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“New York State Museum Bulletin

Entered as second-class matter November 27, 1915, at the Post Office at Albany, New York,
under the act of August 24, 1912

Published monthly by The University of the State of New York

No. 192 | ALBANY, N. Y. DECEMBER I, I916

The University of the State of New York

New York State Museum

Joun M. CLARKE, DIRECTOR

GEOLOGY OF THE BLUE MOUNTAIN, NEW YORK,
QUADRANGLE

By WILLIAM J. MILLER

PAGE - PAGE
General geography and geology.. 7 | Origin of relief features.......... 57
Ptecanivrian TOCKS .<2... 2.2%. 1G2*| *eoucmic' products... 2, Jones 64
le Sig lens, se re SoM sec Sk: SP Ses Paar: < 67
Glacial and postglacial geology.. 48 | / .

ALBANY
THE UNIVERSITY OF THE STATE OF NEW YORK
1917

M83r-Ag16-1500

‘THE UNIVERSITY OF THE STATE OF NEW YORK

Regents of the University
With years when terms expire —

1926 Puy T. Sexton LL.B. LL.D. Chancellor. - ~ Palmyra

1927 ALBERT VANDER VEER M.D. M.A. Ph.D. LL.D.

Vice Chancellor -.- - - —- — — = —- Albany
1922 CHESTER S. Lorp M.A: LL.D. = - — ---- Brooklyn
1918 WiLiiaM NottTincHaM M.A. Ph.D.LL.D. - —- Syracuse
i921 Francis M. CaRPENTER — -—- - -— -— — -— Mount Kisco
1923. ABRAM I. Erxus LL.B. D.C.L. —..—.—*: = ‘= ‘New York

- 1924 ADELBERT Moot LL.D. - - - - - —- -— Buffalo

1925 CHARLES B. ALEXANDER M.A. LL.B. BoM BS

Litt.D. - -— - = - = - — -— - — Tuxedo
1919 JOHN MoorE - - —~- -—- = —- - —- —- -— Elmira
1928 WALTER Guest Kettocc B.A. - - - -— -— Ogdensburg
1917 WILLIAM BERRI- — — —. -— — — — — - Brooklyn
1920 JAMES Byrne B. A. LL.B - - - - —- —- = — New York

' President of the University “Be Commissioner of ‘Education

Joun H. FINLEY M.A. i Oe 0 Oe sb

Deputy Commissioner and Atactant Commissioner for Elementary Education

Tuomas E. Finzcan M.A. Pd.D. LL.D.

Assistant Commissioner for Higher Education

Aucustus S. Downine M.A. L.H.D. LL.D.

Assistant Commissioner for Secondary Education

CHARLES F. WHEELOcK B.S. LL.D.

Director of State Library

- James I. Wer, Jr, M.L.S.

Director of Science and State Mascam

Joun M. Crarke Ph.D. D.Sc. LL.D.

Chiefs and Directors of Divisions

Administration, Gzeorce M. WiLEy M.A. .

Agricultural and Industrial Education, ARTHUR D. DEAN D.Sc.,
. Director

Archives and History, James SuLLIVAN M.A. Ph.D., Dzrector.

Attendance, JAMEs D. SULLIVAN

Educational Extension, W1iLL1AM R. Watson B. =

Examinations and Inspections, HarLan H. Horner M.A., Director

_ Law, FRANK B. Gi_Bert B.A., Counsel for the University

Library School, Frank K. WaLter M.A. M.L.S.

School Buildings and Grounds, Frank H. Woop M.A.

School Libraries, SHERMAN WILLIAMS Pd.D.

Statistics, Hiram C. Casz

Visual Instruction, ALFRED W. ABRams Ph.B.

The University of the State of New York
Department of Science, July 10, 1916

Dr John H. Finley
President of the University

SIR:

I am transmitting to you herewith a manuscript entitled “ The
Geology of the Blue Mountain Quadrangle” with the necessary
- maps and illustrations. This is a report of special investigations
carried on for this Department by Dr William J. Miller and I
recommend that it be published as a bulletin of the State Museum.

Very respectfully
JoHnN M. CLARKE
Director
UNIVERSITY OF THE STATE OF NEW YORK
OFFICE OF THE PRESIDENT
Approved for publication this
r1th day of July 1916

e
4

—_—s————lTlCoEm
President of the Universitw

New York State Museum Bulletin

Entered as second-class matter November 27, 1915, at the Post Office at Albany, N. Y.,
under the act of August 24, 1912

Published monthly by The University of the State of New York

No. 192 ALBANY, N. Y. DECEMBER I, 1916

The University of the State of New York

New York State Museum

cs
% APR 19 1917 a
TAIN,

“tona| Wyse

sonian In
aan Stity
Joun M. Crarke, Director %

GEOLOGY OF THE BLUE MOU
NEW YORK, QUADRANGLE
BY WILLIAM J. MILLER

GENERAL GEOGRAPHY AND GEOLOGY

The territory covered by the Blue Mountain quadrangle? lies
in the heart of the Adirondack mountain region and all in northern
Hamilton county excepting less than 2 square miles of its northeast-
ern corner which extends into Essex county. It comprises an area of
nearly 215 square miles. The geographic center of the 10,000
square miles of Precambrian rock in northern New York lies within,
or close to, the northern portion of the quadrangle. The region is
very typical of the great Adirondack wilderness, being rough, well
watered, densely wooded, sparsely settled, and with few traveled
roads or trails. The difficulties of making a systematic geological
survey of.such a region, especially those portions where forest
fires have wrought havoc, are not easily exaggerated. It is a pleas-
ure to record that several of the writer's former students of geology
—Messrs J. P. Hull, H. Insley, and L. W. Bissell—at different
times accompanied him into some of the roughest country and
rendered valuable assistance.

The only villages in the area are Indian Lake, Blue Mountain
Lake, and Long Lake, no one of which has more than a few hun-
dred residents. Most of the comparatively little farming of the
region is confined to the vicinities of these villages and along
Cedar river. Lumbering is still an important industry, though
much of the first-growth timber has been cut. During the summer

1See map in pocket of back cover of this bulletin.

8 NEW YORK STATE MUSEUM

seasons hundreds of people go to the hotels or occupy cottages on
Long lake and Blue Mountain lake.

No railroad enters the quadrangle, the nearest one being the

Raquette Lake Railroad branch of the New York Central (Adiron-
dack division) with terminus at Raquette Lake village about 8
miles from the western edge of the quadrangle. The traveled roads
are clearly shown on the accompanying map. It is of interest to
note that fully one-third of the area of the quadrangle (or about
75 square miles), including the northern-central and eastern-central
portions, is wholly without a used or well-defined road, or even
trail.

The maximum range of altitudes within the map limits is from
a little less than 1560 feet, where Cedar river leaves the map on
the east, to 3759 feet at the summit of Blue mountain. Ranking
next in altitude are the two summits of Dun Brook mountain, 3580
and 3565 feet respectively, and Fishing Brook mountain, 3550 feet.
The largest, high, rugged mountain group occupies some 35 or 40
square miles bounded by Mount Sabattis on the west and Fishing
Brook and Dun Brook mountains on the east. At least 15 points
within this group reach altitudes of 3000 feet or more. In the
southeast, Blue Ridge and the prominent ridge just south of it
show altitudes of over 3000 feet, the maximum figures being respec-
tively 3481 and 3350 feet. Along the central-southern border, two
points attain altitudes of about 3150 feet, these really being only on
spurs of. the Panther mountain mass of the northern part of the
Indian Lake quadrangle. As compared with the eastern and south-
eastern Adirondacks, there is no very prevalent trend of mountain
masses, though there are some suggestions of the usual northeast—
southwest strike.

An important division of drainage — that between the Raquette
and the Hudson rivers — passes across the quadrangle. Beginning
at the middle of the northern boundary of the quadrangle, this
watershed passes over Burnt mountain, Fishing Brook mountain,
the northern summit of Dun Brook mountain, Buck mountain, Blue
mountain, less than a mile south of Blue Mountain and Eagle lakes,
and along the crest of Blue Ridge to the western border of the area.
This watershed marks essentially the crest of the central portion of
what has been called the main axis of elevation of the Adirondack
region. Two valleys (below described), with greatest altitudes of
only about 1800 feet, cut completely across this axis within the
quadrangle and constitute two of the three or four lowest valleys

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Plates

Photo by G. B. Wells, Blue Mountain Lake, N. Y.

View southwestward across Blue Mountain lake from Merwin’s Hotel. Eagle and
Utowana lakes are just visible in the distance.

4 ; ’ a Ae! ® : i o ae ae i ol
Ur eae Tee ee 7 ae Pee eee es

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 9

of this sort in the Adirondacks. One of these extends across the

quadrangle from the vicinity of Pine lake westward to Blue Mount-

ain and Utowana lakes, and the other across the northern side of
the quadrangle.

Raquette river, a tributary of the St Lawrence, is the largest
north-flowing stream out of the Adirondack region. Blue Mount-
ain lake drains westward through Raquette lake into Raquette river
and into Long lake which latter is merely an enlargement of the
river itself. Two prominent northeast-flowing tributaries of the
upper Hudson river (Cedar river and Indian river) cross the south-
eastern portion of the quadrangle, Cedar river having some 15 or 16
miles of its course, and Indian river only 2 or 3 miles of its course,
within the map limits. Rock river, the largest feeder of Cedar
river within the area, has its source in the hills south of Blue
Mountain lake and flows eastward nearly across the quadrangle, ©
Rock lake being only an enlargement of the river. The Chain lakes,
which are partly within the map limits, drain southward into Rock
river about a mile above its mouth. In all, more than fifty ponds
and lakes, or parts of lakes, lie within the quadrangle.

Excepting the glacial and postglacial deposits, all the rock forma-
tions of the quadrangle are of Precambrian age. Given in the regu-
lar geologic order they are as follows:

Glacial and postglacial deposits: Till, moraines, erratics, kames,
lake deposits, etc. 7

Diabase: Two or three small dikes ; nonmetamorphosed.

Pegmatite: Frequently found cutting nearly all types of the older
rocks, including the gabbro ; nonmetamorphosed.

Gabbro: Occasionally occurring as dikes or small stocks; more or
less gneissoid ; intrusive into the older rocks.

Syenite and granite: These are the most widespread rocks of the
region with many facies from a basic or gabbroic phase of the
syenite to typical granite and granite porphyry; distinctly gneis-
soid ; intrusive into the Grenville and anorthosite.

Anorthosite: ‘Two small masses only which are separated from the
great area lying mostly in Essex county; more or less gneissoid ;
intrusive into the Grenville.

Grenville series: Prominently developed only in the southern half
of the quadrangle; thoroughly crystalline stratified rocks, includ-
ing various gneisses, limestones, and quartzite.

Some normal faults are present but they are far less prominent
than in the eastern and southeastern Adirondack region.

IO NEW YORK STATE MUSEUM

Published statements dealing directly with the geologic features
-of the quadrangle are very scant, consisting of only a few para-
graphs altogether. The following list includes the principal papers
containing references to the quadrangie itself or the Adirondack
region in general:

1839-41. Emmons, E. Geological Reports on the Second Dis-
trict of New York. 1839, p. 224-30; 1841, p. 113-33. These are
the earliest published statements on the geology of Hamilton county.

1842. Emmons, E. Geology of New York, pt 2, on the Geology
of the Second District, p. 414-17.

1897. Kemp, J. F. & Newland, D. H. Preliminary Report on
the Geology of Washington, Warren, and Parts of Essex and Hamil-
ton Counties. 17th Annual Rep’t N. Y. State Geologist, p. 551-53.

1898. Kemp, J. F., Newland, D. H., & Hill, B. F. Preliminary
Report on the Geology of Hamilton, Warren, and Washington
Counties. 18th Annual Rep’t N. Y. State Geologist, p. 156-57.

1905. Cushing, H. P. Geology of the Northern Adirondack
Region. N. Y. State Mus. Bul. 95. A valuable treatise on Adiron-
dack geology in general.

1907. Cushing, H. P. Geology of the Long Lake Quadrangle.
N. Y. State Mus. Bul. 115. A detailed account of the geology of
the region immediately north of the Blue Mountain quadrangle.

1912. Miller, W. J. Early Paleozoic Physiography of the South-
ern Adirondacks. N. Y. State Mus. Bul. 164, p. 80-94. Presents
evidence to show that the central Adirondack area was not sub-
merged during the Paleozoic era.

1913. Miller, W. J. The Geological History of New York State.
N. Y. State Mus. Bul. 168. A book on the geology of the State
with many references to the Adirondack region, particularly in
chapter 3.

1914. Miller, W. J. Magmatic Differentiation and Assimilation
in the Adirondack Region. Geol. Soc. Amer. Bul., 25 :243-64.
Discusses the origin and age relations of the various facies of
Adirondack syenite and granite.

1916. Miller, W. J. Origin of Foliation in the Precambrian
Rocks of Northern New York. Jour. Geology, -24:587—620.

PRECAMBRIAN ROCKS

Grenville Series
General character. The Grenville rocks of the Adirondack
region, so far as our present knowledge is concerned, are to be

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE TI

classed with the oldest known formation in the crust of the earth.
They are very largely, at least, stratified rocks, the original sedi-
ments such as limestones, sandstones and shales having been
thoroughly metamorphosed into crystalline limestones, quartzites,
and various schists and gneisses. Since the foliation and stratifica-
tion planes are always coincident, it seems quite certain that the
Grenville strata have never been subjected to very severe lateral
compression, at least not sufficiently great ever to have obliterated
the bedding surfaces. As judged by the character, great thickness
and areal extent not only throughout the Adirondack region but
also through much of eastern Canada, we may safely conclude that
the Grenville beds were deposited under marine waters much as
were the sediments of later geologic periods. Concerning the
character and location of the lands from which the sediments were
derived and the sea floor upon which they were deposited, we are
at present ignorant. It is certain that the Grenville rocks are many
millions of years old.

Areal distribution. Approximately 26 square miles of Grenville
rocks are separately represented on the accompanying geologic map
of the Blue Mountain quadrangle. There must also be added some
IO or 12 square miles more represented in the mixed gneiss areas
and also inclusions mapped and unmapped in the igneous rocks.
Thus about one-sixth of the area of the quadrangle 1s occupied by
Grenville strata. On the Newcomb sheet the writer has seen large
areas of Grenville; Cushing has mapped considerable areas on the
Long Lake sheet; and the writer has seen many Grenville outcrops
on the Tupper Lake sheet along the road from Long Lake to Long
Lake West. Our knowledge is therefore sufficient to make it
positive that the Grenville is prominently represented in the midst
of the Adirondack region. Accordingly, certain older views
implying very slight development of the Grenville there must be
abandoned.

Within the quadrangle no attempt has been made to map the
different facies of the Grenville separately because the heavy drift
accumulations and consequent scarcity of exposures in certain por-
tions of the Grenville valleys render any satisfactory areal sub-
divisions impossible. To a very considerable extent the crystalline
limestone with its closely associated hornblende and pyroxene
gneisses might be separately mapped, but it has seemed best to
allow the known extent of the limestone areas to be brought out
by indicating the actually observed outcrops of that rock upon the
geologic map.

IZ NEW YORK STATE MUSEUM

An important Grenville area, nearly 4 miles wide from north
to south across the valley at Indian Lake village, extends without
an interruption up the Cedar river valley for 11 miles with a width
usually from one-quarter to 1 mile. The most abundant rock of
this area appears to be coarse, crystalline, graphitic limestone with
closely associated hornblende and pyroxene gneisses. Exceptions

are I to 1% miles north and northwest of Indian Lake village

where the rock is largely a white feldspar-quartz gneiss.

Another prominent Grenville belt extends from Pine lake with-
out a break through the valley of Rock river to Thirty-four marsh
and thence into the basin of Blue Mountain lake. Its widest places
are in the vicinity of Rock lake (nearly 2 miles) and in the Blue
Mountain lake basin (nearly 1% miles). The basin of Blue Moun-
tain lake is largely occupied by Grenville limestone, many ledges
being visible both above and below the water level. Within this
belt the only other limestone exposures were observed on Rock
tiver about a mile below the outlet of Rock lake. In the vicinity

of Thirty-four marsh, gray Grenville gneisses only were seen.

Quartzite and gray gneisses are prominent in the ridge just north
of Pine lake, while on Cedar river, between one-half and 1 mile
above the mouth of Rock river, white feldspar-quartz gneiss
together with quartzite, hornblende gneiss and gray banded gneisses
are prominently developed. Northwest of Rock lake heavy drift
rather effectually conceals the Grenville.

As shown on the geologic map, the two belts of Grenville just
described — one along Cedar river and the other along Rock river
— are certainly connected through the valley south of Rock lake,
but only a few exposures of hornblende and hornblende-garnet
gneisses and white gneisses could be found on account of the heavy
drift in this valley.

The small area extending northeastward from Unknown pond
contains several exposures of Grenville limestone and it apparently
consists mostly of this rock and associated hornblende gneiss.

The prominent depression crossing the line from the Blue Moun-
tain to the Newcomb. sheet and containing the Chain lakes (except
the first and second), Mud, Deer, and Jackson ponds, is certainly
almost entirely occupied by Grenville limestone and its associated
hornblende gneiss.

Where the road to Newcomb crosses the Essex county line, a

small area of Grenville shows various quartzitic and pyroxenic
gneisses in comparatively thin layers. This is really only the west-

Pts

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE I3

ward extension of the large Grenville area in the vicinity of
Newcomb.

In the extreme northeastern corner of the map an area of less
than a square mile shows few outcrops, these being chiefly of
hornblende gneiss.

The inclusions large enough to be separately mapped north of
Sprague pond, 2 miles south-southwest of Sprague pond, west of
Grassy pond, west of Minnow pond, and west of Buck mountain
consist of hornblende gneiss. The small mass on the side of
Stephens pond consists of white feldspar and pyroxene gneiss with
some limestone. The small area on the road 1 mile west of Fishing
brook crossing in contact with, and more or less shot through by,
pink granite consists of hornblende gneiss and nearly white feldspar-
quartz gneiss containing some pyrite and pink garnets.

Three small areas of Grenville within the mixed gneisses are
respectively on the eastern shore of Long lake one-third of a mile.
south of the northern map limit; on the western shore of the lake
directly opposite the last named area; and on the western shore of
Long lake a little south of west of Long Lake village. The first
two areas named show large exposures of white sillimanite gneiss
and gray gneisses containing red garnets and pyrite, while the
second named area shows large outcrops of a greenish gray almost
syenitic looking gneiss with specks of pyrite.

Description of Grenville types. For purposes of comparison
with other areas with the idea of possibly working out certain of
the broader structural and stratigraphic relations of the Grenville
series in the Adirondack region, the more important types of Gren-
ville of the quadrangle are here described somewhat in detail.

Crystalline limestone. The southern half of the quadrangle, in
common with the Newcomb, the southern half of the Schroon Lake,
the North Creek, and the Thirteenth Lake quadrangles, shows rather
extensive development of Grenville limestone, decidedly more so
in fact than the southeastern, southern, and southwestern border

portions of the Adirondacks. Throughout all the area just men-
tioned much of the limestone is very similar, being thoroughly
crystalline, very calcitic, usually graphitic, mostly closely associated
with hornblende, hornblende-garnet or pyroxene gneisses, and of
great thickness — several thousand feet at least.

Sometimes the limestone ledges scarcely show stratification, but
usually the original bedding surfaces are marked by layers in which
the dark minerals are more abundant (see plate 4). Because of

T4 NEW YORK STATE MUSEUM

its plasticity under pressure, the limestone is generally much folded
or twisted so that dips and strikes are very variable.

As already stated, the actually observed limestone outcrops are
indicated upon the accompanying geologic map.

Perhaps the most abundant variety of limestone is medium to
moderately coarse grained, nearly white, with irregular quartz _
grains in varying amount up to 20 per cent, scattering flakes of
graphite (often with perfect hexagonal outlines) up to 4 or 5 mm
across, and sometimes tiny specks of pyrrhotite. Many big
exposures of such rock occur along Cedar river within 2 miles vf
where it enters the quadrangle; in the vicinity of Indian Lake
village, and in and around Blue Mountain lake.

Another variety is much like the above except for numerous
grains or small crystals of pale to dark green pyroxene (coccolite)
scattered through the rock. The pyroxene is often more ‘or less
serpentinized.

Still other variations are due to absence of quartz or graphite
from either of these varieties.

Irregular shaped masses of pyroxene or hornblende gneiss have
sometimes been forced into the relatively plastic limestone under
pressure (see plate 4).

Hornblende-garnet gneisses. Rocks of this kind are frequently
found in contact (or interbedded) with the limestone. The most
common facies is a fine to medium-grained, dark-gray gneiss con-
sisting of about equal parts of hornblende and feldspar and in which
are embedded scattering red garnets (almandite) up to three-
quarters of an inch across. Among the readily accessible exposures
are: one-half of a mile east of Indian Lake village; 114 miles south-
east of Forest House; and on the island one-quarter of a mile
northwest of Blue Mountain Lake village (no. 21, table 1).

A less common facies is somewhat similar to the above but has
some biotite and the scattering, rounded, red garnets (almandite)
up to 5 or 6 inches in diameter which are completely inclosed within
envelops of black hornblende crystals. This type of garnet gneiss
is exactly like that recently described by the writer as occurring
at the garnet mine on Gore mountain near North Creek. Good
outcrops may be seen 214 miles south-southeast of Forest House
in a small mine prospect. Better exposures occur in the old garnet

1Econ. Geol. Magazine, 7:'5, 1912, p. 403-56 wilsow Nery. State Mus.
Bul. 164, 1913, p. 95-103.

Photo by W. J. Miller, 1914

A ledge of Grenville limestone on Cedar river, one-half mile northeast of the
main road bridge across the river. Stratification of the limestone is well shown as
well as the rounded masses (dark colored) of Grenville pyroxene gneiss which
have been kneaded into the relatively plastic limestone under pressure.

Plate 5

Photo by W. J. Miller, 1914

Falls at the head of the gorge on Cedar river due east of Waterbarrell
mountain. The rock is Grenville limestone.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 15

mine one-half of a mile east of Bullhead pond on the adjoining
Newcomb sheet.

Hornblende-feldspar gneiss. These gneisses are also very com-
monly found in contact (or interbedded) with the limestone. They
are to be distinguished from the hornblende-feldspar-garnet gneisses
above described chiefly by the absence of garnet. One facies 1s
medium grained and nearly black with only 10 to 20 per cent of
feldspar. Sometimes this gneiss, within an inch of a limestone
contact, is full of tiny red garnets, the lime for their development
apparently having been furnished by the adjacent limestone during
the process of metamorphism.

_ Another variety is fine to medium grained and contains perhaps
30 to 40 per cent of feldspar together with a few per cent of biotite

These hornblende-feldspar gneisses are nearly. always found
where there are extensive exposures of limestone.

Pyroxene gneisses. So far as could be determined, these gneisses
also mostly appear to be closely associated with the limestone either
clearly interbedded with them or distributed in irregular shaped
masses in them, having been broken up and forced into the relatively
plastic limestone under pressure (see plate 4).

A common variety of the pyroxene gneisses is fine to medium
grained and greenish gray, consisting largely of bright green
pyroxene (coccolite), quartz and feldspar with numerous tiny red
garnets and some titanite through the mass. Sometimes a crude
banded appearance is due to a concentration of the pyroxene in
layers parallel to the foliation. Excellent exposures occur I mile
south-southwest of Indian Lake village in the mixed gneiss area
(nos. 6 and 11, table 1). 7

A rock very similar to this, but with numerous graphite flakes
instead of garnet, outcrops along the river just east of Waterbarrel
mountain.

Another variety consisting mostly of green pyroxene (coccolite)
with some quartz and a little feldspar is very frequently closely
involved with the limestone. Excellent outcrops occur along the
road near the county line g miles east of Long Lake village, and
near the eastern end of the largest island in Blue Mountain lake
(no. 22, table 1).

Quartzites. As compared with the mapped areas of the southern
and southeastern Adirondacks, quartzites are not so prominently
developed in the Grenville of the Blue Mountain quadrangle. Also
they vary greatly in composition, scarcely any two localities showing

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GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 17

the same kind of rock. Most of the quartzites are fine to medium
grained and thin bedded. In general there are two important
varieties — one with feldspar and the other without.

The feldspathic quartzites carry from 10 to 25 per cent of feld-
spar together with 5 to 15 per cent of either biotite, muscovite or
green pyroxene, or slight amounts of tiny red garnets or graphite
flakes.

The nonfeldspathic varieties contain 90 or more per cent of
quartz together with either biotite or muscovite.

Among the better quartzite exposures are the following: on
several islands in the northern part of Blue Mountain lake; in the
ridge just north of Pine lake; and along the road at the county
line 9 miles east of Long Lake village.

Feldspar-quartz-biotite-garnet gneisses. ‘These gneisses are not
very abundant and vary greatly. Perhaps the most common variety
is a fine to medium-grained, crudely banded, light-gray rock made
up mostly of feldspar and quartz in addition to 10 or I5 per cent of
biotite and varying amounts of pale pink garnets.

Good exposures may be seen respectively three-quarters of a mile
and 114 miles east of Blue Mountain Lake village on the road; on
the small island just southeast of next to the largest island in
Blue Mountain lake (no. 23, table 1) ; and on the ridge just north
of Pine lake.

Feldspar-quartz gneisses. These light-gray to white gneisses are
represented in considerable amount.

The most common variety is medium grained and made up very
largely of feldspar and quartz with scattering red or pink garnets
and almost no dark minerals. In exceptional cases grains of
pyrrhotite or pyrite, or flakes of graphite, occur. Rocks of this
sort are extensively exposed from 1 to 1% miles northwest and
north of Indian Lake village. Other good outcrops occur on Cedar
river one-half to three-quarters of a mile southwest of Pine lake
(no. 20, table 1) ; on Cedar river 1% miles northeast of Waterbarrel
mountain ; and on the road respectively 6 miles (no. 53, table 1) and
9g miles (at the map edge) east of Long Lake village.

Apparently these gneisses are the same as certain white gneisses
recently described by the writer as occurring within the Lake
Pleasant! and the North Creek? quadrangles. That these are not
eruptive rocks is quite certainly proved by their interstratification
with definitely known Grenville strata and by their content of

’ Nov eewate: Mus, Bul. 182; peti. “rors.
2N. Y. State Mus. Bul. 170, p. 13. 1914.

18 NEW YORK STATE MUSEUM

graphite at some localities, for example, on Cedar river from one-
half to three-quarters of a mile southwest of Pine lake. This
matter is of considerable importance because these rocks so closely
resemble certain white gneisses recently described from the Sara-
toga quadrangle by Cushing and by him rather thought to be
ancient granites belonging with the so-called ‘‘ Laurentian granite.” 1

Another variety of the feldspar-quartz gneisses is light gray,
medium grained, very homogeneous and rather syenitic looking.
This rock contains specks of pyrite and weathers brown. When
first encountered it was thought to be a special facies of the syenite,
but later the same sort of rock was found interbedded with true
Grenville gneiss. Good outcrops may be seen in the small Grenville
area I mile southwest of Long Lake village (no. 43, table 1); in
the small Grenville area 2 miles northeast of Long Lake village ; and
on Cedar river respectively 1% (no. 7, table 1) and 3% miles north-
east of Waterbarrel mountain.

Sillimanite gneisses. These are also Page gray to white gneisses
but are rare, having been found at only two places. A big ledge,
100 feet across within the small Grenville area 2 miles northeast of
Long Lake village, consists of fine to medium-grained, banded,
feldspar-quartz gneiss with some layers very rich in glistening
needles of sillimanite.

The top of the mountain ridge (mixed gneiss) just southwest of
Unknown pond shows sillimanite and garnet gneisses all shot
through by granite. The sillimanite gneiss is a mass of fine-grained
feldspar through which are scattered delicate, glistening needles of
sillimanite in great abundance.

Tremolite gneiss. At the map edge on the Long Lake-Newcomb
road, tremolite gneiss is interstratified with thin-bedded quartz-
feldspar gneiss and dark pyroxene gneiss. The pone oe of this
rock is shown by no. 51, table I.

Feldspar-graphite gneiss. On the largest of the three small
islands just southeast of the largest (Long) island in Blue Moun-
tain lake, there are good exposures of gray to brown, medium-
grained, thin-bedded, feldspar-graphite gneiss, the graphite being
disseminated through the rock as numerous tinv flakes (no. 26,
fable 1).

Anorthosite-gabbro

Two small areas of anorthosite-gabbro are shown on the geologic

map respectively 114 miles northeast and 1%4 miles north of the

TaN, Vo State Mus. Bul; 160, (p) 21-26. 4 om

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE I9

Long Lake bridge. In spite of considerable variations in the char-
acter of these rocks, they are distinctly different from any other
rocks observed within the quadrangle. In every essential respect
they appear to be like the anorthosite-gabbro border facies and small
outlying masses of the great anorthosite body within the Long Lake
quadrangle as described by Cushing. Also they are precisely like
the border facies of the anorthosite area along the Hudson river
(Newcomb sheet) as seen by the writer during the summer of 1914.
Therefore it is with some confidence that the two small masses of
anorthosite-gabbro within the Blue Mountain quadrangle are
regarded as of the same age as the great anorthosite body, being
simply outlying masses or off-shoots of the large body similar to
those within the Long Lake quadrangle described by Cushing.
Identity of age has of course not been established since the two
small areas are separated from the main anorthosite body by an
interval of nearly 10 miles. According to Cushing the anorthosit
(and associated anorthosite-gabbro) is distinctly older than the
syenite.

In the area on the eastern shore of the lake the best and most
typical exposures are in the immediate vicinity of the southern
end of the diabase dike (see map) on the point which there extends
into the lake.2 This whole point is practically a solid exposure.
Within 30 or 40 feet of the dike the anorthosite-gabbro best shows
its variable character. It is mostly light gray to nearly white,
medium to very coarse grained and largely devoid of gneissic struc-

_ ture. One patch of the rock is almost pure labradorite feldspar with

fresh, bluish gray, rounded cores up to 1 or 2 inches across clearly
showing the twining bands and embedded in a finer grained granular
matrix’ of white plagioclase. These cores clearly represent the
portions of the original large labradorite crystals which were
uncrushed during the process of metamorphism. Most of the rock,
however, is medium to only moderately coarse grained with fewer
and smaller uncrushed labradorite cores, some andesine, a consider-
able percentage of dark minerals (chiefly hornblende, pyrite and
magnetite), and some red garnets. Very locally the dark minerals
may reach 30 to 40 per cent, when the rock is dark gray and dis-
tinctly gneissoid. The gneissoid structure becomes fainter with
diminution of dark minerals, much of the rock not showing it at
all. Some of the rock close to the contact with the diabase dike

tN. Y. State Mus. Bul. 115, p. 473-76. 10907.
2 This anorthosite-gabbro, at the water’s edge, contains a small inclusion
of typical Grenville limestone.

20 NEW YORK STATE MUSEUM

is very light gray and more compact looking, the feldspar having
a dull instead of the usual shiny luster. In thin section (no. 66,
table 2) the feldspar and hornblende appear to be badly decomposed.
Possibly this facies 1s an effect of the heat of intrusion of the dia-
base dike. About 50 feet east of the dike the anorthosite-gabbro
has the same mineral composition (no. 64, table 2) but is con-
siderably weathered to brownish gray, shows very few, small,
uncrushed feldspar cores, and is moderately gneissoid. From 75
to 90 feet east of the dike the rock is weathered to a deep brown,
is clearly gneissoid and looks so much like a basic phase of the
syenite that, seen alone, it would scarcely be regarded as belonging
with anorthosite (no. 65, table 2). All the facies just described
grade perfectly from one into the other, but farther eastward, that
is beyond 100 feet from the dike, there are no exposures at the
base of the mountain so that the relation of the anorthosite to the
syenite of the mountain could not be determined. Along the lake
shore for one-quarter of a mile northward from the rocky point
just described there are ledges of gray anorthosite-gabbro. Then,
after a short interval, there is a ledge of what is taken to be a basic
(gabbroic) phase of the syenite (no. 55, table 4). A few rods
directly south of the rocky point there is a ledge of either gabbroic
anorthosite or a basis phase of syenite, probably the latter (no. 56,
table 4). Still farther south along the lake shore, there are out-
crops of basic facies of the syenite. Thus, although the evidence is
not conclusive, the anorthosite-gabbro appears to grade into a
basic phase of the syenite of the region. Similar gradations have
been quite definitely proved within the Long Lake quadrangle by
Cushing who suggests that “the observed relations seem to point
to the conclusion that the change is due to actual digestion, by the
molten syenite, of material from the adjacent (anorthosite)
gabbro.” ? ake

In the small anorthosite-gabbro area west of the lake, big out-
crops cover fully one-half of an acre. The rock is much like the
main bulk of the anorthosite-gabbro just described as occurring on
the eastern shore of the lake. Toward the interior the mass is
entirely devoid of foliation, is light gray, shows occasional
uncrushed, bluish-gray labradorite crystal cores up to one-half or
three-quarters of an inch across, and contains a considerable per-
centage of dark-colored minerals and some garnet. Otherwise much
of the rock is darker gray and moderately gneissoid to almost black

1N. Y. State Mus. Bul. 115, p. 479. 1907.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 21

and highly gneissoid. Within this anorthosite-gabbro there are
several inclusions of light gray Grenville gneiss up to 2 or 3 feet
wide, some bands of amphibolite and a few masses (one 25 feet
across) of granitic syenite, all of these being arranged approximately
parallel to the foliation of the inclosing rock where that structure
is present. Whether the granitic syenite occurs as inclusions or as
dikelike intrusions could not be positively determined, though they
are most likely the latter.

Table 2— Thin-sections of anorthosite — gabbro

j
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SLIDE 2 3 3 & 2 3 isto 2
ie N |=
NUMBER ES g Seas 3 2 Sf % o 3 2 3 g 2 8
3 S (o/8/¢}/ s1/S/si el. & 3 & 5 Sir ite
& Se eC TE les nore et kneel BS lo me |b. LO
ee r7e 5(c)|an.-Lab. 63] 35|...|... Pais te I .| little} little] little].....].. Sato
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ile hee aes E7e.5(e) |an.-Lab. 7OloTL) ES |i 0s). 0.0% Se nie hes st ie thee lee ep ae y lem ay (mga ;
RSA? ato T7e 5@)ian--Labe 77) TS}. eles. Be eS ee te ewe little} little] little)..... ists
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i 17e glol.-Lab. 66} 6]...| 2 ASPET lralis, (ok, 3 little} little]..... leckeit 8s lerane

Nos. 61 to 66 inclusive are from the area on the eastern shore of Long lake;
no. 58 is from the area west of Long lake andis more acidic than the usual
rock there. ;

A number of small pegmatite dikes cut through the whole mass of
rock. There are no exposures of any kind immediately surround-
ing the anorthosite-gabbro area so that nothing could be learned
regarding its relation to the other rocks of the vicinity.

Syenite and Its Facies

The syenite and its basic and acidic facies are the most wide-
spread of all the rocks. As here considered they vary greatly,
ranging from what may be termed a normal quartz syenite to a
basic (dioritic to gabbroic) facies on one hand to granitic syenite
and granite on the other. Since these facies grade back and forth
into one another, sharp boundary lines between them do not exist
and their separation on the geologic map depends to a considerable
extent upon personal judgment based upon some years of experience
with the rock types and checked up by the study of numerous
thin sections.

As is now well known, the syenite is younger than the Grenville
series and distinctly intruded into it, there often being dikelike

22 NEW YORK STATE MUSEUM

tongues of syenite cutting the Grenville and clearly defined inclu-
sions of Grenville in the syenite. According to the work of Cush-
ing on the Long Lake quadrangle, the syenite is also younger than,
and intrusive into, the anorthosite.1. For most part at least, the
granites of the Blue Mountain quadrangle are only differentiation
phases of the great syenite body and of practically the same age
as the syenite, though the possible presence of some unproved
granite either distinctly older or younger than the syenite must be
admitted. This matter is more fully discussed in connection with
the granite. Both the gabbro stocks or dikes and the diabase dikes
are certainly younger than the syenite.

Normal quartz syenite. More than one-third of the area of
the quadrangle is occupied by the normal syenite, it being widely
distributed in exceedingly irregular bodies.

As usual throughout the Adirondacks, the normal or most
typical syenite is dark greenish gray when fresh and weathers to a
light brown, though apparently fresh pinkish or reddish syenites do
occur rather locally. The depth of weathering usually varies from a
fraction of an inch to several inches or, more locally, to a foot
or more. In general the amount of weathered rock here seems to
be greater than in the border regions of the Adirondacks, doubt-
less due to the fact that the central region was neither so long nor |
so vigorously glaciated. Immediate surfaces of syenite ledges are
sometimes light gray to almost white, probably due to the leaching
out of iron compounds by water rich in decomposing organic
matter. A case in point is the big, bare ledge which looks like a
snow bank in midsummer well up on the side of Blue mountain
and clearly visible from the south for some miles. A hand speci-
men from this ledge shows a thin, white surface layer under
which is a brown zone an inch thick and which in turn merges
downward into the greenish gray fresh rock.

As regards granularity, the normal syenite is. mostly medium
grained; that is, the crystals range in length from I to 5 mm.
Sometimes, however, it is finer grained while again it becomes
moderately coarse to even slightly porphyritic. More or less granu-
lation of the rock is a very common feature, the feldspars showing
the greatest effect of the crushing of the mineral grains.

All the rock is foliated, most of it moderately so. At times the
foliation is very faint, while at other times it is excessively devel-
oped, especially along shear zones where the rock may have an
almost schistose appearance.

1N, Y. State Mus. Bul. 115, p. 479-82. 1907.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 23

The normal syenite always contains quartz, the average amount
being 12 to 20 per cent in the slides examined, and when it is greater
than 20 per cent the rock is no longer regarded as normal, but rather
granitic syenite to granite. Microperthite almost invariably makes
up from one-third to two-thirds of the rock. Orthoclase is much
less constantly present in variable amounts. Plagioclase (albite

' to andesine) never fails in amounts up to 35 per cent. When the

rock is relatively rich in plagioclase it is a monzonite, though here,
for convenience, classed with the normal syenite. Common horn-
blende with yellowish green to dark green pleochroism usually
occurs in variable quantities up to 25 per cent, while green mono-
clinic pyroxene (usually diallage) frequently makes up 2 to 20
per cent of the rock. Enstatite was observed in only one slide.
Both hornblende and pyroxene sometimes occur in the same rock.
Magnetite (ilmenite), apatite and zircon in small quantities rarely
fail. Biotite, garnet, zoisite and titanite are more sporadically
present in small amounts.

The following table will serve to show the mineralogical varia-
tions of thin sections from carefully selected specimens of the
normal syenite.

NEW YORK STATE MUSEUM

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GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 25

Basic (dioritic to gabbroic) facies of the syenite. The rocks
included under this caption really have the composition of diorite
or gabbro though they have been quite certainly produced either by
pure differentiation of the syenite magma or by the assimilation
of country rock through which the syenite magma was intruded.
They are quite different in aspect from the typical later gabbros
which are separately represented on the geologic map in that they
show neither the diabasic texture nor the peculiar mottled appear-
ance of these later gabbros. In fact the color, texture and structural
features are essentially the same as those of the normal quartz
syenite already described.

Mineralogically, the basic facies of the syenite differ from the
normal syenite chiefly by absence of microperthite, reduced amount
or absence of orthoclase and quartz, and predominance of plagio-
clase (oligoclase to andesine).

The following tabular summary illustrates the mineralogical com-
position of typical thin sections from several areas of the so-called
basic syenite.

Table 4— Thin-sections of basic (dioritic to gabbroic) phases of the

syenite
o © = | eg ()
Ww
oe ae eet 8) ae | a | :

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ie rey ear) Sel ey eel eet ai) es eee
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Sty th6 23 gi ee ternal tet I RES ie Eat oF TS < _ 4 ee cea
30. as rpjel ata eal a Ola Galec ie) emetic ies G7 Siew ss Si eet ie little|, 3] little
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Sha. ER Oe ite gt EL 25M s cine. wos |e wie fo axes %| little) little} little
SOI. Tye 4 ....| Ol.-An, 42 35 Aa ae ernie ates flo Pau es 5 6|....| little} little] little

No. 2, 2% miles south-southeast of Sprague pond; no. 36, Buttermilk falls -
on Raquette river; no. 44, eastern base of Owl’s Head mountain; no. 55,
eastern shore of Long lake 114 miles northeast of the Long Lake bridge;
ae 56, eastern shore of Long lake 1% miles northeast of the Long Lake
bridge.

The rock in the small area near the middle southern border of
the quadrangle (no. 2, table 4) is pale greenish gray, medium
grained, clearly gneissoid, with occasional crystals of biotite and red
garnet set in a granular mass of feldspar. This rock appears to
grade into the surrounding normal syenite.

In the area including Buttermilk falls there are many outcrops,
the best being at the falls where, in a great ledge, the rock (no. 36,
table 4) is mostly rather homogeneous, greenish gray when fresh,

20 NEW YORK STATE MUSEUM

though somewhat darker than the normal syenite on account of a
larger percentage of dark minerals, moderately gneissoid, and with
some small garnets. At times there are streaks of dark, basic
gneiss (presumably Grenville) more or less fused in, giving the
rock something of a wavy or contorted aspect and suggesting the
possibility that the basic syenite here has been produced by assimi-
‘lation of such dark gneiss by the syenite magma. Ledges on the low
mountain ridge to the east and southeast of the falls are very similar.

The rock of the Owl’s Head mountain area (no. 44, table 4) is
dark, greenish gray when fresh and weathers to a deep brown. It
is very homogeneous, medium grained, clearly gneissoid, and usually

rather rich in dark minerals though without garnets. The darker

portions have a decided gabbroic look though not like the later

gabbros of the quadrangle. Occasionally a small phenocryst of ©

plagioclase stands out in the medium-grained, granulated matrix.

The area northeast of Long Lake village borders the anorthosite-
gabbro and seems to form a transition between that rock and the
normal syenite, though such a transition is not positively demon-
strable as above discussed in connection with the anorthosite-gabbro.
Exposures occur only close to the lake either side of the anorthosite-
gabbro, the rock (nos. 55:and 56, table 4). being fine to moderately
coarse grained, greenish gray weathering to brown, clearly gneissoid
and fairly rich in dark minerals. Sometimes there is a suggestion
of a porphyritic texture. A few bands of amphibolite parallel to
the foliation occur in the rock along the lake shore south of the
anorthosite-gabbro. |

The Triplet Hill mass is probably only a westward extension,
under the lake, of the area last described, the rock being very simi-
lar though at the summit of the hill some of the rock is rather dis-
tinctly porphyritic.

A very small body of basic syenite shown on the map northeast
of Long Lake village is only a wide band parallel to the foliation
of the syenite and not sharply separated from it. The rock is of
decided igneous aspect, rather hornblendic and with occasional
garnets up to more than an inch across. Apparently this rock has
been produced by the assimilation of some Grenville hornblende-
garnet gneiss by the syenite magma. The rock bears a very close
resemblance to a definitely proved assimilation product of this sort
at the garnet mine on Gore mountain near North Creek in Warren
county.

Granitic syenite. The granitic syenite is really only an acidic
phase of the syenite in which the quartz content lies approximately

tl i elt hi i i -

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F161 ‘soy “£ “AA Aq O}OYg

L 33eId

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 27

between 20 and 25 per cent. So far as could be determined in the
field, this granitic syenite is intermediate between the normal syenite
and the granite, always. grading into one or the other or both.
Nothing like definite evidence was obtained to show that any one
of these rock types cuts another. Though any attempt separately
to delimit the granitic syenite on the geologic map must be rather
arbitrary, it is believed that, as a result of careful attention to
the matter in the field and the study of thin sections, the areal
relation of the granitic syenite to the normal syenite and the
granite are fairly well brought out.

. This granitic syenite occupies nearly one-third of the area of the
quadrangle and, like the normal syenite, is widely distributed in
very irregular shaped bodies.

Much of the rock shows the usual color of the normal syenite, but
pinkish to reddish granitic syenite is not uncommon, thus suggest-
ing the typical granite into which it grades.

Texturally and structurally the granitic syenite shows essentially
the same sorts of variations as the normal syenite.

Mineralogically the granitic syenite differs from the normal
syenite chiefly in the larger content of quartz, somewhat smaller
content of plagioclase, and absence of pyroxene.

In table 5 the compositions of a number of thin sections of granitic
syenite are shown.

Granite

About 15 square miles of the quadrangle are separately mapped
as granite, but, since this rock is abundantly represented in most
of the mixed gneiss areas, the actual extent must be increased to
something like 25 square miles. No field evidence was found to
show that any of the granite is distinctly older or younger than
the syenite or granitic syenite, though in many places perfect
gradations from one to another were observed.

The granite facies vary in color from light gray or greenish gray
to pinkish gray or light red. In some cases the reddish color is a
mere surface weathering effect as, for instance, on the eastern
face of Waterbarrel mountain where, within I or 2 feet, a super-
ficial pink color passes downward into a light brown, and finally
into a greenish gray color where the rock is very fresh. In other
cases the reddish color permeates the rock to depths of 10 or 20
feet as is well exhibited in the quarry on the road 2% miles east
of Long Lake village. In still other places the pinkish or reddish
color seems to be the inherent color of the rock or, if due to

MUSEUM

NEW YORK STATE

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GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 29

weathering, the color change has affected the apparently fresh rock
to depths beyond the zone of observation.

As regards texture and degree of foliated structure, the facies
of granite show practically the same kinds of variations as the
normal syenite already described.

Mineralogically, the granite differs from the facies of the syenite
chiefly in the higher quartz content and more common occurrence
of microcline. ‘Table 5 includes examples of the more common
variations of granite from different parts of the quadrangle.

Various types of light to dark-gray Grenville gneisses occasionally
occur as distinct inclusions in the granite, but limestone inclusions
were never noted. Where such inclusions are of sufficient abund-
ance to make up a considerable percentage of the mass, the rock
has been classed with the mixed gneisses (see below). The inclu-
sions are nearly always flattened and drawn out parallel to the
foliation of the granite almost exactly as in the case of the syenite
and granitic syenite. Also, as in the mixed gneisses below described,
many of the inclusions are sharply separated from the inclosing
rock, while others grade into the granite as a result of partial
fusion. ‘

Long, narrow, amphibolite (presumably Grenville) inclusions,
apparently like those so characteristic of the so-called ‘ Laurentian
granite”? of the Thousand Islands region, also occur in some parts
of the granite, but are not abundant. Perhaps the best observed
locality for such inclusions is on the north shore of Clear pond
where numerous streaks or narrow layers of amphibolite are drawn
out parallel to the foliation of the pink granite and sometimes in
sharp contact with it. Such amphibolite inclusions are, however,
by no means characteristic of the granite since they are about as
commonly present in the facies of the syenite. Thus the normal
syenite and its basic variation on either shore of Long lake north-
east of Long Lake village afford excellent exhibitions of amphibolite
inclusions of the kind just described. The nature and frequency
of the inclusions therefore afford no criterion by which any possible
age differences between the syenite and granite could be determined.

The absence of distinct limestone inclusions from the granite har-
monizes with the Thousand Islands region as described by Cushing
and Smyth! and the Haliburton-Bancroft area of eastern Canada as
described by Adams and Barlow.” According to Adams, the lenses

1N. Y. State Mus. Bul. 145, p. 37. 1910.
2Canada: Department of Mines, Geol. Survey, Memoir 6, p. 62-114.

30 NEW YORK STATE MUSEUM

of limestone caught up by the granite or syenite magma were con-
verted into amphibolite.

Still another feature of interest is the occasional occurrence of
rapid transitions from syenitic to granitic material and vice versa,
giving rise to a kind of banded structure parallel to the foliation
but with the bands not at all sharply separated from each other. A -
case in point is the freshly blasted ledge’on the road 1% miles south-
west of Long Lake village where a band of light-gray hornblende
granite (no. 42, table 5) 214 feet wide passes by insensible grada-
tions on either side into a greenish gray pyroxene syenite (no. 41,
table 3). Such phenomena appear to be rather common in the
Adirondack region, many observations having been made in the
various quadrangles studied by the writer, and also in the Long
Lake and Elizabethtown-Port Henry quadrangles by Cushing and
Kemp respectively. For most part these banded structures are
believed to be a result of magmatic differentiation, but in some cases
it is probable that lenslike inclusions of Grenville rocks have been
more or less assimilated by the inclosing syenite or granite.

Granite Porphyry

Many times the pink or gray granites have suggestions of por-
phyritic texture, though there is but one small area of typical
granite porphyry which could be mapped as such. This is in
marked contrast with the relative prominence of such porphyry
within the Broadalbin, North Creek and Lake Pleasant quadrangles
mapped by the writer in the southeastern Adirondack region.

The small area of granite porphyry occupies about one-quarter
of a square mile in the vicinity of the Indian lake dam.- Some of
the rock has been used in the construction of the dam. There are
many good exposures, the best being at the dam and in the quarries
just east. Where fresh the rock is greenish gray, and where
weathered it is pinkish. The rock is always coarse grained and
rather gneissoid with the porphyritic texture usually well developed
though at times only poorly so. The feldspar phenocrysts are always
highly granulated. Locally biotitic shear zones occur. At times
some small Grenville gneiss inclusions may be seen.

A thin section of the typical rock from near the dam shows the
following mineral percentages: orthoclase 10; microline 25; micro-
perthite 15; oligoclase to andesine 4; quartz 40; hornblende 2;
biotite I; garnet 2; apatite 14; and a little zircon and magnetite.

Plate 8

Photo by W. J. Miller, 1914
The State dam at the end of Indian lake. All of the rock is granite porphyry. A
vertical fault surface is visible at the end of the footbridge.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE ai

Mixed Gneisses

General statements. Under this caption are included chiefly -

Grenville rocks which are cut to pieces by, and more or less closely
involved with, various facies of the syenite-granite body. Some-
times the Grenville, and sometimes the igneous, rocks prevail. Of
the igneous rocks in most of the areas, granite appears to pre-
dominate. In general it may be said that these mixed gneisses
include: long, narrow masses of Grenville and syenite or granite
distinctly recognizable as such but showing rapid alterations at
right angles to the strike of the foliation ; bodies of syenite or granite
containing numerous sharply defined lenslike inclusions of Gren-
ville ; Grenville rocks intimately shot through by igneous rocks after
the fashion of so-called “ lit-par-lit” injection; bodies of syenite
or granite containing a multitude of small, lenslike Grenville inclu-
sions whose borders commonly grade into the inclosing rock so that
the Grenville is often difficult to recognize as such; rocks which
are intermediate in character between the Grenville and igneous
rocks and which have clearly been produced by magmatic assimila-
tion; and still other rocks of variable types and puzzling character
whose origins are admittedly rather uncertain. The small scale
of the map, together with the usual lack of sufficient outcrops has,
for most part, rendered inadvisable any attempt to map separately
very small masses of Grenville or igneous rocks recognizable as
such within these mixed gneiss areas. It is not uncommon to find
small exposures with a so-called “ mixed gneiss” aspect within the
great syenite-granite intrusive body, but here too it would be unsat-

isfactory to attempt any consistent separate delimitation of such -

rocks.

Area south to southwest of Indian Lake village. This area
of about 214 square miles shows many féatures characteristic of a
typical mixed gneiss area.

Along the river and in the fields east of Indian lake dam, there
are numerous outcrops of granite and Grenville rocks (even includ-
ing limestone) which are clearly recognizable as such, while certain
other outcrops consist of more or less intimately associated granite
and Grenville rocks where the distinctive characters are not so
evident.

Very instructive exposures occur along the road 1 mile a little
west of south of Indian Lake village. Going southward the first
outcrop beyond the pink granite is well-banded pyroxene (cocco-
lite), Grenville gneiss, most of which contains considerable feldspar

a ee

—

32 NEW YORK STATE MUSEUM

and quartz together with some calcite and tiny brown garnets and a
little titanite (no. 11, table 1). There are occasional nests, up to
8S inches in diameter, of pure bright-green pyroxene (coccolite).
Some of the layers of Grenville are pyroxene quartzite. The next
ledge on the road, a few yards to the south, contains Grenville
gneisses exactly like those just described, but which are all shot.
through by pinkish granite with more or less assimilation of the
Grenville by the granite. Sometimes Grenville streaks are fairly
distinct, and sometimes they clearly fade into the granite which
latter rock then contains a sprinkling of small crystals of green
pyroxene and has a composition really much more like granitic
syenite to normal quartz syenite, though quite different in outward
appearance. A thin section of this changed rock shows the follow-
ing mineral percentages: orthoclase 18; microcline 24; microperthite
25; oligoclase to andesine 5; quartz 21; pyroxene (coccolite) 6;
and less than 1 per cent each of magnetite, titanite, zircon and
muscovite. It is certain that the pyroxene of this granitic syenite
has somehow been derived from the Grenville gneiss, the evidence
rather clearly pointing to actual absorption or assimilation of some
of the Grenville by the granite.

Area between Indian Lake village and Rock lake. In this area
of some 3 square miles, the most interesting exposures are on the
mountain lying southwest of Unknown pond. For about a mile the
top of the fire-swept mountain is an almost continuous, barren rock-
ledge in which a certain type of the mixed gneisses is beautifully
exhibited. Pink, medium-grained, biotite granite is all shot through
‘Grenville white gneiss and Grenville light-gray, feldspar-quartz-
garnet gneiss, these gneisses usually occurring in wavy, dis-
connected, thin layers throughout the granite. It is evident that
there has been no considerable assimilation, though usually the
gneiss boundaries are not sharply defined against the granite.
Farther down, on the south face of this mountain, fairly large
masses of dark, rusty-looking, Grenville gneisses occur in the
granite.

Along the road directly west of the mountain just described,
there are closely associated gray granite and gray Grenville gneisses.

The mountain directly south of Unknown pond consists mostly
of pink granite with numerous streaks or bands (sometimes 10 to 20
feet wide) of Grenville hornblende gneiss. — 7

Area south of Blue Mountain lake. This area of about 9 square
miles, extending from Blue Mountain lake southward to the base of

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 33

Blue ridge, is in most respects very typical of central and southern
Adirondack mixed gneisses. Throughout the area various types of
Grenville strata have been more or less cut to pieces by pink granite
or granitic syenite, the dips generally being very. steep and the
igneous masses having nearly always penetrated the Grenville
parallel to the foliation. More rapid wearing away of the weaker
Grenville belts accounts for the arrangement of low ridges approxi-
mately parallel to the foliation. Many exposures show either pure
Grenville or pure granite, while in many others the granite and
Grenville are more or less intimately associated, in some cases local
assimilation having taken place. Excellent outcrops in the open
field between Blue Mountain Lake village and Crystal lake afford a
practical demonstration of the very intimate relations of granitic
and Grenville gneisses with some intermediate rocks due to mag-
matic assimilation. The granites are pinkish to grayish and rather
variable though always gneissoid. In certain outcrops gray, biotite
or dark garnet or pyroxene, Grenville gneisses may be seen to grade
into the igneous rock with no visible contacts. In a few cases the
contacts are fairly sharp. Most of the exposures, however, con-
sist of rocks of distinctly intermediate character which are clearly
the products of local assimilation.

Area south to southwest of Grove (Deerland). This body of
mixed gneisses, covering about 2 square miles, mostly comprises
outcrops of gray to pinkish granitic to syenitic gneisses filled with
streaks or inclusions of dark to light-gray gneisses (presumably
Grenville), the rocks being crudely banded, very gneissoid, and
often considerably contorted.

Exceptional exposures occur as big ledges in the bed of the stream
which is the outlet of South pond. The rock, instead of, being
distinctly gneissoid to banded, is streaked or wavy as though small
amounts of dark Grenville had been partially fused and assimilated
by syenite magma, the syenitic character being preserved in spite
of the inclusions. The whole presents what might be-termed a
“marble-cake ” appearance.

Area across the northern portion of the quadrangle. This area
of about 12 square miles extends completely across the northern
portion of the quadrangle and is apparently the southern border
of the so-called ““ Long Lake gneiss’ as mapped by Cushing in the
region immediately to the north. For. most part the rocks of this
area are rather typical mixed gneisses, that is, they are largely
granite or syenite more or less intimately associated with Grenville,

34 NEW YORK STATE MUSEUM

these latter being chiefly dark hornblende gneisses and light-gray
quartz-feldspar gneisses arranged as bands, belts, or lenslike inclu-
sions in the igneous rocks and parallel to the foliation. In some
cases these belts or inclusions of Grenville merge into the inclosing
- igneous rocks because of melting of their borders at the time of the
magmatic invasion. Though the outcrops are rather poor in many
portions of the area, it seems fairly certain that the granitic and
syenitic rocks predominate.

A solid ledge for 200 yards in the gorge of Fishing brook just
east of the county line shows a preponderance of pink granite which
contains distinct belts of both dark and on Grenville gneisses
parallel to the foliation.

Where the secondary roads diverge two-thirds of a mile west of
the Long lake bridge, there are fine ledges of rather variable rock
consisting in part of syenitic and gray granitic gneisses with dis-

tinct amphibolite and gray Grenville gneiss bands parallel to the -

foliation. Much of the rock, however, is streaked to almost thin-
banded due to injection of the gneisses by thin layers of magma
(see plate g). At one place a very small mass of Grenville lime-
stone was noted.

On the shores of Long lake within one-half of a mile of the
northern map edge, there are fine exhibitions of typical mixed
gneisses. Thus on the eastern shore one-eighth of a mile southwest
of the small mapped Grenville mass, there is a big ledge of syenitic
to almost gabbroic looking gneiss with streaks, blotches and bands
of dark, biotite-garnet and gray, biotite-quartz gneisses arranged
parallel to the foliation. The southern portion of this ledge is pink
granite which merges (as a result of fusion) into a biotite-quartzite.

The.end of the sharp point projecting into the lake less than one-
quarter of a mile southwest of the locality last described is a solid
ledge of mixed gneisses which looks as though Grenville strata
had been thoroughly cut up, and more or less fused, by the syenite
magma so that both Grenville and syenite often do not show their
typical features.

In certain other ledges on the lake shores there is good evidence
for some fusion of Grenville strata, and frequently bands of
amphibolite up to 20 or 30 feet wide occur parallel to the foliation
of the syenitic or granitic gneisses.

Other areas. In the bed of Rock river nearly 1 mile below the
outlet of Rock lake, large exposures show green pyroxene, white

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Plate 10

Photo by W. J. Miller, 1914

A ledge of Grenville and granite mixed gneisses, two-thirds of a mile west
of the Long Lake bridge and similar to that shown in plate 9, but with two
veins of pure white quartz parallel to the foliation on the left and a dike of
pegmatite at the lower right. The pegmatite sharply cuts both the gneiss and
one of the quartz veins, the latter not being shown in the picture. The camera
was pointed downward to get the picture. .

AGN *

7 o iy

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 35

granitic-looking and hornblende gneisses cut by masses of granitic
syenite and pink granite.

The small body of mixed gneisses exposed along the river south-
southwest of Sprague pond shows not only normal syenite and
Grenville hornblende gneiss, but also a basic, igneous-looking gneiss
apparently an assimilation product.

The other small areas mapped as mixed gneisses require no special
description. It is of course to be remembered that small exposures
showing the so-called “ mixed gneiss” aspect.are occasionally met
with in many parts of the quadrangle.

Gabbro Stocks and Dikes

Thirteen gabbro stocks or dikes have been discovered and sepa-
rately represented on the accompanying geologic map. They are
rather widely distributed over the quadrangle, though eight of them
are confined to its southern one-fourth. That these gabbro masses
are younger than any facies of the great intrusives already described
is clearly proved by their sharp contacts against those intrusives. In
many respects these gabbros are similar to those of the North Creek
quadrangle recently described somewhat in detail by the writer,?
but they do not present so many. variations. Most of them at
least have rounded to elliptical ground plans and practically vertical
contacts with the country rock, so that they are of the nature of
stocks, but in some cases where the exposures are not very satis-
factory, they may exist as dikelike forms. As a rule, the long
axes of the exposed gabbro bodies are almost, or quite, parallel to
the foliation of the country rock. No branching of any gabbro
mass was noted. The observed variations in size of the areas is
from a single small exposure a few rods across to others from
one-half to three-fourths of a mile long.

A feature of particular interest is the almost invariable associa-
tion of pegmatite dikes or veins with the gabbros, the former cutting
the latter. The same thing has been noted in connection with the
gabbro stocks of the North Creek and Lake Pleasant quadrangles,
but its significance is scarcely known.

Megascopically, the gabbros are seen to be medium to moderately
coarse grained and dark gray when fresh with roughly equal
amounts of feldspar and dark minerals, the latter including horn-
blende or pyroxene or both, biotite, ilmenite and usually tiny reddish
garnets scattered through the rock. On weathering, the gabbros

1N. Y. State Mus. Bul. 170, p. 26-38. 1914.

30 NEW YORK STATE MUSEUM

assume a deep-brown color. The larger and more typical stocks
commonly have a nonmetamorphosed interior facies which has a
more or less well-developed diabasic texture, and a border facies
(often amphibolite) which is so thoroughly gneissoid that the dia-
basic texture has disappeared. The typical nonmetamorphosed
gabbros, with diabasic texture.and large percentage of black
minerals, is readily distinguished irom all other rocks of the region.
Some of the border facies, however, are either amphibolites which
look much like certain dark gneiss inclusions commonly seen in the
granite and syenite, or dark gneisses which might be easily con-
fused with certain basic facies of the syenite.

Under the microscope the mineralogical composition of the gab-
bros is shown by the following examples taken from various stocks
or dikes. )

Table 6 — Thin sections of typical gabbros

i @
- = i S | 2
== S = S = = a
Side no. Z 2 ls Ea a o 2 ae, oe
= = i] = = = paar = = = =
E 3 bl eta ts [2 | ieee
Ee ay |= | & A mo 2 B, o <
i | |
Re See 2cr OlL-Lab. 20 33) MR S,. | rz BTS epee eee ah
eaee re <4 42% An-Lab. 28 20} Is 10 2) tile) hiile 25s.
PES ocala eas am 55 Lab. 34) E5} tS E7 2 ee | Lee
pape ae Sc 19o{f2) An-Lab. 55) 20 rs 4 S| lnttle!.....- Pi Be RS
ye ee 8&8 An—Lab. 55) 25 I5 E rE | ee Ne litle
eee eS 1% 8 Lab-An. 55/....-. ) y | (ee 5 : ee ¥2) 5 ees

No. & 1 mile north of Waterbarrel mountain; no. 15, one-third of a mile
west-southwest of Sprague pond; no. 17, 13%4 miles north-northeast of Indian
Lake village; no. 25, small island one-quarter of a mile southeast of the
largest island in Blue Mountain lake; no. 27, largest island in Blue Mountain
lake; no. 52, eastern side oi stock 4 miles east oi Long Lake village.

The largest gabbro stock, 4 miles east of Long Lake village, is
very typical (no. 52, table 6) and has numerous outcrops with the
amphibolite border facies well exhibited along the road.

On the largest island in Blue Mountain lake the gabbro (no. 27,
table 6) is not so typical, its interior being somewhat gneissoid,
medium grained and with only slightly developed diabasic texture,
while its border facies is fimer grained, more granulated, and
amphibolitelike. Very similar rock (no. 25, table 6) outcrops on
the small island just to the southeast and it is probable that these
two masses are parts of the same gabbro stock now mostly covered
by water. If they are connected, the submerged portion may be
nonmetamorphosed and with better diabasic texture.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE ae

The large stock north of Waterbarrel mountain shows some big
ledges of medium to coarse-grained rock with perfect diabasic tex-
ture, and feldspar laths up to three-quarters of an inch long (no.
8, table 6). Some amphibolite occurs, especially on the north side
of the stock, but much of the gabbro is very gneissoid, this being
true in places (particularly toward the east) of even the coarsest
grained rock, the feldspars having been highly granulated, the dia-
basic texture destroyed and occasional garnets developed. This
very coarse-grained, gneissoid gabbro so greatly resembles a large
mass somewhat doubtfully called gabbro along the West Branch of
the Sacandaga river in the Lake Pleasant quadrangle that this
latter rock is now quite confidently regarded as a metamorphosed
coarse gabbro. Apparently it is a facies of gabbro not often
met with.

The other gabbro masses of the quadrangle are quite typical in

_ every way and require no special description.

Pegmatite

Pegmatite dikes or veins were occasionally met with in many
parts of the quadrangle. One type occurs as narrow masses of °
moderately coarse grain with long axes essentially parallel to the
foliation of, and not very sharply separated from, the inclosing
syenite or granite. Dikes of this sort were, no doubt, injected
practically contemporaneously with the great intrusives, possibly
as a late phase of the intrusions.

Another type of pegmatite, clearly later in origin, is generally
very coarse grained, cuts through rocks of all ages except the dia-
base, shows very sharp boundaries and usually cuts across the folia-
tion of the country rock. Dikes of this sort are wholly devoid of
metamorphism. They range in width from 1 or 2 inches to 100
feet and in length up to 200 yards or more. A few of the most
conspicuous observed examples are as follows: coarse-grained dike
10 or 15 feet wide cutting Grenville hornblende gneiss on Cedar
river 314 miles west of Indian Lake village; a 15 foot wide dike
some 40 or 50 feet long cutting Grenville limestone just southeast
of the small gabbro stock 1 mile north-northeast of Indian Lake
village ; small but very. sharply defined dikes cutting the basic syenite
at the summit of Owl's Head mountain; a dike fully 100 feet wide
and 200 yards long at the western border of the gabbro on the
largest island in Blue Mountain lake; small dikes cutting syenite
near the western end of Long Lake bridge; small dikes cutting mixed

iN. Y. State Mus. Bul 182, p. 29. 1016.

38 NEW YORK STATE MUSEUM

gneisses two-thirds of a mile west of Long Lake bridge; a number
of small dikes cutting the anorthosite-gabbro west of Long lake;
and several small dikes cutting the large gabbro stock 1% miles
north-northeast of Indian Lake village.

Veins of pure white quartz a few inches wide sometimes occur
in the syenite, granite or mixed gneisses and apparently always
parallel to the foliation. On top of Owl’s Head mountain and also
two-thirds of a mile west of Long Lake bridge, sharply defined
pegmatite dikes a few inches wide were observed to cut such quartz
veins (see plate 10). Within the North Creek quadrangle the
writer has found diabase cutting pegmatite of the kind here
described. So far as the evidence goes, therefore, this type of
pegmatite is intermediate in age between the gabbro and the diabase.

Graphite in pegmatite. A feature of particular interest in con-
nection with the pegmatites is the content of graphite in two small
dikes cutting Grenville limestone respectively one-half and three-
fifths of a mile northwest and north of the bridge across Cedar
river. In addition to some large flakes of graphite, these dikes
contain numerous balls or globular masses of graphite from I to 5
mm in diameter. They look exactly like tarnished lead shot. They
occur either as inclusions in feldspar or along contacts between
feldspar and quartz. When broken open these graphite balls are
seen to possess a perfectly developed radiated structure.

Diabase Dikes

Only two small diabase dikes were located within the quadrangle.
It is quite possible, if not probable, that others exist but were not
encountered in the rough and heavily glaciated region, though no
boulders were anywhere found which would lead to the suspicion
of the presence of other dikes. So far as the positive evidence
goes for this and the adjoining Long Lake quadrangle, diabase
dikes are notably smaller and rarer in the central than in the eastern
and southeastern Adirondacks. The finer grained, to sometimes
even glassy, texture of the diabase proves it to be the youngest of
the Adirondack intrusives.

The larger dike cuts the anorthosite gabbro on the shore of Long
lake a little over a mile northeast of the bridge. The best exposures
are on the point already described as showing the most typical
anorthosite-gabbro. Here the dike is considerably branched but
shows a maximum width of 57 feet including two or three bands
or inclusions of the country rock. Sharp contacts against the

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 39

anorthosite-gabbro are visible across the whole rock ledge, the
country rock (in places) at the contacts plainly showing the effects
of the heat of intrusion. Toward the interior of the mass the
diabase exhibits an excellent diabase texture, white feldspar laths
up to one-quarter of an inch long standing out in a finer grained,
dark, bluish gray ground mass. A thin section from the interior of
the dike shows the following mineral percentages: labradorite 44;
augite (pale reddish brown) 18; biotite 8; chlorite 18; magnetite (or
ilmenite) 11; and pyrite 1. Due to more rapid chilling, the dike
borders are very fine grained to even glassy. About 100 yards
northeast at the lake edge, this dike again outcrops. It here also
shows branches, the greatest visible width being 27 feet. The dike
strikes south 40° west. |

The other dike also lies on the shore of Long lake and less than
one-half of a mile northeast of the bridge. Its main body is
exposed for 35 feet with strike south 40° west and a width up te
6 feet, though one wall only is shown. A very small tongue branches
off this portion. It is fairly evident that this dike formerly extended
at least 200 feet farther northward but has been eroded away along
the shore leaving the vertical wall of the country rock distinct.
What appears to be a separate dike here 6 inches to 1 foot wide and
30 to 40 feet long is quite certainly only a branch of the larger
one now eroded away toward the north. This branch dike is
distinctly brecciated due to faulting. In thin section the rock from
the 6 foot wide dike shows practically the same mineral composition
as the larger one farther northward already described.

The perfect alignment of the strikes of these two dikes suggests
the possibility that they are really portions of a single intrusive
which is largely concealed under the lake, but of course they may
be entirely separate. Also the fact that these dikes lie in or close to,
and parallel to, the zone of fracture (fault) which has determined
the position of the Long lake depression, would suggest that the
‘diabase was intruded along this fault zone but, if so, there was
renewed faulting in the same zone because one of the dikes is
brecciated.

ROCK STRUCTURES
Foliation
Except the diabase and certain pegmatites, all the Precambrian

rocks of the quadrangle-show more or less foliation. As a rule, the
gabbro masses are devoid of foliation except around the borders

4O NEW YORK STATE MUSEUM

where they are usually amphibolitic. The members of the syenite-
granite series are mostly distinctly gneissoid, though at times they
are only very faintly so. A striking feature is the frequent rapid
change within a few rods from rocks which are very clearly
gneissoid to others in which foliation is scarcely visible. The
Grenville strata, as usual in the Adirondacks, always show perfect
parallelism of stratification and foliation, these rocks invariably:
being thoroughly crystalline.

Of the many strike and dip observations made in the field, the
better ones, so distributed as to show the principal variations, have
been selected and plotted on the accompanying geologic map. Ina
general way nearly east-west strikes greatly prevail, with southerly
dips most common in the north and northerly dips most common
in the south. To be more exact, the northwestern half of the
quadrangle, or all lying north of a line passing from the northern
base of Blue ridge to the eastern base of Fishing Brook mountain,
shows very few exceptions to a nearly east-west strike and southerly
dip, the amount of the dip generally being from 60 to 80 degrees;
while the southern half of the quadrangle, or all south of the line
above indicated, exhibits more variations but with an average
nearly east-west strike and prevailing northerly dip generally from
25 to 50 degrees. |

A noteworthy feature’is the occasional local occurrence of strikes
making high angles with the general trend of the foliation cf the
quadrangle. An example of this in syenite is in the mountain mass
lying just east of Tirrell pond (see map). Such a sharp change
in strike is more in harmony with the idea that the foliation of
the syenite and granite was produced as a kind of flow structure
during the process of intrusion rather than by a great force of
compression because, if due wholly or even largely to compression,
the foliated structure must everywhere have developed essentially
at right angles to the direction of the compressive force.

Exceptional strikes are of most common occurrence in the Gren-
ville limestones and in the mixed gneisses, these being readily
explained by the fact that such rock masses were most subject to
being twisted and disturbed at the time of the great igneous
intrusions.

A most interesting arrangement of strikes and dips occurs along
the southern side of the quadrangle within a strip 2 or 3 miles wide.
Thus, within the eastern portion of this strip the strikes are mostly
northwest-southeast, with dips to the northeast ; toward the middle

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE Al

the strikes are nearly east-west, with northerly dips; and within the
western portion of the strip the strikes are northeast-southwest,
with dips to the northwest. The dips seem to radiate from a center
not far south of the middle of the southern boundary of the map or
apparently from the great Panther-Snowy mountain mass of the
Indian Lake sheet. A series of flattened elliptical curves drawn
from the center just mentioned would approximately parallel the
strikes as shown on the southern side of the Blue Mountain quad-
rangle. It would be interesting to know how the strikes and dips
run across the northern few miles of the Indian Lake quadrangle.
The significance of this symmetric arrangement of strikes and dips
is not precisely known, though the presence of the belt of Grenville
some distance out (along Cedar river) with strike practically
parallel to the curving strike of the igneous rock may imply some-
thing. This belt of Grenville on the east is known to continue from
the vicinity of Indian Lake village across the southeastern corner
of the Newcomb sheet and for at least several miles southward
on the Thirteenth Lake sheet. On the west this same Grenville belt
quite certainly continues southward for some miles through the
Cedar river valley in the northwestern part of the Indian Lake
sheet. Thus the great Panther-Snowy mountain mass of igneous
rock is known to be completely bounded on the west, north and
northeast by this belt of Grenville strata whose strikes and dips
show it to lap upon the flanks of the great igneous mass. ‘The
writer is inclined to believe that we have here a large scale radial
development of strikes and dips produced in the syenite as a kind of
flow structure when the magma was being intruded, and if we con-
sider the Grenville to have been more or less raised or domed over
the surface of the invading magma, this readily accounts for the
existing circumferential belt of Grenville whose dips show it to lap
upon the flanks of the syenite, the general cover of Grenville having
been removed from the dome by erosion. In other words, we here
appear to be dealing with something of the nature of a laccolithic
intrusion.
Folds

The general change from southerly dips in the northern portion
of the quadrangle to northerly dips in the southern portion may
possibly indicate a great synclinal fold in the foliation with axis
passing from the northern base of Blue Ridge through Dun Brook
mountain. This may, however, be interpreted simply as due to
differences in flowage of the great masses of intruding magma.

Cite OO

=—_— oe eee

+ + ee
nara. <a

—_——

42 NEW YORK STATE MUSEUM

Very local twisted or contorted structures within the Grenville
limestones and associated pyroxene and hornblende gneisses, and
also within portions of the mixed gneisses, are frequently met, but
practically nothing like distinct folds could be determined within
the Grenville formation, or rather such fragments of the formation
as now remam. There is no evidence that the Grenville strata were
ever thrown into folds as a result of any great compressive or
mountain-making force brought to bear upon the region, the present
strikes and dips probably, for most part at least, having been due to
tiltmg and upturning of the strata as a result of the great igneous
intrusions.

Faults

General considerations. In marked contrast with the eastern
and southeastern Adirondack regions, recognizable faults are few
in number and their topographic influence relatively mimor. Of
the five faults represented on the accompanying geologic map, four
strike northeast-southwest or parallel to the predominating fracture
lines of the Adirondacks. All five of the faults might more properly
be called zones of fracture or crushed zones which are nearly
straight for considerable distances. In no case was the whole dis-
placement found to follow a sharply defmed fault-surface, but
rather there are broken-rock zones from 25 or 30 to 100 or more
feet wide in which fault breccias, slickensided surfaces, and local
fault surfaces are frequently seen.

Referring to apparently similar phenomena on the Long Lake
sheet, Professor Cushing says: “Lines of excessive faulting are
not infrequent in the eruptives. In such places from two to four
joint sets are well marked, and the joints are closely spaced, their
distance apart being measured in inches rather than feet, chopping
up the rock into a multitude of small blocks, and forming prominent
lines of weakness in it. Often multiple faulting has taken place
along these strips on one of the joint sets. grinding and slicken-
siding the rock surfaces.”! The longest shattered-rock zone of this
kind mentioned by Cushing on the Long Lake sheet is in the
Raquette falls gorge which is nearly a mile long. Within the Blue
Mountain quadrangle, the writer has in several instances observed
crushed-rock zones frequently occurring along nearly straight lines
for from 2 to 8 miles, and with distinct topographic influence.
Such alignments of crushed-rock zones are regarded by the writer
as due primarily to faulting, probably multiple faultmg. Further-

iN. Y. State Mus. Bul. 115, p. 488. 1907.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 43

more, within the quadrangle, finely developed crushed zones have
been observed in the Grenville as well as in the eruptives.

Long Lake fault. This fault, with a length of 8% miles and
strike north 30° east, is the longest one within the quadrangle. It
has a decided topographic influence, the long, straight, narrow
valley now occupied by Long lake having been determined by the
crushed-rock zone of weakness. The topography suggests its con-
tinuation for at least a few miles into the Raquette Lake quadrangle,
and it almost certainly continues the length of Long lake and thence
probably along the channel of Calkins brook across a part of the
Long Lake sheet. The evidence for the continuation of the fault
beyond the limits of the Blue Mountain quadrangle is, however,
largely topographic, since but few field observations were made by
the writer there. |

Passing diagonally across the ledge at Buttermilk falls (plate 7)
there is a very distinct crushed-rock zone of considerably decom-
posed rock 2 or 3 feet wide and traceable for 50 yards with strike
north 30° east. Just on the east side of the falls there are two
smaller broken-rock zones parallel to the first. Other places where
broken-rock zones, with strike north 30° east, may be seen are on
the west shore of the lake three-fourths of a mile north of Grove
(Deerland) ; on the shore of the lake just south of the Adirondack
Hotel in Long Lake village; on the lake shore nearly one-half of a

mile northeast of the eastern end of the bridge across the lake (at

the brecciated diabase dike) ; and on the eastern shore of the lake
directly east of Triplet hill where a long ledge shows a broken-rock
zone 20 feet wide.

There is no satisfactory evidence for a determination of the up-
throw side or amount of displacement of this fault.. At present
one side of the fault is not notably raised above the other, thus
suggesting that any displacement along the fracture zone antedated
the development of many of the fault scarps and blocks of the
eastern and southeastern Adirondacks. The movements may have
taken place even as early as Precambrian time as suggested by
Cushing for similar phenomena on the Long Lake sheet.

Cedar river-Squaw brook fault. This fault, with north 30° east
strike, extends for over 6 miles across the southeastern corner of
the quadrangle, being coincident with the course of Cedar river
north of Indian Lake village and continuing southward along Squaw
brook of the Indian Lake sheet for fully 6 or 8 miles. Due north
of the village, Cedar river follows a remarkably. straight course,

AA NEW YORK STATE MUSEUM -

mostly in a narrow rock channel, for at least 2 miles, this being due
to the fact that the position of the channel there has been determined
along the crushed zone of weakness. Along this gorgelike channel
wide crushed-rock zones are beautifully developed at many places,
one fine example being in the Grenville white gneiss about 134 miles
due north of the village. The continuation of the fault across the
valley west of Indian Lake village is not actually demonstrable, the
outcrops being scarce with heavy drift covering the apparently
critical localities. Its extension along the Squaw brook valley of
the Indian Lake sheet is, however, certain as shown by the topog-
taphy and the presence of crushed-rock zones.

Somewhat higher altitudes immediately on the eastern side of
this line of fracture within the adjoining Indian Lake and New-
comb quadrangles, suggest that the upthrow side is on the east,
though the difference is not enough to make this at all certain. The
prominent scarp northwest of Indian Lake village is due to differ-
ence in rock character rather than faulting, the Grenville limestone
on the east side having been much more readily worn down than
the relatively hard gneisses on the west side. If any movements
took place along this line of fracture since the existence of the
Cretaceous peneplain, they must have been relatively slight. The
principal movements are certainly much older and they may pos-
sibly date back to Precambrian time.

Indian Lake fault. This long prominent fault, with northeast-
southwest strike, has but 2 miles of its course across the south-
eastern corner of the quadrangle. The granite porphyry near the
western end of the Indian Lake dam is full of shear zones and
much of the rock is broken up into a multitude of small blocks.
Just at the end of the dam there is a distinct slickensided fault
scarp 100 feet long and 15 feet high with some fault breccias. This
scarp dips 80° west. There is also a distinct crushed zone parallel
to this in the eastern of the two quarries just across the river. No
other exposures of the zone of fracture were seen within the
quadrangle, but it continues with very prominent topographic in-
fluence into both the adjoining Newcomb and Indian Lake sheets.
The remarkably straight channels of the Indian and Hudson.rivers
on the Newcomb sheet are almost certainly developed along a fault
which is but a continuation of the Indian Lake fault.

On the Indian Lake sheet this fault has a most decided topog-
raphic influence, the long, straight, Indian Lake depression having
been determined along the zone of weakness with the Snowy

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 45

mountain mass rising very steeply for more than 2000 feet above
the lake. The fault divides with one portion following the Miam1
river valley and the other the long, narrow southern extension of
Indian lake, the Mossy Vly brook valley, and thence along the
western side of Piseco lake on the Piseco Lake sheet, the southern
portion of this line of fracture having already been described by the
writer in his report on the Lake Pleasant quadrangle.

From these statements it will be seen that there is a prominent
line of fracture, with decided topographic influence, extending from
Piseco lake northeastward to near Lake. Harris on the Newcomb
sheet, or a distance of some 45 or 50 miles. This Indian Lake fault,
therefore, ranks as the longest continuous line of fracture yet
located in the Adirondack region. This fault is also the only one
touching the Blue Mountain quadrangle which gives quite certain
evidence regarding the relation of upthrow and downthrow sides.
The upthrow side is clearly on the west with the amount of dis-
placement ranging up to 1000 feet or more, as, for example, on the
Indian Lake sheet. On the Blue Mountain and Newcomb sheets
the amount of displacement is much less. In the vicinity of Indian
Lake village the fault has no conspicuous topographic influence
because the soft Grenville limestone has there readily been worn
down on both sides of the line of fracture.

The generally much greater altitudes on the west side, even in
homogeneous igneous rock, shows that important movements have
taken place along this fault since the development of the Cretaceous
peneplain. Hence this fault is in most respects very similar to
many of the prominent ones of the eastern and southeastern
Adirondacks.

Other faults. The fault along Cedar river east of Pine lake
strikes north 40° east and shows excellent crushed zones but it can
not be traced far. On Cedar river, one-half of a mile above the
mouth of Rock river, a beautifully developed crushed-rock zone 50
to 75 feet wide is exhibited in the bed and in one wall of the river
channel and it can be traced several hundred yards. Absence of
any notable topographic influence, except the local determination .of
the river channel here, suggests that the principal movements along
this fault must have antedated the Cretaceous peneplain.

Another line of fracture extends for 2 or 3 miles from the Cedar
river valley into the eastern end of the deep valley just south of
Blue ridge in the southeastern part of the quadrangle. Crushed-
rock zones are well developed with strike north 70° east along the

46 NEW YORK STATE MUSEUM

river and also at several places along the brook in the valley just
mentioned. Nothing is known regarding the upthrow side or
amount of displacement. It is possible that this fault may extend
farther westward through the valley south of Blue ridge.

It is quite possible that other minor zones of fracture occur
within the quadrangle but, if so, they are either effectually con-
cealed under heavy drift or escaped detection in the rough, densely
wooded country.

Irregular Surface of the Syenite-Granite Intrusive Body

Since the Blue Mountain quadrangle lies in the rugged moun-
tainous district west of that portion of the Adirondacks which is
profoundly affected by comparatively recent faulting and contains
considerable areas of Grenville strata through which the great in-
trusions of syenite-granite have taken place, an excellent oppor-
tunity is afforded to study the character of the surfaces of the
great bathylithic masses. )

A glance at the southern half of the accompanying geologic map
will reveal the fact that mountains of syenite or granite frequently
rise conspicuously above the masses of Grenville. Differences in
altitude, often quite abrupt, between syenite or granite and Gren-
ville commonly range from a few hundred to 2000 or more feet.
Such marked differences in altitude must be accounted for in
either of two ways: (1) by faulting, whereby the Grenville has
been relatively dropped down with respect to the igneous masses;
or (2) by irregularities on the surfaces of the igneous masses pro-
duced during the process of intrusion. That faulting can not be
invoked as an explanation in many cases at least is perfectly clear
by the fact that direct evidence for faulting is absent from many
places where outcrops are good at critical localities, and also by the
fact that certain mountain masses of syenite or granite are so
nearly surrounded by Grenville strata as to preclude the explanation
by faulting. A few concrete examples will serve to prove that the
bathylithic surfaces have very notable original irregularities.

Just east and northeast of Rock lake a mountain of granite rises
fully 600 feet above the Grenville which latter reaches continuously
almost two-thirds of the way around the mountain. Even if we
grant the possibility of a fault on one side (though there is not the
slightest field evidence for it), we are still forced to conclude that
the magma rose at least a few hundred feet above the Grenville now

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 47

nearly surrounding the mountain and across its strike. A very
similar example is furnished by the mountain south of Rock lake.

The great igneous mass making up Blue mountain rises 2000
feet above the Grenville immediately to its southwest and south.
Also the presence of glacial boulders of Grenville limestone and the
nature of the topography very strongly suggest that Grenville now
is, or formerly was, present in the Tirrell pond valley. No rock
exposures occur around the shores of the pond or along its outlet
for some distance southward. At any rate, it is clear that much of
the great difference in altitude between Blue mountain and the
adjacent Grenville must have been caused by the intrusion of the
magma through the Grenville.

Perhaps the finest example of marked irregularity of a bathy-
lithic surface is that of the great Panther-Snowy mountain mass
occupying the southern portion of the Blue Mountain quadrangle
and the northern portion of the Indian Lake quadrangle and already -
described in detail under “ foliation.” This large body of syenite,
as above explained, apparently rose under and raised up (domelike)
the Grenville strata which have all been removed by erosion except
the peripheral belt now remaining on the west, north, and north-
east. As a result of this intrusion and subsequent removal of Gren-
ville, the higher portions of the syenite mass now rise fully 2000
feet above the Grenville. |

A striking illustration of another type of irregularity of bathy-
lithic surface is furnished by the basin (partly on the Blue Moun-
tain and partly on the Newcomb sheet) which contains the Chain _
lakes (except the first and second lakes), Deer pond, Mud pond,
and Jackson pond. The bottom of this basin, which has a length of
4 miles and maximum width of 1% miles, is wholly occupied by
Grenville limestone and its associated hornblende gneiss at an
altitude of 1600 to 1700 feet. This valley is completely surrounded
by a body of syenite and granite which everywhere rises (usually
abruptly) from about 150 to over 800 feet above the valley floor
except in the vicinity of the outlet in the southwest. The distinct
basinlike character of the depression is clearly brought out on the
topographic maps. It is certain that, very largely at least, the
differences in altitude between the Grenville and surrounding
igneous rocks is due to original irregularities of the surface of the
igneous mass produced at the time of the intrusion.

One further point needs emphasis, namely, that the figures above
given as representing the amounts of irregularity of bathylithic sur-

43 NEW YORK STATE MUSEUM

faces are im all cases mmuma, because mo account has beem taken of

the fact of the depth of the extstmg Grenville below the surface.

In many places thts depth must amount to some hundreds of feet
at least

GLACIAL AND POSTGLACIAL GEOLOGY

Ice Movement. Depth, and Erosion

Fighteem sets of glacial stmae have beem observed and plotted
upon the accompanymg geologic map. Ther bearmgs and ds
tribution are as follows: ie.

ES 25° W. On the road three-fourths of 2 mile south of In-
dian Lake village.

2, 3 S 20° W. On roads respectively 2% mules south-southeast,
and 134 mules a Itttle east of south, of Indram Lake willage.

4, 5 5 30° W-. On the road respectively 3 miles, and 2)% miles,
southeast of Forest House.

6S 45° W. On the road 2 miles east-southeast of Forest House.

7, %S 40° W. Near the road at Forest House, and om the road
1% mules east-southeast of Forest House.

g@ S 30° W. On the road 1% miles north of Blue Mountam
Lake willage. Several sets of striae m this wicmty-

to S 40° W. On the road 15% miles southwest of Deerland

(Grove).
Tr S 45° W. On the road 1% mules southeast of Deerland
(Grove).

12 S 20° W. On the road ome-fourth of 2 mile northeast of
Deerlamd (Grove).

13 S 50° W. Near the Mount Sabatts trad one-half of 2 mile
south of Long Lake village and at am altitude of about 2000 feet.

“‘r4 S 4zo* W-. On the branch road to the Sagamore Hotel just
southwest of Lomg Lake village.

rs S 40° W-. Close to the eke shore 1% mules north-northeast
of Long Lake village

16 S 50° W-. On the road 1% omles west-northwest of Long
Lake village.

t7 S 50° W. On the road nearly 4 miles east of Long Lake
village.

18 S 40° W. Near the mountam top (at altitude 2550 feet) 2%
miles west of where the road to Newcomb crosses the county Ime

According to this list, it is seem that the extreme range m direc-
tions of the glacial striae is from south 20° west to south 50° west,

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 49

with an average direction of about south 30° to 40° west. All but
three of these sets of striae were found along roads, a reason for
this being that unweathered, glaciated rock surfaces are there fre-
quently stripped of drift artificially, thus exposing the glacial marks.

‘This is quite the rule in the Adirondack region.

No striae were noted in the southwestern portion of the quad-
rangle, nor on the great mountain mass between Mount Sabattis
and Dun Brook mountain. The eighteen observed striae are, how-
ever, so distributed over the quadrangle as to furnish positive evi-
dence that the general ice current was southwestward across this
portion of the Adirondacks. This accords essentially with, the
observations made by Cushing on the Long Lake quadrangle im-
mediately to the north, and by the writer on the Lake Pleasant quad-
rangle to the south.

Certain striae, as, for example, those of the Long Lake basin,
closely follow the trend of, and may have been influenced by, the
topography, though it is quite possible that such parallelism may be
largely a coincidence. Other striae are so situated as to demon-
strate independence of direction of ice flow and trend of the topog-
raphy. Examples of such are in the depression between the
mountains southeast of Forest House; on the south side (several!
hundred feet below the top) of the northwestern spur of Blue
mountain; and well up on the mountain (altitude 2550 feet) in the
northeastern part of the quadrangle.

That the great ice sheet was thick enough to overtop the highest
mountains of the region is practically demonstrated by the per-
sistence of the southwesterly ice current in spite of the topography.
Actual striae 2550 feet above sea level near the top of the mountain
in the northeast and distinctly glaciated ledges (without striae)
above 3000 feet on the side of Dun Brook mountain conclusively
prove ice currents at such altitudes. Well-worn pebbles and small
boulders of Potsdam sandstone derived from the St Lawrence valley
were occasionally observed on mountain tops at altitudes of from
2500 to 3500 feet. Again, the great surfaces of comparatively hard
and fresh rock on such mountains as Owl’s Head, Mount Sabattis,
Blue mountain, etc., were quite certainly stripped of rotten rock by
the ice and have since been only slightly modified by Postglacial
weathering.

The great ice sheet, in its passage across the region, was a suffi-
ciently active agent of erosion to remove most of the Preglacial
soils and rotten rock from their original positions. For this reason,

50 NEW YORK STATE MUSEUM

it is quite the rule to find ledges of relatively fresh rock, such ledges
frequently being in sharp contact with overlying loose glacial debris.
Deeply weathered to even rotten rock is, however, not of very rare
occurrence, and the writer believes that such decomposed rock is
appreciably more common in this central Adirondack region than,
for example, in the southeastern portion. This is quite in harmony
with the generally accepted belief that the central Adirondacks
were neither so long ice occupied nor subjected to such vigorous ice
currents as were the border portions oi the mountains.

Rock basins due to ice erosion are not known within the map
limits though certain valleys, like those of Long Lake and Blue
Mountain lake, may have been deepened by ice erosion, the available
data not being sufficient to make any certain decision.

Glacial Deposits

Erratics. Erratics (glacial boulders) are numerous and widely
scattered over the quadrangle. As usual they are mostly of very
local origin so that, in the absence of sufficient outcrops from cer-
tain areas, some idea of the underlying rock formations may be
gained by noting the relative numbers of glacial boulders.

Among the erratics which have been derived from ledges wholly
without the area under consideration are those of anorthosite and
oi Potsdam sandstone. Anorthosite boulders, with maximum
diameters of 8 or 10 feet, are not very common, they having been
most frequently noted in the northern portion of the quadrangle.
In view oi the fact that the extensive anorthosite body is exposed in
great force on the quadrangles immediately to the north and north-
east, with the nearest exposures only 5 to 7 miles distant, it is some-
what surprising that fragments of this formation are not more
common over the Blue Mountain quadrangle. The combination of
shorter time of ice occupancy and less vigorous ice currents over
the central Adirondacks than around its borders probably accounts
for the relative scarcity of anorthosite boulders within the Blue
Mountain quadrangle.

Pebbles and small boulders of Potsdam sandstone occasionally
noted, even on mountain tops at altitudes of from 2500 to 3000 feet,
are of special interest because of the long distance they have been
transported, the nearest known outcrops being some 50 to 55 miles
away in the St Lawrence and northern Champlain valleys. These
ertatics are always well worn and hard.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 51

Kames and eskers. Kames, generally in groups, were some-
times observed, but the dense vegetation and lack of proper ex-
posures have often prevented the definite recognition of this type of
glacial deposit. A group of low kamelike hills spreads across the
valley at the eastern end of Blue Mountain lake and forms the dam
which holds up the water of the lake. Most of the area between
South pond and Mud pond appears to be of kame or kame-morainic
origin. Along the road between Long Lake village and Deerland
(Grove) there are many good exposures of kame deposits, this
being a fine example of an extensively developed kame-moraine
along the eastern side of the valley. Along the northern border of
the quadrangle for several miles eastward from Long lake kames or
kame-moraines are well developed.

A very typical esker about a mile long, 20 to 30 feet high, with
winding course and just wide enough for the main road at its top,
lies in Thirty-four marsh from 1 to 2 miles east-southeast of Blue
Mountain Lake village. It consists of stratified sands and gravels.
This esker looks much like an artificial embankment built through
a portion of the swamp, very little grading having been necessary to
convert it into a highway. About one-half of a mile southeast of
the outlet of South pond, the main road follows another, though
smaller and less typical, esker. These long, low ridges of stratified
glacial materials were no doubt deposited in streams either at the
bottom of the ice or in channels within the ice during the waning
of the great ice sheet.

Moraines. Ground morainic material (till) 1s very widespread,
particularly over the lower lands. As usual in the Adirondacks,
it is very sandy or gravelly with numerous small to large embedded
boulders. Typical boulder clay was nowhere noted. Ground
morainic material is abundantly present in the vicinity of Indian
Lake village, and in the Cedar river valley from the village west-
ward for several miles. Good exposures may also be seen along
the new state road for 8 or g miles eastward from Long Lake
village, and along the road between 1 and 3 miles north of Blue
Mountain Lake village. Perhaps the most extensive morainic
deposits occupy much of the area from 1 to 5 miles east of Long
Lake village and thence northward to the border of the quadrangle.
Nothing like a distinct boulder moraine across the quadrangle or
any portion of it was recognized.

52 | NEW YORK STATE MUSEUM

Lakes and Their Deposits

Extinct lakes. In a general way it is important to note that
extinct glacial lakes of considerable size are less common in this
central Adirondack region than they are farther out toward the
borders. In part this may be due to the fact that the central
Adirondack region, which was first freed from the ice sheet, was
too small to permit of much gathering of water against either the
ice margin or morainic deposits across valleys. Also the relatively
less thick morainic deposits were probably not so effective in
forming dams across the valleys as they were when the ice had
retreated much farther toward the borders of the region.

A series of small glacial lakes of short duration, and of suc-
cessively lower levels, once occupied the bottom of the Cedar river
valley between 3 and 8 miles west of Indian Lake village. Thus,
between 7 and 8 miles west of the village the surface of a small
lake stood at an altitude corresponding approximately to the 1880
foot contour. The delta sands, chiefly brought in by the large
stream from the west, are well shown at several places along the
road. Between 5% and 7 miles west of the village another lake
stood at a level now corresponding to 1820 to 1840 feet with flat-
topped delta sands well exhibited along the road. At a still lower
level, from 3 to 4% miles west of Indian Lake village, there existed
another glacial lake with delta sands now lying at about 1760 feet.
These lakes were drained in succession either by retreat of the ice
front or cutting down morainic deposits either of which must
have formed dams across the valley.

Most of the swamp areas, particularly those of considerable size
which are nearly flat, were formerly occupied by shallow lakes held
up by drift dams, the lakes having been destroyed by filling. with
vegetable matter and sediment and cutting down of outlets.
Excellent examples are the swamp areas along Sixmile brook and
Fishing brook, just east of the south end of Tirrell pond; O’Neil
flow ; Thirty-four marsh; and just northeast of Indian Lake village.

Existing lakes. Existing lakes of the quadrangle illustrate all
stages from those which are only remnants of formerly much larger
bodies of water to those which are now nearly as large as they
ever were. Some examples of the former are Unknown pond, the
first of the Chain lakes, and the Grassy ponds; while examples of
the latter are Long lake and Blue Mountain lake.

As already stated, there is no positive evidence that any lake
occupies a true rock basin scoured out by the action of the great

GEOLOGY OF THE BIUE MOUNTAIN QUADRANGLE 53

ice sheet. The maximum depth of Blue Mountain lake is said to
be about go feet. If so, it appears that this basin has, very locally
at least, been ice eroded to a depth below any possible Preglacial
outlet. The comparatively soft Grenville rocks of this basin would
have been very susceptible to ice erosiom The basin of the third
of the Chain lakes, mostly in soft Grenville limestone, is said to
have a depth of 40 or 50 feet and it may thus also have been locally
somewhat deepened by ice erosion.

The present water levels of the existing lakes all appear to be
held up by glacial drift dams, usually across the outlets. Notable
exceptions to dams across the outlets are Blue Mountain lake with
drift dam across the eastern end, and Long lake with drift dam
blocking a. Preglacial channel on the east side of the present lake
either 114 miles south of the outlet of the lake or about 2 miles
northeast of Long Lake village. The first named locality is much
the more likely as will be pointed out below. South pond, judging
by the rock ledges across the outlet, appears to be held up by the
heavy morainic deposits just southwest of the pond.

None of the existing lakes appear ever to have been more than
Io or 15 feet higher than their present levels. Along the shores
of Long Lake there are occasional sand flats or delta deposits
representing a former lake level 8 or 10 feet higher than the present.
Perhaps the best of these sand flats is one-quarter of a mile long on
the south side of the cove 114 miles southwest of Long Lake village.
There is no evidence that Blue Mountain lake was ever more than
a few feet higher than now.

Drainage Changes Due to Glaciation

As would be expected, because the watershed between the Hudson
and St Lawrence basins passes across the quadrangle, there are
certain rather delicately balanced drainage conditions.

Blue Mountain-Eagle lake basins. Before the ice age the basins
now occupied by Blue Mountain and Eagle lakes quite certainly
drained eastward into the Hudson river by way of Rock river
instead of westward as at present through Raquette lake and thence
northward into the St Lawrence (see figure 1). Evidence in sup-
port of this view is twofold, namely, the rock barrier at the eastern
end of Utowana lake and the drift dam at the eastern end of Blue
Mountain lake. Rock ledges are practically continuous across the
narrow channel at the eastern end of Utowana lake, while the
channel connecting Eagle and Blue Mountain lakes is entirely in

54 NEW YORK STATE MUSEUM

drift deposits. Thus the movement of water must here have been
eastward in Preglacial time. Thirty-four marsh on Rock river
comes to within one-half of a mile of Blue Mountain lake and it
is about 20 feet lower than the lake surface, the intervening space
being occupied by loose sands and gravels. It would be a simple
matter, by shoveling out a trench nowhere over 20 feet deep, to
cause Blue Mountain and Eagle lakes to drain eastward. Years
ago such an attempt was actually made but stopped by law. The

PRESLACIAL STREAMS

@ PREGLACIAL Divides

Bivet
MousTAIn

Fig. 1. Sketch map of a portion of the central Adirondack region showing the
relations oi the principal Preglacial stream courses to those of the present. Preglacial
streams show only where essentially different from those of today. The rectangulag
area shows the position of the Blue Mountain quadrangle.

Preglacial drainage eastward through the lake basins was more in
harmony with the course of the upper waters of Rock river which
has its sources in and around Wilson pond about 3 miles southwest
of Blue Mountain lake village.

Utowana-Raquette lake basins. That the Preglacial drainage
through the Utowana lake basin passed westward into the basin

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 5

now occupied by Raquette lake is certain, there being only a drift
dam at the western end of Utowana lake. From the Raquette lake
basin the Preglacial drainage was either northeastward by way of
Raquette river as now, or southwestward by way of the valley now
occupied by the Fulton Chain lakes. Although this problem has
not been carefully studied in the field, the presumption favors the
southwesterly course. Thus, the interval of a mile between Brown's
Tract inlet and Eighth lake is wholly occupied by drift deposits,
while the valley occupied by the upper lakes of the Fulton Chain
has its bottom covered with drift which, because of irregular thick-
ness, at times acts as dams to pond the waters of the upper lakes.
A maximum thickness of less than 100 feet of drift just north of
Eighth lake is all that is necessary to account for the blockade of
the southwesterly Preglacial channel with resultant ponding of the
waters to form Raquette lake. Further evidence for this view lies
in the fact that between Forked lake and Long lake, Raquette river
descends more than 100 feet in about 3 miles mostly by a series
of cascades over rock ledges which extend across the narrow
channel. Apparently a Preglacial col was situated not far below the
outlet of Forked lake, the drift accumulation southwest of Raquette
lake being sufficient to pond the waters of the Raquette and Forked
lake basins to overflow this col (see figure 1).

Long lake basin. Granting the source of a Preglacial stream
on a col (near the outlet of Forked lake) a few miles above the
upper end of Long lake, did this stream follow the present course
of Raquette river into the St Lawrence? That the depression now
occupied by Long lake was a Preglacial stream channel is certain,
and also there is strong evidence that the drainage from this channel
passed eastward into the Hudson river rather than northward by
way of Raquette river. Regarding Raquette falls, on the river a
few miles below the outlet of Long lake, Cushing says: “There
is a fall of 70 to 80 feet in a gorge three-quarters of a mile long,
in which the water is rapid throughout, but with two principal falls.
There is an impassable rock barrier here, with no opportunity for a
buried channel, so that there could have been no Preglacial drainage
line; rather, there was here a col between small streams flowing
both ways from the obstruction.” 1! Thus, in Preglacial time, two
streams drained into the depression now occupied by Long lake, one
north-flowing from the col near the outlet of Forked lake (Raquette
lake quadrangle), and the other south-flowing from the col at

1N. Y. State Mus. Bul. 95, p. 444. 1905.

56 "NEW YORK STATE MUSEUM

Raquette falls (Long lake quadrangle). These streams met to flow
eastward into the Hudson river, as Cushing has suggested, either
through the Sixmile-Fishmg brook valley in the northeastern part
of the Blue Mountain quadrangle, or through the Catlin lake-Round
pond valley in the southeastern part of the Long lake quadrangle.
In the writer's opinion, the best evidence favors the Catlin lake-
Round pond channel (see figure 1). The surface of Catlin lake
is over 30 feet below that of Long lake and the two lakes are
now separated by a divide of loose glacial debris only about 20 feet
high. Years ago an attempt was made to cut a trench throtigh this
divide in order to drain Long lake through Catlin lake and thence
mto the Hudson river.

Sixmile-Fishing brook valley. The Sixmile-Fishing brook valley
is heavily drift-filled, especially on the west where, m the vicinity —
of Polliwog pond, the drift at the bottom of the valley is nearly 1oo
feet above the level of Long lake. From its sources on Fishing
Brook mountain, Fishing brook pursues a northwesterly course for
several miles after which it swings sharply eastward to even south-
eastward to near its mouth, thus showing a striking tendency to
double back on its course. Sixmile brook also shows a sharp east-
ward swing. The more normal Preglacial courses of these streams
would appear to have been westward into the Long lake valley.
Evidently the eastward deflection of these streams was caused by
glacial drift accumulations, especially in the vicinity of Polhiwog
pond, and the narrow gorge of Fishing brook cut in solid rock near
the map edge is of Postglacial origin.

Cedar river. Near Indian Lake village a very low divide of loose
glacial debris separates Cedar river and Indian river which are
here only about 2 miles apart, the latter river being about 7o feet
lower than the former. North of the village one-half of a mule,
the crest of the divide is less than 20 feet above the level of Cedar
river which is only two-thirds of a mile distant. West of Indian
Lake village Cedar river pursues a meandering course with low
gradient, while from 2 to 3 miles north of the village the river is
very swift and usually confined to a deep, narrow, gorgelike
channel in solid rock with no possibility of a buried channel on
either side. Thus the evidence is clear that there was a Preglacial
col between 2 and 3 miles north of Indian Lake village, and that
the Preglacial Cedar river, which emptied into Indian river east or
southeast of the village, was deflected over the col by the accumula-
tion of drift north of the village.

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 57

~ ORIGIN OF RELIEF FEATURES

Influence of Rock Character

In common with the Precambrian rock area of northern New
York in general, differences of rock character have been very
influential in the production of the existing relief features of the
quadrangle. Most important is the relatively weak Grenville forma-
tion which almost invariably occupies valleys or lowlands. As a
result of the long Preglacial time of weathering and erosion, the
Grenville strata were much more readily worn down than the very
hard and resistant syenites and granites. Fine illustrations of this.
principle are the two prominent belts of Grenville represented on
the southern half of the accompanying geologic map. One of these
belts extends for 11 miles from the vicinity of Indian Lake village
westward through the Cedar river valley, and the other from the
vicinity of Pine lake westward nearly across the quadrangle to
Blue Mountain lake, these two belts being connected through the
valley south of Rock lake. There are smaller areas of Grenville
from Unknown pond northeastward, and in the vicinity of the third
of the Chain lakes. These Grenville areas include most of the
lowest land of the southern half of the quadrangle, the prevailing
rocks of the lowlands being Grenville limestone with more or less
closely associated hornblende and pyroxene gneisses.

About 1%4 miles northwest of Indian Lake village the Grenville is
much more resistant than usual, being a white feldspar-quartz gneiss
which stands out 300 to 500 feet above the valley bottom. It is a
very unusual example of this kind. The deep valley immediately
south of Blue ridge has probably been developed by removal of a
belt of Grenville. If so, the removal of the Grenville has been
almost, if not quite, complete since no outcrop of such rock was
anywhere found. The small fault at the eastern end of the valley
may have been a factor in determining the location of the valley,
but its influence was probably not sufficient to account for so large
a valley. A similar explanation probably applies to the long, narrow
depression between Blue mountain and the sharp ridge immediately
to the south of it, and also to the deep depression now in part
occupied by Tirrell pond.

The mixed gneisses, because of their considerable content of rela-
tively weak Grenville, also tend to occupy the lower lands. Within
such areas, the bolder relief features are due to the local presence
of the more homogeneous and resistant igneous masses, the weaker

oe)

NEW YORK STATE MUSEUM

Lom

Grenville strata generally having been removed or at least much
worn down parallel to the foliation. Two large areas — one across
the northern side of the quadrangle, and the other south of Blue
Mountain and Eagle lakes—afford fine illustrations of such
phenomena. In those mixed gneiss masses where the Grenville is
unusually resistant and intimately involved with the granite or
syenite, the rocks may stand out in rather bold relief as, for instance,
south and southwest of Unknown pond, and west of the south
end of Long lake.

It is important to note that the main axis of elevation of the
Adirondack region which extends across the Blue Mountain quad-
rangle is cut through by two of the few lowest passes with maxi-
mum altitudes of about 1800 feet. One of these is the Grenville
valley across the quadrangle from Pine lake westward to Blue
Mountain lake, and the other is the broad lowland belt of mixed
gneisses across the northern side of the quadrangle.

The highest mountain masses always consist of facies of the
great syenite-granite intrusive body with rarely more than slight
amounts of admixed Grenville. Such rocks are exceedingly resist-
ant to weathering and erosion, and it would require a very long
time (a few million years perhaps) to cut down these mountains
to the general level of the valleys now occupied by the Grenville
strata.

The gabbro appears to be about as resistant as the syenite or
granite, but its small masses do not permit any notable topographic
influence. Where completely surrounded by weak Grenville, the
gabbro usually stands out distinctly as small knobs like those either
side of Sprague pond. The rather prominent gabbro knob between
3 and 4 miles east of Long Lake village shows outcrops of inclosing
rock on one side only, and it is possible that more or less Grenville
or mixed gneiss has been removed from around it.

Influence of Rock Structures

Where relatively weak Grenville strata dip downward against
large masses of homogeneous syenite or granite, high and very steep
slopes, simulating fault scarps, are usually developed as a result
of weathering and erosion. Cases in point are the steep escarpment
on the western face of the mountain from 1 to 2 miles south of
Rock lake, and the steep eastern front of Waterbarrel mountain,
each rising fully 700 feet. There is some reason to believe, as
already suggested, that a mass of Grenville has been removed from

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 59

the depression now in part occupied by Tirrell pond. If so, the
very steep mountainside just east of the pond (see plate 11) may
be accounted for in a similar manner.

Where weak Grenville beds overlie the granite or syenite, and
both show moderate dips in the same direction, the effect has been
to produce longer and more gentle slopes due to removal of the
Grenville. Ina general way, the whole southern side of the Cedar
river valley from Indian Lake village westward illustrates this
principle. |

If granite or syenite and overlying Grenville both show steep
dips in the same direction, removal of the Grenville may leave a
steep slope, as seems to be the case on the mountainside just north-
west of Blue Mountain lake.

The Blue Mountain region, unlike the eastern and southeastern
Adirondacks, shows no prevalent tendency of mountain ridges to
trend northeast-southwest because of faulting. Faulting has, how-
ever, been a prime factor in the production of a few important
topographic features of the quadrangle, the known faults having
_ been described above. We need only to repeat here that the straight,
narrow depression the full length of Long lake; the straight, deep
channel of Cedar river north of Indian Lake village; and the great
depression which contains Indian lake all have been developed
along fault zones of weakness. Very little of the topographic
effect of the last named fault, however, shows within the Blue
Mountain quadrangle.

Influence of Exfoliation

Exfoliation has produced some interesting, though comparatively
minor, topographic effects. The steep eastern face of Water-
barrel mountain is almost impossible of ascent because its upper
400 feet is completely covered with smooth, mostly barren exfolia-
tion slabs from 50 to 100 feet across and several feet thick. Asa
result of the sliding of such great rock slabs down the scarp, and
their breaking up into large angular blocks, an extensive talus
deposit has been built up toward the base of the mountain. Because
of gradual removal of weak Grenville strata which dip under the
granite of this mountain, the face of the mountain has, for a long
time, been retreating westward by splitting off of exfoliation slabs.

Other fine exhibitions of exfoliation on large scales are on the
steep mountainsides northeast of Tirrell pond, east of Salmon

60 NEW YORK STATE MUSEUM

pond, and west of Salmon pond. In many other places more or less
exfoliation was observed, but the ones above mentioned are the
most interesting.

Influence of Glaciation

The glaciation of the quadrangle having already been described,
it is now necessary to refer briefly to only a few effects of the
ice sheet which have modified the relief.

Ice erosion appears to have modified the relief to a very minor
extent only. The soil and rotten rock were largely scraped off down
to the fresh rock particularly on the higher lands. Mountain masses
may have been somewhat rounded off. As already pointed out,
the basins of Long lake, Blue Mountain lake, and the third of the
Chain lakes may have been locally slightly deepened by ice erosion.

The principal topographic effect of glaciation has been the almost
universal tendency to accumulate the scraped off soil and rotten
rock in the valleys. Accordingly the relief is lower now than at the
time immediately preceding the ice age. Most of the valleys contain
large accumulations of glacial debris, stratified and unstratified, with
thickness up to several hundred feet. Most of the streams have
only here and there cut through these deposits to the underlying
rock.

The Cretaceous Peneplain

It is well known that toward the close of the Cretaceous period,
a more or less well-developed peneplain existed over the northern
Appalachian district, central and southern New York, the western
side of the Adirondacks, and southern New England. As a result
of the uplift and dissection of this great peneplain, the chief relief
features of the northern Atlantic coast have been produced. Any
very satisfactory evidence for a well-developed Cretaceous pene-
plain over the central and eastern Adirondacks has so far not been
obtained, and the topography of the Blue Mountain quadrangle does
not throw much light upon the problem. The most probable
explanation is that the great masses of very resistant igneous rocks
in the Adirondack region favored the existence of rather numerous
and prominent monadnocks which rose above only a crudely devel-
oped peneplain surface. Hence it is difficult, if not impossible, to
locate remnants of the peneplain surface with any certainty.

Within the Blue Mountain quadrangle, many mountain summits
lie at altitudes of from 3000 to 3500 feet, with many others only a
little higher or lower. This is well shown in the large mountain

‘UOlJEITOFXI O} ONP YIoI1 JO
Sqe[s asi1e] yo Yo suds 94} JO Joyo sy} SMOYS apisure}UNOU ay} JO UOT}I0d Uds1eq sy], ‘puod JJ9441. SsO1oe preMysoM MII
“RON ‘O98 ureyunoyw oaniq ‘ssoljoy “A a Aq 004g

Il eg

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 61

group lying between Chain lakes and Long lake. Adjoining quad-
rangles show the common occurrence of similar altitudes. It would
seem, therefore, that, if at all recognizable, remnants of the old
peneplain surface now lie somewhere between 3000 and 3500 feet,
altitudes higher than this representing what were the more promin-
ent monadnocks. The concordance of altitudes is not very satis-
factory, and so it must be admitted that the proof is by no means
conclusive. At any rate, it is quite certain that the principal valleys
and depressions of the quadrangle have been carved out of what
Was an upraised and at least crudely developed Cretaceous peneplain.

OUTLINE OF GEOLOGIC HISTORY

Those interested in the natural history of the Adirondack region,
but not familiar with geologic lore, might do well first to consult
the writer's New York State Museum Bulletin 168 entitled “ The
Geological History of New York State.” .This work has been
prepared primarily for laymen. The only treatise on Adirondack
geology in general is Cushing’s excellent Museum Bulletin 95.7 In
the very brief summary immediately following, the attempt is to
present only the most salient events now known to be recorded
within the Blue Mountain quadrangle with some reference to the
relation of these events to the geologic history of the Adirondacks
in general. |

Precambrian History

The oldest known geologic records in the Blue Mountain quad-
rangle are contained in the rocks of the Grenville series which,
in the light of present knowledge, are to be grouped with the oldest
known rocks of the earth’s crust. Since these rocks are distinctly
stratified, very thick (many thousands of feet), and of wide areal
extent not only throughout the Adirondacks but also in eastern
Canada, we may be sure that the earliest known condition of the
area of the quadrangle was the presence of a sea in which the
Grenville strata were being deposited layer upon layer. As yet
nothing is known either regarding the floor of this very ancient sea
or of the land masses from which the sediments were derived. Dur-
ing part of Grenville time the sea water was very clear as shown
by the comparative purity of the great masses of limestone. That
the Grenville ocean persisted for some millions of years is proved

1 Since the above was written the author has prepared a small treatise for
laymen entitled ‘The Adirondack Mountains.” This contains an account of
the geography and geology of the region in simple language. It is now being
published by the New York State Museum.

62 NEW YORK STATE MUSEUM

by the great thickness of the sediments. A most conservative esti-
mate by geologists gives the age of the Grenville strata as no less
than 25 or 30 million years, though of course we have no means of
accurately determining geologic time in terms of years.

After the deposition of the Grenville strata came vast intrusions
of igneous rocks, including first the eruption of a great body of
anorthosite mostly in Essex county and including the two small
masses in the Blue Mountain quadrangle, and ther the still greater
bodies of syenite and granite, examples oi which are so well
shown in the quadrangle. Also the whole Adirondack region was
raised well above sea level probably at or near the time of the erup-
_tion of the syenite-granite series. The tilting and metamorphism
of the Grenville strata were most lkely largely concomitant with
the great igneous intrusions.

The great Precambrian land mass underwent profound erosion
for some millions of years at least, extending through later Pre-
cambrian time and even into the early Paleozoic, as shown by the
facts that the oldest rocks deposited upon the Precambrian are of
late Cambrian age, and that the Precambrian rocks immediately
below the Cambrian exhibit textures and structures which could
have developed no less than some thousands of feet below the
earth’s surface. |

Following the great intrusions and during the time of erosion
above referred to came the minor intrusions of gabbro and diabase.
The gabbro is definitely known to be much older than the diabase,
the fine-grained texture oi the former proving it to have cooled
comparatively near the surface of the earth either in late Pre-
cambrian or very early Paleozoic time.

Paleozoic History

By late Cambrian time the profound erosion above mentioned had
worn down the whole Adirondack region to the condition of a more
or less well-developed peneplain. This we know because late Cam-
brian strata (particularly the Potsdam sandstone), which are the
oldest to have been deposited upon the Precambrian, everywhere
rest upon a peneplain surface of the Precambrian.

There is no evidence that Paleozoic strata were ever deposited
over the area of the quadrangle, though late Cambrian or Ordovician
strata now almost completely surround the whole Adirondack region.
These Paleozoic rocks formerly mantled all but the central Adiron-
dacks. A number of erosion remnants of the Paleozoic rock cover

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 63

still exist in the southeastern Adirondack region, the nearest to
the Blue Mountain quadrangle being a small area of Potsdam sand-
stone near the village of North River about 16 miles a little south
of east of Indian Lake village.

The best available evidence shows that the ancient peneplain
became sufficiently submerged during late Cambrian time to allow
the sea to cover all but a considerable part of the central Adiron-
dack region, and that the maximum submergence occurred during
mid-Ordovician (Trenton) time when only a comparatively small
portion of the central Adirondack area (including the Blue Moun-
tain quadrangle) remained as a small low island. During this
Trenton time the sea may have extended over some of the south-
eastern portion of the Blue Mountain quadrangle, though of course
any positive evidence is entirely lacking.1

At some time (or times) during the middle or late Paleozoic era
the whole Adirondack region, then largely mantled with Paleozoic
sediments, was raised well above sea level. Some of the upward
movement may have taken place at the time of the Taconic revolu-
tion (close of the Ordovician), though it is generally considered
that the major uplift occurred at the time of the Appalachian revo-
lution (toward the close of the Paleozoic). In northern New York
this upward movement was not accompanied by folding, but there
was a general tilting of the strata downward toward the south or
southwest.

Mesozoic History

The erosion cycle inaugurated by the Paleozoic elevation of
northern New York continued for a vast length of time or till the
close of the Cretaceous period when the Paleozoic strata were
largely removed from the Adirondack area and another eroded
surface approaching the condition of a peneplain was produced.
Apparently this peneplain was least perfectly developed in the cen-
tral and east-central Adirondacks where various hard rock masses
(monadnocks) stood out more or less prominently above the general
peneplain surface. This peneplain was upraised about the close of
the Cretaceous period so that remnants of it in northern New York
now lie at altitudes of from 2000 to 3000 feet or possibly more.
Within the quadrangle no very accurate idea of this peneplain or

1 Certain oscillations of level between land and sea, which are clearly
recorded in the rocks around the Adirondacks, may also have affected the
central Adirondack area, but the utter absence of all Paleozoic strata from
the central area renders any determination of this kind difficult if not
impossible.

64 NEW YORK STATE MUSEUM

its remnants can be gained because it was only imperfectly devel-
oped there.

It is quite certain that much of the faulting, including the Indian
lake fault, which has so largely influenced the major topographic
features of the southeastern half of the Adirondacks took place
after the development of the Cretaceous peneplain and probably
at the time of its uplift. Other zones of fracture, however, like
the Long Lake fault, whose displacements show little if any in the
existing topography, are probably much older, and they may im part
at least be of even Precambrian age.

Cenozoic History

The existing relief features of the Blue Mountain quadrangle
have been produced chiefly by the dissection of the upraised. Cre-
taceous peneplain. As a result of the uplift the streams were
greatly revived as erosive agents and they proceeded to carve out
channels and valleys principally along the comparatively weak
Grenville belts and the fault zones of weakness.

Late in the Cenozoic era the area of the quadrangle, in common
with most of the State, was deeply buried under the great ice
sheet of the glacial epoch. Many local details of topography, especi-
ally in the valleys, are due to accumulation of glacial deposits.

ECONOMIC PRODUCTS

As compared with many portions of New York State, the Blue
Mountain quadrangle is notably deficient in geologic deposits of
value under present-day commercial conditions. The lack of cheap
transportation facilities prevents the working of certain deposits
which might otherwise have some value. Building stones, so-
called “road metal,” sands and gravels for local use are the only
materials now taken out. No ore deposit of any kind which may
ever be successfully mined was observed by the writer. All the
stone quarries and prospect holes of the quadrangle are indicated on
the accompanying geologic map.

Building Stones
Fresh rock from any of the facies of the large masses of syenite
or granite would yield building stones of great strength, resistance
to weather and adaptability to high polish, but no large quarry exists
in the region. Some typical greenish gray, quartzose syenite has
been taken out for local use from the quarry one-half of a mile

GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 65

northeast of Long Lake village. From two or three small quarries
close together 1 mile northeast of Grove (Deerland) some pink
granite has been taken out. Near the dam across the end of Indian
lake two considerable openings have been made in the granite
porphyry to furnish stone for the masonry of the dam.

Road Metal

The building of state roads between Grove (Deerland), Long
Lake, and Newcomb has caused the recent opening of several large
road metal quarries within the quadrangle. One of these is in
typical, greenish gray, quartzose syenite on the road 1% miles south-
west of Long Lake village. This rock makes a good grade of road
metal.

Another quarry in pink granite, and a third in greenish gray
granite are situated along the road about 2% and 7 miles, re-
spectively, east of Long Lake village. On account of their content
of mica, these granites are not quite so satisfactory for road work
as the normal and basic facies of syenite or gabbro. The large
body of gabbro, crossed by the road between 4 and 5 miles east of
Long Lake village, was not used for state road work but it would
have been excellent for the purpose on account of its richness in
iron-bearing minerals.

In some cases the coarse, crystalline Grenville limestone, where
sufficiently weathered to crumble easily, is used to repair roads.
Such limestone is taken from the pit indicated on the map one-third
of a mile northwest of where the road crosses Cedar river.

Sand and Gravel

Sand and gravel of good quality are present in abundance, especi-
ally in the valleys where the sorting power of Glacial and Post-
glacial streams has been most effective. Such materials are taken
from many localities for road and concrete work and for making
mortar.

Garnet Deposits

The development of the garnet industry in northwestern Warren
county has led to considerable exploration for similar workable de-
posits for some miles around Indian Lake village. At two places,
indicated on the map, respectively 114 miles southeast and 21%
miles south-southeast of Forest House, several small prospect holes
have been opened in the hornblende gneiss which is so commonly
associated with Grenville limestone. At the first-named locality the

66 NEW YORK STATE MUSEUM

garnets are of the red almandite variety up to 5 inches in diameter
and without hornblende rims, while at the second-named locality
similar garnets up to 6 or 7 inches in diameter are enveloped in
black hornblende, these latter, therefore, presenting an appearance
very similar to those long known from the mine on Gore mountain
in Warren county near North Creek. It is this Grenville, horn-
blende gneiss which is most likely to yield large garnets, but lack of
transportation facilities and the general condition of the garnet
market have thus far prevented any real mining within the quad-
rangle. A number of years ago some garnet was shipped from an
excellent deposit, similar to those above described, about 2%4 miles
northeast of Indian Lake village (one-half of a mile east of Bull-
head pond) on the adjoining Newcomb sheet. Garnets are crushed
and used for abrasive purposes.

Feldspar

For some years those engaged in pottery and chinaware industries
have been seeking suitable deposits of feldspar. While feldspar is
the most common mineral within the quadrangle, it is not commer-
cially valuable unless occurring as the white potash (orthoclase)
variety in large masses, usually in pegmatite dikes or veins. There
are many pegmatite dikes ranging from a few inches to a hundred
feet wide within the quadrangle, but none promising to be of com-
mercial value could be located. Some of the largest observed de-
posits are located as follows: 1 mile a little east of north of Indian
Lake village where there is a dike or vein about 15 feet wide and 40
or 50 feet long; just southeast of the small gabbro stock on the
largest island in Blue Mountain lake and in contact with the gabbro
on the west, this dike being fully too feet wide and 200 yards long;
and a dike 10 or 15 feet wide cutting Grenville hornblende gneiss on
Cedar river 3% miles west of Indian Lake village.

INDEX

Adams, cited, 29

Adirondack mountains, new publica-
tion on, 61

Anorthosite, 9, 50, 62

Anorthosite-gabbro, 18-21

Barlow, cited, 29

Blue mountain, 8, 47, 40, 57

Blue Mountain—Eagle lake basins, 53

Blue Mountain lake, 7, 9, 12, 14, 15,
17, 36, 37, 50, 52, 54, 57, 58, 59, 50,
66; area south of, 32; depth of, 53

Blue Mountain Lake village, 14, 17,
Sar 5

Blue ridge, 8, 40, 41, 45, 57

Brown’s Tract inlet, 55

Buck mountain, 8, 13

Building stones, 64

Burnt mountain, 8

Buttermilk falls, 43

Calkins brook, 43

Catlin lake, 56

Catlin lake-Round pond valley, 56

Ceast biver, 7, 0; 12, 14, 17, -1S, 37,
41, 43, 45, 56, 65, 66

Cedar river—Squaw brook fault, 43

Cedar river valley, 12, 51, 52, 57, 59

Cenozoic ,history, 64

Chain lakes,.q, 12, .47;/52,.53, 57, 60, 61

Clear pond, 29

Cretaceous peneplain, 60

Crystal lake, 33

Crystalline limestone, 13

Cushing, HP) cited, 10; 18, 19722,
29, 30, 33, 42, 43, 49, 55, 61

Deer pond, 12, 47

Deerland (Grove), 33, 43, 51, 65

Diabase, 9

Diabase dikes, 38

Drainage changes due to glaciation,
53

Dun Brook mountain, 8, 41, 49

Eagle lake, 8, 53, 58
Economic products, 64-66
Eighth lake, 55

Emmons, E., cited, 10
Erratics, 50

Eskers, 51

Exfoliation, influence of, 59

Faults, 42-46, 64

Feldspar, 66

Feldspar-graphite gneiss, 18

Feldspar-quartz-biotite-garnet
gneisses, 17

Feldspar-quartz gneisses, 17

Fishing brook, 13, 34, 52

Fishing Brook mountain, 8, 40

Folds, 41-42

Foliation, 39-41

Forest House, 14, 49, 65

Forked lake, 55

Fulton Chain lakes, 55

Gabbro, 9, 65

Gabbro stocks and dikes, 35-37

Garnet deposits, 65

Geologic history, outline of, .61

Glacial and postglacial geology, 9,
48-56

Glacial deposits, 50-51

Glaciation, influence of, 60

Gneiss, see Grenville rocks

Gneisses, mixed, 31-35, 57

Gore mountain, 14, 66

Granite, 9, 27-30, 46, 64, 65; thin
sections of, table, 28

Granite porphyry, 30, 65

Granitic syenite, 26

Graphite in pegmatite, 38

Grassy pond, 13, 52

Gravel, 65

Grenville hornblende gneiss, 35

Grenville rocks, 9, 10, 29, 31, 46, 57,
59, 61, 65; description of, 13; thin
sections, table, 16

Grove (Deerland), 33, 43, 51, 65

» [67]

68 NEW YORK STATE MUSEUM

Hornblende-feldspar gneiss, 15
Hornblende-garnet gneisses, 14

Indian lake, 7, 65

Indian lake fault, 44, 64

Indian ‘Lake villawe; 2,4. 5) 17, on,
37538) AL 44, 2 5 52 n50s 1575 050,700

Indian river, 9, 56

Jackson pond, 12, 47

Kames, 51
Kemp; Ji cited, 10,740

Lake Harris, 45

Lakes and their deposits, 52

Laurentian granite, 18

Long lake, 7, 9, 13, 34, 38, 50, 52, 53,
55, 56, 58, 59, 60, 61

Long lake basin, 55

Long lake bridge, 37, 38

Long lake fault, 43, 64

Long lake gneiss, 33

Long Lake village, 15, 17, 18, 26, 27,
29, 30, 36, 43, 51, 53, 65

Mesozoic history, 63
Miami river valley, 45
Miller, W. J., cited, 10
Minnow pond, 13
Moraines, 51

Mossy Vly brook valley, 45
Mount Sabattis, 8, 49
Mud pond, 12, 47, 51

Newcomb, 13

Newland, D. H., cited, 10

Normal quartz syenite, 22; thin sec-
tions of, table, 24

North River, 63

Owl’s Head mountain, 26, 37, 38, 40

Paleozoic history, 62

Panther mountain, 8, 47
Pegmatite, 9, 37

Pine take, 9, 12, 17, 18, 4s) 57, /58
Piseco lake, 45

Porphyry, 30

Potsdam sandstone, 49, 50, 63
Precambrian history, 61
Pyroxene gneisses, 15

Quartzites, 15

Raquette falls, 55

Raquette falls gorge, 42
Raquette lake, 9, 53, 55
Raquette river, 9, 55

Relief features, origin of, 57-64
Road metal, 65

Rock character, influence of, 57
Rock lake, 9, 12, 32, 46, 47, 57, 58

Rock river, 9, 12, 34, 45, 53, 54
Rock structures, 39; influence of, 58

Salmon pond, 60

Sand, 65

Sillimanite gneisses, 18

Sixmile brook, 52

Sixmile-Fishing brook valley, 56

Smyth, cited, 29

Snowy mountain mass, 45, 47

South pond, 51, 53

Sprague pond, 13, 35

Squaw brook, 43

Stephens pond, 13

Syenite, 9, 21-23, 47, 64, 65; basic
facies of, 25; granitic, thin sections
of, table, 28; normal quartz, thin
section of, table, 24

Syenite-granite intrusive body, ir-
regular surface, 46

Thirty-four marsh, 12, 52, 54
Tirrell pond, 40, 52, 57, 59
Tirrell pond valley, 47
Tremolite gneiss, 18

Triplet hill, 26, 43

Unknown pond, 12, 18, 32, 52, 57, 58
Utowana lake, 9, 53
Utowana-Raquette lake basins, 54

Waterbarrel mountain, 15, 17, 18, 27,

37, 58
Wilson pond, 54

a
eta aL
yA ae Y a =< i)
rae % rh es i

7 Pa

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atti
’

JOHN M, CLARKE
STATE GEOLOGIST

=
s
SH
8
Ne
3
SE

H.M.Wilson, Geographe

Sure n 1B88-1800.

“sunveveo COOPERATION WITH THE STATE OF NEWYORK.
se

‘Tria lation by W.J.Peters and
To. M,

UNIVERSITY OF THE STATE OF NEW YORK

STATE MUSEUM

BULLETIN 192
BLUE MOUNTAIN QUADRANGLE

Geology by W. J. Mi
1913-1914.

LEGEND

Glacial and post-glacial
deposits: a
Shown only where
pretty effectually con-
cealing the solfd roc!
formations,

SURFICIAL SERIES

Igneous Rocks.

9
Diabase dikes.

LATE SERIES

Gabro Stocks and Dikes.
More or less gneissoid.
Clearly Younger than
the syenite or granite.

OAVATSA|
Granite Porphyry.
A gneissold, porphyritic

phase ofthe granite.

Granite.

A gneissold, ve: uart-
zose phase Of the ayenite,

Granitic Syenite.
Intermediate between
the syenite and granite.

EARLY INTRUSIVE SERIES

Basic Syenite,
A gneissoid, basic
(ioritic to gabbroic)
phase of the syenite.

Quartz Syenite,
Distinctly gneissold and

[oe |

Anorthosite-Gabbro,
More or less gneissoid,
Older than the syenite
but younger than the
Grenyille.

Mixed Rocks.

MIXED SERIES

Grenville and Syentte-
granite mixed gneisses,
more or less Closely in-

yolyed.
3

By
Sedimentary rocks,
Grenville.

Various gneisses and
schists, and mou ai

GRENVILLE SERIES

limestones mostly dis-
tinctly stratified.

Dip and strike of
Tollation,

+
Limestone outcrops.

ees

Glazial striae

Quarries and mines

~—

PLEISTOCENE

eee

PRECAMBRIAN

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