. The
McGregor and Hoffman fronts of the Saratoga quadrangle would
be much less imposing than they are had it not been for this.

It is by no means unlikely that further westward movement of the
eastern basin rocks along the thrust fault planes also took place at
this time.

GEOLOGY OF THE CAPITAL DISTRICT l8l

During the first part of the Cenozoic, the Tertiary, minor oscil-
lations of level took place in the region, but we lack the precise
knowledge of just when and what they were. Later in Tertiary time
an additional uplift took place, considerably increasing the altitude
of the region, not improbably with renewed faulting. The pene-
plane that had formed during the preceding Tertiary time and that
was now uplifted, is recognized in the Tertiary peneplane of the
Helderberg mountains and the Rensselaer plateau, described in
another chapter. A still lower peneplane began then to form in
the inner lowland of the Helderberg and Rensselaer plateaus ; this
is the Albany peneplane. It is still growing into the surrounding
plateaus.

Finally the region was invaded by the ice sheets of the glacial
period. The Pleistocene history, or the fate of our district during
the glacial period, will be fully described by my colleague, Professor
John H. Cook.

THE GLACIAL GEOLOGY OF THE CAPITAL DISTRICT

BY JOHN H. COOK

In the capital district broad areas of the bedrock are concealed by
overlying deposits of laminated clay, sand, gravel and glacial till or
boulder clay, all of which are referable to late glacial or recent time.
With the exception of certain clayey or sandy residual soils (formed
in place by the weathering of exposed rocks), an occasional talus
and a moderate amount of alluvium, these unconsolidated materials
are products of the action of moving land ice, having been plucked
or rubbed from the bedrock by the overriding Wisconsin ice sheet
and subsequently more or less sorted and redistributed by water
and wind. Wherever the beds accumulated in such manner that they
present definite characteristics of form or internal structure, it is
possible to infer from them something of the conditions under which
they were laid down, and these inferences, supplemented by those
which may be drawn from the distribution and relations of the
several types of deposit, constitute the evidence to be interpreted
in reconstructing the salient phases of this part of the geological
history.

During the recent period the familiar processes grouped under the
term erosion have altered the topography of the region by removing
portions of the ice-derived deposits from their original positions ;
the wind has deflated the sand plains west of the Hudson river, and
streams of water have etched the whole district with valleys. Much

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182

of the fine wind-blown sand has escaped lodgment in the water
courses and has piled up in mounds or dunes,1 but, of the materials
excavated by the numerous streams, by far the greater part has been
carried out of the district. That part which has remained, notably
the coarser elements, has been left as sediment in the Hudson valley
and now forms an extensive filling in the channel from Troy south-
ward for a distance of 30 or 40 miles.

This deposit is made up principally of the sand and silt brought
down by the river system above Troy (although each small creek
discharging into the Hudson below that point has contributed its
quota of sediment) and constitutes the sea-level delta of that system
at the present attitude of the land with regard to the sea, its higher
portion projecting as a series of islands and mud flats as far south
as Coxsackie. From Troy to Coxsackie the deltas of the side
streams are commingled with the sediments of the Hudson proper,
but south of the latter place they may be distinguished as independent
deposits.

That the accumulation does not at once suggest its nature is due
to its undeltalike form. When free to do so, the constantly shifting
distributaries of a river emptying into a lake or the sea spread the
sediments into a rude fan ; but when, as in the present instance, these
distributaries are confined by high ground to a more or less
straightened course, the delta will, of necessity, be linear in form.

There is no way of determining how long it has taken to make
this recent fill in the channel, but we know that the beginning of
sedimentation coincided in time with a subsidence of the land which
carried the old valley floor of the Hudson below sea-level and per-
mitted the sea to invade the main trench and the lower portions of
the contributary valleys to a point only a few miles south of the
Mohawk confluence. This can be shown to have taken place more
recently than any other important geological event affecting the
region. Not only was the glacial ice gone and the “lakes” in which
the clays were deposited drained, but the development of the valleys
of the modern drainage system had progressed well toward the con-
dition found today. The proof is as follows :

While the Hudson river itself, from Hudson Falls southward,
lies within an older (preglacial) valley, which for convenience we
shall continue to call the Hudson valley, practically all of the con-
tributary streams follow new or postglacial courses as they approach

1 The three principal dune areas lie (1) between Albany and Schenectady;
(2) about Clifton Park, Saratoga county; and (3) in the town of Stillwater
northeast of Round lake.

GEOLOGY OF THE CAPITAL DISTRICT

183

this old valley, and they come to the brink of its steep rock wall,
on one side or the other, at points not previously breached by the
action of flowing water. When these lateral streams began to
intrench themselves the land stood higher above sea-level than it
does now and the trunk stream (the Hudson) into which they
emptied made its way over a bed of rock and boulders, sweeping
most of the finer particles of its load along with it. Then the land
began to subside and sea water crept into the valley system from
the south. But before the crustal movement ceased, with the sea
reaching inland as far as Troy and the lower part of the system
drowned and dismembered, the greater part of the material washed
away by the lateral streams in making their valleys had been
removed. This is indicated by the comparatively small amount of
sediment which has been dropped by them in the existing estuary;
that is to say, the modern delta of any one of the creeks entering the
estuary below Coxsackie represents but a small fraction of the total
material excavated from the basin which it drains. It would thus
appear that the time during which the present stand of the land has
determined the location of such sedimentary deposits has been short
in comparison with that represented by the erosional work in the
basins supplying the sediments.

We may, therefore, divide postglacial or recent time by the
criterions given above into a longer and a shorter period, the former
measured by stream erosion and the latter by deposition in the
estuary. During the earlier and longer period, the land began to
subside and continued to do so until the present stand was reached ;
during the shorter period the earth’s crust has been stable. The
Hudson’s delta was built during the second period which has been,
geologically speaking, a very brief time interval.

Geologists are quite generally agreed that the weight of the cover-
ing of land ice during the glacial period was sufficient to upset the
balance of forces which maintains the subcrustal rocks in a rigid
condition ; that material some 60 or more miles below the surface
moved out from under the ice field to sections of the periphery until
equilibrium was reestablished ; and that, when the ice melted off, this
displaced material slowly returned to something like its former posi-
tion. Thus both the greater elevation of the land in the capital dis-
trict at the time of maximum glaciation, and the gradual lowering
of the crust after the ice had disappeared, are accounted for. It is
interesting and important to note how lately the last movement of
readjustment took place.

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NEW YORK STATE MUSEUM

In attempting to gain a reasonably accurate estimate of the amount
of erosion accomplished by the modern stream systems, it is neces-
sary to make allowance for certain channels which were in existence
before the ice invasion and for others which appear to have
been made by streams of ice water during the final stages of melt-
ing of the Wisconsin ice. For example, the Hudson Valley itself
is preglacial. Again, the disproportion between Drummond creek
from East Line northward (east of Ballston Spa) and the channel
which it occupies suggests at once that the latter was cut by a larger
stream, probably of ice-derived water. Another channel of similar
origin, but carrying no stream, is found about four miles a little
west of north from Schenectady. It is a small gorge cut through
the rock of the ridge which extends southeasterly from Town House
Corners in the town of Glenville, particularly instructive in that it
bears no relation to the lines of existing drainage.

Allowance must also be made for certain features along the courses
of streams which appear to be erosional expansions of their valleys
but which are in reality cavities left by sizable masses of dead ice
which have melted. Many of the lake basins of the district were
formed in this way and a few of them have been mistaken for
excavations made by the modern drainage. They will be mentioned
later. The Hudson valley itself appears not to have been filled with
glacial deposits and reexcavated, but to have been protected in
large measure from such filling by the remnants of a tongue of ice
remaining in the gorge.

It will be seen, therefore, that a quantitative estimate of the
amount of material removed by the Hudson river system above
Troy is difficult if not impossible, but, in view of the criterions
furnished by the small valleys southward from Coxsackie, we may
be confident that the modern delta is but a small part of it.

The glacial deposits consist of (1) “till,” the unassorted mixture
of clay and stones of moderate size, dropped from the melting ice ;
(2) more or less assorted gravels laid down in the presence (fre-
quently banked against the edges) of stagnant remnants of the
glacier and distributed in part by the waters of melting ice; (3)
thick beds of laminated clay marking the sites of former lakes held
up on the rock terraces bv unmelted ice, in the Hudson valley
especially, but also at other places as for example : the headwater
part of the Alplaus kill basin ; and (4) quantities of yellow sand
rather generally distributed over the surface of the clays and, in large
part, to be referred to the stage of temporary lakes. The lacustrine

GEOLOGY OF THE CAPITAL DISTRICT 185

beds taken as a whole belong to a stage which is later than that
shown by the till and gravels.

In dissecting these beds, the streams excavated the softer materials
rapidly, until downward cutting was checked by bedrock or till of
a resistant character. At each point where such harder material
was encountered a rapid or fall was formed and, upstream from
each rapid or fall, a reach or comparatively level stretch was devel-
oped. In the reaches sediment accumulated and from time to time
forced the stream against one side or the other of its valley, thus
enabling it to widen the sections between rapids by lateral cutting.
As a steep-walled gorge was eroded through each barrier of rock
or other resistant material, the reach controlled by that barrier was
trenched more deeply and portions of the leveled floor thus
abandoned were left above the new high-water mark of the stream
as terraces.

It is convenient at this point to note that a body of standing water,
as for instance a glacial lake, in the path of one of these modern
streams would have acted to hold up the development of its valley
to the level of the lake surface, and, as that surface lowered, the
abandoned deposits made at each stage of fall would now be repre-
sented by terraces, similar to those in a reach but not correlated
with any down-stream control. Since such features do not appear
along the streams which were clearly formed of meteoric waters
alone after the lacustrine beds were exposed to their action, we con-
clude that those streams were not in existence during the lake stage.
This can mean only that the climate at that time was much drier
than at present. Such physiographic evidence is of considerable
importance in the attempt to separate the lines of glacial drainage
from those of the modern system. We shall mention the more
important of the latter in more detail.

The valley of the Mohawk, within the area of our map, is wholly
postglacial although west of Schenectady the river occupies an older
valley. This preglacial valley in the bedrock is continued eastward
from Schenectady to the Hudson valley which it joins near Albany.
This part of the preglacial channel was filled up by sediments, and
the modern river, directed by the new slopes so created and possibly
also by low places where ice blocks were melting out, has taken
a course to the northeast, spilling over a rock barrier at Aqueduct
and thence making its way to the Hudson at Cohoes. There is a
rather pronounced reach level indicated in the Schenectady district
which may be correlated either with the Aqueduct barrier or one

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NEW YORK STATE MUSEUM

south of Ballston lake, the elevation of both being about the same.
The fact that a terrace of this series continues along the west side
of the broad channel in which lies the lower course of Alplaus kill
has led to the supposition that the glacial equivalent of the Mohawk
(the Iro-Mohawk) followed this channel for a time before the pres-
ent course was established. We shall consider this possibility later.

The Hoosick river is in a preglacial valley from its upper basin
to near Schaghticoke, but from this point westward it occupies a
postglacial channel cut through a broad delta built by the river dur-
ing a stage of the glacial lakes. This delta was laid down over a
large block of ice anchored in the Hudson gorge, which ice persisted
through the earlier phases of the dissection of the deposit and was
effective as a barrier, delaying the downward cutting by the river
long enough to permit the formation behind it of several successive
terraces. As the levels of these terraces are not matched by the
equivalent deposits of other, presumably contemporaneous streams,
in the vicinity, it seems evident that they were not controlled by the
surface of a wide and open body of water covering a considerable
area, but are of strictly local origin.

The sites of other large masses of ice which outlasted the lake
stage are the basinlike areas in the bottom of which lie Round and
Saratoga lakes. The basin of Ballston lake was gouged out of the
bedrock by the passage of the glacial ice and it too must have con-
tained ice during this stage, or it would have been filled with sedi-
ment, for the upper part of the Alplaus kill system, that is, all that
lies west of the trench followed by the Delaware and Hudson Rail-
road, was the site of a temporary ice-confined lake receiving sedi-
ments which today present a surface from 360 to 380 feet above
tide. Although the trench fronting this deposit and, farther north,
containing Ballston lake, may have been used later by the Mohawk
or the Iro-Mohawk, its glacial predecessor, it seems that parts of it
were still occupied by ice, or dissection and sedimentation would
have left it with the leveled structure of a reach slightly above 300
feet (A. T.) to conform with the normal development behind the
barrier at that level, caused by the divide just south of Ballston
lake. It is only frank to admit that the drainage lines north of the
Mohawk from the Ballston channel to the Hudson present a puzzle
which has not as yet been satisfactorily solved.

The valleys appearing west of the Hudson between the Mohawk
and the base of the Helderbergs have all developed along courses
predetermined by the surface of the lacustrine sands and clays.

GEOLOGY OF THE CAPITAL DISTRICT

187

East of the Hudson the drainage lines are very largely due to
the slope produced by the irregular deposition of glacial materials
(sands, till and gravels at the higher elevations, clays below about 260
feet), and the numerous lakes and alluvial flats shown on the map
mark the outlines of lingering masses of ice or valleys dammed by
glacial drift. The largest and most striking of these is the trough
occupied by Tomhannock creek north of Raymertown, which was ice
filled while glacial waters were silting up the valley south of that
point along the course of the Quacken kill.

The foregoing will serve to introduce to the reader three of the
outstanding pictures in the geological record which may be conjured
up from the evidence furnished by the unconsolidated deposits: (1)
the stage of coarse gravels and sands being laid down as the last
stagnant shreds of the glacier were melting off ; (2) the stage of
clay beds evidencing lacustrine conditions; and (3) the recent sub-
sidence.

To recapitulate: There is a series of deposits made along the
edges of remnants of the disappearing cover of ice or pocketed in
crevasses and other openings. Next, there may be inferred a transi-
tion stage, as the standing waters of a “lake” rose about the remains
of the glacier and began to float the fragments while the rock flour
and fine sands washed out of the ice settled in horizontal layers over
the previously deposited gravels. The ice had not completely melted
away when the “lake” waters had reached their maximum depth and
the last beds of sand and clay referable to this stage had been laid
down. The falling levels of this body of water appear to be vaguely
shown by occasional terraces on the bluffs above the estuary and also
bordering the river and its larger tributaries above Troy. But it is
to be inferred from the absence of such terraces at many critical
points that the climate was still deficient in rainfall and we are
probably justified in concluding that the water of all the streams
feeding the shrinking lake was derived from melting ice.

Then the climate altered to one characterized by greater precipita-
tion, the present-day drainage lines were established, and valley
cutting began. After an interval during which many deep trenches
were corraded in the glacial deposits and softer rocks, the last im-
portant crustal movement in the region took place, drowning part
of the Hudson river system and confining erosion to the area left
above the level of the newly formed estuary in which deltas began
to build.

Before describing the pleistocene deposits in greater detail, we
shall repeat briefly the description given in a previous chapter of the
topography of the bedrock underlying them.

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NEW YORK STATE MUSEUM

Figure 38 Diagram of the valley now occupied in part by the Hudson river.
A-A, Cretacic peneplane; B-B, 200-foot terrace; C-C, floor of outer gorge;
D, inner gorge.

First, there is an old land level known as the Tertiary peneplane
now uplifted to an elevation of some 2000 feet above tide, the much
dissected flat top of which can be detected from many high points
in the Helderbergs and along the extreme eastern edge of the Troy
quadrangle (A-A in the ideal diagram, figure 38). Into this plain
an ancient drainage system sank its valleys, the principal one of
which extends north and south through eastern New York. Most of
the area with which we have to do in this discussion lies within this
great meridional valley, the much worn sides of which slope down to
a flattish floor. This latter comes to the edge of an inner valley as
a rock terrace standing, in the vicinity of Albany, at an elevation
of some 200 feet above tide (B-B of figure 38). The inner valley
has steep side walls and is properly to be spoken of as a gorge ; its
floor now lies some 20 or 30 feet under the waters of the estuary
at the southern boundary of the Albany quadrangle and comes above
sea-level at Troy (C-C of figure 38). This, in turn, is threaded by
a much deeper and narrower gorge (D-D of figure 38) with which
we are not concerned except that it would appear to be this deeper
trench to which the now drowned mouths of the lateral valleys were
adjusted in the period just preceding the recent subsidence. At the
site of the new railroad bridge near Castleton, it coincides in
position with the navigable channel.

Probably more or less adjusted to the levels of both the gorges
are two deep preglacial valleys (now buried) joining the meridional
valley near the point where the city of Albany stands. One is the
previously mentioned continuation of the valley now occupied by the
Mohawk river as far east as South Schenectady which, borings
show, lies approximately parrallel to and not far north of the
Normanskill. The other is located under the plains of clay and
sand west of the Pludson, passing through the basins of Saratoga
and Round lakes, the expansion of the Mohawk valley between

GEOLOGY OF THE CAPITAL DISTRICT

189

Vischer’s Ferry and Dunsbach Ferry, and so to West Albany some-
where near which place the two buried valleys join. This rock
surface was subjected to glacial erosion several times, but as none
of the local features demand explanation as the results of earlier
glaciations, we are concerned only with the last of the great ice
sheets, the Wisconsin.

At its maximum extent this ice sheet maintained a front just
south of Manhattan island and was thick enough to pass over the
highest peaks of the Catskill and Adirondack mountains. The
movement of the ice was subject to change in direction both hori-
zontally and vertically as the avenues of least resistance were shifted.
We may picture the character of this movement best by assuming
the whole mass to lie immovable except as increasing pressure now
and again passed the critical point beyond which the deeper ice could
no longer maintain its rigidity and moved out radially from under
the overload, frequently coming to the upper surface of the ice field
some distance away and there leaving a moraine derived from a
lower elevation. Such a moraine would be ephemeral in the sense
that, being built upon ice, it would not be preserved to reach the
ground in recognizable form, if at all.

The record of one such movement is found in the capital district.
It took the form of a fan with a more extended branch, running,
like a broad stream, westward nearly to Utica, attached to its north-
ern edge. This westerly moving arm would appear to mark the
earlier phase of the movement for the northern part of its basal
portion is rather abruptly truncated. The fan proper spread over
the dissected plateau north of the Catskills among the northern
peaks of which mountains the moving ice probably sheared upward
over stagnant ice. At any rate there is no moraine marking its
periphery or frontal edge as there probably would be if the land to
the south and west were uncovered.

This glacial flow in the midst of the ice while it was still very
thick carried a large amount of drift from the low basin area up
over the Helderbergs and across the intervening valleys to the limits
to which its traces on the land can be found. It scored the ground
from present sea-level to more than 2000 feet above it before over-
riding the ice in front ; it was the last recorded streaming, obliterat-
ing the marks left by all former passages of ice throughout the field
which it covered, fluting the land with elongated hills of till (drum-
lins) and scoring the bedrock with deep furrows, of which latter
the basin of Ballston lake is the most striking example.

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NEW YORK STATE MUSEUM

Figure 39 is intended to show, diagrammatically, by a vertical
section through the glacier, the phenomena of a movement in the
ice caused by local overloading at a distance behind the periphery,
or by a general thickening of the central field of the ice cap. In-
creased pressure at N (and to the right of the diagram) has set the
ice crystals of the deeper portion in positions so nearly horizontal
that they slide over each other with great freedom, and a forward
motion of the superincumbent mass results, which may eventually
be transmitted to the bottom of the sliding zone. As the frontal
field of the glacier is in a state of equilibrium and, at the time,
without motion, it acts as a barrier to be overcome. In consequence,
the pressure behind the moving ice will be too weak to rearrange
the crystal axes in the position necessary for motion everywhere
and to an unlimited distance from its point of origin. When the
limit of its power so to do is reached, the front of the area (or the
periphery if movement is radially distributed) sheers up over the
surrounding motionless ice until a new temporary equilibrium is
established.

Figure 39 A north-south section showing ice moving out from under an
overload and overthrusting on motionless ice in front. C, Catskill moun-
tains ; H, the Helderbergs. Arrows indicate the direction of movement ; the
short arrow continues the plane of overthrust.

It is probable that this is a common method of both thickening
and advance in an ice sheet of continental proportions. A mountain
glacier is dependent for its pressure upon the accumulation of snow
in a comparatively small field, but a vast area of land ice receives its
snowfall on its surface, is thickened locally and often responds by
local adjustments taking the form of saucers, the arcuate edges of
which sheer up onto the ice at a distance from the center of pressure
created by local increases in the precipitation. At its maximum
extension such an ice cap would be apt to have wide sections of
its marginal zone in a stagnant condition and, as the snowfall
decreased with an amelioration of the climate, the local thrusts from
within the field would become less frequent and finally cease alto-
gether, leaving the marginal zone to melt of? in situ. This is what
appears to have occurred in eastern New York and in New England.

GEOLOGY OF THE CAPITAL DISTRICT 191

In the higher parts of the capital district we find little to mark
the form of the large ice masses resulting from the slow melting
of the stagnant glacier, but, as the ice thinned and the land surface
began to appear through it, streams of ice-derived water distributed
sands, gravel and clay beds over the dead ice and here and there
left a deposit against a hillside in what was evidently a pocket
between the land and a mass of ice. Such accumulations are known
as lateral terraces but, where the ice was stagnant the term “mar-
ginal” is perhaps more accurate. They are characterized by the
partial preservation of the slope where they lay against the ice ; if
the ice edge was steep, as in A of figure 40, the outer boundary of

AA BB

Figure 40 Types, of contact with the ice. I, the ice; R, the land slope; D,
the deposit which in A becomes the steep-faced terrace in AA as the ice
melts, and in B collapses into a field of knobs and hollows BB.

the terrace drops off steeply, a comparatively small amount of
material having slumped when the supporting ice melted (A A of the
figure). If, as in B, the terrace was built over thin ice, it may have
collapsed into a belt of knobs and hollows (kame-kettle terrace) and
now retains little more than a hint of its original form (BB). One
such terrace occurs at the southeastern base of Copeland hill on the
Helderbergs, its leveled top just above the 520-foot contour line,
and the contact slope as in A A.

A second type of deposit which has been preserved by having
been built on the ground is illustrated by a rudely conical mound of
waterwashed gravels at the north end of Bennet hill three and one-
half miles northwest of the terrace just mentioned. Its top rises
above the 66o-foot contour and it was evidently made in a hole or
small crevasse in thin stagnant ice.

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192

So scattered are the isolated deposits at the higher levels that
no relations can be established among them, but it is quite evident
that, as the ice thinned, the outline of its southern margin became
more and more complex. At first its surface was interrupted only
by land islands where the hilltops of the dissected plateau came
through ; these small bared areas spread and joined and became con-
nected with the ice-free district to the south. With each stage of
thinning, a thicker insulating blanket of detritus accumulated on the
surface of the ice, some of which was transported and deposited by
superglacial and subglacial streams ; but only as a part of this
accumulated debris was carried or dumped from the ice onto a rock
surface could it remain sufficiently undisturbed to furnish evidence
to the geologist. A topography partly of land and partly of ice
and threaded by shifting streams of water of inconstant volume
will normally give less opportunity for leaving accumulations in the
positions in which they could be preserved when there is a com-
paratively small land surface exposed. Therefore, while the ice
was thick enough to cover the Hudson valley and the lower slopes
leading up to the top of the plateau, only the first few scattered
terraces were built against those slopes.

Without the action of running water the entire drift content would
eventually have come to rest on the ground previously occupied by
the land ice as an undifferentiated mantle of “till,” but where stream-
borne materials have been washed out over thin ice in sufficient
quantity, the subsequent melting of the ice, though destroying any
form which the deposit may have had and nearly, if not quite,
obliterating its stratified or bedded structure, will not alter its char-
acter as washed or sorted material. Many of the gravelly beds of
the capital district are without an admixture of clay or fine sand
and are interpreted as having been partially washed by superglacial
streams and marginal streams with little grade or sorting power.

A series of glacial plains in the basins of the Poestenkill and the
Wynant kill (Troy quadrangle) presents a congeries of features,
including much of this poorly washed gravel, which indicates that
the ice which overlay the district was for a time in the path of a
major line of superglacial drainage. As the higher rock hills ap-
peared through the lowering surface of the ice, their slopes received
deposits, and from about 800 feet A. T. downward plains and kame-
kettle terraces built among masses of stagnant ice constitute a notable
element of the landscape. At an elevation of about 400 feet the
outline of the ice tongue filling the Hudson valley and thinly cover-
ing the rock-benches of the basin area can be partly reconstructed

GEOLOGY OF THE CAPITAL DISTRICT

193

by direct evidence. The stream-borne waste carried over the ice at
the earlier stage began to be washed and dumped into cavities created
by irregular melting and the two basins mentioned present excellent
examples of the topographic characteristics produced under such

conditions.

Other openings in the ice reaching to the underlying rock subse-
quently appeared (1) north of Albany (one-half mile west of New-
tonville), and (2) south of Meadowdale along the foot of the Helder-
bergs. These openings through the thinning glacier remnant were
also in the paths of superglacial streams and, as the ice broke up
around their margins, and the open spaces were enlarged, they appear
to have been filled in rapidly with deposits of gravel (or till, if
the amount of available drift on the ice nearby was too great to
admit of sorting by the streams handling it). At last a stage was
reached where extensive terraces were built on the ground, or partly
on the ground and partly over thin ice, and the elevations of their
flattish tops give evidence of the levels of down-stream controls.
Nearly all of the barriers acting as controls were of dirty basal ice
more or less blanketed with debris and, in consequence, there is very
little evidence of the action of flowing water (either through the
“glacial drift” as it now lies or on the rock surfaces) which can be
definitely correlated with the terraces.

The opening which appeared south of Meadowdale (Albany
quadrangle, near the western edge) is marked by two conical piles
of partly washed materials at the eastern end, rising above the 440-
foot contour line, and by a similar though more irregular heap one
and one-quarter miles a little north of west from the others. There
are also some small crude terraces and one short narrow channel
cut in the rock on the steep slope leading up to the limestone cliffs
to the southwest, showing that the Helderberg (at least locally) was,
at this time, practically free from ice-border drainage. This open-
ing was enlarged southward along the foot of the “mountain,” past
New Salem; and the waters which governed the upper levels of the
group of terraces found here, apparently spilled over the divide south
of New Salem into the basin of the Oniskethau creek while it was
still partly cumbered with remnant ice. There is, along this creek
(west of the railroad, at South Bethlehem) a deltalike terrace built
in a pocket between the rock wall and an ice wall along its eastern
margin, and it is possible that, for a time at least, the forced drain-
age contributed to the building of its highest level (at about 300 feet) .

A second enlargement of the Meadowdale-New Salem opening
took place eastward with terrace levels falling to 350 feet, and

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NEW YORK STATE MUSEUM

channels cut by ice-water streams below the 340-foot contour. The
most marked level is just over 360 feet and extends almost to
Voorheesville, where persistent ice prevented the accumulation of
any definite terrace. To the southeast the deposit continues to within
less than a mile of New Scotland at a somewhat lower elevation and
here it ends abruptly.

The enlargement of the cavity south of Newtonville finally per-
mitted the building of a terrace at an elevation of 370 feet A. T.
with a few mounds rising above it, marking the slightly earlier stage
of somewhat thicker ice and a smaller opening to the bedrock. The
highest point reached by any of these kames is about 430 feet. The
terrace extends southward into the limits of the city of Albany and
would seem to be continued on the opposite side of the river by a
broad terrace (named by Woodworth the Schodack terrace) which
exhibits a dominant level of 370 feet where it begins at East Green-
bush. It slopes southward and at the southern edge of the map is
some 20 feet lower. Its contact with the ice tongue which still
occupied the lower ground in the Hudson valley is well outlined by
the slope running from the 300-foot contour line to that of 360 feet
(or, at the south, 340 feet). This belt of gravelly materials can be
traced along the margin of the stagnant ice for many miles to the
south. ,

There are a number of smaller deposits of similar origin scattered
over the northern part of the district, as at Burnt Hills west of;
Ballston lake, a mile southeast of Groom Corners and one-half mile
northeast of Tomhannock, but they do not throw much light on the
outline of the persistent ice mass. (

It will be remembered that the lower accumulations of glacial
sand and gravel, relied upon to interpret this stage of ice evacuation, ;
are largely buried under later lake sediments and are only occasionally
exposed in natural or artificial cuttings or in exceptional situations
near ice masses contemporaneous with the lake deposits. In 1905
Professor J. B. Woodworth gave the name “Lake Albany” to that
body of water in which the clays of the capital district were laid
down, and he regarded all the clay beds southward to Kingston as
belonging to the same series. This conception is too simple to
account for the very complicated problem presented by high level
clays and low level gravel terraces for the former demand standing
water and the latter flowing water. Thus, from East Greenbush
northeasterly, the Schodack terrace is continued as a strip of
mounded, cross-bedded, coarse sands inclosing ice-block kettles, to the
east side of Teller hill at an elevation of about 220 feet. From Oak-

GEOLOGY OF THE CAPITAL DISTRICT

195

wood Cemetery in Troy northward is a gravelly shelf which appears
to mark a water level at about 310 feet. There are secondary terrace
levels at South Bethlehem at 240 feet and a large cavity left by
melting ice in the course of the Sprayt kill. At this point the glacial
stream following the Oniskethau valley seems to have found its way
into the ice at a level below 200 feet (the level to which the clays
rise locally).

There are many exposures of water-laid gravels underlying the
clays of the Hudson valley within Woodworth’s “Lake Albany” dis-
trict which indicate a free run-off of the glacio-natant waters through
the ice at a time preceding the lacustrine conditions. One of the
best is that of the North Albany gravels in the northern part of the
city of Albany. The deposit has the structure of a short esker and
represents crevasse or tunnel filling clearly connected with drainage
from the southern end of the Newtonville terrace.

In addition to the coarser gravels which appear always to have been
dumped or washed from the dead ice at no great distance from
where they lie, there is a large amount of fine yellowish sand (partly
redistributed in the lake waters) which is probably best interpreted
as a deposit on the stagnant ice. Some of it can be shown to have
been brought into the district by way of the Hoosick valley, and
some by way of the Adirondack section of the Hudson river’s course.
In the latter case an ice- water stream was prevented from following
the present course of the river from Corinth eastward by thick ice
athwart that course; the stream was forced southward over thin ice
in an old valley to the vicinity of Ballston Spa, northwest of which
place it built a sand plain against an ice margin with a control just
above the 400-foot contour line. There is hardly room for doubt
that quantities of the sand were washed out over the ice at that level ;
it forms the topmost layer of the Newtonville terrace and would
have been thought to be a wind deposit had it not appeared in two
sections exposed in gravel pits more or less involved with the under-
lying cross-bedded gray sands.

Concerning the glacial lake or lakes we know much less than we
would like to know. It has been shown that there was a period of
free run-off down the Hudson valley prior to the deposition of the
clays, and we are called upon to explain how this could have become
so impeded as to create a basin capable of retaining a body of water
in which from 100 to 300 feet of sedimentary beds accumulated.
For lack of a more satisfactory explanation, the writer will venture
to offer his opinions.

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NEW YORK STATE MUSEUM

It is certain that ice filled the gorge of the Hudson and overlapped j ]il
the rock terrace east of the river at the time when the 370-foot w
glacial terraces near Albany were made, and that this east bank si
drainage was kept out of the deeper part of the valley as far south, to
at least, as a point opposite Catskill village by a tongue of ice /
remaining in the gorge and extending southward an unknown dis- I j
tance. Nevertheless there is much to suggest that there were lines |i
of free run-off through or under this tongue for such streams as had 5
access to them. The gradual melting of the ice would tend to open j
these lines still further but the sediments carried into them would
tend to close them, and only when the subglacial and other low 3
channels were choked up (as they might easily be more than once l
to be subsequently partly reopened) would the ice tongue act as an [
efficient barrier. Such a conception will account for innumerable (
temporary water levels throughout the district and permit the con- '
sideration of an hypothesis of a series of fugitive lakes, some of j
longer life than others, but all subject to changes of level occasioned ;
by changes in the unstable outlets through the lower valley.

At any rate, there was a lake or a series of lakes in which clays and
fine sand accumulated to varying summit levels : 300 feet near Schen-
ectady ; 280 feet six miles northwest of Albany ; 220 feet in the west-
ern parts of that city ; and barely 200 feet on the rock terrace above
Rensselaer. Along the base of the Helderbergs and southward they
maintain a rather uniform level of about 180 feet as far as the mouth
of Catskill creek. If the clay beds could be regarded as a continuous
series laid down in a single extended lake, we might place the surface
of the latter at something above the elevation of the highest clays, that
is, about 320 feet, and if necessary, assume that the old water plane
is somewhat tilted up at the north or down at the south in conse-
quence of the crustal movement of recent times or one or more earlier
movements. In the absence of independent evidence demanding
such explanation it does not seem justifiable to postulate these earlier
crustal adjustments. We know that after the ice had disappeared from
the basin of Lake Champlain the northern part of New York State
stood some 600 feet lower than it does now, letting the open waters
of the ocean invade that basin as far south as Whitehall. But when
we allow for the tilting which accompanied the recent rise of the
Champlain basin and the subsidence of the lower Hudson valley, we
have not accounted for “Lake Albany” nor have we discovered its
shore line. A well-developed shore line would be easy to recognize,
but, apart from the deltas built by the Hoosick river and by the out-
flow from Lake Iroquois, forced down the Mohawk valley, there is

GEOLOGY OF THE CAPITAL DISTRICT

197

little to suggest the marginal phenomena of a broad open body of
water. Except where slowly melting masses of ice, lingering in the
smaller drainage basins, gave rise to weak streams, those basins appear
to have been dry, indicating a xerothermic climate as previously stated.
And when all the deposits which may legitimately be regarded as
deltas are mapped, and profiles taken through their theoretic water
levels, we do not find ourselves much further advanced toward a
solution. Certainly ice lay over the depressions in the bottom of
which lie Round, Saratoga and Ballston lakes even after “Lake
Albany” was extinct. The large delta of the Hoosick was built over
a block of ice in the gorge and it is possible that the level indicated
by its flat top represents approximately the surface of a local pond
held behind ice not far to the south. The larger deltalike flats east
of Troy were built by ice-water streams following the basins of the
Wynantskill and the Poestenkill and were laid against masses of
ice. (The only free deposit in this locality is a small fan of sand at
an elevation of about 300 feet.) At Catskill the head of a delta
built in the presence of ice lying to the south of it, is slightly above
180 feet. These levels are confusing and discordant and the de-
posits do not seem to belong to a single lake with a stable surface.
Moreover, it is difficult to regard the present valley of the Hudson,
between the clay bluffs mantling the rocky walls of the gorge, as the
result of the reexcavation of a formerly clay-filled trench. The
character of the terrace from Glenmont southward to Cedar Hill at
an elevation of less than 100 feet above the estuary (except for some
hills of rock and washed gravel) would appear to be decisive on
this point. It is difficult to believe that the river could have removed
a fill so completely before shifting into the narrower channel to the
east, or could have failed to leave recognizable traces of its scouring
action over ground which must have been its bed. The steep-sided
knolls of gravel east of Wemple have more the appearance of hav-
ing been confined in open pockets in the remnant ice, than that of
river bars or earlier deposits once covered and now revealed by
removal of the cover.

Practically all of the exposures of the lake sediments which are
useful for study are furnished by the clay pits which have been dug
in the bluffs bordering the Hudson in connection with the manufac-
ture of bricks. The predominant color of the lower clay beds is
blue, indicating the derivation of the rock flour composing them to
have been from the underlying shales of the region, but a closer
examination shows many layers (laminae) of green and red. There
are occasional thin partings of fine sand, and many sections exhibit

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the succession of varves (alternate finer and coarser deposits) inter-
preted as annual fluctuations in the conditions of sedimentation, the
coarser materials representing summer melting of the ice, the finer
representing the winter deposition. The upper clay beds are weath-
ered to a dull yellowish hue and are, as a rule, overlain by yellow
sand. There are very few evidences of the presence of the disin-
tegrating ice sheet to be found in these exposures, and the small
stones and boulders now and again come upon would appear to have
been dropped from floating ice cakes. It is probable that the last
important dam of ice in the gorge was far enough south of the
capital district to permit the formation of a lake behind it which
was comparatively free from ice remnants.

As the level of the ponded water in the Hudson valley lowered
toward final draining, any streams entering the lake would cross the
exposed sediments, trenching them and building a delta at each halt
of the falling surface. As has been stated, there is reason to believe
that the only streams of this time were those derived from the melt-
ing ice, and of these the Mohawk valley carried the largest. Pro-
fessor James H. Stoller, who surveyed the Cohoes and Schenectady
quadrangles for the State Museum, is of the opinion that this river
at first spilled northward through the Ballston channel and was
effective in making the rock channels from East Line (1) to Sara-
toga lake and the Hudson by way of Fish creek, and (2) to Round
lake and the Hudson by way of the Anthony kill before finding its
way into the course now held from Aqueduct to Cohoes. Doctor
Stoller considers some of the sand plain levels of the vicinity as
deltas made in the shrinking lake. If this is the correct interpreta-
tion of the topography of this part of the district, the Iro-Mohawk
must have followed these more northerly courses for a comparatively
short time, since the excavations in rock are inconsequential when
contrasted with the cutting accomplished along the course of the
modern Mohawk after it turns aside from the Ballston channel at
Aqueduct.

With the draining of the glacial lakes we come to that part of the
history which may be regarded as recent and the principal events of
which have been outlined as follows: a period of (probably) xero-
thermic climate followed by a climatic change bringing more
abundant summer rains and a higher temperature. The deflation of
the areas of light sand seems to have begun as soon as these appeared
above water, probably under the force of strong northwest winds
coming off the land ice in the Ontario basin, but the trenching of the
land by the modern streams was delayed until the amelioration of

GEOLOGY OF THE CAPITAL DISTRICT

199

climate which brought with it the meteoric waters to form such
streams. Finally came the crustal movement whereby the land
locally was depressed, creating the estuary and causing the Hudson’s
delta to accumulate.

At the present time, the activities of man in grading and tunnel-
ing constitute the most notable geologic process bringing about
changes in the topography and, were man to forget or be forced to
abandon the technology of engineering, his descendants, however
familiar they might be with so-called “natural” processes and their
results, would be sorely puzzled to account for many of the features
of the landscape.

ECONOMIC GEOLOGY

The capital district is not so fortunate as to contain in its rocks
any important minerals, such as the salt of the Syracuse region, that
would form the foundation of a large industry. There has never
been any mining carried on and there is no prospect that valuable
minerals ever will be found. It is true that even to this day samples
of supposed “coal,” in every case slickensided black shale, usually
from the Normanskill beds, or of “silver ore,” white mica from the
Rensselaer grit, and “gold,” iron pyrite from the black shale, are
brought to the office of the State Survey by excited prospectors.
Much money has been lost in the last century in futile prospecting
for coal and other minerals.

Still the capital district has one economic product of its geologic
resources that is known over the whole country for its excellence,
and that is the molding sand. Besides this it furnishes building stone
and road metal, as well as clay for the manufacture of brick, a
flourishing industry in the district, and gravel and building sand.

Considerable quarrying for dimension stone was formerly carried
on in the Schenectady beds. The sandstone of the formation that
is used for building is fine-grained and of a light gray or greenish
gray or bluish color, weathering to a mellow yellowish tint. The
even-bedded and well-marked jointed structure makes the quarrying
relatively easy. Large quarries were formerly worked in this rock
in Schenectady and Aqueduct and some are still active in Sche-
nectady. Many of the older buildings in the capital district are built
of this Schenectady bluestone. Smock (’90, p. 329) says regarding
the Albany buildings :

Schenectady bluestone is seen in St Peter’s Protestant Episcopal
church, on State street; in St Joseph’s Roman Catholic church, Ten
Broeck street (walls) ; in the Protestant Episcopal Church of the
Holy Innocents, corner of North Pearl and Colonie streets ; in the

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Second Presbyterian church on Chapel street, and in St John’s
Roman Catholic church, Ferry street. The stone in the walls of
St Peter’s church is nearly all natural-face blocks, and many of them
have mellowed on exposure, to soft yellowish and light brown tints,
which give the building the appearance of age.

Also No. 425 State street is, according to Smock, a noteworthy
example of Hudson river bluestone, where the blocks are in course-
work and have bush-hammered surfaces.

In Schenectady itself the rock has been used with fine result in
the Memorial Hall of Union University, in the East Avenue Presby-
terian church, and in the new Armory. It is further seen in the
church at Menand’s station, and in St Patrick’s Roman Catholic
church in Watervliet.

The rock has not only been used in ashlar work in the older stone
buildings in the capital district, but much is still used in common
wall-work and for foundations. The bluestone industry of Sche-
nectady county amounted in 1925 (the last available figure) to
$28,640.

In Troy the sandstone has been quarried for many years from the
Normanskill and Snake Hill beds (in the Brothers quarry, south of
the Poestenkill), but the industry is inactive at present.

More recently the Normanskill sandstone, as also the Schenectady
bluestone at Aqueduct, has been used for crushed stone. The quarry
at Kenwood was opened in Normanskill sandstone for this purpose.
An important stone industry is the quarrying and crushing of lime-
stone for road metal and railroad ballast. There are two great
quarries and crushers in operation now at the Helderberg cliff,
namely, the quarry of the Albany Crushed Stone Company, one and
one-half miles southeast of Feura Bush, and Callanan’s quarry at
South Bethlehem. The production in 1925 was worth $345,062.
The rock used is the Manlius and the Coeymans limestones. There
are also smaller quarries, worked only intermittently, like the one
above New Salem. The Onondaga limestone is at present quarried
by the town of New Scotland on the north side of the New Salem-
Wolf hill state road ; and smaller quarries, temporarily opened for
road metal in the Manlius, Coeymans, Becraft or Onondaga lime-
stones, are scattered through the Helderbergs.

The Rensselaer grit also has been used for crushed stone and rail-
road ballast. It makes a most excellent material for that purpose.
The Rensselaer Quarry Company had a large quarry and crushing
plant near Brainard station, in the farthest southeast corner of the
capital district. The rock proved too tough on the drills and work
stopped some years ago.

GEOLOGY OF THE CAPITAL DISTRICT

201

The Snake Hill shale is being ground and used for improving
sandy soils; the shale containing 4 per cent of potash, 16.5 per cent
of aluminum oxide, and 0.15 per cent of phosphoric acid, a small
proportion only of which, however, is soluble in distilled water.
The plant (Werner’s Natural Fertilizer Company) is in Mechanic -
ville.

The other economic products are derivatives of the Pleistocene or
Glacial period. Commercially the most important of these are the
clays. The clays were deposited in a lake — or lakes — that formed at
the end of the Glacial period, according to Woodworth, as the result
of a rising of the land above the Highlands. This lake, which is
known as Lake Albany, extended from the Kingston region to
Schenectady and Saratoga. The well-laminated clays one sees so
often exposed in Albany, where streets are cut through or cellars
dug out, were deposited in this lake. These often thick deposits of
clay, which extend on both sides of the river, have been the founda-
tion of a great industry. The principal use of the clay is for brick-
making. There are brickyards in Albany (north end : Murray &
Riberdy, Van Woert street; at the south end: E. J. Smith, on First
avenue) and in Watervliet, Troy, Crescent, Mechanicville and Still-
water. In Troy, also, hollow building tile and sewer pipe, as well
as stove lining are manufactured. The General Electric Company in
Schenectady also produces porcelain electric supplies and saggers,
mostly from imported material.

The following figures, supplied by C. A. Hartnagel, give an idea
of the importance of the industry. The clay products made in
Albany county in 1925 were valued at $1,442,923 ; those in Rensselaer
county at $755,744; in Saratoga county, $878,983; and in Sche-
nectady county at $953,641 (General Electric Company).

To this must be added the slip clay, which is dug in Albany near
the Dudley Observatory, and which in 1925 had a value of $34,943.

The Clay Products Cyclopedia, 1924, p. 35, describes the slip clay
as follows:

A slip clay is one that contains such a high percentage of fluxing
impurities, and is of such texture, that it melts at a low cone to a
greenish or brown glass, thus forming a natural glaze. . . . While
easily fusible clays are not uncommon, all do not melt to a good
glaze.

Several fair slip clays have been found in different parts of the
country, but the most thoroughly satisfactory material comes from
Albany, N. Y., and is shipped to all parts of the United States for
potters’ use.

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The most interesting economic product of the capital district is
the molding sand, which is known all over the United States as
“Albany molding sand,” or “Albany sands.”

D. H. Newland (T6) and C. M. Nevin (’25) have published
interesting accounts of their investigations of the Albany sands
which they made for the New York State Survey. From these
authorities we gather the following facts :

The Albany molding sand consists almost wholly of quartz grains
bonded by clay, while the common sand that we see drifting about
in the dunes to the west of the city lacks this clay bond. The
Albany molding sand has been recognized as being specially adapted
for brass, aluminum and the smaller types of iron castings. “These
sands,” Nevin says, “have been shipped to every part of the United
States and have established an enviable reputation for long life and
satisfactory performance.” Nevin (p. 69) states that certain grades
are shipped as far as Tacoma, Wash., for brass and as far as Mil-
waukee for malleable castings.

The Albany molding sands, which are often sold under the trade
name of Selkirk, Crescent and North River sands, are distributed
on both banks of the Hudson river over a stretch of about 100 miles
from Glens Falls on the north to Kingston on the south. Albany
lies near the center of the area that in the south usually does not
reach back more than a mile or two from either bank but broadens
with the expansion of the valley at Albany through the entrance of
the Mohawk, extending to Schenectady.

The molding sand always forms a layer directly below the soil,
ranging in thickness from a few inches up to four or five feet ; the
thickness being not much more than 18 or 20 inches in the usual
run of the bank. As one can often observe in driving through the
country about Albany, this layer is carefully excavated and the sod
replaced on the gray sand below. The mostly buff-colored sand can
be seen piled up for shipment or in stock piles in various places,
as at Glenmont and at Selkirk.

The origin of the molding sand has been found by the authorities
cited above, to consist in the weathering of the easily attacked par-
ticles of “Hudson River shales” into a clayey substance which now
forms the bond of the molding sand. The weathering takes place
only under the soil under the influence of humic and other organic
acids. For this reason the sharp gray glacial sand with intermixed
particles of Hudson River shale, which everywhere underlies the

GEOLOGY OF THE CAPITAL DISTRICT

203

molding sand, is, like the dune sand, potential molding sand and
may change into it under proper conditions.

The important centers of production in the capital district are:
Ballston Spa, Mechanicville, Reynolds, Ushers, Round Lake,
Schaghticoke, Elnora, Alplaus, Carmen, Schenectady, Waterford,
Van Hoesen, Vischer Ferry, Karners, Crescent, Niskayuna, West
Albany, Elsmere, Delmar, Slingerlands, Glenmont, Wemple and
Selkirk. Albany county produced in 1925 molding sand worth
$328,100; Saratoga county, $515,564; Schenectady county, $53,549;
and Rensselaer county $13,206.

There is finally a considerable amount of building sand and gravel
obtained in the capital district. In Albany the Rensselaer gravel pit
in North Albany is known to everybody. The production of sand
and gravel is by no means a small industry in the State. It had a
value in 1924 of $13,397,540. Albany county produced in 1925,
$146,953 worth; Rensselaer county $60,130; Saratoga county,
$35,358; and Schenectady county, $151,453.

Water being a mineral, the sale of spring water, amounting to
$36,855 in Rensselaer county, is also properly considered a mineral
industry.

There is also a slight possibility that gas may be found in com-
mercial quantities in the capital district, for two gas wells, of short
production only, were drilled in the shales in the ’8o’s at Altamont
(then Knowersville) ; gas was struck in 1906 at the Hilton farm
at Voorheesville and it ran for several years in sufficient quantity to
light a street lamp. C. A. Hartnagel is of the opinion that the gas
was derived from the underlying rocks (Schenectady beds) and
accumulated in glacial sands below the Albany clay. Also at the
site of Keeler’s Hotel in Albany a few years ago, a small amount
of gas was found in a well. If anywhere a proper trapping struc-
ture is present, gas may have accumulated in larger quantity.

In round figures the four counties of the capital district furnish
$3,000,000 worth of clay products a year, not counting those of the
General Electric Company; over three-quarters of a million dollars
in molding sand ; close to $400,000 in limestone and sandstone ;
and nearly $400,000 in sand and gravel. Counting all mineral
products the industry amounts to over four and a half million dollars
a year, certainly an astounding figure for a region lacking the major
mineral resources.

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NEW YORK STATE MUSEUM

POINTS OF GEOLOGIC INTEREST IN ALBANY, TROY,
SCHENECTADY AND VICINITIES

There have come such frequent requests for information on the
geology of the cities of the capital district that we consider it worth
while to publish separate notes on the principal geologic features of
the three cities of Albany, Troy and Schenectady, inclusive of their
vicinities.

Albany is built on the clay deposited in Lake Albany at the end
of the Glacial period. This clay, that can be seen in practically all
building operations, and in the clay pits in north and south Albany,
as well as in the street cuts in West Albany, rests on a very irregular
rock surface which appears to have a deep depression directly under
the city. The rock comes to the surface north of Albany along the
New York Central Railroad tracks at “Black Rock cut” near Tivoli
lake, and in South Albany in Lincoln Park, in the ravine, where
formerly it formed “Buttermilk fall.” The rock is mostly gray and
black shale, all belonging to the Snake Hill formation. The same
rock, with some sandstone and grit beds, is also exposed at Normans-
ville below and above the bridge, and it is especially well seen in the
cliff below the bridge.

The south end of Albany is, however, underlain by the Normans- j
kill beds. The shales and grit beds of this formation are well
shown at Kenwood in the cut of the Delaware and Hudson Rail-
road and in the stone quarry where the grit beds are worked. The
fossils, graptolites, for which the formation is noted among geolo-
gists, were first collected and described (Hall, ’47) from a temporary
outcrop, produced in the mill race of and in excavations for a mill
that was located just above the bridge. Remains of the mill and
mill dam are still visible. Other fine collections were obtained in
the West Shore Railroad cut at Glenmont. Graptolites can still be
found at Kenwood about the old mill, in the railroad cut, and at
Glenmont. At the latter place, along the road on both sides of the
viaduct, the white-weathering chert of the Normanskill beds is well
exposed.

Within easy reach of Albany, and visible from State street, is
the interesting geologic locality of Rysedorph hill, one and one-half
miles southeast of Rensselaer. There the Rysedorph Hill conglom-
erate, which has furnished large and interesting faunas, is exposed.
The loose pebbles on the west side of the hill will always furnish
fossils, especially Trenton brachiopods, as Plectambonites and
Rafinesquina.

GEOLOGY OF THE CAPITAL DISTRICT

205

Albany is also the natural starting point of geologic parties study-
ing the Helderbergs. Prosser, in the Guide to Excursions (’99) has
already described the following excursions : ( 1 ) Albany-Clarksville-
Reidsville- Albany ; (2) Albany-New Salem-Countryman hill- Albany ;
(3) Albany-Indian Ladder-Thompson’s lake- Altamont- Albany. Miss
Goldring is engaged in a detailed description of the New Salem and
Indian Ladder region. The state roads that have been constructed
since Prosser’s time have much improved the outcrops. Complete
sections are now exposed along the New Salem-Indian Ladder road,
New Salem-Wolf hill-Berne road, and the Albany- Clarksville road.

Schenectady is also built on the Albany clay. The rock founda-
tion, although so deeply buried that it is nowhere seen in the city,
consists of the Schenectady beds. The shales and sandstones of this
formation are well seen on the hillside two and one-half miles west
of Schenectady where the road, after crossing the tracks of the
West Shore Railroad, leads up the hill. The best outcrops are now
at Aqueduct and Rexford where formerly large quarries were
worked, and the alternating shales and sandstones are still beauti-
fully exposed, especially in the cliff below the Aqueduct-Rexford
bridge. The shales in these localities have afforded numerous speci-
mens of the remarkable seaweed Sphenophycus latifolius, at Aque-
duct, with air sacs as floating apparatus. Excellent opportunity for
collecting was formerly afforded in the Dettbarn quarries between
Van Vrancken avenue and the river. The Schenectady eurypterids
were discovered there. These shallow quarries have been filled in
and built over.

The cliffs on both sides of the river below Aqueduct are in the
Schenectady beds. They exhibit the small disturbances of the
region, faults and low folds.

In the farther vicinity of Schenectady, the outcrops about Balls-
ton lake are noteworthy, most of all, the fault line in Forest Park
where the vertical Schenectady beds can be seen in the ridge on the
west of the lake. On the other side of the lake, the undisturbed
Schenectady beds with much sandstone are exposed along the shore
of the southern part of the lake, and the Snake Hill shales to the
best advantage in road cuts and road metal pits along the road
paralleling the northern portion of the lake.

Troy. By far the most interesting city of the capital district
geologically is Troy. There are numerous outcrops scattered about
the city, revealing most remarkable geologic features.

Beginning with the campus of the Rensselaer Polytechnic Insti-
tute, the Lower Cambrian limestone, containing fossils, as Obolella

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crassa, is exposed at the east end of the dining hall; close by th<
greenish gray Cambrian shales are shown. At the gate leading ou
to Sage avenue on the north side of the campus the Poestenkill fauf
breccia is well shown in a small cliff, and a little below, on the othei
side of the avenue, the Snake Hill shale has been quarried for roac
metal. It is thus apparent that the overthrust line separating the
overlying Lower Cambrian rocks from the subjacent Snake Hil!
beds passes through the campus. This same Snake Hill shale car
be traced along the Fitchburgh railroad to Lansingburg, where it is
replaced by similar Normanskill shale.

The best exposure of the great overthrust line, the so-called
Logan’s line, is in the bed and banks of the Poestenkill below the
falls. Coming up from Spring street, one finds first, close to the
bridge, on the north side, Normanskill shale in which the writer
once collected a fairly representative graptolite-fauna. Going
up-stream, one passes over the heavy typical Normanskill grit beds,
and then just above the dam and below the high falls comes upon
the Poestenkill fault breccia, best shown at low water in the creek
bed. The Ordovician-Cambrian contact is at the upper end of the
pool below the falls, and the overthrust plane can be distinctly seen,
from the edge of the water at the foot of the cliff, rising on the
opposite (north) side toward the west. On the other (south) side
of Spring street is the Brothers quarry, just north of the Seminary
(popularly known as “Four Steeples”), where the Snake Hill shale
and sandstone are well exposed in highly folded condition. Fossils
were found here in the shale.

The Normanskill shale is well shown in several places in Troy,
notably at the north end of Lansingburg, in the wooded hill north
of the Lansingburg-Waterford bridge, where the white-weathering
chert also is found. The ridges to the east of this locality also consist
of Normanskill shale and chert. The isolated hill known as Mount
Olympus, close to River street, north of the Green Island bridge,
consists of Normanskill shale and has afforded good collections of
graptolites. The Normanskill grits are well exposed along upper
Congress street below Mount Ida Park. A cliff to the west of the
street furnished Normanskill graptolites in the grit.

The Lower Cambrian rocks are well exposed at the Oakwood
Cemetery, and especially at the locality known as Diamond Rock
where the quartzite forms a ridge. The oldest and best known
Cambrian locality in Troy is the old quarry back of Beman Park.
It was here that W. S. Ford collected his brachiopods and trilobites
that first established the Lower Cambrian age of these rocks. The

GEOLOGY OF THE CAPITAL DISTRICT

207

fossils occur there in the pebbles of what appears to be a conglom-
erate but is in reality an alternating limestone and shale in which
the limestone bed has been torn apart into a crush breccia by the
intense folding (see under Structural Geology). Here also the
Lower Cambrian shale is seen in strong development. Along the
Wynantskill below Albia may also be seen old road metal quarries
with the Lower Cambrian olive grit in characteristic development.
Going down the creek, one passes Normanskill grit and finally the
dark gray Snake Hill shales.

Two miles east of Troy, in the gorge of the Poestenkill, the red
Cambrian shale is found, which there has afforded the calcareous alga
Oldhamia occidens.

Across the river from Troy numerous outcrops of the Snake Hill
beds can be found along the shores of Green island, Van Schaick
island and Peobles island. Some of these have afforded excellent
opportunities for collecting (for these, see stars on the map).

Finally, the Cohoes gorge is also worth visiting in this neighbor-
hood. The Snake Hill shale, much contorted and affected by cleav-
age, is here well exposed in the cliffs.

Series of limestone concretions are seen in the bottom of the
gorge, intercalated in the shale. The gorge also shows in the deep
central channel the formation of such channels by a series of potholes
which finally become united. The bank of the channel has also become
scalloped by this confluence of successive potholes. It was also,
over 60 years ago, in this gorge that James Hall, by counting the
growth rings of a cedar tree whose roots had been exposed by
erosion at the edge of the cliff, got estimates of the age of the
gorge and incidentally the first figures on the length of postglacial
time.

BIBLIOGRAPHY OF PAPERS CITED IN TEXT

Adams, G. I., Butts, C., Stephenson, L. W. & Cooke, W.

1926 Geology of Alabama. Geol. Surv. of Alabama Spec. Rep’t 14, 362P.

Bassler, R. S.

1909 The Cement Resources of Virginia West of the Blue Ridge. Va. Geol.
Surv. Bui. II a, 309P.

1915 Bibliographic Index of American Ordovician and Silurian Fossils.
U. S. Nat. Mus. Bui. 92. 2v., I52ip.

Beecher, C. E.

1883 List of Species of Fossils from an Exposure of Utica Slate and Asso-
ciated Rocks within the Limits of the City of Albany. 36th Ann.
Rep’t N. Y. State Mus. Nat. Hist., p. 78. Describes the first Snake
Hill faunule, from Black Rock cut near Albany.

Bishop, I. P.

1886 On Certain Fossiliferous Limestones of Columbia County, N. Y., and
Their Relation to the Hudson River Shales and the Taconic System.
Amer. Jour. Sci., 3d ser., 32:438-41.

208

NEW YORK STATE MUSEUM

1890 A New Locality of Lower Silurian Fossils in the Limestone of Columbia
County, N. Y. (Pul vers station, near Philmont). Amer. Jour. Sci.,
3d ser., 39 169-70

Chadwick, G. H.

1908 Revision of “the New York series.” Science, new ser., 28:346-48
1910 Downward Overthrust Fault at Saugerties, N. Y. N. Y. State Mus.

Bui. 140:157-60

Clark, P. E., see Van Ingen, 1903

Clark, T. H.

1921 A Review of the Evidence for the Taconic Revolution. Boston Soc.
Nat. Hist. Proc. 36, no. 3:135-63

Clarke, J. M.

1899 Guide to the Excursions in the Fossiliferous Rocks of New York State.
N. Y. State Mus. Handbook 15, i2op.

Gives guides by C. S. Prosser to excursions: (1) Albany-Clarksville-Reids-
ville-Albany ; (2) Albany-New Salem-Countryman hill-Albany; (3) Albany-
Indian Ladder-Thompson’s lake-Altamont-Albany.

1903 A New Genus of Paleozoic Brachiopods, Eunoa. N. Y. State Mus.

Bui. 52:606-15

1904 The Naples Fauna. N. Y. State Mus. Mem. 6, 454p.

1909 Early Devonian History of New York and Eastern North America.

Part 2. N. Y. State Mus. Mem. 9, 250P.

& Schuchert, C.

1899 Nomenclature of the New York Series of Geologic Formations.

Science, Dec. 15. Also Amer. Geologist, Feb. 1900; State Mus.
Mem. 3 :8-9

Cook, J. H.

1909 Some Pre-Glacial Valleys in Eastern New York, etc. Science, 29:750

Cornelius, H. P.

1927 Ueber tektonische Breccien, tektonische Rauchwacken und verwandte
Erscheinungen. Centralbl. f. Min., Geol. & Pal. Abt. B, no. 4:120-30

Cumings, E. R.

1897 See Prosser.

1900 Lower Silurian System of Eastern Montgomery County, N. Y. N. Y.

State Mus. Bui. 34:419-68

Cushing, H. P. & Ruedemann, R.

1914 Geology of Saratoga Springs and Vicinity. N. Y. State Mus. Bui. 169,
I77p.

With geologic map of the Saratoga and Schuylerville quadrangles, situated
directly north of the capital district. Proposes names for the subdivisions
of the Lower Cambrian, describes the overthrust and distinguishes the forma-
tions of the eastern and western troughs, which are briefly described.

Dale, T. N.

1893 The Rensselaer Grit Plateau in New York. 13th Ann. Rep’t U. S.
Geol. Survey, pt 2 :29i-340 and map, pi. 97

A thorough geologic and petrographic description of the Rensselaer grit
formation. The latter is correlated with the Oneida conglomerate (Silurian).

1896 Structural Details in the Green Mountain Region and in Eastern New
York. 16th Ann. Rep’t U. S. Geol. Survey, pt 1, p. 551, 568

1899 The Slate Belt of Eastern New York and Western Vermont. 19th

Ann. Rep’t U. S. Geol., pt 3, p. 188

Description of thin sections of “Hudson grit’’ (Normanskill) from Troy
and East Greenbush.

1900 A Study of Bird Mountain, Vermont. 20th Ann. Rep’t U. S. Geol.

Survey, pt 2, p. 21, 22

On the age of the Rensselaer plateau, in reply to Doctor Ella.

GEOLOGY OF THE CAPITAL DISTRICT

209

1902 Structural Details in the Green Mountain Region and in Eastern New
York (second paper). U. S. Geol. Survey Bui. 195:12

1904 Geology of the Hudson Valley between the Hoosick and the Kinderhook.

U. S. Geol. Survey B'ul. 242, 639.

With geologic map (2 miles equal 1 inch). Careful description of the
areal petrographic and structural geology of the region. The map distin-
guishes Lower Cambrian, Beekmantown shale, Hudson shale and Hudson
schist and Rensselaer grit.

1905 Taconic physiography. U. S. Geol. Survey Bui. 272

Darton, N.. H.

1894 Preliminary Report on the Geology of Albany County. Rep’t State

Geologist for 1893, 1894, p. 423-56

Accompanied by geologic map of Albany county, first geologic map of
Helderberg region.

Davis, W. M.

1884 The Folded Helderberg Limestones East of the Catskills. Mus. Comp.
Zool. Harvard Coll. Bui. 7:311-29

Ells, R. W.

1895 The Rensselaer Grit Plateau. The Ottawa Naturalist, 9:9-11

Believes that Rensselaer grit should be correlated with the Sillery and
Levis beds in Canada, as had been done by Logan, being of the same lithologic
character.

Emmons, Ebenezer

1855 American Geology, v. I, pt 2. The Taconic System. 25 ip.

Describes the Taconic system and Cambrian and Ordovician fossils (some
graptolites of Normanskill shale).

Fairchild, H. L.

1917 Postglacial Features of the Upper Hudson Valley. N. Y. State
Mus. Bui. 195, 22p.

1919 Pleistocene Submergence of the Hudson, Champlain and St Lawrence
Valleys. N. Y. State Mus. Bui. 209-10, 769.

Ford, S. W.

1871 Notes on the Primordial Rocks in the Vicinity of Troy, N. Y. Amer.
Jour. Sci., 3d ser., 2:32-34

Announces the discovery of a “Primordial” (Cambrian) fauna near Troy.
(Beman Park quarry in Troy limestone.)

1875 Note on the Discovery of a New Locality of Primordial Fossils in

Rensselaer County, N. Y. Amer. Jour. Sci., 3d ser., 9:204-6

1876 On Additional species of Fossils from the Primordial of Troy and

Lansingburg, Rensselaer County, N. Y. Amer. Jour. Sci., 3d ser.,
11 : 369-7 1

1880 On the Western Limits of the Taconic System. Amer. Jour. Sci., 3d
ser., 19:225-26

1884 On the Age of the Glazed and Contorted Slaty Rocks in the Vicinity

of Schodack Landing, Rensselaer County, N. Y. Amer. Jour. Sci.,
3d ser., 28:206-8

1885 Observations upon the Great Fault in the Vicinity of Schodack Land-

ing, Rensselaer County, N. Y. Amer. Jour. Sci., 3d ser., 28 : 206-8

Points out presence of fault with Cambrian fossils on one side and
Ordovician on other.

1885 Age of the Slaty and Arenaceous Rocks in the Vicinity of Schenectady
N. Y. Amer. Jour. Sci., 29:397-99

Describes faunule from Schenectady beds, referred to Utica shale.

Girty, G. H.

1895 A Revision of the Sponges and Coelenterates of the Lower Helderberg
Group of New York. Rep’t State Geol. for 1894, 2:279-322

210

NEW YORK STATE MUSEUM

Grabau, A. W.

1906 Guide to the Geology and Paleontology of the Schoharie Valley in

Eastern New York. N. Y. State Mus. Bui. 92, 386p.

A very complete description of the formations in the Schoharie valley with
figures of the characteristic fossils. Accompanied by geologic map of the
Schoharie and Cobleskill valleys.

1910 Continental Formations in the North American Paleozoic. Compte
Rendu du XI :e Cong. Geol. Int, p. 979-1003

Claims continental origin for a number of the formations here described,
as Oriskany sandstone, Esopus shale.

Gurley, R. R.

1896 North American Graptolites. Jour. Geol., v. 4, no. 1 ; v. 4, no. 3, 59p.

Is a preliminary paper giving lists of fossils in the Levis shales of Quebec
and description of new species from the Normanskill shale.

Hall, James

1847 Paleontology of New York. v. 1, i38p.

Describes the fossils of the Normanskill shale.

1852 Paleontology of New York. v. 2, 35ip.

Describes the fossils of the Lower Helderberg limestones.

1859-61 Paleontology of New York, v. 3, pts 1 and 2, 532p.

Describes and figures the fossils of the Upper Helderberg limestones and
Oriskany sandstone.

Harris, G. D.

1904 The Helderberg Invasion of the Manlius. Amer. Pal. Bui. 4, no. 19, 27p.
Gives a detailed section of the lower escarpment of Countryman hill.

Hartnagel, C. A.

1907 Upper Siluric and Lower Devonic Formations of the Skunnemunk

Mountain Region. N. Y. State Mus. Bui. 107 :39~54

1912 Classification of the Geologic Formations of the State of New York.

N. Y. State Mus. Handbook 19, 969.

1927 The Mining and Quarrying Industries of New York from 1919 to
1924, including Lists of Operators. N. Y. State Mus. Bui. 273, i02p.

Holtedahl, O.

1921 The Scandinavian Mountain Problem. Quart. Jour. Geol., 76,
pt 4 1387-402

Holzwasser, F.

1926 Geology of Newburgh and Vicinity. N. Y. State Mus. Bui. 270, 93p.

House, H. D.

1924 Annotated List of the Ferns and Flowering Plants of New York.

N. Y. State Mus. Bui. 254, 759p.

1925 Report of the State Botanist for 1924. N. Y. State Mus. Bui. 266,

n 6p.

Kayser, E.

1921 Lehrbuch der Geologie. Allgemeine Geologie, v. 2, 436p.

Kimball, J. P.

1890 Siderite Basins of the Hudson River Epoch. Amer. Jour. Sci. 40:155

Kindle, E. M.

1913 The Unconformity at the Base of the Onondaga Limestone in New

York and its Equivalent West 6f Buffalo. Jour. Geol., 21 1301-19

Lapworth, C.

1891 On Olenellus callavei and Its Geological Relationships. Geol. Mag.

for December 1891, p. 529-36

Leszinski, W. von

1913 Ueber erdgeschichtliche Kalteperioden. Compt. Rend. 12 Int. Congr.
p. 501

GEOLOGY OF THE CAPITAL DISTRICT

211

Mather, W. W.

1843 Geology of New York; Report on the First District. 653P.

Nevin, C. M.

1925 Albany Molding Sands of the Hudson Valley. N. Y. State Mus. Bui.
263, 8 ip.

Newland, D. H.

1916 Albany Molding Sand. N. Y. State Mus. Bui. 187:107^-15
Prosser, C. S.

1899 Classification and Distribution of the Hamilton and Chemung Series of

Central and Eastern New York. Part 2. Rep’t N. Y. State Geol.
and Pal. for 1897-99, P- 65-315. Also Mus. Rep’t 51, pt 2, 1899,

P- 65-315

1900 Notes on Stratigraphy of Mohawk Valley and Saratoga County;

N. Y. State Mus. Bui. 34:469-82

1900 Sections of the Formations along the Northern End of the Helder-
berg Plateau. N. Y. State Mus. Rep’t for 1898, p. 51-72
1903 Notes on the Geology of Eastern New York. Amer. Geol., 32:380-84

Makes some corrections in regard to the Helderberg sections.

1907 Section of the Manlius Limestone at the Northern End of the Helder-
berg Plateau. Jour. Geol., 15:46-51

A very careful measurement and description of the Manlius limestone at the
Indian Ladder.

& Cumings, E. R.

1897 Sections and Thickness of the Lower Silurian Formation in West
Canada Creek and in the Mohawk Valley, N. Y. 15th Rep’t State
Geol. for 1895, p. 615

With map of Amsterdam quadrangle, adjoining the Schenectady quadrangle
on the west. Gives section of Canajoharie shale and Schenectady beds
(called there Utica and Lorraine beds) north of Mohawk.

& Rowe, R. B.

1899 Stratigraphic Geology of the Eastern Helderbergs. 17th Rep’t State
Geol. for 1897, p. 330-54

Describes the New Salem and Countryman hill section and the geology of
Clarksville and the Oniskethau creek. Also furnishes fossil lists of the
formations.

Raymond, P. E.

I9J3 Quebec and vicinity, in Guide Book no. 1. Canada Dep’t Mines: 24-46
Richardson, C. H.

1902 The Terranes of Orange County. Rep’t Vermont State Geol. : 901-2,
p. 61-101

Rowe, R. B. See Prosser, 1899 >•

Ruedemann, R.

1895 Development and Mode of Growth of Diplograptus, McCoy. Rep’t
State Geol. for 1894, p. 219-49

1901a Hudson River Beds near Albany and Their Taxonomic Equivalents.
N. Y. State Mus. Bui. 42, iogp.

Distinguishes Normanskill shale and fauna from Snake hill shale (correlated
before with Utica and Frankfort shales).

1901b Trenton Conglomerate of Rysedorph Hill and Its Fauna. N. Y. State
Mus. B‘ul-, 49:1-114

Describes and illustrates fauna of the conglomerate.

1902 Graptolite Facies of the Beekmantown Formation in Rensselaer

County, N. Y. N. Y. State Mus. Bui., 52:546-75

Shows presence of graptolite shale of Beekmantown age and describes Deep
Kill graptolite zones.

1903 Cambric Dictyonema Fauna in the Slate Belt of Eastern New York.

N. Y. State Mus. Bui., 69:934-58

Describes the Schaghticoke shale, the lowest graptolite horizon Skncwm in
America.

212

NEW YORK STATE MUSEUM

1904 Graptolites of New York, pt 1. N. Y. State Mus. Mem. 7, 346p.

Describes the graptolites of the Schaghticoke and Deep Kill formations.

1908 Graptolites of New York, pt 2. N. Y. State Mus. Mem. 11, 583P.

Describes Normanskill, Snake hill and Canajoharie shale graptolites and
establishes succession of graptolite shales.

1909 Types of Inliers Observed in New York. N. Y. State Mus. Bui.,

I33:i64-93-

Suggests the presence of “fensters,” outcrops of younger rocks underlying
older rocks that have been overthrust on it.

1912 The Lower Siluric Shales of the Mohawk Valley. N. Y. State Mus.
Bui. 162, i5ip.

Distinguishes for the first time the Canajoharie, Schenectady, Snake hill
beds and Indian Ladder shale, and describes their faunas.

1914 See Cushing

1916 Account of Some New or Little Known Species of Fossils. Paleon-
tologic Contributions from the N. Y. State Museum. N. Y. State
Mus. B'ul. 189, 226p.

Describes form of Serpulites from Snake hill beds.

1919 The Graptolite Zones of the Ordovician Shale Belt of New York.
Paleontologic Contributions from the N. Y. State Museum No. ix.
N. Y. State Mus. Bui., 227-28 : 1 16-30

Gives all the graptolite zones observed in the Hudson river valley.

1919 The Age of the Black Shales of the Lake Champlain Region. Paleon-
tologic Contributions from the N. Y. State Museum No. 10. N. Y.
State Mus. Bui., 227-28:108-16

1919 Additions to the Snake Hill and Canajoharie Faunas. Paleontologic

Contributions from the N. Y. State Museum No. 9. N. Y. State
Mus. Bui., 227-28:101-8

1922 The Existence and Configuration of Precambrian Continents. N. Y.

State Mus. Bui., 239-40:65-152

1928 Note on Oldhamia (Murchisonites) occidens (Walcott). N. Y. State
Mus. Bui., 281 :47-5o

Smock, J. C.

1890 Building Stone in New York. N. Y. State Mus. Bui. 10, v. 2,
p. 191-395

Stoller, J. H.

1911 Glacial Geology of the Schenectady Quadrangle. N. Y. State Mus.
Bui. 154, 44P-

1920 Glacial Geology of the Cohoes Quadrangle. N. Y. State Mus. Bui.

215-16, 49p.

Schuchert, Charles

1899 See Clarke

1902 See Ulrich

1903 On the Manlius Formation of New York. Amer. Geol., 31 1160-78
1919 The Taconic System Resurrected. Amer. Jour. Sci., 5 ser., 47:113-16

1923 Sites and Nature of the North American Geosynclines. Bui. Geol.

Soc. Amer., 34:151-230

Ulrich, E. O. & Schuchert, C.

1902 Paleozoic Seas and Barriers in Eastern North America. N. Y. State

Mus. Bui., 52:633-63

Sets forth presence of separate troughs in Appalachian geosyncline.

Van Ingen, G. & Clark, P. E.

1903 Disturbed Fossilifero'us Rocks in the Vicinity of Rondout, N. Y.

N. Y. State Mus. Bui., 69:1176-1227

Vanuxem, Lardner

1842 Geology of New York; Report on the Third District. 3o6p.

GEOLOGY OF THE CAPITAL DISTRICT

213

Walcott, C. D.

1888 The Taconic System of Emmons and the Use of the name Taconic
in Geologic Nomenclature. Amer. Jour. Sci., 3d ser., 35 :229~327,
395-401

Walcott here clearly separates in description and on a map the Cambrian
and Ordovician (Hudson River beds) both by lithologic and faunistic
characters.

1890 Value of the Term “Hudson River Group” in Geologic Nomenclature.

Bui. Geol. Soc. Amer., 1 :335~57

Cites some fossils ( Orthis testudinaria, Trinucleus concentricus ) from
“Hudson River shale” at foot of Indian Ladder road.

1891 Correlation Papers, Cambrian. Bui. U. S. Geol. Survey, 81 198

The Lower Cambrian fossils are brought together and described (as Middle
Cambrian).

1894 Discovery of the Genus Oldhamia in America. Proc. U. S. Nat.
Mus., 17, no. 1002, p. 313-15

1912 Cambrian Brachiopods. U. S. Geol. Survey Mem. 51, 2v., 872p.

Woodworth, J. B.

1905 Ancient Waterlevels of the Champlain and Hudson Valleys. N. Y.
State Mus. Bui., 84, 265P.

1907 Postglacial Faults of Eastern New York. N. Y. State Mus. Bui.,,
107 :5-28

Supplementary Note

The exchange of the base map of 1929 f or that of 1902 on which the geologic
map had been drawn, without knowledge of the author, until the proofs were
received, has made so many small errors, that it was impossible to make all
the changes. Minor discrepancies between the geology and topography, particu-
larly in the Helderberg cliff region, could not be avoided.

A serious error is the omission of the overprint for pleistocene deposits in
the city of Albany (see p. 204).

‘

INDEX

Aqueduct, 7

Adams, Dr Charles C., assistance
given by, 5

Adams, G. I., cited, 207
Adirondacks, 6
Agoniatites limestone, 69
Albany, points of geologic interest
in, 204

Albany molding sand, 202
Albany peneplane, 19, 21
Albany quadrangle, 5
Alplaus kill, 22

Amsterdam limestone, 28, 169
Anthony kill, 21
Aries lake, 22
Ashokan shale, 71

Bald mountain, 16
Bald Mountain limestone, 95, 167
Barrell, cited, 126
Bassler, R. S., cited, 107, 207
Becraft limestone, 52-56, 173
Becraft mountain, 171
Beecher, C. E., cited, 207
Bellvale flags, 176
Bennett hill, 10

Bibliography of papers cited in text,
207-13

Bishop, I. P., cited, 116, 207
Blodgett hill, 10
Bomoseen grit, 83
Brayman shales, 40
Building sand, 203
Burden lake, 22
Butts, C., cited, 107, 207

Calciferous sandstone, 105
Cambrian and Ozarkian history, 165
Canajoharie beds, 28
Canajoharie shale, 28, 29-33, 169
Capital district, four quadrangles in,
Si area, 5

Cashaqua shale, 176

Cass hill, 10
Catamount hill, 16
Catskill beds, 176, 177
Catskill mountains, 6, 10, 20
Cedar hill, 14
Cenozoic history, 180
Chadwick, G. H., cited, 47, 50, 61, 66,
103, 156, 208

Chamberlin T. C., cited, 130
Cherry Valley limestone, 69
Clark, P. E., cited, 156, 2x2
Clark, T. H., cited, 133, 208
Clarke, Dr John M., assistance given
by 5; cited, 47, 49, 50, 103, 127, 128,
208

Clarksville, 11
Clay deposits, 13, 201
Clay plain, 12
Clay products, 201, 203
Cleavage, 157
Coeymans creek, 22
Coeymans limestone, 47-49, 173
Coeymans sea, 173
Cohoes gorge, 7
Cohoes quadrangle, 5
Cook, John H., Glacial geology of
the capital district, 5, 181-99 ; cited,
161, 208

Cooke, W., cited, 207
Copeland hill, 10
Cornelius, H. P., cited, 115, 208
Cornwall shale, 71
Corynoides gracilis, zone of, 103
Countryman’s hill, 9, 20
Cove Fields faunas, 102
Cretaceous peneplane, 21
Crooked lake, 22

Cryptograptus tricornis insectiformis,
zone of, 103
Cryptozoon Park, 166
Crystal lake, 22

Cumings, E. R., cited, 34, 158, 208,
211

Curtice, Cooper, cited, 81, 83

[215]

216

Index

Curtis mountain, 16
Cushing, H. P., cited, 26, 130, 162,
178, 179, 180, 208

Dale, T. N., cited, 9, 74, 75, 76, 77,
78, 80, 81, 83, 88, 97, 98, 99, 103,
no, 1 16, 123, 124, 125, 126, 130,
133, 144, 148, I5C 158, 162, 208
Darton, N. H., cited, 45, 47, 50, 52,
54, 57, 58, 59, 62, 64, 67, 70, 15 1,
158, 160, 209

Davis, W. M., cited, 156, 209
Dawson, G. M., cited, 102
Deep kill, 22

Deep Kill shales, 22, 86, 167
Devonian beds, 176
Devonian history, 173
Diamond rock, 77
Diamond Rock quartzite, 82
Dickhaut, H. E., cited, 80, 81
Dip slopes, 10
Drainage, 21

Eaton, Amos, cited, 124, 126
Economic geology, 199
Eights, Dr James, cited, 13
Ells, R. W., cited, 209
Emmons, Ebenezer, cited, 73, 105,
124, 209

Encrinal limestone, 52-56
Esopus grit, 58-60

Fairchild, H. L., cited, 209
Faults of western trough, 159
Fish kill, 22

Foerste, Dr A. F., cited, 116
Folded rocks, three stories of fold-
ing in capital district, 157
Ford, S. W., cited, 209
French’s mills, 7

Gas wells, 203
Genesee beds, 176
Genesee black shale, 176
Genundewa limestone, 176
Geology, descriptive, 25
Georgian group, 73
Gilbert, cited, 126
Girty, G. H., cited, 46, 209

Glacial deposits, 184
Glacial geology of the capital dis-
trict, 181-99
Glass lake, 22

Glens Falls limestone, 28, 169
Glenville hill, 14

Goldring, Winifred, assistance given
by, 5; cited, 50, 5L 54, 55, 61, 67
Grabau, A. W., cited, 40, 41, 47, 50,
59, 62, 67, 71, 210
Grafton Center region, 8
Grafton hill, 20
Grandview hill, 16, 19
Grant hollow, 144
Gravel, 203
Green, cited, 123
Green mountains, 6
Gurley, R. R., cited, 102, 210

Hall, James, cited, 46, 52, 56, 81, 96,
105, 124, 210

Hamilton beds 69-72, 176
Hanging valleys, 24
Harris, G. D., cited, 47, 210
Hartnagel, C. A., cited, 127, 201, 203,
210

Helderberg cliff, 172
Helderberg folds and faults, 151
Helderberg mountains, 8, 9, 10, 20
Helderberg, plateau, 6, 9
Helderberg War, 10
Historical geology, 162
Hitchcock, cited, 73
Hoosic river, 21, 23, 186
Holtedahl, O., cited, 210
Holzwasser, F., cited, 119, 210
House, Dr Homer D., acknowledg-
ment to, 11 ; cited, 13, 210
Hoyt limestone, 28, 166
Hudson river, 21, 23
Hudson River beds, 103
Hudson River bluestone, 200
Hudson River shale, 85

Indian Ladder beds, 38-40, 170
Iro-Mohawk, 186
Ithaca beds, 176

Jones, Robert, cited, 156

Index

217

Kalkberg limestone, 49-52
Kayaderosseras creek, 22
Kayser, E., cited, 146, 210
Kilfoyle, Clinton F., assistance given
by, 5

Kimball, J. P., cited, 210
Kimball, James O., cited, 117
Kinderhook creek, 22
Kindle, E. M., cited, 210
Kittatinny peneplane, 20

Lake Albany, 20, 194, 195, 196
Lapworth, C., cited, 73, 101, 102, 103,
167, 210

Leszinski, W. von, cited, 130, 210
Levis trough, 132
Limestone, 203
Lisha kill, 22

Little Falls dolomite, 28, 166
Logan, Sir William, cited, 124, 143
Logan’s fault, 74
Logan’s line, 143
Lower Cambrian rocks, 73-79
Lower Cambrian formations, areal
distribution, 84

Magog shale, 102, 103
Manck, cited, 91
Manlius limestone, 44-47
Manlius sea, 172, 173
Map, statement concerning, 3-5
Marcellus beds, 66-69
Marcellus sea, 175
Marr, cited, 167

Mather, W. W., cited, 85, 124, 126,
133, 211

Meadowdale-New Salem, opening,
193

Mesozoic history, 179
Mohawk, glacial equivalent, 186
Mohawk river, 21
Molding sands, 202, 203
Moordener kill, 22
Mount Marion shale, 71
Mount Rafinesque, 16, 19, 146
Mourning kill, 22

Nassau beds, 83
“Near-plane,” 20
Nevin, C. M., cited, 202, 21 1

New Scotland beds, 49-52
Newland, D. H., cited, 202, 21 1
Normanskill, 22
Normanskill gorge, 7
Normanskill shales and sandstones,
14, 96, 200

Olcott’s hill, 8, 16
Olive grit, 76
Oneonta beds, 176, 177
Oniskethau kill, 22
Onondaga limestone, 63-66, 175
Ordovician history, 166
Ordovician rocks of the eastern
trough, 85

Oriskany-Esopus beds, 174
Oriskany sandstone, 56-58
Ozarkian history, 165

Paleozoic rocks of the eastern
trough, 72

Paleozoic rocks of the western trough,
28

Patroons creek, 22

Peneplanes of capital district, 19

Pentamerus limestone, 47-49

Pinebush, 12

Pinnacle hill, 16

Plants, 11

Poestenkill, 22; glacial plains in
basins of, 192

Poestenkill fault breccia, 113, 144
Poestenkill gorge, 144
Potsdam sandstone, 28, 165
Precambrian rocks, 162
Prindle, L. M., cited, 81
Prosser, C. S., cited, 40, 41, 44, 47,
50, 52, 55, 57, 58, 59, 61, 62, 64,
67, 68, 70, 156, 161, 21 1

Raymond, P. E., cited, 33, 89, 104,
107, 21 1

Reichard pond, 22
Rensselaer gravel pit, 203
Rensselaer grit, 8, 123, 200
Rensselaer plateau, 6, 8, 20
Rexford, 7 .

Rice mountain, 16, 19
Richardson, C. H., cited, 102, 21 1
Ries, H., cited 119

218

Index

Rondout waterlime, 41, 172
Rothpletz, Professor, mentioned, 144
Rowe, R. B., cited, 40, 41, 48, 52, 57,
59, 61, 62, 63, 64, 66, 67, 68, 69,
7 1, 21 1

Ruedemann, R., cited, 26, 29, 32, 33,
34, 38, 40, 41, 50, Si, 54, 61, 69,
83, 84, 85, 88, 89, 91, 95, 96, 99,
102, 103, 104, 105, hi, 1 12, 1 13,

1 14, 1 17, 1 19, 123, 127, 130, 132,

140, 141, 144, 163, 167, 178, 179,

180, 208, 21 1
Rysedorph hill, 8, 16, 19
Rysedorph conglomerate, 99, 104,

168

Salina formations, 41, 172
Sand, 203
Sand hills, 12
Sand lake, 22
Sandstone, 203
Sarle, cited, 59
Schaghticoke, 144
Schaghticoke shale, 85, 167
Schenectady, points of geologic in-
terest in, 205

Schenectady beds, 28, 33-37, 199, 200
Schenectady quadrangle, 5
Schodack shale and limestone, 80-82
Schoharie grit, 60-63, 174
Schoonmaker, Walter J., assistance
given by, 5

Schuchert, Charles, cited, 47, 50, 73,
132, 163, 208, 212
Scutella limestone, 52-56
Sheldon, P. G., cited, 34
Sherburne sandstone, 176
Silurian history, 172
Simpson, G. B., cited, 49, 71
Smock, J. C. cited, 212
Snake Hill beds, 99, 1 17, 200
Snake Hill shale, 168, 201
Snyders lake, 22
Sprayt kill, 22
Spring water, 203

Stein, Edwin, photographs taken by,
5

Stephenson, L. W., cited, 207
Stephentown, 8
Stephentown hill, 20
Stoller, James H., work on glacial
geology, 5 ; cited, 142, 212
Strike and dip, 158
Structural geology, 130

Tackawasick creek, 22
Tackawasick limestone and shale, 99,
1 15, 168 ,

Taconian, 73-79
Taconic mountains, 6
Teller hill, 16, 19
Tertiary peneplane, 21
Theresa formation, 28, 166
Tomhannock creek, 21
Tomhannock lake, 23
Topography, 8

Troy, points of geologic interest in,
205

Troy quadrangle, 5

Troy shales and limestones, 82

Tully limestone, 176

Ulrich, E. O., cited, 104, 116, 132,
165, 212

Valatie kill, 22

Van Ingen, G., cited, 156, 212

Vanuxem, Lardner, cited, 56, 212

Vlauman kill, 22

Vly creek, 22

Volcanic rocks, 162

Walcott, C. D., cited, 73, 80, 81, 83,
105, 113, 124, 213
West River shale, 176
Whitfield, R. P., cited, 71
Woodworth, J. B., cited, 161, 194,
213

Wynantskill, 22, 192

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Figure 4 7 Traveling sanddunes, one mile east of Reynolds. (H. P. Whit-
lock, photo.)

Figure 48 Normanskill valley at Kenwood. Shows the folded Norman-
skill shale and grit in railroad cut and rapids of creek. Type locality of
Normanskill shale. (J. N. Nevius, photo.)

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Figure S3 Nearer view of lower Helderberg cliff, showing massive Manlius limestone below and Coeymans lime-
stone above, also jointing of rock and talus slope. A fault is near the pillar in center. (E. Stein, photo.)

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Figure 54 Road-metal pit in Esopus shale on south side of New Indian Ladder road. The shale is much weathered.

(E. Stein, photo.)

Figure 55 Boulder composed of alternating layers of Schoharie grit and Onondaga limestone, on road, 1%

miles south of Keefer Corners. (E. Stein, photo.)

Figure 56 Cliff of Lower Cambrian brecciated limestone on road to Snyder’s lake. Bedding plane seer..

(E. Stein, photo.)

Figure 5 7 Enlargement of portion of top of the cliff seen in figure 56 to show thin broken limestone bands
(Edgewise conglomerate) in section of beds. (E. Stein, photo.)

Figure 58 Diamond Rock in Lansingburg. Lower Cambrian quartzite (Diamond Rock quartzite), projecting vertically in ledge
from Cambrian shale. Albany plain in background across the Hudson River valley and Tertiary peneplane in far distance.

(E. Stein, photo.)

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Figure 61 Rysedorph hill The cliff of Rysedorph hill conglomerate is seen on the left of the tree on the hill. Normanskil!
shale on left slope of hill (Stoss-side) and in hill on right. (G. Van Ingen, photo.)

Figure 62 Poestenkill fault breccia (mylonite) in bottom of Poestenkill in Troy, below the fall. General view
showing the enormous size of the blocks, as the one on the right, incorporated in the breccia. (E. Stein, photo.)

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Figure 63 Nearer view of the mylonite, showing its shaly matrix and variety of
boulders. (E. Stein, photo.)

Figure 64 Cliff of mylonite on campus of Rensselaer Polytechnic Institute, showing variety of material incorporate
especially Bald Mountain limestone (white) and Normanskill chert (black) and grit. (E. Stein, photo.)

Figure 65 Fault line (‘‘Logan’s line”) of Cambrian-Ordovician overthrust in
south wall of Poestenkill gorge below fall in Troy. Cambrian shale on left
of fault line, mylonite and Normanskill grit on right. (E. Stein, photo.)

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Figure 66 Intensely folded (crumpled) Schaghticoke shale in north bank of Hoosic river
at Schaghticoke below fall. (G. Van Ingen, photo.)

Figure 67 Cohoes Falls, showing the “hanging valley” of the Mohawk river and the Snake Hill shale, forming the
fall. In background intense folding is seen in the cliff. (Museum photo.)

Figure 68 Top of anticline in Rensselaer grit at Barberville. Red shale, overlying the grit, is seen on the left.

(E. Stein, photo.)

Figure 70 Closer view of left end of fold with small intersecting thrust fault. Picture also shows jointed
character of grit beds and intercalation of thin shale seams. (E. Stein, photo.)

Figure 72 Unconformable contact of Normanskill shale (left) and Manlius limestone (right). View taken oppo-
site figure 71. (E. Stein, photo.)

Figure 73 Synciine on Sprayt Kill near South Bethlehem. The rock is Coeymans limestone. (E. Stem, photo.)

Figure 74 Syncline in Callanan’s quarry. Manlius limestone below and Coeymans limestone on top.

(H. Ries, photo.)

Figure 75 Small overturned fold and overthrust in bed of Oniskethau creek at Clarksville. (E. Stein, photo.)

Figure 76 Overthrust fault in western leg of syncline in Callanan’s quarry in Manlius limestone. (E. Stein, photo.)

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Figure 78 Rensselaer gravel pit at North Albany. Shows stratification and structure of an esker. (J. N. Nevius, photo.)

Figure 79 Stone crushing plant at Callanan’s quarry at South Bethlehem. (E. Stein, photo.)

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•• -»V? -•'

Idealized Geologic Sections

UNIVERSITY OF THE STATE OF NEW YORK

NEW YORK STATE MUSEUM
CHARLES C. ADAMS, DIRECTOR

BULLETIN NO. 285
ALBANY, COHOES, TROY AND
SCHENECTADY QUADRANGLES

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Topography by U. S. Geological Survey
and the State ol New York

Geology by
Rudolf Ruedemann
1920-28.

GEOLOGY OF THE CAPITAL DISTRICT

(ALBANY AND VICINITY)

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