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Full text of "Geology of the Albemarle Quadrangle, North Carolina"

CI 



North Carolina 

Department of Conservation and Development 

Robert L. Stallings, Jr., Director 



Division of Mineral Resources 
Jasper L. Stuckey, State Geologist 



Bulletin 75 



GEOLOGY OF THE ALBEMARLE QUADRANGLE, 

NORTH CAROLINA 



By 
James F. Conley 



Raleigh 
1962 



North Carolina 
Department of Conservation and Development 

Robert L. Stallings, Jr., Director 



Division of Mineral Resources 
Jasper L. Stuckey, State Geologist 



Bulletin 75 



GEOLOGY OF THE ALBEMARLE QUADRANGLE, 

NORTH CAROLINA 



By 
James F. Conley 



Raleigh 
1962 



I 



Members of The Board of Conservation and Development 

Hargrove Bowles, Jr., Chairman... —Greensboro 

R. Walker Martin, Vice Chairman... Raleigh 

John M. Akers Gastonia 

Dr. Mott P. Blair Siler City 

Robert E. Bryan Goldsboro 

Mrs. B. F. Bullard Raleigh 

Daniel D. Cameron.... Wilmington 

Mrs. Fred Y. Campbell .. Waynesville 

Dr. John Dees Burgaw 

William P. Elliott. Marion 

E. Hervey Evans, Jr. Laurinburg 

E. R. Evans... .. Ahoskie 

Andrew Gennett... Asheville 

Luther W. Gurkin, Jr. Plymouth 

Woody R. Hampton ... Sylva 

Charles E. Hayworth .High Point 

Gordon C. Hunter.. Roxboro 

Roger P. Kavanaugh, Jr. __ Greensboro 

Carl G. McGraw Charlotte 

Lorimer W. Midgett Elizabeth City 

Ernest E. Parker, Jr. Southport 

R. A. Poole _..Clinton 

Eric W. Rodgers ...Scotland Neck 

Robert W. Scott Haw River 

James A. Singleton... Red Springs 

J. Bernard Stein Fayetteville 

Paul H. Thompson Fayetteville 

Charles B. Wade, Jr Winston-Salem 



11 



Letter of Transmittal 

Raleigh, North Carolina 
December 14, 1962 

To His Excellency, Honorable Terry Sanford 
Governor of North Carolina 

Sir: 

I have the honor to submit herewith manuscript for publication 
as Bulletin 75, "Geology of the Albemarle Quadrangle, North 
Carolina", by James F. Conley. 

This report contains the results of detailed geologic mapping 
and mineral studies carried out in the Albemarle quadrangle and 
should be of value to those interested in the geology and mineral 
resources of the area. 



Respectfully submitted, 

Robert L. Stallings, Jr. 
Director 



in 



Contents 

Page 

Introduction 1 

Location and description of the area 1 

Purpose and scope 1 

Field work and acknowledgments _ 2 

General geology 2 

Previous investigations 3 

Stratigraphy .' 4 

Lower-volcanic sequence: Felsic tuff unit 4 

Volcanic-sedimentary sequence 5 

Argillite unit 5 

Tuffaceous argillite unit 5 

Felsic tuffaceous argillite—- -. 6 

Felsic crystal tuff 6 

Vitric tuff 6 

Felsic tuff of the "Flatswamp Mountain Sequence" 7 

Mafic tuffaceous argillite 7 

Mafic tuff _ : 7 

Graywacke unit 7 

Gray wacke 7 

Mafic tuff 8 

Lithic tuff 8 

Upper volcanic sequence 8 

Andesitic tuffs unit 8 

Basaltic tuffs unit 9 

Rhyolite unit 9 

Intrusive rocks 10 

Gabbro sills 10 

Rhyolite dikes . 11 

Diabase dikes , 11 



IV 



Page 
Chemical composition 12 

Environment of deposition —12 

Structure 13 

Troy anticlinorium 13 

New London synclinorium 13 

Angular unconformity 14 

Shear zones 15 

Jointing __•_ , __ 15 

Cleavage 15 

Metamorphism .15 

Geomorphology 15 

Stage of development ___15 

Drainage pattern and development 15 

Erosional surfaces 17 

Economic geology 17 

Gold ■. 17 

Coggins mine 17 

Morris Mountain mine 17 

Worth placer mine 17 

Moratock ( ?) mine '. 17 

Parker mine 1 8 

Cottonpatch mine 18 

Gold mine, name unknown . 1 8 

Dutchmans Creek and Island Creek placer mines 18 

Lead and zinc 18 

Quartz 18 

Crushed stone 19 

Flagstone 19 

Brick clay 1 19 

Lightweight aggregate 20 

References cited 26 



• 



Illustrations 

Page 
PLATES 

Plate 1. Geologic Map of the Albemarle quadrangle in pocket 

Plate 2. Photomicrographs of Typical Volcanic Rock Page 22 

Plate 3. Photographs of Typical Rock Specimens Page 24 

FIGURES 

Figure 1. Index Map Showing Location of Albemarle quadrangle._Page 2 
Figure 2. Topographic Cross Sections Showing Erosion Surfaces-Page 16 



Yl 



GEOLOGY OF THE ALBEMARLE QUADRANGLE, 

NORTH CAROLINA 

By 
James F. Conley 



INTRODUCTION 

Location and Description of Area 

The Albemarle quadrangle is bounded by latitude 
35° 15' and 35° 30' N. and 80° 00' and 80° 15' W. 
longitudes and contains approximately 244 square 
miles. The quadrangle covers parts of western Mont- 
gomery and eastern Stanly counties. 

In the northeastern part of the quadrangle, the 
Uwharrie and Yadkin rivers join to form the Pee 
Dee River. The Yadkin River flows to the southeast 
draining the northcentral part of the quadrangle, 
and the Uwharrie River flows to the southwest 
draining the northeastern part. From the conflu- 
ence of the Yadkin and Uwharrie rivers, the south 
flowing Pee Dee River drains the southern part of the 
quadrangle. The western part of the quadrangle is 
drained by Town, Long, and Little Long creeks 
which join Rocky River southwest of the quad- 
rangle. 

The Albemarle quadrangle is located in the Pied- 
mont province. The rolling hills constituting the 
western two-thirds of the quadrangle are typical of 
the Piedmont and contrast to the Uwharrie Moun- 
tains in the eastern one-third of the map area. 

The highest ground elevation in the quadrangle 
is 945 feet above sea level on top of the mountain 
southeast of Blaine. The second highest elevation 
is the top of Morrow Mountain which is 936 feet 
above sea level. A number of hills in the area be- 
tween Blaine and Morrow Mountain exceed eleva- 
tions of 800 feet. In the northwest part of the 
quadrangle the Piedmont uplands average 600 feet 
above sea level ; whereas, in the southwest part of 
the quadrangle the uplands elevations average 500 
feet. Lake Tillery whose spillway is at 278 feet, 
forms the lowest level in the Albemarle quadrangle. 

Albemarle has an average annual rainfall of 46 
inches. The greatest amount of rainfall occurs in 
the late spring and late fall. The Albemarle quad- 
rangle has an average July temperature of approxi- 
mately 78° F. and an average January temperature 
of approximately 44° F. The area is free of frost on 



an average of 200 days per year. 

A considerable amount of the quadrangle is cov- 
ered by second growth hardwood and to a lesser ex- 
tent to mixed forest. The most abundant varieties 
of trees are white oak, red oak, and pine. In places 
the Uwharrie Mountains support a lush growth of 
mountain ivy and laurel. Cedar is abundant in 
parts of the quadrangle and columnar varieties are 
observed. 

Albemarle, the county seat of Stanly County, is 
the largest town in the quadrangle. The quadrangle 
also contains the towns of New London and Badin, 
and the villages Eldorado, Isenhour, Uwharrie, 
Blaine, and River Haven. 

The western half of the quadrangle is served by 
federal, state and county highways and roads. Due 
to the hilly topography and lack of development, the 
eastern one-third is relatively devoid of roads and 
highways, The Winston-Salem Southbound Rail- 
road, which lies in a north-south direction across the 
west central part of the quadrangle, passes through 
Albemarle. The Southern Railway passes through 
New London, terminating at Albemarle with a spur 
line which serves Badin. 

The principally agrarian economy is complement- 
ed by the Wiscasset Textile Mill at Albemarle and 
the Aluminum Corporation of America's plant at 
Badin. Recreation facilities are available at Mor- 
row Mountain State Park, Lake Tillery, and Badin 
Lake. Hunting is provided by the Uwharrie game 
preserve, east of Badin. 

Purpose and Scope 

Although a generalized sequence of rocks com- 
prising the Carolina Slate Belt has been recognized 
for over 100 years, little is known about its strati- 
graphy and structure. A reconnaissance survey of 
the Albemarle quadrangle and surrounding area in- 
dicated that a relatively complete stratigraphic se- 
quence could be worked out within the quadrangle, 
and that metamorphism and structural deformation 
had affected this area less than most parts of the 



VIRGINIA 







GEORGIA 






SCALE 

25 50 75 MOMiieS 



fifc / -Index map of North Carolina showing the location of the Albemarle quadrangle 



Carolina Slate Belt. For these reasons the quad- 
rangle was chosen for a study of the stratigraphy 
and structure of the Carolina Slate Belt. 

By subdividing the lithologic units as much as 
possible and paying particular attention to struc- 
tural control, certain beds evolved as marker hori- 
zons some of which have been traced for many 
miles. The lithologic units were plotted on the U. S. 
Geological Survey topographic map, preliminary 
sheet, of the Albemarle quadrangle, scale 1 to 48,000. 
Field mapping was supplemented by petrographic 
analyses of the major rock units. Chemical analyses 
of representative samples of these units were made 
by P. M. Sales, North Carolina State College Min- 
erals Research Laboratory, Asheville, North Caro- 
lina. In practice it was found that soil as well as 
color and texture of weathered saprolite gave good 
indications of rock types. 

Field Work and Acknowledgments 

Field mapping began in February 1958 and con- 
tinued until October 1959. The area was field 
checked in February and June 1961. William F. 
Wilson, Division of Mineral Resources, assisted in 
the field mapping from May to October 1958. Sam 
D. Broadhurst, Division of Mineral Resources, super- 
vised the field work. In addition, he gave freely of 
his experience and time and aided in every way pos- 
sible to bring the project to a successful conclusion. 
Jasper L. Stuckey, State Geologist, visited the area 
from time to time and critically reviewed the final 
paper. 

Since 1955, Arvid A. Stromquist, U. S. Geological 
Survey, has been mapping the Denton quadrangle 
just to the north of the Albemarle quadrangle. Co- 
operation between the members of the two projects 



has resulted in a more thorough understanding of 
the geology of both quadrangles. In addition, Mr. 
Stromquist reviewed the final manuccript. 

W. A. White, Department of Geology, University 
of North Carolina, read the geomorphology section 
of the report. His suggestions greatly improved 
this section of the report. E. F. Goldston, Depart- 
ment of Soils, North Carolina State College, visited 
in the field and gave valuable information on the 
relationship of soil types to underlying rock types. 
Oscar B. Eckhoff, Division of Mineral Resources, 
prepared most of the thin sections and accompanied 
the author in the field on several occasions. Kenneth 
M. Drummond, Division of Mineral Resources, aided 
considerably in the final field checking of the quad- 
rangle and the preparation of the report. 

General Geology 

The Carolina Slate Belt is a northeast trending 
band of low rank metamorphic volcanic and sedi- 
mentary rocks cropping out from southwestern Vir- 
ginia to central Georgia. This belt of rocks lies in 
the central and eastern Piedmont section of North 
Carolina. To the west, the Carolina Slate Belt is in 
contact with the Charlotte Belt; to the northwest, 
it is in contact with gneisses and schists of the cen- 
tral Piedmont; and, to the east, it is overlapped by 
sediments of the Coastal Plain (N. C. State Geologic 
Map, 1958). 

At the Virginia state line the outcrop area is 
about 70 miles wide, in the central part of North 
Carolina it is 130 miles wide, and along the South 
Carolina border it is exposed in an area only 50 
miles wide. 

Oil test wells drilled through Coastal Plain sedi- 
ments in Onslow and Camden counties penetrated 



Carolina Slate Belt rocks, indicating they extend 
under the Coastal Plain for a considerable distance. 
The central part of the belt in North Carolina is 
interrupted by the Deep River Triassic basin. East 
of Raleigh the Carolina Slate Belt has been intruded 
by a large granitic pluton which can be traced 
northward to the Virginia line. This pluton has 
metamorphosed the surrounding country rock into 
gneisses and schists. A number of smaller granitic 
bodies have intruded the Carolina Slate Belt along 
both its northeastern and northwestern borders. 

Previous Investigations 

Olmstead (1822) described novaculite, slate, horn- 
stone, and talc from areas now known to be under- 
lain by the Carolina Slate Belt. In 1825 he referred 
to the "Great Slate Formation", which "passes 
quite across the State from northeast to southwest, 
covering more or less the counties of Person, Orange, 
Chatham, Randolph, Montgomery, Cabarrus, Anson, 
and Mecklenburg." He described the rocks of this 
"formation" as consisting of clay slate, argillite, 
porphyry, soapstone, serpentine, greenstone, and 
whetstone. Eaton (1830), in a report on gold in 
North Carolina, added "talcose slates". He stated 
that they occur in association with novaculite, and 
might have been referring to sericite developed in 
silicified zones so often found in gold and pyrophyl- 
lite deposits. 

Ebenezer Emmons (1856) placed the Carolina 
Slate Belt, which he considered to be subaqueos 
deposited sediments of very ancient age, in his Ta- 
conic system. He divided this system into an upper 
and a lower member. The upper member consisted 
of clay slates, chloritic sandstones, cherty beds, flag- 
stones, and brecciated conglomerates. The lower 
member consisted of talcose slates, white and brown 
quartzites, and (on his cross section, plate 14, he 
added) conglomerates. He did not recognize vol- 
canic rocks in the Carolina Slate Belt. In his lower 
unit, Emmons found what he thought to be fossils 
and named them Paleotrochis. These were later 
identified by Diller (1899) as spherulites. Emmons 
recognized both the anticline near Troy and the syn- 
cline near New London. 

Kerr (1875) described the rocks of the Carolina 
Slate Belt and proposed that they were of Huronian 
age. 

Williams (1894) first recognized volcanic rocks in 
the Carolina Slate Belt. The following year Becker 
(1895) published a paper in which he noted the 
presence of volcanic rocks and proposed that they 
were Algonkian age. 



The name Carolina Slate Belt was first applied by 
Nitze and Hanna (1896). They recognized volcanic 
rocks interbedded with the slates, and proposed that 
the volcanic rocks were laid down during times of 
volcanic outbursts, followed by inactivity at which 
time the slates were deposited. They observed that 
some of the rocks had true slaty cleavage, whereas 
others were schistose. They proposed that these 
rocks were altered by dynamo and hydrometamorph- 
ism. 

Weed and Watson (1906) studied the copper de- 
posits of the Virgilina mining district. They believ- 
ed that the country rock in this area was an altered 
andesite of Precambrian age. 

Laney (1910) published a report on the Gold Hill 
mining district of North Carolina. In this report 
he divided the rocks into slates with interbedded 
felsic and mafic flows and tuffs. He stated that the 
slates differ from the fine dense tuffs only in the 
amount of land waste they contain, indicating the 
slates, in part, were derived from volcanic mate- 
rial. He did not define "land waste", nor did he 
explain how it might be recognized. He stated that 
the rocks all show much silicification and are only 
locally sheared. 

Pogue (1910) published a report on the Cid min- 
ing district, and Laney (1917) published a report 
on the Virgilina mining district. These reports are 
in general repetitions of ideas expressed in Laney's 
report of 1910. 

Stuckey (1928) published a report which included 
a geologic map as well as a description of the Caro- 
lina Slate Belt of the Deep River region of Moore 
County. He divided these rocks into slates, acid 
tuffs, rhyolites, volcanic breccias, andesite flows, and 
tuffs. He noted that the schistosity dipped to the 
northwest and interpreted the structure as closely 
compressed synclinorium with the axes of the folds 
parallel to the strike of the formations. In addition, 
he pointed out that metamorphism is not uniform 
throughout the area. 

Theismeyer and Storm (1938) studies slates show- 
ing fine graded bedding near Chapel Hill, North 
Carolina, and proposed that they represented sea- 
sonal banding. Theismeyer (1939) proposed that 
similar sediments found in Faquier County, Virginia 
were deposited in pro-glacial lakes during late Pre- 
cambrian and early Cambrian times. The bedding 
was thought to be seasonal varves. In addition he 
proposed that, "The Hiawassee slates of Tennessee 
and the slates in North Carolina, near Chapel Hill, 
belong to the same category ; even may have been 
deposited more or less contemporaneously". 



F. 0. Bowman (1954) studied the structure of 
the Carolina Slate Belt near Albemarle, North Caro- 
lina. He recognized sedimentary rocks, volcanic 
tuffs and flows, and mafic intrusives in the area. He 
proposed that the structure was a series of undulat- 
ing open folds. 

Stratigraphy 

Until more mapping has been completed within 
the Carolina Slate Belt, time-stratigraphic designa- 
tions would be premature. Consequently, this re- 
port designates the rocks by their lithologic charac- 
ters rather than by stratigraphic names, and the 
various rock types have been assembled into se- 
quences and units (see map and legend, pi. 1). 
However, although the rock types are not yet offi- 
cially named the entire "Carolina Slate Belt" should 
be thought of as the equivalent of a supergroup, the 
"sequences" as groups, the "units", within the 
sequences, as formations. In this paper sequence 
has no implication on origin as defined by Sloss, 
Krumbein, and Dapples in the textbook by Krumbein 
and Sloss (1958). 

The Albemarle quadrangle contains three distinct 
sequences of rocks: (1) Lower Volcanic sequence, 
consisting largely of felsic tuffs that have been fold- 
ed into an anticline plunging to the southwest; 
(2) Volcanic-Sedimentary sequence, consisting of a 
lower argillite unit, an intermediate tuffaceous argil- 
lite unit, and an upper graywacke unit, which have 
been folded into a syncline also plunging to the 
southwest; (3) Upper Volcanic sequence, consisting 
of mafic and felsic volcanic rocks which unconform- 
ably overly the first two sequences named. Because 
of an error during final preparation of the map 
legend, the word unit was inadvertently omitted 
after andesitic tuffs, basaltic tuffs, and rhyolite of 
the Upper Voncanic Sequence. However, these rocks 
are regarded as units as the term is used in this 
paper. 

These sequences of rocks constitute a strati- 
graphic succession which is probably over 30,000 
feet thick. The exact thickness of the sequence can 
not be determined because the base of the succession 
has not been recognized. Determining overall thick- 
ness of individual sequences is complicated by fold- 
ing, thickening, and thinning of individual beds. 

Lower Volcanic Sequence 

The Lower Volcanic sequence crops out from 
western Montgomery County to central Moore 
County and can be traced from southern Montgom- 
ery County northward to northern Randolph County. 



Recent mapping by Edwin Floyd, U. S. Geological 
Survey, in Union County indicates that the Lower 
Volcanic sequence reappears along the western bor- 
der of the Carolina Slate Belt in contact with plutonic 
rocks of the Charlotte Belt. 

The Lower Volcanic sequence lies at the bottom of 
the stratigraphic succession in the Albemarle quad- 
rangle and contains the oldest rocks thus far recog- 
nized in the Carolina Slate Belt. This sequence is 
at least 3,500 feet thick and could be as much as 
20,000 feet thick. The contact between Carolina 
Slate Belt and basement rock has not been observed, 
but Laney (1917) proposed that the Carolina Slate 
Belt was underlain by gneisses and schists of the 
Piedmont to the west. 

The Lower Volcanic sequence consists of inter- 
bedded felsic lithic tuffs, crystal and lithic-crystal 
tuffs, welded flow tuffs, flows, occasional mafic pyro- 
clastic beds and rare bedded argillites. The tuffs 
which make up the Lower Volcanic sequence, exposed 
in the Albemardle quadrangle, are felsic in compo- 
sition (1ft). The best exposures of the Lower Vol- 
canic sequence are found along new Highway N. C. 
27 from 1 mile east of the Pee Dee River to the east- 
ern edge of the quadrangle. These rocks are light 
grey in color and weather to white clay. They are 
especially susceptible to spheroidal weathering and, 
in many places, the outer surfaces are covered by a 
thin white weathering rind. The rocks are exceed- 
ingly dense, emitting a metallic ring when struck 
with a hammer, and break with a concoidal fracture. 
Rocks of the Lower Volcanic sequence are generally 
massive except near the top of the stratigraphic 
section where they contain faint bedding. They 
have been closely jointed and many of the joint 
planes have been healed by thin veins of quartz, 
some of which are not over Vs mcn thick. In gen- 
eral, axial plane cleavage is poorly developed. 

The felsic tuff is composed predominantly of lithic 
tuff with interbeds of crystal tuff and at least one 
flow tuff. The lithic fragments consist of red and 
grey rhyolites containing flow lines, light grey fine 
grained felsite, and rare mafic crystal tuff. Red 
rhyolite fragments have been observed only in the 
Lower Volcanic sequence. The subrounded to angu- 
lar fragments are exceedingly poorly sorted and 
range in size from y$ inch to over 2 feet in diameter. 
Some of the felsite fragments have pitted amygdular 
surfaces, indicating they were liquid when ejected. 

The crystal fragments are composed of both quartz 
and feldspar. The quartz crystals are somewhat 
spheroidal in outline; whereas, the feldspars occur 
as both broken laths and euhedral crystals. They 



range in size from 1/32 inch to over ^8 mcn * n 
diameter. 

Under the microscope (see pi. 2, No. 1) the feld- 
spars make up from 3 to 5 percent of the rock and 
were determined to be predominantly orthoclase, 
with some oligoclase, and rare sanidine? and ande- 
sine. They were cloudy from primary inclusions, 
but did not appear to be greatly altered. About 30 
percent of the rock was composed of quartz. The 
quartz occurs as embayed beta crystals, but more 
often as lenticular shaped granular masses. Except 
for rare porphyritic specimens, the lithic fragments 
are too fine grained to be identified under the petro- 
graphic microscope. The groundmass, which makes 
up approximately 60 percent of the rock, is also 
exceedingly fine grained, but appears to be predomi- 
nantly granular masses of quartz, with sericite, 
kaolinite, and numerous small crystals of pyrite and 
aggregates of chlorite. 

A welded crystal flow tuff is interbedded with 
the felsic tuff one mile northeast of Stony Fork 
Church. It is an exceedingly dense, pale pink rock 
which breaks with a concoidal fracture (see pi. 3, 
No. 1 ) . The rock contains about 6 percent semi- 
rounded pink-orthoclase and microcline crystals in- 
terspersed throughout the matrix. The most promi- 
nent structures are the numerous collapsed pumice 
fragments and wispy flow lines. Originally the rock 
must have been exceedingly porous, but the vessicles 
are filled with granular quartz which now composes 
as much as 60 percent of the rock. The groundmass 
could not be resolved, but appears to be predominant- 
ly quartz with some kaolinite. 

Volcanic-Sedimentary Sequence 

The Volcanic-Sedimentary sequence crops out 
from northwest of Asheboro southward to the South 
Carolina line. It covers most of the western three 
fourths of the Albemarle quadrangle. In the quad- 
rangle it is made up of three dominant rock types : 
the argillite unit, the tuffaceous argillite unit, and 
the graywacke unit. The Volcanic-Sedimentary se- 
quence apparently conformably overlies the Lower 
Volcanic sequence and in turn is unconformably 
overlain by the Upper Volcanic sequence. The Vol- 
canic-Sedimentary sequence is estimated to be about 
10,000 feet thick. The only fossils recognized in the 
Volcanic-Sedimentary sequence are worm trails 
(Conley, 1960) and one questionable Ordovician 
brachiopod (Stuckey, personal communication). 
The resemblance between this sequence and Ordo- 
vician Arvonia and Quantico slates also suggest 
Ordovician age for this sequence. 



Argillite Unit 

The argillite unit (ar) has been traced from north- 
west of Asheboro to the Triassic contact in southern 
Montgomery County. The outcrop belt of this unit 
is from 3 to 8 miles wide in the Albemarle quad- 
rangle. It trends northeast-southwest and parallels 
the Uwharrie River in the northern part and the 
Pee Dee River in the southern part and underlies the 
eastern one fourth of the quadrangle. This unit is 
variable in thickness along strike, but averages 
about 500 feet thick. 

The argillite unit directly overlies the felsic tuffs 
of the Lower Volcanic sequence. Although a discon- 
formity cannot be ruled out, the contact between 
these units appears to be gradational over a thick- 
ness of a few hundred feet. Bedded and sorting 
increases upward from the base as argillite becomes 
predominant. The major characteristic of this rock 
is its thin graded beds (see pi. 3, No. 2) . The graded 
beds range in thickness from 1/16 to 1/2 inch. The 
fresh rock is dark grey, changing to ocherous browns 
and reds upon weathering. The rock has a well de- 
veloped bedding plane cleavage and an incipient 
axial plane cleavage which causes it to weather into 
small thin chips. 

Thin interbeds of lithic crystal tuff occur near the 
base, indicating that volcanic activity was still going 
on during the time of deposition. The basal part 
of the unit also contains thin conglomerate beds. 
The conglomerate pebbles are composed of volcanic 
rocks which might have been derived from erosion 
of the Lower Volcanic sequence. Slump bedding has 
been observed near the base of the unit along Clarks 
Creek in the southeastern part of the quadrangle. 
These structures indicate the basal portion of the 
argillite unit was deposited on a slope at an angle 
high enough to cause plastic flowage and deforma- 
tion before the argillite was compacted and lithified. 

The graded bedding is easily observed in thin sec- 
tion (see pi. 2, No. 2). The bedding consists of a 
bottom silt layer which grades upward into a clay 
layer. The silt sized particles are predominantly 
angular quartz grains with some feldspar fragments, 
as well as relic outlines of ferromagnesian minerals 
now completely changed to chlorite. The clay layers 
are altered to sericite. Chlorite and kaolinite occur 
sparingly in all thin sections observed. 

Tuffaceous Argillite Unit 

The argillite unit grades upward into the tauffa- 
ceous argillite unit. The contact between the two is 
an arbitrary line based on the predominance of thick 
bedded, water laid, fine grained tuffs over argillite 



exhibiting graded bedding. The thickness of the 
unit is variable from northeast to southwest. The 
unit probably does not exceed 2,000 feet in the north- 
ern part of the quadrangle, but could be as much as 
10,000 feet thick to the south. The great thickness 
of massive tuffaceous argillite in the southwest 
part of the quadrangle, as opposed to its relative 
thinness in the northeast part, indicates that vul- 
canism was affecting sedimentation to the southwest 
long before it began to affect the northeast. This is 
further indicated by the gradational and pulsating 
nature of the graded beds at the base of the tuffa- 
ceous argillite. The graded beds gradually become 
further spaced and finally die out as intermittent 
pulses of pyroclastics became more pronounced and 
constant. 

Felsic Tuffaceous Argillite 

The major rock type of the tuffaceous argillite 
unit is felsic tuffaceous argillite (fta). The best 
exposure of the felsic tuffaceous argillite is at the 
southern city limits of Albemarle. The felsic tuffa- 
ceous argillite is coarsely bedded with beds ranging 
in thickness from 6 to 24 inches. It is medium grey 
when fresh, but weathers light grey and becomes 
creamy white when completely decomposed. The 
fresh rock breaks into splintery fragments oriented 
at right angles to bedding planes; whereas, the 
weathered rock breaks with a concoidal fracture. 

In hand specimens, the felsic tuffaceous argillite 
appears to be a fine dense tuff containing a few feld- 
spar crystal fragments scattered throughout the 
matrix. Wispy particles which might represent de- 
vitrified glass shards are scattered through some 
beds and are in places concentrated at the base of 
the beds (see pi. 2, No. 3 and pi. 3, No. 3) . The best 
outcrop of rock containing these particles is exposed 
north of Badin along Highway N. C. 740, 50 yards 
west of the Southern Railway. From Albemarle 
southward, thin beds and lenticular masses of impure 
calcite, usually not over 3 to 4 inches thick, form 
interbeds within the felsic tuffaceous argillite. 
These carbonates probably represent thin primary 
limestone beds. When fresh they are lighter grey 
than the tuffaceous argillite, but readily weather 
brown. In the zone of weathering these beds are 
usually completely decomposed, leaving a silty clay 
along the bedding planes. 

In thin section the felsic tuffaceous argillite is a 
micro-crystalline tuff, (see pi. 2, No. 3). The only 
two readily identifiable minerals are quartz and 
orthoclase. The remainder has been altered to seri- 
cite and kaolinite. The wispy particles are now 



completely altered to kaolinite and quartz. Outlines 
of relic crystals and felsite fragments can still be 
observed. These outlines average about .02 milli- 
meter in length with an occasional feldspar frag- 
ment reaching up to .5 millimeter. The carbonate 
beds are composed of interlocking crystals of calcite 
and detrital quartz. Tiny cubic crystals of pyrite 
are disseminated throughout the rock. The parti- 
cles making up the rock appear to be well sorted. 

Felsic Crystal Tuff 

Thin beds, consisting of crystals in a tuffaceous 
argillite matrix, are interbedded with the felsic 
tuffaceous argillite. In hand specimens (see pi. 3, 
No. 4), the felsic crystal tuff (ca) is a lathwork of 
white feldspar crystals, ranging in length from 1 
to 2 millimeters, in a fine grained granular ground- 
mass indistinglishable from that of the felsic tuffa- 
ceous argillite. Rare angular lithic fragments, rang- 
ing from 1 to 2 centimeters in diameter, some con- 
taining cellular structures which are probably ves- 
sicles, are found in the crystal tuff. 

Under the microscope the feldspars generally ap- 
pear to be abraded and rounded and vary from 
euhedral crystals to broken laths (see pi. 2, No. 4). 
Almost all of the feldspars exhibit albite twinning, 
but a few are both albite and carlsbad twinned. The 
feldspars range from oligoclase to andesine, and are 
partially altered to sericite and kaolinite. Some of 
the lithic fragments are an exceedingly fine mesh- 
work of crystals too small to be identified under the 
microscope. Others are completely altered to chlo- 
rite. The matrix is composed of minute unoriented 
needl-like crystals with originally fine-grained vol- 
canic debris, now altered to sericite and kaolinite, 
filling the interstices. When fresh, the rock is medi- 
um grey, but it weathers to a light grey color sim- 
ilar to that of the felsic tuffaceous argillite. 

Vitric Tuff 

Vitric tuff beds (vt) are very resistant to erosion 
and form a series of northeast trending hills across 
the east-central part of the quadrangle. 

These beds make excellent key horizons which can 
be traced over wide areas. The vitric tuff is usually 
underlain by thin beds of lithic tuff and grades up- 
ward into thick bedded massive felsic tuffaceous 
argillite. 

In hand specimens (see pi. 3, No. 5), the vitric 
tuff is a light grey massive rock which when hit 
with a hammer, emits a metallic sound and breaks 
with a concoidal fracture. Bedding planes are ob- 
scure and consist of alternating light and dark bands 



which become more pronounced upon weathering. 
The rock is well jointed, giving the outcrops a some- 
what blocky appearance. These joint surfaces are 
in many places healed with quartz, ranging in width 
from hair lines to 1/16 inch. The fresh rock has a 
glassy appearance and when broken into thin slivers 
is translucent. It develops creamy white weathering 
rinds which often gives the misconception that it is 
a white colored rock. 

Under the microscope the rock is an interlocking 
meshwork of crypto-crystalline quartz, sericite, and 
possibly kaolinite. It is similar in composition and 
texture to rhyolites in the area. As the rock con- 
tains bedding planes and does not contain either 
lithic or crystal fragments, it may be a devitrified 
welded vitric tuff. Possibly the devitrification of 
the glass released free silica which crystallized as 
crytocrystalline quartz to produce a highly silicic 
rock. 

Felsic Tuff of the "Flatswamp Mountain Sequence" 

During reconnaissance in both the Denton and 
Albemarle quadrangles, as well as surrounding area, 
it was found that an associated stratigraphic se- 
quence could be traced as a key horizon for over 35 
miles. For the purpose of field mapping, this marker 
horizon was given the informal term Flatswamp 
Mountain sequence (Stromquist and Conley 1959). 
This term is used in this report and on the accom- 
panying map. 

The major rock type of the "Flatswamp Mountain 
sequence" in the Albemarle quadrangle is a light to 
dark grey, fine grained to aphanitic, massive felsic 
tuff (fft) which weathers chalky white. Scattered 
throughout its matrix are occasional crystal frag- 
ments of orthoclase, oligoclase, and rare fragments 
of quartz. One small bed of mafic lithic crystal tuff 
was located south of Blaine in the Albemarle quad- 
rangle. However, Stromquist (personal communi- 
cation) suggests that the Flatswamp Mountain se- 
quence may interfinger with mafic members of the 
tuffaceous argillite unit in the Denton quadrangle. 
The rocks of the Flatswamp Mountain sequence in 
the Albemarle quadrangle rarely show bedding or 
other sedimentary features. They grade upward 
into water deposited felsic tuffaceous argillite, but 
Stromquist (personal communication) feels the low- 
er part of the sequence was deposited subaerially on 
a local landmass. 

Mafic Tuffaceous Argillite 

Beds of mafic tuffaceous argillite (mta) are found 
within the tuffaceous argillite unit and in the over- 



lying graywacke unit. In fresh outcrop the medium 
grey mafic tuffaceous argillite is difficult to dis- 
tinguish from felsic tuffaceous argillite, but on 
weathering the mafic tuffaceous argillite turns to an 
easily recognizable dun brown. It is predominantly 
a siltstone, but contains numerous fissle lenticular 
clay beds. Individual beds range from 2 to 6 inches 
thick. Well developed bedding plane cleavage is 
apparent in the rock. Graded bedding has been 
noted in some outcrops. 

Because of the minute size of the particles, the 
individual minerals could not be identified under the 
microscope. However, they appear to be mostly 
quartz and feldspar. The groundmass is apparently 
an aggregate consisting almost entirely of chlorite. 

Mafic Tuff 

Two lenticular beds of mafic lithic crystal tuff 
(mt) occur in two small areas south of Albemarle 
(see pi. 1). They are composed of angular lithic 
fragments and feldspar crystals dispersed in a chlo- 
ritic groundmass. The angular to subrounded frag- 
ments range in size from l/16th to ] /o inch in 
diameter. A few fragments contain amygdaloidal 
structures filled with chlorite and epidote. The feld- 
spars range from l/16th to 3/16th inch in length, 
and are lath shaped broken crystals of andesine, 
laboradorite and bytownite. The matrix is a mesh- 
work of needle like pyroxene? crystals and chlorite. 

Graywacke Unit 

The graywacke unit is about 3,000 feet thick and 
crops out in a belt approximately 5 miles wide be- 
ginning at the northcentral part of the quadrangle 
and is traceable southwestward into Union County. 
It is predominantly a graywacke sandstone with 
minor interbeds of mafic tuffaceous argillite, mafic 
crystal tuff, and felsic lithic tuff. Thin beds of mafic 
tuffaceous argillite occur at the base of the gray- 
wacke unit. 

Graywacke 

Graywacke sandstone (gr), the major rock type 
of the graywacke unit, (see pi. 3, No. 6) is dark 
grayish green when fresh, but weathers to light ma- 
roon and vermillion saporlite. Upon complete de- 
composition it produces a sticky sand clay. It has 
a massive blocky appearance in outcrop due to the 
wide spacing, 2 to 5 feet, of major bedding and joint 
planes. The wide spacing of the joint planes and 
major bedding planes makes the graywacke usually 
susceptible to spheroidal weathering. 



Stratification in the form of graded bedding and, 
less common, southwest dipping cross-bedding exists 
between these planes. The graded beds consist of a 
sand sized layer which grades upward into a silt 
sized layer. The contact between individual graded 
beds is in many places irregular. The coarse gray- 
wacke found in the north-central part of the quad- 
rangle grades to the southeast into finer grained 
equivalents. 

In thin section (see pi. 2, No. 5) the graywacke 
is composed of equal parts of slightly rounded chlo- 
ritized rock fragments and quartz grains with occa- 
sional albite twinned feldspar laths ranging in com- 
position from oligoclase to andesine. Argillite frag- 
ments are relatively rare in the graywacke but have 
been observed in some hand specimens. When grad- 
ed bedding is present the matrix varies in compo- 
sition from the base to the top of individual graded 
beds. The base, or sand sized particles, consist of 
equal parts of kaolinite and sericite with some chlo- 
rite. The chlorite becomes more prominent toward 
the top, or silt sized layer, where it almost completely 
displaces the kaolinite and sericite. Pyrite cubes 
ranging in size from 1/16 inch to 2 inches are dis- 
seminated throughout the rock. 

Mafic Tuff 

Two lenticular bands of mafic tuff (mt) occur 
within the graywacke unit in the north central part 
of the quadrangle. These tuffs are massive in ap- 
pearance, and show neither bedding nor cleavage. 

The mafic tuff is dark green when fresh, weather- 
ing to a rust brown. Subsoils are deep chocolate 
brown clays. The rock is susceptible to some 
spheroidal weathering along joint planes, but it is 
generally more resistant than are the graywackes 
and produces elongate hills paralleling the strike of 
the strata. 

In thin section, the mafic tuff contains stubby 
crystals of feldspar which do not exceed 1 millimeter 
in length. These crystals are, for the most part, 
euhedral but rare broken crystals have been observ- 
ed. Albite twinning is absent, but carlsbad twinning 
was noted in about 10 percent of the crystals. The 
feldspars are so extremely saussuritized as to be 
rendered unidentifiable. Large light emerald-green 
crystal masses, up to 1 millimeter across, were ob- 
served. These masses might be antigorite replacing 
augite. The dense, green, aphanitic groundmass is 
too fine to be resolved, but appears to be dark green- 
ish black chlorite with a light yellow anisotropic 
aggregate which might be sericite. 



Lithic Tuff 

One small interbed of felsic lithic tuff (It) occurs 
in the graywacke unit approximately 0.2 mile due 
west of Isenhour. It consists of a fine grained 
groundmass composed of crystalline quartz and seri- 
cite containing angular, dense, white, light and dark 
gray aphanite and porphyritic rhyolite, as well as 
rare flattened mafic fragments. The fragments 
range in diameter from 2 to 4 inches. The fresh 
rock is light grey with a speckled appearance due fo 
the lithic fragments. On exposure it develops white 
weathering rinds and weathers to a kaolinitic clay. 

Upper Volcanic Sequence 

The Upper Volcanic sequence has been found from 
near Asheboro, Randolph County, to southeast of 
Albemarle, Stanly County. Rocks of this sequence 
occur in all but the southwestern part of the Albe- 
marle quadrangle. The Upper Volcanic sequence 
is approximately 450 feet thick and rests uncon- 
formably on both the Lower Volcanic sequence and 
the Volanic-Sedimentary sequence (Conley, 1959). 
The Upper Volcanic sequence comprises the youngest 
rocks thus far recognized in the Carolina Slate Belt. 
This sequence from base to top is composed of the 
andesitic tuff unit, basaltic tuff unit, and rhyolite 
unit. 

The age of the rocks of the Upper Volcanic se- 
quence is purely conjectural. However, they might 
easily be of Silurian or younger age, because the 
angular unconformity that separates them from 
underlying rocks is similar to the one found at the 
base of the Silurian in many places in the Appa- 
lachian geosyncline. 

Andesitic Tuffs Unit 

The andesitic tuffs unit (uat) is found only in the 
area east and south of New London. They attain 
a maximum thickness of 140 feet. These tuffs occur 
at the base of the Upper Volcanic sequence and un- 
conformably overlie the graywacke unit and are 
conformably overlain by basaltic tuffs unit. The 
andesitic tuffs are massive and bedding can be ascer- 
tained only by observing flattened pumice fragments 
and orientation of lithic fragments. They are grey- 
black when fresh, but are exceedingly susceptible 
to chemical weathering, developing deep clayey, 
maroon colored saprolite. The partially weathered 
rock has a red-gray mottled appearance caused by 
accentuation of lithic fragments. The tuffs are 
spongy in appearance and emit a dull sound when 
struck with a hammer. The major rock of this unit 



8 



is composed of numerous vessicular fragments which 
resemble scoria and range in diameter from 1/16 
inch to 4 inches (see pi. 2, No. 6). The vessicles are 
now usually filled with calcite. Many of these frag- 
ments contain flow banding and are irregular in 
outline which suggests they were molten when de- 
posited. In places these fragments have collapsed 
into lenticular shaped masses which locally comprise 
as much as 60 percent of the rock. The matrix is a 
dark grey translucent mass with numerous crystals 
ranging from 0.3 to .15 millimeter in diameter. 
Large quantities of hematite were noted ; locally, 
masses of hematite make up as much as 25 percent 
of the rock. 

An exposure of slightly different character was 
noted southeast of New London on the road parllel- 
ing Mountain Creek. It is a purple to red-gray 
porphyria rock containing feldspar laths and exhib- 
iting faint flow lines. It is exceedingly dense, and 
when struck with a hammer, emits a metallic ring 
and breaks with a concoidal fracture. This rock is 
interbedded with the andesitic tuffs and might be 
a welded ash flow but it is more likely an andesitic 
lava flow. 

Balsatic Tuft's Unit 

The basaltic tuffs and flows (ubt) attains a maxi- 
mum thickness of 200 feet and crop out over a wide 
area in the central and northern part of the quad- 
rangle, the basaltic tuffs unit unconformably over- 
lies the argillite and tuffaceous argillite units of the 
Volcanic-Sedimentary sequence and probably con- 
formably overlies the andesitic tuffs of the Upper 
Volcanic sequence. These rocks are well jointed, 
but do not exhibit cleavage. They are susceptible 
to spheroidal weathering and develop dark brown 
clay soils. 

A number of exposures of the basal section of the 
basaltic tuffs in the area near Morrow Mountain and 
Badin contain a basal conglomerate composed of 
mafic lithic fragments and rounded argillite pebbles, 
derived from the underlying argillite unit, in a 
matrix of fine grained mafic tuff. Basaltic flows 
have been observed near the base of the basaltic 
tuffs, but are not everywhere present. One such 
flow occurs in a roadcut a few hundred yards south 
of Badin Dam. Amygdaloidal basalt is found north- 
west of Blaine. The amygdules are ovoid in shape 
and are up to 2 inches in length. Many of the cavi- 
ties are filled with secondary quartz and resemble 
miniature geodes when broken open. Columnar 
jointing has been noted in a questionable flow east 
of the Badin power plant. This rock contains num- 



erous secondary masses of calcite and highly dis- 
persed minute grains of native copper. Above its 
base the basaltic tuffs unit consist of faintly bedded, 
well jointed lithic-crystal tuffs. 

In the north central and northwestern parts of 
the quadrangle the basaltic tuffs take on a spotted 
appearance due to the increase in quantity of lithic 
fragments (see pi. 3, No. 7). These fragments 
range in size from 1/16 inch to over 8 inches in 
diameter. They are rounded to sub-angular in out- 
line and exhibit an inconspicuous graded bedding 
characteristic of air laid pyroclastic rocks. 

In thin section the matrix of the basaltic tuff is 
composed of a meshwork of exceedingly fine grained 
particles which appear to be predominantly chlorite. 
Intermixed with the tiny particles are numerous 
needlelike crystallites which appear to be feldspar. 
Larger crystals of both euhedral and broken laths 
of feldspar and stubby hornblende crystals are scat- 
tered throughout the matrix. The lithic fragments 
are of different composition than the matrix (see 
pi. 2, No. 7). They are composed of aggregates of 
needlelike crystals in a matrix even finer grained 
than the rock matrix and might represent devitrified 
glass. 

The flow rocks are a mesh of angular interlocking 
needlelike crystals consisting of feldspar, horn- 
blende, and pyroxene — probably augite. Chlorite 
is present as an interstitial material. Faint flow 
banding, outlined by the development of chlorite, 
can be occasionally observed in most thin sections. 

Rhyolite Unit 

The rhyolite unit (ur) is as much as 200 feet 
thick and apparently caps only the highest hills in 
the eastern part of the quadrangle. This rock is 
interpreted to conformably overlie the basaltic tuffs 
where present, but unconformably overlies the Low- 
er Volcanic sequence and the Volcanic-Sedimentary 
sequence. The rhyolite is exceedingly resistant to 
erosion and produces steep sloped, flat topped hills. 
This rock is well jointed, but does not exhibit schis- 
tosity. The color of fresh rhyolite is grey to greyish 
black. Upon exposure to weathering it develops a 
white, chalky outer coating. The saprolite is white 
to buff in color. Subsoils, if present, are sandy 
loams which vary from buff to vermillion in color. 
Topsoils are light grey silty loams. 

In most places the basal part of the rhyolite sec- 
tion in Morrow Mountain State Park consists of a 
lithic tuff composed of rhyolite fragments. The 
lithic fragments are angular and range in maximum 
dimensions from 14 inch to 3 inches. One of the 



9 



better exposures of this tuff is located in Morrow 
Mountain State Park where the park office road 
crosses Sugarloaf Creek. 

Above the base, the rock is a dark greyish black 
porphyritic rhyolite containing numerous flow bands 
(see pi. 3, No. 8) . The phenocrysts consist of white 
feldspar laths, 0.5 to 2 millimeters long; and beta 
quartz crystals, 1 millimeter in length. The flow 
lines are of a lighter color than the rest of the rock. 
In fresh outcrops the flow lines are relatively incon- 
spicuous, becoming accentuated by weathering. 
Numerous strikes and dips were taken of the flow 
banding; however, the results were too erratic to 
form a reasonable pattern. 

Rhyolite flows on the higher peaks of the Uwharrie 
Mountains in the eastern part of the quadrangle 
contain numerous spherulites which range from i/fc 
inch to over 2 inches in size (see pi. 3, No. 9) . Some 
are cone shaped, others have the form of a double 
cone. The sides are usually striated, ribbed, and 
sometimes have a depression in the center which 
resembles the calyx of a tetracoral, giving Emmons 
(1856) the impression that they were fossils. The 
spherulites are usually replaced by quartz ; however, 
specimens collected north of Zion Church still con- 
tain radiating feldspar laths. 

The rhyolite exposed on top of the Uwharrie 
Mountains southeast of White Crest Church is a 
light grey brecciated porphyritic flow rock contain- 
ing angular blocks 4 to 6 feet across. These blocks 
appear to have been rotated in place and might rep- 
resent a brecciated flow top. 

The groundmass of the rhyolite flows can not be 
resolved under the microscope, but appears to be a 
mixture of kaolinite, sericite and cryptocrystalline 
quartz (see pi. 2, No. 8). Interlocking unoriented 
lenticular masses of quartz occur parallel to the flow 
banding. Sericite masses also seem to be concen- 
trated parallel to the flow bands. Unoriented pheno- 
crysts of orthoclase, oligoclase, and beta quartz are 
sparingly distributed throughout the ground mass. 
The orthoclase phenocrysts are usually euhedral and 
are seldom carlsbad twinned. Oligoclase phenocrysts 
are lath shaped and exhibit carlsbad, albite and peri- 
cline twinning. Some of the oligiclase crystals are 
clustered as though they began growth from a cen- 
tral point. They are clouded because of replacement 
by another mineral, probably zoisite. In addition 
the feldspars contain inclusion of sericite oriented 
parallel to the C-axis of the feldspar crystals as well 
as sericite alterations around the outer edges. The 
beta quartz phencrysts, though normally euhedral in 
outline, are in places much embayed and corroded. 



The quartz phenocrysts contain minute dust-like in- 
clusions of zircon, many of which are oriented paral- 
lel to the axes of the quartz crystals and exhibit 
simultaneous extinction with the quartz. Most of 
the quartz phenocrysts show reaction rims, are 
slightly corroded, and reabsorbed. Rare masses of 
emerald green chlorite, which might represent altera- 
tion of biotite, have been noted. 

Under the microscope the spherulites have usually 
been replaced by quartz. However, some consist of 
identifiable feldspars, whereas others are composed 
of fiberous radiating crystals which show undulatory 
extinction and a biaxial character. These might 
represent feldspar crystallites. The center of many 
of the spherulites is a mass of interlocked, sutured, 
unoriented quartz grains, indicating that the spheru- 
lites have been replaced by quartz from the inside 
outward (see pi. 2, No. 9). 

INTRUSIVE ROCKS 
Gabbro Sills 

A number of northeast trending gabbro sills have 
intruded the argillite and tuffaceous argillite units 
in the southern part of the quadrangle. They are 
greenish black in color, highly variable in grain size 
and usually contain large lath shaped dark green 
amphibole phenocrysts from 1/16 inch to 2 inches 
in length. The country rock in contact with the sills 
exhibit baked zones which are from 2 to 3 feet wide 
near minor sills and are tens of feet wide near larger 
instrusive bodies. These zones are not easily per- 
ceptible unless the rock is weathered ; then it turns 
to a distinctive dark brown. The larger sills appear 
to have domed the overlying country rock. This is 
especially true of the sill at Stony Mountain and 
the sill located due west of Albemarle at the western 
margin of the quadrangle. Some of the sills south- 
east of Porter near the south edge of the map con- 
tain amygdules, first noted by Bowman (1954) which 
indicate a near surface emplacement (see pi. 3, No. 
10). The sills located on the peninsula caused by 
the entrance of Mountain Creek into the Pee Dee 
River and along new Highway N. C. 27, have been 
intruded by mafic pegmatites consisting of horn- 
blende, 40 percent, and plagioclase 60 percent. Small 
basaltic dikes, thought to have originated from the 
sills, occur sparingly throughout the southeastern 
part of the quadrangle. 

In thin section the gabbro is porphyritic and ex- 
hibits ophitic texture. It mainly consist of amphi- 
bole, apparently hornblende, which in some instances 
makes up as much as 60 percent of the rock. The 



10 



amphibole is much embayed and might represent 
uralitization of pyroxene. Rare subhedral and eu- 
hedral feldspar laths are scattered throughout the 
rock. The feldspar phenocrysts are usually embay- 
ed and partly replaced by serpentine around their 
borders. They still show carlsbad and albite twin- 
ning and are near labadorite in composition. The 
feldspars have for the most part been altered to 
kaolinite, sericite, pinite, and zoisite. It was noted 
in one feldspar crystal that one set of the albite 
twins was replaced by zoisite, whereas the other set 
appeared to be relatively unaltered. Unless pleo- 
chroism were noted in plain light, this might easily 
go unnoticed. Occasional embayed crystals of il- 
menite, altered to leucoxene, were observed. Cubic 
crystals of pyrite are present. The matrix adjacent 
to the faces of the pyrite appeared to be altered and 
formed a halo around the crystal. The matrix of 
the rock is composed of calcite, fiberous serpentine 
and zoisite. 

Some of these rocks were evidently emplaced and 
then altered by late hydrothermal solutions. This is 
further indicated by the presence of mafic pegma- 
tites which occur within the sills, but not in the 
country rock. The original constiuents have been 
partially to completely altered to hornblende, ser- 
pentine, leucoxene, zoisite, kaolinite, and pinite. 

The gabbro sills have been observed intruding the 
Volcanic-Sedimentary sequence, but have not been 
observed intruding the Upper Volcanic sequence. 
This suggests that the gabbro might be of the same 
age as the Upper Volcanic sequence. In fact, they 
could represent feeders for the basaltic tuffs of the 
Upper Volcanic sequence. Such a hypothesis is fur- 
ther substantiated by the presence of amygdules in 
the gabbros, and the presence of occasional basaltic 
dikes in the vicinity of the gabbros. Although proof 
is lacking, it is possible that the gabbros might be 
extensions of the Charlotte igneous belt. 

Rhyolite Dikes 

Essentially vertical dipping rhyolite dikes, seldom 
over 10 feet in width, have been observed in the 
southeastern and south central parts of the quad- 
rangle. The dikes are medium grey in color and 
usually are more resistant to weathering than the 
surrounding country rock. They are dense, massive, 
well jointed, emit a metallic ring when struck with 
a hammer, and break with a conchoidal fracture. 
The dikes are rhyolite porphyrys containing mega- 
scopic lath shaped orthoclase and plagioclase feld- 
spar and beta quartz phenocrysts in an aphanitic 
groundmass. The plagioclases have a subhedral out- 



line and exhibit reaction rims in the form of sericite 
alteration along the contact with the matrix. The 
crystals are both pericline and albite twinned and are 
oligoclase in composition. The orthoclase feldspars 
are relatively rare, and appear as euhedral, usually 
untwinned crystals. The beta quartz phenocrysts 
are much embayed and enclose numerous minute zir- 
con phenocrysts ranging from dust sized particles 
up to about .02 millimeters in length. The matrix of 
the rhyolite is a meshwork of unoriented crypto- 
crystalline quartz, sericite, and kaolinite. 

About 2 miles southeast of Badin a large coarse 
grained prophyritic rhyolite dike has been traced 
from the spillway at Falls Dam along the north- 
eastern flank of Falls Mountain into the rhyolite 
unit of the Upper Volcanic sequence which caps the 
mountain. This rhyolite, as well as the other rhyo- 
lite dikes, resembles the rhyolite of the Upper Vol- 
canic sequence in hand specimen and thin section 
and has been mapped with the rhyolite of the Upper 
Volcanic sequence. It is thought that the rhyolite 
dikes probably represent feeders for the rhyolites 
of the Upper Volcanic sequence. 

Diabase Dikes 

Diabase dikes, considered to be of Triassic age, 
(Reinemund, 1955) have intruded rocks of the Caro- 
lina Slate Belt in the Albemarle quadrangle. The 
dikes are most prevalent along the eastern border of 
the quadrangle and are less so to the west. In gen- 
eral, they trend in a northwesterly direction although 
a few trend to the northeast. 

The diabases are greyish black when fresh and 
weather to a rusty brown color. They are extremely 
susceptible to spheroidail weathering. In many 
places all that could be observed in the field were 
dark brown clayey soils containing rusty spherical 
boulders of diabase. 

The diabase dikes range in thickness from 3 to 
10 feet, rarely exceeding more than 10 feet. They 
have produced exceptionally narrow baked zones 
and do not appear to have altered the surrounding 
country rock to any great extent. 

The dikes are fine grained with only a few min- 
erals exceeding a millimeter in length. In hand 
specimen the only minerals identifiable are the 
needle-like greenish black pyroxene and grey albite 
twinned plagioclase. In descending amount of oc- 
currence, the diabases are composed of lath shaped 
crystals of plagioclase corresponding closely to la- 
boradorite, lath shaped greenish brown augite, green 
hornblende, and occasional olivine and magnetite. 
The diabases exhibit diabasic texture with the py- 



11 



roxenes filling interstices between feldspar laths. 
The minerals making up the diabases occur as a 
meshwork in which no preferred orientation could 
be detected. 

CHEMICAL ANALYSES OF CAROLINA 
SLATE BELT ROCKS 



higher, and the K.,0 and JNa.,0 contents are lower 
than published data for similar rocks. Furthermore, 
the rocks which were originally thought to be com- 
posed predominantly of volcanic glasses — the weld- 
ed flow tuff, vitric tuff, and rhyolite — contain a dis- 
proportionately high SiO., in proportion to their low 
K.,0 content. 



Chemical analyses of selected samples of Caro- 
lina Slate Belt rocks were run by Mr. P. N. Sales, 
Chemist, N. C. State College, Minerals Research 
Laboratory, using standard silicate procedures. The 
results of these analyses are given below : 

TABLE I 
Major Constituents of Carolina Slate Belt Rocks 

* ** I g n . 

Si0 3 R2O3 FezOs CaO MgO Na-0 l< 2 Loss 



Frrphyriiic rhyoht; 
rhyolite unit. 



rhyolite unit. 



79.0 13.0 1.3 0.1 nil 1,55 2.70 0.60 
83.6 9.94 0.86 0.1 nil 1.19 2.29 0.35 



l. % .Mafic lithic-crystal tuff, 58.9 IS. 4 5.1 4.9 4.2 1.03 0.77 4.00 
Sc/3 basaltic tuff unit. 



3 Amygdaloidal basalt. 53. C 18.4 
basaltic tuff unit. 



7.0 5.9 1.88 0.25 



5.07 



Graywacke, 
Graywacke unit. 



>7.7 4.3 2.5 0.4 0.69 11.76 4.8 



a Felsic tuffaceous argil- 62.9 12. S 3.2 2.3 0.4 1.46 1.47 3.47 

"£ lite, tuffaceous argillite 

£ c unit. 

._ ° 

IS Mafic tuffaceous argil- 54.1 24.2 2.0 4.2 3.2 .30 1.47 6.80 

CO „ lite, tuffaceous argillite 

.2 ,? unit. 



Vitric tuff, 78.0 

tuffaceous argillite unit. 



Argillite 
Argillite unit. 



8.8 5.6 1.7 0.3 2.17 0.12 1.15 
68.9 16.5 7.2 1.5 2.8 1.40 1.5 3.8 



: Felsic tuff. 



73.1 15.1 2.5 2.5 0.3 2.04 0.55 1.07 






Gabbro .sill. 



11.1 15.5 5.0 8.9 16.3 0.60 0.10 5.61 



2§ 



•Predominantly AI2O3 but could contain amounts of Ti02, M11O, P2O5 
and other elements precipitated by NH*OH after silica dehydration. 
**Total iron content reported at Fe20 2 . 

A general comparison of the chemical composition 
of analyzed rocks of the Albemarle quadrangle with 
published rock analyses of the average composition 
of similar rocks (Pettijohn, 1957) indicates that the 
argillite approaches the composition of an average 
slate with the exception that the K-0 content is low. 
This had been previously noted by Laney (1910), 
Pogue (1910), Stuckey (1928), and Councill (1954). 
The graywacke is much lower in R_.0 : j and total iron 
than is average graywacke. 

The chemical analyses supported the field and 
petrographic classification used in this report. It 
is further noted that the SiO.. content is consistently 



Environment of Deposition 

The general lack of sorting and bedding in the 
felsic tuffs of the Lower Volcanic sequence (1ft) 
indicates that they were deposited under subaerial 
conditions. The interbedded welded flow tuff also 
indicates subaerial conditions, because it is unlikely 
that volcanic ejecta deposited in water could retain 
enough heat to weld and flow. The top of the unit 
is composed of bedded tuff and grades upward into 
the argillite unit, suggesting a change from subaerial 
to subaqueous deposition. 

The argillite unit (ar) was deposited below wave 
base in quiet water. This is indicated by the fine 
graded bedding which could only develop in rela- 
tively quiet water not subjected to wave action or 
strong currents. The source of the sediments of the 
argillite units is not known, but it contains thin 
basal conglomerate apparently derived from the 
Lower Volcanic sequence. If the Lower Volcanic 
sequence were exposed as a landmass, erosion of this 
landmass could have provided the sediments of the 
argillite unit. 

The contact between the argillite unit and the 
overlying tuffaceous argillite unit is locally grada- 
tional but may also be abrupt, which indicates an 
increased volcanic activity which rapidly overwhelm- 
ed the environment of deposition of the argillite 
unit and produced the tuffaceous argillite unit. The 
felsic tuffaceous argillite of the tuffaceous argillite 
unit probably originated as volcanic ash blown into 
the air, where it was sorted and carried by wind 
currents, after which it settled directly into a body 
of quiet water. This is indicated by the excellent 
sorting, coarse bedding and presence of wispy glass 
shards which could not have survived reworking. In 
addition the unit contains mafic and felsic crystal 
and lithic tuffs and flows which further attest to the 
volcanic nature of the rock. 

Two source areas for the tuffaceous argillite unit 
are indicated by the interbedded coarse pyroclastic 
rocks of the "Flatswamp Mountain sequence" which 
grade both vertically and laterally into tuffaceous 
argillite and die out to the south, and the vitric tuffs 
and associated coarser pyroclastics which also grade 
vertically into tuffaceous argillite and die out to the 



12 



north. These two groups of volcanic rocks suggest 
that there were two active sources during time of 
deposition of the tuffaceous argillite unit, one to the 
south and the other to the north of the quadrangle. 

The change in lithology from waterlaid tuff to 
graywacke sandstone (gr) indicates a change from 
volcanic to clastic sedimentation as well as a change 
from a predominantly felsic to a mafic source area. 
The source of the graywacke sediments was to the 
northeast as indicated by southwest dipping cross- 
bedding and decrease in particle size to the south- 
west. The presence of mafic crystal tuff (mt) and 
felsic lithic tuff (It) interbeds in the graywacke 
unit suggests that brief periods of volcanic activity 
occurred during sedimentation. The mafic tuffaceous 
argillite (mta) underlying and interbedded with 
the graywacke unit may be a fine grained equivalent 
of the graywacke. This is further indicated by the 
similarity of the chemical composition of these two 
rocks. 

The graywacke in the Albemarle quadrangle could 
be the product of turbidity currents and probably 
was deposited in marine water under reducing con- 
ditions. This is indicated by the presence of graded 
bedding and diagenetic pyrite cubes. Rapid erosion, 
transportation, and deposition is indicated by the 
presence of mineral and rock fragments in the de- 
posit. 

As the andesitic tuff (uat) only occurs in the area 
around New London, it probably originated from 
nearby fissures. The absence of recognizable water 
deposited material and poor bedding and sorting of 
the tuff suggests subaerial deposition. A flow rock 
found associated with the andesitic tuff unit did not 
contain pillow structures further indicating its sub- 
aerial deposition. 

The widespread occurrence of the basaltic tuffs 
unit (ubt), the variation in its composition, and the 
presence of isolated flows near its base suggest that 
the basaltic tuffs must have originated from a num- 
ber of vents. The absence of pillow structures in 
the interbedded flows, apparent absence of interbed- 
ded clastic sediments, and general poorly defined 
stratification suggests that the tuffs represent sub- 
aerial deposits. 

The rhyolite (ur) probably represents a subaerial 
series of coalescing flows originating from several 
vents which produced an almost sheet-like deposit 
in some parts of the quadrangle. The flows in the 
Morrow Mountain area were preceded by a deposi- 
tion of pyroclastic rocks which are now found at the 
base of the rhyolite unit in parts of this area. 



Structure 

Structurally the mapped area is characterized by 
the northeast trending folds and foliation (axial 
plane cleavage) . The larger of these folds have wave 
lengths on the order of 10 to 12 miles and plunges 
gently to the southwest; generally the axial plane 
cleavage dips steeply to the northwest. Although 
minor faults are common, no major faults have been 
mapped in the Albemarle quadrangle. Because of 
the great thickness of some of the stratigraphic 
units, faults of considerable displacement could exist 
and show little or no signs of their presence. 

Troy Anticlinorium 

The southeastern part of the Albemarle quad- 
rangle contains the nose of the southwest plunging 
Troy anticlinorium, the axis of which apparently 
passes northeastward close to Troy in Montgomery 
County. Reconnaissance in this area and more de- 
tailed work in Moore County indicates the develop- 
ment of an axial plane cleavage dipping to the north- 
west at approximately 60°, suggesting that the struc- 
ture is asymmetrical, with the axis inclined to the 
southeast. The Troy anticlinorium appears to be 
composed of a series of asymmetrical minor open 
folds. On the eastern flank of the anticlinorium the 
axial planes are inclined to the southeast. 

Exposed in the center of this structure is the 
Lower Volcanic sequence, the oldest rocks in the 
quadrangle. These rocks crop out from near the 
Pee Dee River in the west to central Moore County 
in the east to where they plunge under the argillite 
unit to the southwest, around the nose of the Troy 
anticlinorium. The rocks have been traced along 
the axis of the fold from the southeastern part of 
the Albemarle quadrangle northeastward to beyond 
Asheboro. As previously noted, a northeast trend- 
ing belt of felsic tuffs cropping out from the southern 
part of the Albemarle quadrangle northward to the 
Virginia state line is shown on the 1958 State Geo- 
logic Map of North Carolina. If this felsic tuff 
actually represents a belt of rocks of the Lower 
Volcanic sequence, then the Troy anticlinorium is 
one of the major structures of the Carolina Slate 
Belt. 

New London Synclinorium 

The New London synclinorium is a north 30° east 
trending fold, the axis of which passes approxi- 
mately 2i/o miles east of New London. It is slightly 
asymmetrical with the axial plane dipping to the 
southeast at 75°. The structure plunges to the 



13 



southwest causing the sedimentary units in the 
northwestern part of the quadrangle to wrap around 
its nose. The graywacke unit, the youngest strati- 
graphic unit below the Upper Volcanic sequence, is 
exposed in the center of the structure. The tuffa- 
ceous argillite unit wraps around the nose of the 
structure and is exposed along both its limbs. Down 
plunge the tuffaceous argillite unit has been warped 
into a series of minor folds having wave lengths on 
the order of 50 to 500 feet. The axis of these folds 
parallels the axis of the major structure. Axial 
planes of these minor folds converge upward, indi- 
cating that the major structure is a normal synclino- 
rium. Even with the development of minor folds on 
the major structure, overall dip remains in the direc- 
tion of the axis of the synclinorium. 

Angular Unconformity 

An angular unconformity separates rocks of the 
Upper Volcanic sequence from the underlying Vol- 
canic-Sedimentary sequence and Lower Volcanic 
sequence. The contact between the upper volcanic 
sequence and the underlying units is rarely observed 
because it is usually covered by soil and talus slump. 

The actual unconformable contact is best exposed 
in two places. The first is in Morrow Mountain Park 
where the road to the Ranger's office crosses Sugar- 
loaf Creek, here rhyolite is in contact with argillite. 
The other is on the east shore of Badin Lake approx- 
imately one mile north of Badin Dam, where basal 
conglomerate of the basaltic tuff unit is in contact 
with argillite of the argillite unit. 

Further indications of the unconformity are: 

1. From east to west, rocks of the Upper Volcanic 
sequence overlie and are in direct contact with the 
felsic tuff of the Lower Volcanic sequence and the 
argillite, tuffaceous argillite, and graywacke units of 
the Volcanic-Sedimentary sequence. 

2. Where bedding can be observed in both the 
Upper Volcanic sequence and underlying rocks, the 
Upper Volcanic sequence is essentially flat lying, 
whereas the underlying units dip at fairly steep 
angles. 

3. Rocks below the Upper Volcanic sequence have 
well developed bedding plane cleavage and incipient 
axial plane cleavage both of which are totally absent 
in rocks of the Upper Volcanic sequence. 

4. Rocks of the Upper Volcanic sequence occur as 
erosional remnants capping the highest hills through- 
out the area. They always occur on the hilltops and 
can not be traced across major drainage valleys. 



5. Hills, not capped by the Upper Volcanic se- 
quence, are formed by resistant interbeds which 
produce elongate northeast trending ridges parallel 
to regional structure. However, hills capped by the 
unconformable, flat lying, Upper Volcanic sequence 
are highly irregular in outline and do not exhibit a 
regional trend. 

6. In Morrow Mountain State Park the basal 
beds of the rhyolite unit of the Upper Volcanic se- 
quence, in most places, is composed of a lithic rhyo- 
lite tuff. The tuff beds can be traced completely 
around some of the monadnock-like hills. 

7. East of Badin the basaltic tuff unit, the basal 
beds of the Upper Volcanic sequence in this area, 
rests on the argillite unit of the Volcanic-Sedimen- 
tary sequence. In many places the basaltic tuff unit 
contains a basal conglomerate. Within this con- 
glomerate are pebbles, derived from the underlying 
argillite unit, which indicate the argillites were 
eroded before the basaltic tuffs were deposited. These 
conglomerates are a widespread recognizable hori- 
zon, occurring in the eastern, central, and western 
areas of outcropping basaltic tuff unit. The fact 
that the basal beds of both the rhyolite and basaltic 
tuff units can be traced over wide areas disproves 
any suggestion that these units are interbedded with 
the underlying Volcanic-Sedimentary sequence. 

8. Small discrepancies in elevation of some of 
the basal contacts of the Upper Volcanic sequence 
suggest that it was laid down on a mature, well- 
developed erosional surface having a relief less than 
present topography. In addition, it has been noted 
that these rocks have been slightly warped into gen- 
tle open folds. These folds are of a much less magni- 
tude of deformation than those developed in the 
underlying rocks. 

The time span represented by this unconformity 
represents a major break in Carolina Slate Belt 
time. This is the only unconformity recognized in 
mapping the Albemarle quadrangle. However, the 
possibility that a disconformity might exist between 
the basaltic tuff and rhyolite of the Upper Volcanic 
sequence is suggested by the fact that in the east 
central part of the quadrangle the rhyolites (ur) 
rest on the basaltic tuff (ubt) ; whereas, in the 
eastern part they rest directly on the argillites; (ar) 
and in the southeastern part of the area they rest 
on felsic tuffs of the Lower Volcanic sequence (1ft) . 
Whether or not the basaltic tuff unit was eroded 
away from the eastern and southeastern parts of the 
quadrangle or was not deposited in this area has not 



14 



been positively determined. Such an abrupt ending 
of the basaltic tuff unit to the east suggests that they 
were eroded away. 

Shear Zones 

Two northeast trending shear zones, developed in 
the argillite unit, have been noted in the northeast- 
ern part of the quadrangle. One of these occurs 
from north of the Coggins mine in the northeast to 
beyond Eldorado in the southwest. The second can 
be traced from Uwharrie southwestward to the Pee 
Dee River. When shearing parallels bedding plane 
cleavage, phyllites are developed, and when it is at 
an angle to bedding, slates are developed. Often- 
times these shear zones have been mineralized. They 
contain the lead and zinc mine at Eldorado, the Cof- 
gins gold mine, and a number of gold prospects. 

Jointing 

Two major joint systems are developed in the 
Albemarle quadrangle. One strikes from N. 45° to 
N. 60° E. and dips N.W. at 85° ; the other strikes 
approximately N. 60° W. and dips S.W. at 80°. Two 
minor joint systems are also noted. One strikes 
from N. 10° to 20° W. and dips from 80° to 86° S.E., 
and the other strikes N. 30° E. and dips from 78° 
to 85° N.W. 

Jointing is poorly developed in the argillite unit. 
These rocks were evidently plastic and bent rather 
than broke when regionally folded. With the excep- 
tion of the argillite, well developed jointing is pres- 
ent in all rocks of the quadrangle. It is probably 
best developed in the vitric tuffs of the Volcanic- 
Sedimentary sequence and the rhyolites of the Upper 
Volcanic sequence, both of which are dense, brittle 
rocks. 

Cleavage 

Bedding plane cleavage is locally well developed 
throughout the quadrangle. Outside of shear zones, 
shear cleavage is poorly developed. Axial plane 
cleavage is best developed in the argillite unit and 
locally appears to parallel northwest trending minor 
folds developed perpendicular to the axis of the New 
London synclinorium, along its eastern limb. It is 
faintly developed, but discernible, in the tuffaceous 
argillite and graywacke units and parallels the axis 
of the New London synclinorium. 

Metamorphism 

Metamorphism is of exceedingly low rank and 
would be classified as near the bottom of the green- 



schist facies. Recrystallization has usually affected 
only the groundmass and for the most part has not 
greatly altered the mineral crystals in porphyrys 
and crystal tuffs. The major changes have been the 
development of sericite, kaolinite and chlorite, as 
well as complete devitrification of the volcanic 
glasses. General absence of alignment of secondary 
minerals is caused by lack of development of axial 
plane cleavage. Reconnaissance indicates that meta- 
morphism and shearing increase markedly near the 
Charlotte Belt, west of the quadrangle ; and increase 
gradually toward the Deep River Triassic basin, 
east of the quadrangle. 

Geomorphology 

Stage of Development 

The area covered by the Albemarle quadrangle 
has reached a mature stage of development. Drain- 
age is well integrated and approaching grade. Hills 
have a generally rounded appearance and most of 
the stream valley are in a late youth or mature stage 
of development. Their valley walls have diminished 
slope from the steep walled V-shape of youth and a 
few have begun to develop floodplains. 

Drainage Pattern and Development 

Tributary streams which head and flow over areas 
underlain by rocks of the Upper Volcanic sequence 
have a generally random orientation, apparently 
because these rocks are essentially flat lying. In 
contrast, streams flowing over areas underlain by 
rocks stratigraphically below the Upper Volcanic 
sequence have developed a trellis pattern which is 
parallel with the northeast trending regional struc- 
ture. The stream valleys have developed in the least 
resistant rocks leaving more resistant rocks hold- 
ing up divides. 

Drainage, in general, has been highly modified by 
stream capture. The major diversion of drainage 
was the capture of the Yadkin River by the Rocky 
River, (located southwest of the Albemarle quad- 
rangle) . Both of these rivers flow across structures 
and are antecedent streams. The Pee Dee River is 
thought to have once been a northeast flowing tribu- 
tary to the Yadkin River. With the passage of time 
the Pee Dee eroded headward through the divide 
which separated the Rocky and Yadkin Rivers and 
diverted the Yadkin drainage into the Rocky River. 

Almost all the northwest-southeast flowing tribu- 
tary streams of the Yadkin and Pee Dee rivers have 
been offset by numerous, short, right angle captures. 
Several of the streams change direction of flowage 



15 




i 



16 



by this means a number of times before reaching 
the trunk stream. It is worth noting that tributaries 
flow into the trunk streams in either a northwest or 
southeast direction across structure, indicating that 
the trunk stream captured most of its tributaries. 
It is also interesting to note that both the Pee Dee 
and Uwharrie rivers flow in a southwesterly direc- 
tion parallel to major northeast trending structures. 
Whereas, the Yadkin River flows in a southeasterly 
direction across structure and in places has cut 
through northeast trending ridges composed of dif- 
ferentially resistant dipping strata. This has pro- 
duced several rather spectacular water gaps. 

Erosional Surfaces 

A number of topographic cross sections across the 
Albemarle quadrangle indicate the presence of 6 
erosional surfaces at elevations above present flood- 
plains (see Fig. 2). These levels are found at the 
approximate elevations of 800, 700, 600, 500, 450, 
and 400 feet. The best developed surface occurs at 
the 500 foot elevation. 

The upper two levels are primarily represented by 
hill tops. Surfaces below the upper two levels are 
represented by both rock terraces and hill tops. 

Most of the erosional surfaces are products of 
stream capture and readjustment to new base levels. 
On the basis of present evidence, it is difficult to 
determine whether uplift in this area was a gradual 
slow process or a series of pulsations. 

ECONOMIC GEOLOGY 

Gold 

Coggins Mine 

The Coggins mine is located in northwestern 
Montgomery County, 1.4 miles north-northeast of 
Eldorado. The ore zone is located in the argillite 
unit. The country rock has been sheared into slate 
with a pronounced axial plane cleavage which 
strikes N. 45° E. and dips N.W., at 70° to 
78°. The slate has been sericitized, chloritized, and 
silicified. This deposit is part of the mineralization 
which occurs along the shear zone which can be 
traced from the northern boundary of the quadran- 
gle southwestward through Eldorado. 

Some free gold occurs in the weathered zone, but 
with depth the ore is principally sulphides carrying 
gold. The ore is disseminated throughout quartz 
veins and adjacent country rock. Bryson (1936) 
stated that the mineralized zones are lenticular in 
outline and varied in width up to 50 or 60 feet. 



Nitze and Hanna (1896) stated that there appears 
to be two ore bodies. 

Bryson noted that the mine had been worked to a 
depth of 250 feet with drifts at the 50, 100, 200 and 
250 feet levels. The assays of the ore ranged from 
$1.00 to $6.77 per ton, but certain zones from the 
200 to 250 feet level gave values of approximately 
$20.00 per ton with some high grade samples run- 
ning as high as $53.00 per ton. He stated that the 
mine was partially dewatered in 1933-1934, but no 
further exploration was done. 

Morris Mountain Mine 

The Morris Mountain mine (incorrectly located 
on the geologic map) is located .6 of a mile due 
north of Eldorado, just a few hundred yards north- 
west of the Eldorado-Coggins mine road. A con- 
crete foundation of the mill, a trench, and a shaft 
are all that remain to indicate the existence of the 
mine. 

The country rock is the argillite unit. The mode 
of occurrence of the ore is similar to that of the 
Coggins mine. Nitze and Hanna (1896) reported 
that the gold is occasionally concentrated in the joint 
planes. They gave two assays as follows : 

Gold per ton ... $3.61 $82.68 

Silver per ton. .68 trace 



$4.29 $82.68 

Worth Placer Mine 

Nitze and Hanna (1896) discussed the Worth 
placer mine, located near the junction of the Uwhar- 
rie and Yadkin rivers. This mine could not be located 
during the present field investigation. 

Moratock(?) Mine 

Old mine workings, a few hundred yards north of 
highway N. C. 27 on the western edge of the Uwhar- 
rie Mountains, are thought to be the Moratock mine. 
Nitze and Hanna (1896) located this mine 8 miles 
south of Eldorado and stated that the country rock 
is a highly silicified quartz porphyry and brecciated 
tuff. 

The remnants of the old mine consist of two north- 
east trending caved open cuts approximately 200 
feet long, a caved shaft, and the foundation of a 
building, probably the mill. The country rock is a 
slightly sheared felsic lithic crystal tuff of the felsic 
tuff unit. Quartz veins, a few inches to 10 inches 
in width, are exposed in the open cuts. They strike 



17 



N. 50° E. and dip N.W. at 50". Nitze and Hanna 
stated that the gold occurred in the quartz veins. 
Some chalcopyrite, copper carbonate, and pyrite 
were noticed in the deposit. Nitze and Hanna re- 
ported that the pyrite assayed less than $1.00 gold 
per ton. 

A ten stamp mill equipped with a cyanide plant 
was erected on the property and operated until 1893. 
The failure of the venture was caused by ore of too 
low grade to be profitably worked. 

Parker Mine 

The Parker mine is located at the western city 
limits of New London. The deposit occurs in the 
andesitic tuff unit near the contact with the over- 
lying basaltic tuff unit. Nitze and Hanna (1936, 
page 83) stated, "numberless auriferous quartz 
stringer veins, from less than 1 to 18 inches in thick- 
ness, intersect the country rock in all directions. 
Besides these, several larger and more persistent 
veins occur. The quartz is imperfectly crystallized 
and often cellular. Weathering agencies have dis- 
tributed the gold through the decomposed rock 
(soil) to depths of 10 to 20 feet". The ore was 
richest in the vein quartz, $4.00 to $6.00 per ton at 
pre 1934 prices; however, the most profitable part 
of the operation was the placer mining of old gravel 
channels whose values ran from $.44 to $3.20 per 
yard. It is reported that over $200,000 in gold was 
produced from these gravels (Nitze and Wilkens, 
1897). 

The gold occurred as coarse nuggets, the largest 
found weighed 8 pounds 3 ounces and 2 dwts. Bryson 
(1936) reported that in 1935 a rich seam was en- 
countered which contained nuggets weighing from 

1 to 214 pounds each. 

The principal method of mining was hydraulick- 
ing the auriferous saprolite. However, Bryson 
(1936) stated that three shafts were sunk on the 
property; the "Ross shaft," 120 feet in depth; the 
"Crib shaft," 80 feet in depth; and another shaft, 
over 100 feet in depth. He reported that in 1935 
the North Carolina Mining Corporation assumed 
control of the property and drove a 250 feet tunnel 
into the hillside. At 150 feet a quartz vein was 
encountered, and a shaft about 15 feet in depth was 
sunk on the vein. From this shaft about 15 or 20 
pounds of large gold nuggets were removed. 

Cotton Patch Mine 

The Cotton Patch mine is located approximately 

2 miles east of New London. It has the same geo- 
logic setting as the Parker mine. The ore occurs as 



free gold in a quartz vein approximately 18 inches 
wide. The gold nuggets are coarse, usually crystal- 
line and range in size from 1/16 inch to over 14 inch 
across. The major work carried out prior to 1865, 
was confined to placer mining a small creek which 
drains the property to the south. In 1958 interest 
was renewed and a crosscutting trench was bulldozed 
on the property. Sufficient reserves were not dis- 
covered and the mine was abandoned until 1961, 
when it was reopened to the public for mineral speci- 
men collecting. 

Gold Mine, Name Unknown 

A gold mine consisting of a series of open cuts and 
prospect pits is located on the south side of Big 
Island Creek, approximately 0.1 mile east of the 
junction of Big Island Creek with the Pee Dee River. 
A number of quartz veins cross this area, and min- 
ing seems to have been confined to the quartz veins 
and adjacent saprolite. If shafts were put down 
they are not caved and unnoticeable. 

Dutchmans Creek and Island Creek Placer Mines 

Extensive dumps along the floodplains of both 
Dutchmans Creek and Island Creek attest to the 
fact that these areas were extensively placer mined. 
Nitze and Hanna (1896) stated that these and other 
mines along the western edge of the Uwharrie 
Mountains were profitably worked as long as the 
naturally concentrated material lasted and the prox- 
imity of water favored work. 

Lead and Zinc 

A mine located approximately 100 yards northeast 
of the village of Eldorado was supposedly worked 
for lead, zinc, and gold. This locality is thought by 
local residents to be the site of the Henderson mine. 
It consists of a shaft of unknown depth and a series 
of northeast trending prospect pits. Galena, spha- 
lerite and pyrite are prevalent on the dumps. The 
main shaft was dewatered in 1957, but mining was 
not activated. 

Quartz 

Milky white vein quartz, used as a facing for 
ornamental exterior blocks in building construction, 
is being mined from a large quartz vein located ap- 
proximately 0.8 mile northeast of Eldorado. Other 
large quartz veins which might be used for this 
purpose are: on the east bank of Richland Creek, 
on the hill west of White Crest Church ; west of the 
road to Uwharrie, between the junction of Woods 
Creek and Big Island Creek with the Pee Dee River ; 



18 



in the center of the village of Palmerville; and 
south of Halls Ferry Junction at the intersection of 
the Southern Railway spurline to Badin with the 
road connecting New London and Albemarle. These 
veins are variable in size throughout their exposure 
and a detailed investigation would be required be- 
fore any type of mining could be commenced. In 
the event that architectural demands for milky vein 
quartz continues at its present rate, these veins 
might be exploited. Also, the iron content of these 
veins might be low enough to meet the specifications 
for manufacture of optical glass and metallic silicon. 
The feasibility of using vein quartz for this purpose 
is highly questionable because of the prohibitive cost 
of mining. 

Crushed Stone 

The felsic lithic crystal tuff of the Lower Volcanic 
sequence was used in the construction of Highway 
N. C. 27 between the Pee Dee River and Troy. It 
is exceedingly hard and causes excessive wear on 
the jaw crushers, but was used because of its prox- 
imity to the road construction. 

Several state highway quarries have been and 
some are presently in operation in the felsic tuffa- 
ceous argillite of the tuffaceous argillite unit. These 
rocks are easily quarried, crushed, and meet state 
highway aggregate specifications. One disadvantage 
is that the rock forms splinters which readily punc- 
ture tires when used as road gravel without an 
asphalt bond. However, it is satisfactory when 
cemented with a bonding agent and rolled until the 
splinter pieces lie parallel to the surface of the road. 

Rhyolite of the Upper Volcanic sequence has not 
been quarried to any extent in the quadrangle, prob- 
ably because it is a massive, hard rock, difficult to 
quarry and crush. For these reasons it is doubtful 
if it would be preferred in highway construction. 
Still, a possible use for this material might be in the 
manufacture of fine aggregate for composition roof- 
ing shingles. 

Two rock types which have not been quarried or 
used for road aggregate in the Albemarle area are 
the basaltic tuffs of the Upper Volcanic sequence 
and gabbro sill-like bodies. Gabbro sills in the Albe- 
marle area are similar to that satisfactorily used 
in road construction in Randolph County and should 
make an excellent road material. A second use for 
these rocks might be ornamental stone as they take 
a good polish and resemble verde antique. One of 
the better quarry localities would probably be Stony 
Mountain, which is composed of a large mass of 
relatively unweathered gabbro. 



Flagstone 

Argillite which would apparently produce good 
flagstone occurs east of Blaine. This flagstone is on 
strike with that quarried by the Jacobs Creek Flag- 
stone Company at their Nor-Carla Bluestone quarry 
north of Albemarle quadrangle. The argillites at 
Blaine have a closely spaced nearly perfect bedding 
plane cleavage, widely spaced jointing, and axial 
plane cleavage is absent. For these reasons, it ap- 
pears that large masses could be easily quarried, 
and cleaved into structurally strong sheets varying 
in thickness from about '/•> to 1 inch. 

The argillites at the Nor-Carla quarry lie along 
the contact between the argillite and the tuffaceous 
argillite units. They appear to contain a small quan- 
tity of tuffaceous material, and on weathering take 
on a chalky appearance resembling the tuffaceous 
argillite. Because of this added tuffaceous material, 
the argillite at the Nor-Carla quarry is lighter color- 
ed, coarser bedded and upon metamorphism is more 
resistant to plastic flow, and development of in- 
cipient axial plane cleavage than are the argillites 
normally found in the argillite unit. As these rocks 
still contain graded bedding they are considered 
part of the argillite unit. 

The argillite, which makes flagstone, can be 
traced southward along strike to the north shore of 
Badin Lake. Further south in the area around 
Badin the rock becomes a felsic tuffaceous argillite, 
and contains too much coarse bedding to split into 
flagstone. 

A quarry in Morrow Mountain State Park has 
been opened in argillite. Stone from this quarry was 
used in constructing the rough flagging for the 
bridges and walls in the State Park. Fine bedding 
and incipient axial plane cleavage hampered split- 
ting of the stone in other than rough angular blocks. 

A quarry located on the west bank of the Uwharrie 
River south of Uwharrie was opened in a phyllite. 
The direction of shear was parallel to the bedding, 
causing the rock to split into thin fissile plates which 
might be used for roofing slate. Unfortunately, the 
rock contained a closely spaced joint system which 
substantially reduced the size of the material quar- 
ried and the venture was not a success. 

Brick Clay 

Yadkin Brick Yards, at Isenhour is the only brick 
plant in the Albemarle quadrangle. Their clay pit 
is located in graywacke (gr) saprolite. This sapro- 
lite ranging from 10 to 20 feet in depth and consists 
of particles ranging in size from sand to clay. Upon 



19 



firing, an excellent red brick is produced from this 
material. 

Stanly Shale Products, at Norwood, south of the 
quadrangle, produces brick from saprolite of the 
argillite unit (ar). The argillite unit is usually cov- 
ered with a thick mantle of saprolite, and numerous 
brick clay pits could be opened in this unit in the 
Albemarle quadrangle. 

Another possible source of brick clay is the sapro- 
lite of the felsic tuffaceous argillite (fta) of the 
tuffaceous argillite unit. This material might be 
used to manufacture buff burning brick and blended 
with other materials to produce lighter colored brick. 
Although no firing tests have been run, this saprolite 
appears to contain enough clay to give a bondable 
mixture. However, the tuffaceous argillites are not 
as susceptible to weathering as either the gray- 
wackes of the argillites and for this reason, reserves 
could be limited. 

Lightweight Aggregate 

The Southern Lightweight Aggregate Corporation 
at Aquadale, just south of the Albemarle quadrangle 
uses felsic tuffaceous argillite to make a lightweight 
aggregate. Lightweight aggreate is produced by 



heating this material until it reaches fusion tempera- 
ture and expands as gases are released from decom- 
position of certain minerals such as calcite and 
pyrite within the rock. Maximum expansion is 
achieved when fusion and emission of gasses occur 
simultaneously. The process of bloating is aided 
by the decomposition of certain quantities of cal- 
cium carbonate. However, an excess of calcium 
drops the fusion temperature below the temparature 
at which gases are released and produces a vitreous 
slag (Burnett, 1960). 

An excess of calcium carbonate could be a prob- 
lem in bloating the felsic tuffaceous argillite because 
calcite nodules and thin beds of calcite, ranging in 
thickness from 1 to 3 inches, locally occur within 
the tuffaceous argillite unit. Excess calcium car- 
bonate content could be controlled by selective min- 
ing. 

During field mapping it was noted that the calcite 
beds thinned to the northeast, along the eastern 
flank of the New London synclinorium and almost 
completely disappeared north of Albemarle. This 
suggests that felsic tuffaceous argillite not contain- 
ing an excess of calcium carbonate might be found 
in the area north of Albemarle. 



20 



BULLETIN 75 



PLATE 2 



»«ks«M 




Photomicrographs of Typical Volcanic Rocks 



22 



WELDED LITHIC CRYSTAL FLOW TUFF, felsic tuff unit, 
Diam. 2.5 mm., crossed nicols. Light colored lithic fragment 
and dark cloudy albite twinned feldspar crystals in a cropto- 
crystalline groundmass of quartz, sericite, and kaolinite. 



2. ARGILLITE exhibiting graded bedding, argillite unit. Diam. 
2.5 mm., crossed nicols. Graded bedding ranging in size from 
light colored coarse silt at the bottom to fine silt and clay at 
the top. The darker color of the fine grained portion of the 
bed is due to the increase in amount of chlorite in the matrix. 



FELSIC TUFFACEOUS ARGILLITE, tuffaceous argillite unit. 
Diam. 2.5 mm., crossed nicols. Devitrified glass shards, now 
altered to kaolinite, in a cryptocrystalline groundmass. 



5. GRAYWACKE, graywacke unit. Diam. 2.5 mm., crossed 
nicols. Sand sized grains of quartz, feldspar, and rock frag- 
ments in a fine grained chloritic matrix. 

6. ANDESITIC TUFF, andesitic tuff unit. Diam. 2.5 mm., cross- 
ed nicols. Dark colored, collapsed, scoriacerous fragment in 
a fine grained groundmass of volcanic debris. 

7. LITHIC FRAGMENTAL TUFF, basaltic tuffs unit. Diam. 2.5 
mm., plane polarized light. A large, lighter colored fragment 
composed of feldspar crystals in a fine grained groundmass 
completely surrounded by the rock matrix which is made up 
of broken feldspar crystals and chlorite. 

8. RHYOLITE, rhyolite unit. Diam. 2.5 mm., crossed nicols. 
Untwinned orthoclase and albite twinned plagioclase crystals 
in a devitrified cryptocrystalline groundmass. 



FELSIC CRYSTAL TUFF, tuffaceous argillite unit. Diam. 2.5 
mm., crossed nicols. Large broken feldspar laths in a matrix 
of fine crystals and other volcanic debris. 



9. SPHERULITE in rhyolite, rhyolite unit. Diam. 2.5 mm., cross- 
ed nicols. Note the fiberous masses of quartz which are re- 
placing the center of the spherulite. 



23 



BULLETIN 75 



PLATE 3 












24 



Photographs of Typical Rock Specimens 



1 . Welded crystal flow tuff, felsic tuff unit. 

2. Outcrop of argillite exhibiting graded bedding, argillite unit. 

3. Massive bed of felsic tuffaceous argillite sandwiched between 
two beds composed of wispy, flattened masses of devitrafied 
volcanic glass, tuffaceous argillite unit. 

4. Felsic crystal tuff which occurs interbedded with the felsic 
tuff, tuffaceous argillite unit. 

5. Vitric tuff of the type often interbedded with felsic tuff, 
tuffaceous argillite unit. 



6. Graywacke containing crude graded bedding, graywacke 
unit. 

7. Basaltic lithic tuff composed of dark green rock fragments 
in a lighter colored matrix, basaltic tuffs unit. 

8. Porphyritic rhyolite, rhyolite unit. 

9. Spherulitic rhyolite, rhyolite unit. 

10. Amygdaloidal gabbro from a gabbro sill. 



25 



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26 



STATE LIBRARY OF NORTH CAROLINA 




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