Geology and mineral resources of Moore County, North Carolina

              C /
North
, state Library
^
North Carolina
Department op Conservation and Development
Hargrove Bowles, Jr., Director
Division of Mineral Resources
Jasper L. Stuckey, State Geologist
Bulletin 76
Geology and Mineral Resources of Moore County,
North Carolina
By
James F. Conley
Raleigh
1962
North Carolina
Department of Conservation and Development
Hargrove Bowles, Jr., Director
Division of Mineral Resources
Jasper L. Stuckey, State Geologist
Bulletin 76
Geology and Mineral Resources of Moore County,
North Carolina
By
James F. Conley
Raleigh
1962
.
Members of the Board of Conservation and Development
Governor Terry Sanford, Chairman Raleigh
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 r Waynesville
Dr. John Dees I Burgaw
William P. Elliott, Sr Marion
E. Hervey Evans, Jr Laurinburg
E. R. Evans Ahoskie
E. D. Gaskins Monroe
Andrew Gennett Asheville
Luther W. Gurkin, Jr Plymouth
Woody R. Hampton , Sylva
Charles E. Hayworth , High Point
Gordon C. Hunter ___.__Roxboro
Roger P. Kavenagh, Jr ... Greensboro
Carl G. McGraw Charlotte
Lorimer W. Midgett Elizabeth City
Ernest E. Parker, Jr Southport
R. A. Pool .' Clinton
Eric W. Rodgers : Scotland Neck
Robert W. Scott Haw River
W. Eugene Simmons Tarboro
James A. Singleton Red Springs
J. Bernard Stein Fayetteville
Charles B. Wade, Jr Winston-Salem
11
Letter of Transmittal
Raleigh, North Carolina
May 2, 1962
To His Excellency, Honorable Terry Sanford
Governor of North Carolina
Sir:
I have the honor to submit herewith manuscript for publica-tion
as Bulletin 76, "Geology and Mineral Resources of Moore
County, North Carolina", by James F. Conley.
This report contains the results of detailed investigations of
the geology and mineral resources of Moore County and should
be of value to those interested in the geology and mineral re-sources
of Moore County and adjacent areas.
Respectfully submitted,
Hargrove Bowles, Jr.
Director
in
Contents
Page
Introduction 1
Location and area 1
Purpose and scope 1
Geography ^ 1
Culture 1
Climate 1
Physiography 2
Topography 2
Drainage 2
9>
Geology - 2
The Carolina Slate Belt 2
Stratigraphy 3
Lower volcanic sequence 4
Felsic tuffs and flows - 4
Mafic tuffs 4
Andesite tuffs 5
Volcanic-sedimentary sequence 6
Slates 6
Environment of deposition 6
Structure 7
Folds 7
Troy anticlinorium 7
Minor folds 7
Faults 7
Longitudinal faults 7
Glendon fault 7
Robbins fault 8
Other longitudinal faults 8
Cross faults 8
iv
Page
The Deep River Triassic Basin 8
Stratigraphy 9
Pekin formation 9
Cumnock formation 9
Sanford formation 10
Unnamed upper conglomerate 10
Triassic diabase 10
Environment of deposition 11
Structure 12
Folds 12
Faults 12
Border faults 12
Jonesboro fault 12
Western border fault 12
Cross faults 12
Longitudinal faults 13
The formation of the Deep River basin 13
The Coastal Plain 13
Stratigraphy :. .13
Upper Cretaceous Tuscaloosa formation 13
Lower member 14
Upper member : 15
Environment of deposition 16
Tertiary Pinehurst formation 18
Stratigraphy 18
Environment of deposition 19
Structure 19
Other Deposits . 20
Terrace gravel 20
Alluvium 20
Economic Geology 20
Pyrophyllite 20
Pyrophyllite mines and prospects 20
McConnell prospect 21
Jackson prospect 21
v
Page
Bates mine 21
Phillips and Womble mine 21
White mine : 21
Jones prospect 21
Currie prospect 21
Standard Mineral Company mine 21
Dry Creek mine 22
Ruff mine ' 22
Hallison prospect 22
Sanders prospect 22
Origin of pyrophyllite —
:
22
Rock types 23
Faults . . 23
Outline of pyrophyllite bodies 23
Mineralogy 23
Zoning 23
Discussions and conclusions 24
Gold -24
Mode of occurrence 24
Gold mines 24
Clegg mine 24
Wright mine 24
Cagle mine 25
Red Hill mine : 25
Allen mine 25
Burns mine 25
Brown mine : 25
Shields mine 25
California mine _ 25
Dry Hollow placer mine 26
Jenkins mine : 26
Richardson mine 26
Monroe mine 26
Bell mine . 26
Ritter mine 26
Donaldson mine , 26
vi
Page
Copper 27
Coal i 27
Quality and reserves .1 27
Coal mines 27
Murchison mine _- 27
Garner mine 27
Black shale and black band 28
Stone 28
Sand and gravel 28
Pinehurst formation 28
Terrace gravel 28
Upper member of Tuscaloosa formation 28
Triassic gravel 28
High silica quartz : 29
Vein quartz :
-29
Unconsolidated quartz sands and gravels 29
Clay . 29
Residual kaolin in the Carolina Slate Belt 29
McEnnis pit 29
William pit 30
McDuffy pit 30
Other clay in the Carolina Slate Belt 30
Pottery clay 30
Hancock pit 30
Cagle mine clay 30
Sedimentary clay in the Deep River basin 30
Sedimentary kaolin in upper member of the Tuscaloosa
formation 31
Acknowledgements 31
References cited 38
vn
Illustrations
Plates
Plate 1. Geologic Map of Moore County in pocket
Plate 2. Geologic Map of Pyrophyllite Deposits, Glendon in pocket
Plate 3. Geologic Map, Standard Mineral Company Pyrophyllite
mine, Robbins in pocket
Plate 4. White Pyrophyllite Mine, Glendon in pocket
Plate 5. Geologic Map of Dry Creek Pyrophyllite mine in pocket
Plate 6. Photomicrographs of Typical Volcanic Rocks page 32
Plate 7. Photographs of Typical Rock outcrops page 34
Plate 8. Photographs of Typical Rock outcrops page 36
vin
GEOLOGY AND MINERAL RESOURCES OF MOORE COUNTY,
NORTH CAROLINA
By
James F. Conley
INTRODUCTION
Location and Area
Moore County is located in the south central part
of North Carolina, between 35 degrees 04 minutes
and 35 degrees 31 minutes north latitude and 79
degrees 12 minutes and 79 degrees 46 minutes west
longitude. The county is irregular in outline with
much of its boundary following streams and other
natural features. It is bounded on the north by
Randolph and Chatham counties ; on the east by Lee,
Harnett, and Cumberland counties ; and on the west
by Richmond and Montgomery counties. Scotland
County lies immediately to the south, but has a
common boundary at only one point. Moore County
contains about 862 square miles and ranks 18th in
size among the 100 counties of the State.
Purpose and Scope
A geologic mapping program was initiated in
Moore County, North Carolina in the fall of 1959
by the North Carolina Division of Mineral Resources.
The purpose of this research program was : (1) map
the geology in as much detail as time permitted;
(2) locate both the active and abandoned mines,
study their economic possibilities, mode of origin
and relationship to the regional structure; and (3)
attempt to locate new mineral deposits which might
be of economic value.
Only the southern half of ,the county is covered
by topographic maps. Therefore, a base map for
the northern half was prepared from aerial photo-graphs
at a scale of one inch equals one mile. The
geology was plotted directly on contact prints and
transferred to the base map.
In the area underlain by rocks of the Carolina
Slate Belt, outcrops vary from poor to non-existant
and in several instances saprolite and soils had to
be relied on to deduce the underlying rock type.
Outcrops in the Coastal Plain are better exposed,
except in a few instances where drainage is poorly
developed. The northern part of the Triassic Deep
River basin was mapped by John A. Rinemund
(1955) during the period 1946-1949. Portions of
his map are reproduced as part of the geologic map
accompanying this report, with only minor changes.
GEOGRAPHY
Culture
Moore County was established on July 4, 1784,
from land which originally comprised part of west-ern
Cumberland County. An additional tract bound-ed
by James Creek, Little River, Hector Creek, and
the Harnett County line was transferred from Hoke
County in 1959. The county was named in honor of
Alfred Moore, a military colonel in the American
Revolution. Carthage, located near the center of the
county, was established as county seat in 1803 and
has served in that capacity since. Other principal
towns include Aberdeen, Pinehurst, Robbins and
Southern Pines.
The county is served by three railroads. The Sea-board
Air Line Railroad passes through the towns
of Cameron, Vass, Southern Pines, Aberdeen and
Pinebluff and is the main north-south route. The
Norfolk Southern Railway has two east-west lines
which serve the area. One crosses the northern
part of the county passing through Glendon and
Robbins, and the other, located in the southern part,
passes through Aberdeen, Pinehurst and West End.
From Aberdeen, southward, the area is served by
the Rockfish and Aberdeen Railroad. A network of
federal, state and county roads provide easy access
to all parts of the county. In addition, regularly
scheduled airlines operate out of Knollwood Airport,
located a few miles north of Southern Pines.
Moore County has a well balanced economy and a
great variety of income-producing resources. Among
the major of these are agriculture, mining, recrea-tion,
and retail and wholesale trades.
Climate
Moore County is noted for its hot summers and
mild winters, which make it a "mecca" for winter
golfing and equestrian sports. The mean annual
temperature is 61.1° F. The summer temperature
averages 73.2° F; the winter temperature raverages
L
50.2° F. The average precipitation is 44.61 inches,
most of which occurs in the spring and early sum-mer
(U. S. Weather Bureau, 1961).
Physiography
Moore County contains parts of two of the major
physiographic provinces of the United States. The
northern two-fifths of the county lies within the
Piedmont Plateau province, locally referred to as
the "clay country", whereas the southern three-fifths
of the area is in the Sandhills subdivision of
the Atlantic Coastal Plain province.
In the area where the softer unconsolidated ma-terials
of the Coastal Plain come in contact with the
more resistant rocks of the Piedmont, there is a
relatively narrow transition zone which in other
places is marked by an abrupt change in relief. This
contact is referred to as the Fall Line or Fall Zone.
The Fall Zone occurs in Moore County as an uneven
contact from near White Hill at the northeastern
boundary westward through Carthage to a point on
the western boundary about two miles north of
Highway N. C. 211. In contrast to other areas, the
Fall Zone in Moore County is a conspicuous topo-graphic
ridge which forms a drainage divide be-tween
northeast and southeast flowing streams.
A third physiographic subdivision is the Triassic
basin which lies in a northeast-southwest direction
across the county. This depression or trough is
about 10 miles wide and is tarecable from the north-east
corner of the county southeastward to Harris,
where it is covered by the sediments of the Coastal
Plain. Even where covered by the Coastal Plain,
the area underlain by Triassic sediments is lower
than the surrounding countryside. The Triassic
basin contains relatively soft sedimentary rocks
which are much less resistant to erosion and have
been removed at a more rapid rate than the crystal-line
rocks of the uplands to the west.
Topography
Moore County is an area of contrasting topography.
The uplands, underlain by crystalline rocks range in
elevation from 600 feet above sea level in the north-western
part of the county to only 300 feet in the
northeastern part. Topography is typical of the
Piedmont with rounded hills and V-shaped valleys.
The hilltops rise from 75 to 100 feet above the
valley floors, with a few rising as high as 150 feet.
The Triassic basin ranges in elevation from 250
to 500 feet. The eastern and western rims of the
Triassic basin lie as much as 250 feet above its
floor and form prominent escarpments. From the
escarpments the land slopes rapidly to the basin
floor. Northeast trending ridges of low relief occur
in the basin. These usually do not rise more than
75 feet above the valleys. Valleys in the Triassic
basin are wider than in the uplands and some con-tain
floodplain deposits.
The average elevation of the Coastal Plain is
about 400 feet; however, it ranges from 500 feet
along its northern limits to less than 190 feet in
river valleys at the extreme eastern tip of the county.
The Coastal Plain is sculptured into alternating
flat-topped ridges with convex sides that rise as
much as 150 feet above broad, flat valleys filled with
floodplain deposits. This topography is typical of
the Sandhills region. Relief is considerably greater
than found in the Coastal Plain outside of the Sand-hills.
Drainage
Moore County is drained by three major streams;
Deep River, Little River, and Drowning Creek.
Deep River enters the county along its north-central
border and flows in a semicircle leaving the county
at its northeastern corner. It drains almost all of
the northern half of the area and has several major
tributaries, including Bear Creek, Buffalo Creek,
Falls Creek, McLendons Creek and Governors Creek.
Little River heads up in central Moore County
and flows eastward draining the central and east-central
part of the area. Its main tributaries are
Crane Creek, James Creek and Nicks Creek.
The southwestern and southern boundary of the
county is formed by Drowning Creek, which also
drains this area. Its major tributaries are Jackson
Creek, Horse Creek, and Aberdeen Creek.
GEOLOGY
The Carolina Slate Belt
The northwestern part of Moore County is under-lain
by low-grade metamorphic rocks of volcanic
and sedimentary origin. The area in which these
rocks crop out is known as the Carolina Slate Belt.
The name Carolina Slate Belt was first applied by
Nitze and Hanna in 1896. This name is a misnomer
and should be replaced because the predominant
rocks are not slates, and they do not form a belt.
West of Moore County they are dominantly argil-lites,
but in the county they are mostly phyllites
with some slates. Although the outcrop area ap-pears
as a belt, it is now known that these rocks
extend under the Coastal Plain for a considerable
distance. This is indicated by oil-test wells drilled
in Bladen and Pender Counties, which bottomed in
these rocks.
In 1822 Olmstead described novaculite, slate,
hornstone, and talc from areas now known to be
underlain 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 or argillite porphyry, soapstone, serpentine,
greenstone and whetstone. Eaton (1820) in a re-port
on gold in North Carolina, added "talcose
slates" to the list of rocks occurring in the belt. He
stated that they occur in association with novacu-lite.
Ebenezer Emmons (1856) probably one of the
most competent geologists of his time, placed these
rocks in his Taconic system which he divided into an
upper and a lower member. He considered these
rocks amongst the oldest in this county. The upper
member consisted of clay slates, chloritic sandstones,
cherty beds, flagstones, and brecciated conglom-erates.
The lower member consisted of talcose
slates, white and brown quartzites and (on his cross
section, Plate 14, he added) conglomerate.
Emmons, not recognizing volcanic rocks in his
series, considered them water-laid sediments. The
divisions of his system into an upper and a lower
member is used, with modifications, in this report.
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. Becker (1895) publish-ed
a paper recognizing the presence of volcanic
rocks in the sequence and proposed that they were
Algoncian age.
Nitze and Hanna (1896) recognized volcanic -
rocks interbedded with the slates that they proposed
were laid down during times of volcanic outbursts,
followed by inactivity during which time slates were
deposited. They noted that some of the rocks had
true slaty cleavage, whereas others were truly schis-tose.
They believed these rocks were altered by
dynamo-and-hydro-metamorphism.
Weed and Watson (1906) studied the Virgilina
copper deposits and proposed that the country rocks
were metamorphosed andesites. The age was thought
to be Precambrian.
Laney (1910) described the Gold Hill Mining
District of North Carolina. In this report he divid-ed
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 that the slates,
in part, were derived from volcanic material. 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.
He proposed that a major fault, the Gold Hill fault,
separated the igneous rocks to the west from the
slates. Pogue (1910) described the Cid Mining
District, and Laney (1917) described the Virgilina
Mining District. Interpretations in these reports
are, in general, repetitions of ideas as expressed in
Laney's report of 1910.
Stuckey (1928) presented a report which included
a geologic map of the Deep River Region of Moore
County. He divided these rocks into slates, acid
tuffs, rhyolites, volcanic breccias, and andesite flows
and tuffs. He noted that the schistosity dipped to
the northwest and interpreted the structure as close-ly
compressed synclinorium with the axes of the
folds parallel to the strike of the formations. He
stated (p. 23) "The minor folds dip steeply to the
northwest side of the troughs and flatten out to the
east. The synclinal troughs pitch and flatten out in
places as is indicated by the way the slate bands,
which are all synclinal in structure, occur in long
narrow lenses often pinching out. This pinching
and flattening indicates some cross folding". He
noted the slates seem to have consolidated readily
and to have folded as normal sediments; whereas,
the tuffs and breccias remained in a state of -open
texture and tended to mash and shear instead of
folding. He stated that there is little evidence for
faulting, although minor displacements amounting
to a few inches were noted. Stuckey, from a com-parison
of his investigation with work by Laney and
Pogue, concluded that the rocks of the whole slate
belt are of the same general types. He noted that
metamorphism is not uniform throughout the area.
Theismeyer and Storm (1938) studied slates near
Chapel Hill that showed fine-graded bedding, and
proposed that they represented seasonal banding.
Theismeyer (1939) proposed that similar sediments
found in Faquier County, Virginia, were deposited
in pro-glacial lakes during late Precambrian and
early Cambrian times. The bedding is thought to
be seasonal "varves". In addition he proposed that
"the Hiwassee 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".
Stratigraphy
The rocks of the Carolina Slate Belt have been
divided, by Conley (1959) and Stromquist and Con-ley
(1959) in the areas covered by the Albemarle
and Denton 15-minute quadrangles, into a lower
unit composed of volcanic rocks, a middle unit com-posed
of volcanic and sedimentary rocks, and an
upper unit of volcanic rocks which unconformably
overlies the two lower units. In Moore County only
the lower and middle units appear to be present;
however, some rhyolites in the area might belong
to the upper unit. The exact stratigraphic relation-ships
of some of the rocks in the county are in doubt
because of the gradational nature of the contacts, a
condition further complicated by intense folding and
faulting and lack of outcrops.
Lower Volcanic Sequence
Felsic Tuffs and Flows : Rocks of the Lower Vol-canic
sequence are the oldest rocks exposed in the
county. This unit on the order of 3500 feet thick,
is composed predominately of fine, usually sheared,
felsic crystal tuffs. The tuffs vary in color from
white or light cream to light grey. They weather
white and sometimes white weathering rinds are ob-served
on fresh rock. Topsoil developed on these
rocks is a cream-colored silty loam; the subsoil is a
white clay loam. The rocks are usually massive.
However, in a small area on Mill Creek west of
West Philadelphia, they contain obscure bedding
planes.
In thin section the tuffs are composed of quartz,
orthoclase, and plagioclase, probably albite in com-position,
in a fine groundmass of what appears to be
cryptocrystalline quartz accompanied by sericite and
kaolinite. Feldspars appear as clouded, angular
lath-shaped fragments partly replaced by sericite.
The sheared appearance is much more apparent in
thin section than in hand specimen. The quartz
grains are crushed and drawn out in the direction
of shearing. The groundmass has a banded appear-ance
resulting from segregation of kaolinite and
sericite along planes of shear.
Interbedded with the felsic crystal tuffs are felsic
lithic-crystal tuffs, rhyolites, and mafic crystal tuffs.
The contact between the felsic crystal tuffs and the
felsic lithic-crystal tuffs usually is gradational with
well defined contacts being the exception. The lithic-crystal
tuffs have the same matrix composition as
the crystal tuffs, but in addition contain grey por-phyritic,
rhyolite fragments which range from one
eighth of an inch to more than six inches in diameter.
These fragments range from well rounded to highly
angular masses ; others appear to be flattened. The
groundmass is now composed of cryptocrystalline
quartz, sericite and kaolinite. The phenocrysts con-sist
of quartz and lath-shaped orthoclase and pla-gioclase
feldspars, the latter varying in composition
from albite to oligoclase. Some of the tuffs are
welded and exhibit flow lines. They could easily
be mistaken for rhyolites if it were not for the pres-ence
of lithic fragments. The flow lines usually are
well defined in thin section due to the development
of sericite along the flow structures.
The rhyolites occur in small outcrops in the ex-treme
northwestern corner of the county near West
Philadelphia and on the hill above the Dry Creek
pyrophyllite mine. Rhyolites are difficuilt to differ-entiate
from flow tuffs, even in unmetamorphosed
rocks, and these may be flow tuffs. They are classi-fied
as rhyolites on the basis of swirl flow banding,
euhedral feldspar phenocrysts, and the absence of
either broken crystal of lithic fragments.
The rhyolites are porphyritic, containing visible
feldspars up to one-sixteenth of an inch in length.
They are light grey in color, weathering to chalky
white on the surface. They are exceedingly dense,
emitting a metallic ring when struck with a hammer.
This rock usually is not sheared even when tuffs on
either side of some outcrops have suffered consid-erable
shearing. They contain prominent swirl-banded
flow lines which are accentuated by weather-ing.
Because of their resistance to weathering the
rhyolites form elongate hills. Soils developed on
the rhyolite are extremely shallow, ranging from
12 to 15 inches in thickness.
In thin section, the rhyolites are composed of ag-gregates
of unoriented, interlocking, angular, quartz
grains; untwinned orthoclase; and albite and carls-bad
twinned oligoclase. The groundmass is exceed-ingly
fine and can not be resolved to individual crys-tals,
but appears to be an interlocking network of
cryptocrystalline quartz, sericite and kaolinite.
Mafic Tuffs: The mafic tuffs shown on the geo-logic
map (Plate 1) are not limited to any one rock
sequence, but are found interbedded with the felsic
tuffs, and andesitic tuffs of the Lower Volcanic
sequence as well as slates of the overlying Volcanic-
Sedimentary sequence. However, mafic tuffs are
more frequently associated with the andesitic tuffs.
Evidently, outburst of mafic ejecta occurred over a
considerable span of geologic time. Because of the
lithologic similarity of the mafic tuffs they are all
shown, for convenience, as the same color on the
map.
These rocks in general are andesitic in composi-tion,
but contain some material that might be classi-fied
as basalt. They are composed of lithic frag-ments
ranging from one-sixteenth of an inch up to
eighteen inches in diameter, and crystal fragments,
ranging from microscopic up to one fourth of an
inch in diameter. From place to place, the ratio of
crystals to lithic fragments is exceedingly variable,
as is the size of the elastics making up the rock.
The tuffs usually are sheared. They have a grey-ish-
green or olive-green color when fresh, becoming
dun-brown on weathering from the oxidation of
their iron. Topsoils developed on these rocks are
tan-colored silty loams; the subsoils are usually
dark-brown to chocolate-brown colored heavy clay
loams.
In thin section the matrix of the rock appears to
be made up almost entirely of chlorite bands strung
out parallel to shearing. Feldspars have been alter-ed
to sericite and kaolinite. In highly sheared
rocks, phenocrysts have, been rolled parallel to schis-tosity
and have an augen-like appearance. One thin
section contained quartz masses that appear to be
crushed, unoriented, and strung out parallel to
schistosity. These quartz masses might be second-ary
fillings of vessicles.
The lithic fragments appear to be of different
composition than the matrix of the rock. Some
specimens are composed of a mesh of lath-shaped
feldspar crystals about 0.02 of a millimeter in length
with chlorite filling the interstices. Augite, not al-tered
to chlorite, is present in rare isolated frag-ments.
The groundmass of some of the fragments
is composed of sericite and kaolinite rather than
chlorite.
In general, the rock is not bedded. However, in
the area north of High Falls the mafic tuffs contain
numerous interbeds of graywacke. These interbeds
range from a few tens of feet to more than over a
hundred feet in thickness. The graywacke is green-ish-
grey when fresh, becoming light-brown on
weathering. It is composed of quartz, feldspar, rock
fragments, and a small quantity of argillaceous ma-terial.
The rock exhibits graded bedding consisting
of coarse sand, rock fragments up to two centimeters
across, and intermixed fine sand at the base, which
grades upward into fine sand at the top of the bed.
The rock fragments, so prominent in hand specimen,
are reduced in thin section to aggregate of kaolinite,
chlorite and sericite. This suggests that the frag-ments
are completely altered and are only recogniz-able
in hand specimen by the preservation of relic
structures.
Andesite Tuffs : The andesite tuffs are about 2500
feet thick and are composed of interbedded crystal
tuffs, lithic-crystal tuffs, argillaceous lithic conglom-erates,
argillaceous beds and questionable flows.
These tuffs are highly susceptible to shearing and
usually exhibit axial plane cleavage. Many of them
are sheared and pass into phyllites in which primary
fragments are flattened and elongated in the direc-tion
of movement. The andesite tuffs have a dis-tinctive
greyish-purple color when fresh, and on
weathering become a lighter purple. This coloring
is due to primary hematite in the rock. Topsoil de-veloped
on the andesite tuffs is a dark, red-clay loam
and the subsoil is a dark-maroon to maroonish-pur-ple
colored heavy plastic clay. ,
Crystal fragments in the more tuffaceous phases
rarely exceed 40 percent of the composition of the
rock. They consist almost entirely of lath-shaped
feldspar fragments and rare euhedral crystals, rang-ing
in length from microscopic to three millimeters.
The feldspars are highly sericitized and are both
carlsbad and albite twinned. Gross composition is ap-proximately
that of andesine. In addition to feld-spar,
lath-shaped masses of chlorite are also present.
This chlorite probably represents altered amphibole
and pyroxene. Quartz is rare in the crystal tuffs;
however, one questionable flow tuff consisted of 30
percent of almost spherical quartz grains ranging
up to two millimeters across. This is probably sec-ondary
quartz filling vessicles. The interstices are
filled with hematite which obliterates the ground-mass.
Lithic-crystal tuffs are readily differentiated from
argillaceous lithic conglomerate. The fragments
are angular and the matrix contains crystal frag-ments
in the lithic tuffs ; whereas, the fragments are
rounded and the matrix is argillaceous in the lithic
conglomerates. The rock fragments in both the tuffs
and conglomerates are similar in composition. They
rarely exceed two inches in diameter in the conglom-erates,
but range up to ten inches across in the tuffs.
Megoscopically these fragments are of two types.
One is a massive aphanite, and the other is a crystal
flow rock. Microscopically the aphanite fragments
consist almost entirely of sericite and hematite; the
flow-rock fragments appear as an aggregate of
unoriented feldspar laths averaging about 0.02 of a
millimeter in length in a matrix of hematite. Aside
from flow lines and crystals, the original composi-tion
and texture of the flow rock fragments are
masked by hematite.
The groundmass of the tuffs is so fine grained that
it can not be resolved under the microscope. It
appears to be composed predominately of elongate
masses of opaque hematite, sericite, chlorite, and
kaolinite. Epidote occurs sparingly in some thin
sections. The matrix of the argillaceous rocks is
even finer grained and also is obscured by hematite.
Near the top of the stratigraphic section the ande-site
tuffs become more argillaceous and bedding is
observed more frequently. As the contact with the
overlying slates is approached, graded bedding, so
common in the slates, begins to predominate.
Volcanic-Sedimentary Sequence
Slates : The slates are about 6,000 feet thick and
form the basal unit of the Volcanic-Sedimentary se-quence?
They attain the greatest elevation of any
stratigraphic unit found in Moore County? There
is no sharp contact between this rock and the under-lying
andesitic tuffs, but there is a gradational strati-graphic
change from tuff to slate. Fine graded bed-ding,
resembling varved bedding, is a characteristic
of the slates. The bedding planes vary from one-sixteenth
to one-fourth of an inch in thickness. Axial
plane cleavage usually is more pronounced than bed-ding.
The fresh slate is dark grey in color and
weathers to ocherous reds and yellows. Topsoils are
usually light brown-colored silts; whereas, subsoils
are light red silty loams.
In thin section graded bedding is easily observed.
It consists of a silt layer at the bottom which grades
upward into clay layer. The silt sized particles pre-dominately
consist of quartz grains as well as some
feldspar and what were probably ferromagnesian
minerals, now chloritized. The clay layers are now
predominately sericite. The slates outcropping in
the eastern part of the county, along the western
contact with the Triassic basin, contain interbeds of
graywacke sandstone, which in places make up as
much as fifty percent of the rock. These graywackes
have a different composition and texture than those
interbedded with the mafic tuffs. They are greyish-green
when fresh and weather light maroon. They
usually appear to be massively bedded; however,
closer inspection reveals thin bedding planes and
graded bedding ranging in size from sand at the bot-tom
to silt at the top. The rock is composed of equal
parts of chloritized rock fragments and quartz with
occasional grains of albite-twinned sericitized feld-spar
which ranges in composition from oligoclase to
andesine. The rock varies in composition from the
base to the top of the graded beds. The matrix fill-ing
the interstices between the sandgrains in the
lower parts of the beds consist of about equal parts
sericite and kaolinite with a trace of chlorite. As
the beds become finer grained toward the top, chlo-rite
increases until the upper silt fraction of the
bedding is composed of approximately sixty percent
chlorite, fifteen percent sericite, fifteen percent kao-linite
and ten percent quartz.
Environment of Deposition
The Lower Volcanic sequence is thought to be vol-canic
ejecta deposited on land. This is indicated by
6
the general angularity of lithic and crystal frag-ments
and the general lack of sorting in the sedi-ments.
Pillow structures, which only form in subaqueous
flows, are not present in the interbedded rhyolites,
even though flow lines are well preserved. If pillow
structures had developed, they should be as well pre-served
as the flow lines.
The presence of welded flow tuffs also suggest
subaerial deposition because it is unlikely these rocks
could have retained enough heat to flow and weld
if they were deposited in water. The tuffs on Mill
Creek contain bedding and might be water laid.
However, air laid tuffs often contain bedding and
are deposited in water. The presence of graywacke
interbeds in the mafic tuffs suggest an aqueous en-vironment
and turbidity currents. These gray-wackes
were probably, for the most part, derived
from reworking of the mafic tuffs. The coarse mafic-lithic
breccias and mafic crystal tuffs, so commonly
interbedded with the andesitic tuffs, were evidently
blown out of volcanoes and deposited directly in
water without reworking.
The numerous rounded lithic fragments, bedding
planes, and fissle graded bedding suggest that the
andesite tuffs were water laid. The presence of
inter-bedded lithic-crystal tuffs and argillaceous
lithic conglomerates of essentially the same chemical
composition suggests that these rocks were derived
from the same source. One probably represents vol-canic
ejecta deposited directly in water without re-working,
and the other a reworked sediment.
The gradual increase in graded bedding toward
the contact with the overlying slates suggest a
change in environment from shallow to deep water.
The andesite tuffs are thought to represent a transi-tion
unit and a transition environment between the
terrestial tuffs and flows of the Lower Volcanic
sequence and the deep-water sediments of the over-lying
Volcanic-Sedimentary sequence.
The slates were deposited in quiet water, below
wave base. This is indicated by the fine graded
bedding which could only develop in quiet waters.
The mechanism which produces fine graded bed-ding
is not thoroughly understood. Theismeyer
(1939) proposed that the slates were varved sedi-ments
deposited in pro-glacial lakes during late Pre-cambrian
or early Cambrian times. No glacial de-posits
have been identified in the rocks of the Caro-lina
Slate Belt and this theory is not acceptable.
It has been suggested that varve-like graded bed-ding
can only occur in water of low salinity because
of flocculation. This is indicated by Fraser's (1929)
experimental studies which showed the maximum
salinity permitting the formation of varves of coarse
clay to be about one fiftieth that of sea water. Petti-john
(1949) stated that graded bedding occurs in
sediments from Precambrian to the present and sug-gested
that flocculation by sea water is a doubtful
concept. Kuenen and Menard (1952) believed that
graded bedding in graywackes is caused by turbidity
currents and can occur in normal sea water.
Two methods are proposed which might produce
graded bedding in the slates. One postulates that
the sediments were derived from silt and clay sized
ash blown out of volcanoes. The larger sized par-ticles
would immediately settle out of the air allow-ing
them to be deposited in the water first. The
smaller sized particles Would be thrown higher in the
air and, buffeted by air current and take longer to
settle out. This would produce a graded sediment
due to air sorting before the material reached the
water. The second method postulates that the grad-ed
bedding was produced by turbidity currents.
During rainstorms, streams would become charged
with sediments. Upon reaching the basin of depo-sition,
the water charged with sediments would be
more dense than water in the basin; and would
move slowly down the sub-aqueous slope as a weak
turbidity current. As this current moved outward
it would deposit a silt layer. As it lost its turbidity
and velocity, the clay sized particles would gradually
settle out on top of the silt layer. The presence of
graywacke sandstones containing graded bedding
adds strength to the turbidity current theory, be-cause
graywackes are now usually regarded as' tur-bidity
current deposits (Pettijohn 1957).
Structure
Folds
Troy Anticlinorium : The major structure in
Moore County is the Troy Anticlinorium, which
trends in a northeast-southwest direction and
plunges toward the southwest. This structure has
been traced from southern Montgomery County to
northern Randolph County. The anticlinorium is
over 30 miles wide, lying between the Pee Dee River
on the west and western Moore County in the east.
The axis of the fold is located near Troy, Montgom-ery
County, and the southeastern limb occupies
northwestern Moore County. The felsic tuffs of
the Lower Volcanic sequence crop out in the center
of the structure, whereas the overlying andesite tuffs
and slates dip off its southeastern flank.
Minor Folds : A series of usually double-plunging
anticlines and synclines, varying in wavelengths
from one to three miles are developed on the south-east
flank of the Troy anticlinorium. These folds are
overturned to the southeast and cleavage developed
parellel to the axes of the folds dips monotonously
to the northwest at angles varying from fifty-five to
seventy degrees. Schistosity and shearing increased
from northwest to southeast across the county. In
the northwestern part of the county the Lower Vol-canic
sequence dips under the overlying rocks but
reappears in the center of anticlinal folds across the
central and southwestern part of the county. The
slates, the youngest Carolina Slate Belt stratigraphic
unit found in Moore County, occupy the center of a
number of overturned synclines in the central and
eastern part of the area. The slates are contorted
into a series of undulating open folds varying in
wavelength from ten to thirty feet across. These
folds probably developed due to plastic flowage
within the slates during regional folding.
Faults
Faults can be divided into two groups; namely,
northeast trending longitudinal faults developed
parallel to the axes of folds, and northwest trending
cross faults. Because of slippage parallel to the
axes of overturned folds, many of the longitudinal
faults are reverse in nature. The zones of displace-ment
along the major northeast trending faults
usually have been intruded by quartz veins and are
occasionally silicified and mineralized. The quartz
veins and silicified zones are invariably sheared,
indicating movement occurred along these faults
after intrusion of the quartz veins and silicifica-tion.
The cross faults have displaced the longitudinal
faults in a number of places, clearly indicating that
they developed after the longitudinal faults. Major
movement along the cross faults was strike slip-page.
Along the Deep River in the northern part
of the county these cross faults can be traced into
the Triassic basin. The cross faults have displaced
the Carolina Slate Belt units as much as a mile
along the strike, but have displaced Triassic rocks
only a few hundred feet. This indicates the major
movement took place in pre-Triassic time with a
later movement of much smaller scale taking place
after deposition of the Triassic sediments.
Longitudinal Faults
Glendon Fault: One of the major longitudinal
faults in the area is the Glendon fault. It lies ap-proximately
three miles northwest of Glendon and
can be traced from the northern county line south-eastward
to just north of Robbins. It strikes north
60 degrees and dips 60 to 70 degrees northwest.
Drag folds indicate that it is a reverse fault, with
movement from northwest to southeast. It is offset
by several cross faults along its length. A wide
mineralized shear zone containing workable pyro-phyllite
deposits accompanies the fault. Movement
along the fault has placed the andesite tuffs in con-tact
with the slates, except north of McConnell,
where it has placed felsic tuffs underlying the ande-site
tuffs in contact with the slates. This suggests
that the throw in this area must be in the order of
several thousand feet.
Robbins fault: The Robbins fault passes through
the western city limits of Robbins and is traceable
from approximately one mile north of Robbins,
southeastward to approximately one mile northeast
of West Philadelphia. It trends north 60 degrees
east and dips northwest at approximately fifty de-grees.
Drag folds indicate that it too is reverse in
nature and the hanging wall to the northwest moved
upward over the footwall to the southeast. The
shear zone accompanying this fault is as much as
a mile wide and contains pyrophyllite and gold de-posits.
The reverse nature of this fault and pres-ence
of pyrophyllite deposits along its trace sug-gests
that it is the same type as the Glendon fault.
In fact, if the strike of the Glendon fault were ex-tended
to the southwest (see Plate 1), it would in-tersect
the Robbins fault south of Robbins.
Other Longitudinal faults : A horst structure, ly-ing
between two north sixty-five degrees east trend-ing
vertical faults, occurs in the area between Put-nam
and Hallison. This structure places felsic tuffs
of the Lower Volcanic sequence in contact with
slates of the Volcanic-Sedimentary sequence. The
andesite tuffs lying stratigraphically between the
felsic tuffs and the slates are omitted, indicating a
throw in the order of several thousand feet. This
horst is adjoined on the northwest by a graben
which lies between the fault north of Putnam and
the Glendon fault.
Cross faults : Vertically dipping northwest trend-ing
normal cross faults, which strike from thirty to
seventy degrees northwest, occur throughout the
central and eastern part of the county. Some of
these appear to be hinge faults; whereas others
show strike slippage. A number of strike-slip faults
along Deep River have a horizontal displacement
varying from half a mile to over a mile. The Deep
River has entrenched along these faults producing
a series of parallel meanders.
Southeast of Spies a pair of northwest-trending
faults have produced a graben structure, downfault-ing
andesite tuffs against felsic tuffs.
A number of transverse faults have been intruded
by diabase dikes. The dikes evidently were emplaced
along zones of weakness; however, it is not under-stood
why they preferred northwest trending faults
and generally ignored those trending northeast.
DEEP RIVER TRIASSIC BASIN
The Deep River Triassic basin lies in a northeast-southwest
direction across Moore County. In the
northern part of the county it is bounded on either
side by the Carolina Slate Belt. In the southern
part of the county it. is overlapped by Coastal Plain
sediments.
Emmons (1852) on the basis of fossil and litho-logic
evidence, concluded that the sediments of the
Deep River basin were Triassic age. However, in
1856 he proposed that the lower sandstones and coal
beds were of Permian age, because of the presence
of Thecodant saurian teeth in some of the shales
associated with the coal beds. Overlying sandstones
were still considered Triassic age.
Redfield (1856) found that the rocks in New Jer-sey,
Eastern Pennsylvania and in the Connecticut
Valley were Upper Triassic age and proposed that
they be named the Newark group. He found that
fossil vertebrates in Emmons collection were identi-cal
to those occurring in the northern basins and cor-related
sediments in the Deep River basin with the
Newark group.
Rocks of the Deep River basin consist of red,
maroon, reddish-grey fanglomerates, conglomerates,
sandstones and siltstones. In addition the basin
contains coal beds and associated grey and black
shales, mudstones, siltstones and sandstones.
Emmons (1852) subdivided the stratigraphy of
the Deep River Basin into three units. These are
:
3. Sandstones, soft and hard with freestones,
grindstone grits, and superior conglomerates ; crop-ping
out along the eastern edge of the basin.
2. Coal beds and black slates with their subordi-nate
beds and seams ; cropping out in- the center of
the basin.
1. Inferior conglomerates and sandstones below
the coal beds and black slates; cropping out along
the western edge of the basin.
This was a logical conclusion because the strata
dip toward the eastern edge of the basin. Although
he devised this classification, Emmons (1856) recog-nized
marked resemblance between certain strata
on the eastern and western part of the basin and
suggested that they might be the same unit.
In 1856 he repeated this classification in his text;
however, on the map accompanying the report, in-serted
an additional unit which he called "Salines"
between the middle and upper units. Campbell and
Kimball (1923) stated that the "Salines" are nothing
more than drab shales, containing salt, above the
coal beds, and belong with the middle division.
Campbell and Kimball (1923) mapped and named
Emmons' three units calling the lowest the Pekin
formation, the middle the Cumnock formation and
the upper the Sanford formation.
Prouty (1931) discussed the formation of the
Deep River basin. He proposed that it was caused
by downwarping aided by development of an eastern
border fault.
Reinemund (1955) published a detailed study of
the structure and stratigraphy of the Deep River
basin with special emphasis on the economic geol-ogy.
Stratigraphy
Pekin Formation: Campbell and Kimball (1923)
named the basal Triassic unit, the Pekin formation
after a small town in southern Montgomery County.
No type section or type locality was established, but
they stated that it is best exposed on the road trend-ing
due east from Mt. Gilead. The formation under-lies
the western third of the Deep River basin in
Moore County and is exposed along the western bor-der
of the basin from Deep River southward to the
Coastal Plain overlap. The formation is estimated
to be from 1750 to 1800 feet thick. Its basal part is
supposed to rest on the eroded- surface of the Caro-lina
Slate Belt, (Reinemund 1955). To the south,
along Drowning Creek, the western border of the
basin is flanked by a lithic fanglomerate composed of
angular to subrounded rock fragments, derived from
the Carolina Slate Belt, ranging from one inch to
over a foot in diameter.
An elongate conglomerate bed, lenticular in out-line,
resembling a shoestring sand lies along the
western border of the northern part of the basin.
This bed was extensively quarried before 1900 to
make millstones, and is known locally as the Mill-stone
Grit.
The bed varies in thickness from 2 to 30 feet, and
is composed of quartz pebbles, varying from one to
three inches in diameter, in a matrix of coarse sand.
The conglomerate is well cemented and the pebbles
can be broken without being dislodged from the
matrix.
A paleosoil underlies the Millstone Grit in an out-crop
on Highway N. C. 22 at the old Parkwood quar-ry.
It is a grey, carbonaceous, partly-kaolinized
clay containing numerous root impressions.
East of the western border, the Pekin formation
is composed of lenticular beds of red, brownish-red,
and maroonish-purple clayey siltstones, sand-stones
and occasional beds of brown or grey, medium
to coarse grained, cross bedded, arkosic sandstones
and conglomerates. Rare thin beds of claystone are
also present. Many of the sandstones contain root
impressions on weathered surfaces.
Toward the center of the basin the sediments be-come
finer grained, with siltstones predominating.
To the southeast the sediments become progressively
coarser, and frequently contain more arkosic beds
as well as coarse-grained, grey-colored, cross-bedded
sandstones.
Cumnock Formation: Campbell and Kimball
(1923) named the middle coal-bearing Triassic beds
the Cumnock formation after the Cumnock mine.
The type section was located in the main shaft of
the mine. The Cumnock formation is exposed in
northern Moore County from Deep River southward
to the Coastal Plain overlap. On the road between
Glendon and Carthage it-is repeated four times by
faulting.
In the north-central part of the basin the Cum-nock
formation is 750 to 800 feet thick and consists
of coal, black and grey shales, with thin sandstone
beds in the middle and upper part (Reinemund
1955). The Pekin-Cumnock contact was placed by
Emmons at the top of the last redbed below the coal
beds, and the Cumnock-Sanford contact at the first
redbed above the coal. The two workable coal beds
occur about 200 feet above the base of the Cumnock
formation. The lower coal bed, called the Gulf
seam, has been found only at the Carolina and Black
Diamond mines and lies from 25 to 45 feet below
the second, or Cumnock bed (Reinemund 1955)
.
The Cumnock formation and associated coal beds
is the thickest near the center of the basin, thinning
rapidly toward the edges. The formation is best
developed at Carbonton and Gulf and apparently
thins rapidly to the southwest. This is indicated by
the Cumnock coal bed which is reported to be 42
inches thick at Cumnock, but only 14 inches thick
at an exposure at the Gardner mine. Campbell and
Kimball (1923) noted the area, two miles wide,
northwest of Carthage in which the Cumnock
formation does not crop out. They postulated that
this might be caused by either lateral gradation of
the grey Cumnock strata into the red beds of the
Pekin and Sanford formations, or down faulting,
but seemed to favor faulting as the explanation.
The Cumnock formation dips under the Coastal
Plain sediments four miles southwest of Carthage,
and has not been observed in outcrop south of the
point. An exception to this might be the grey silt-stone
and mudstone exposed in a stream valley one
and one-half miles southwest of Eagle Springs, on
the road to Samarcand Manor. Whether or not this
is actually the Cumnock formation or a variation of
the Pekin formation is open to question, because this
exposure lies considerably north of a projection of
the last Cumnock outcrop. It is thought that the
reason the Cumnock formation does not crop out
south of Carthage is because it is downfaulted along
the continuation of the Governors Creek fault. The
Cumnock formation reappears further to the south-west
as indicated by a coal prospect located in Mont-gomery
County near the Moore County line.
Sanford Formation: The Sanford formation was
named by Campbell and Kimbell (1923) after the
town of Sanford and included all rocks above the
Cumnock formation. The Sanford formation con-formably
overlies the Cumnock formation, and in
Moore County this contact might best be described
as gradational. The Sanford formation is estimated
to be from 3500 to 4000 feet thick (Reinemund
1955) and covers the eastern half of the Deep River
basin. Reinemund (1955) stated that the Sanford
formation contained few distinctive beds which can
be traced over any appreciable distance. The beds
are lenticular and laterally gradational. Measured
sections would only apply to rocks in the immediate
vicinity and correlation is not feasible over wide
areas.
The Sanford formation similar to the Pekin
formation, is predominately a sequence of redbeds.
It also is composed of sandstones, siltstones, con-glomerate
and fanglomerate. To the southwest, the
formation becomes progressively coarser and con-tains
more frequently occurring beds of coarse
arkosic sandstone.
Fanglomerate crops out, in a belt varying in
width from three-fourths to over a mile wide, along
the southeastern edge of the basin. It is composed
of unsorted rock fragments ranging from one-half
an inch to more than a foot in diameter. These frag-ments
were derived from rocks of the Carolina Slate
Belt and usually are poorly indurated. Material
filling the interstices between the fragments usually
is composed of red and maroon sandstones and silt-stones.
The fanglomerate shows very poor bedding
;
however, the general dip of the rock can be ascer-tained
by observing the orientation of tabular rock
fragments. From the eastern border and toward
the center of the basin, the fanglomerat grades lat-erally
into conglomerate. In addition to the fan-glomerate,
the Sanford formation contains well-defined
lenticular beds of quartz conglomerate which
are sometimes cross-bedded. These lenses usually
grade into sandstones.
Beyond the border of the basin the majority of
the Sanford formation consists of interbedded red
and maroon siltstones and sandstones. Claystones
and shales are almost totally absent. The coarser
sandstones are most prevalent along the eastern edge
of the basin with siltstones becoming predominant
toward the center of the basin. These sandstones
are similar to the sandstones of the Pekin forma-tion,
along the northwestern edge of the basin and
contain numerous root impressions.
Unnamed Upper Conglomerate: Northeast of
Carthage a grey conglomerate lies on the eroded sur-face
of the Sanford formation (see Plate 1). Prob-ably
the best exposure is in a new road cut on a
hill rising above the east bank of the east fork of
Big Governor's Creek. The conglomerate consists
of well rounded quartz pebbles, ranging in size from
one-half to two inches in diameter, intermixed with
a minor amount of coarse angular sand. In addi-tion
it contains minor lenses of siltstone. The rock
is poorly consolidated and usually is not stained
with the red iron oxides as generally is the case with
Triassic rocks. The Triassic age of the conglom-erate
is well established because it has been intruded
by a diabase dike.
After observing this conglomerate, J. L. Stuckey
informed the author that similar gravels occur near
Apex, North Carolina. The Apex locality was visit-ed
by Reinemund and Stuckey in 1948, at which
time they reached the conclusion that the gravels
were of Triassic age and appeared to be younger
than the Sanford formation.
It might be argued that these gravels are part of
the Sanford formation because unconformable beds
within the formation are relatively common. This
possibility certainly cannot be ruled out. However,
a better explanation is that these gravels probably
are post Sanford floodplain deposits as indicated by
the preservation of old stream channels.
Triassic Diabase : Diabase dikes generally regard-ed
to have been emplaced in late Triassic time, have
intruded both the Deep River Triassic basin and the
Carolina Slate Belt. In the Deep River basin a num-ber
of dikes have intruded the Sanford formation
northwest of White Hill. Dikes and large sills have
intruded the Cumnock formation northeast and
southeast of Glendon. Dikes occasionally occur in
the Pekin formation west of Carthage. Diabase
dikes have been mapped in the Carolina Slate Belt
and are most numerous in the area between High
Falls and Parkwood.
10
The diabase dikes in general trend northwest,
with a few exceptions trending either north or
northeast. These dikes dip either vertically or
slightly to the northeast. They range in thickness
from one to several tens of feet. Diabase dikes oc-curring
in the Carolina Slate Belt are usually smaller
than those in Triassic sediments. This leads to the
conclusion that the magma could more easily intrude
and incorporate the less resistant Triassic sedi-ments.
The existence of low refractory shales and
coal in the Cumnock formation might explain why
large sills occur in this unit. Even where they in-trude
Triassic sediments, the baked zones on either
side of the diabases are rarely over twice the thick-ness
of the dikes, and- in the Carolina Slate Belt
these zones do not exceed a few inches. The baked
zones usually are dark grey at the contact with dia-base,
becoming reddish grey away from the contact.
The diabases are exceedingly susceptible to spher-oidal
weathering producing rusty boulders scattered
through the surficial soil. Soil, developed on weath-ered
diabase is a conspicuous dark-yellow brown, but
occasionally is a dark-chocolate brown.
During the field investigation for this report little
attention was given to the petrography of the dia-base
dikes. Reinemund (1955) studied the diabases
in detail. He found that they contain the primary
minerals olivine, plagioclase feldspars, varying from
andesine to bytownite, augite, orthoclase and quartz
;
the accessory minerals magnetite, ilmenite, pyrite,
chromite, titanite, apatite, and basaltic hornblend;
and secondary minerals antigorite, limonite, horn-blende,
calcite, and magnetite. Olivine is usually
present in varying amounts. The rock usually con-tains
as much as two-thirds plagioclase and as much
as one-third augite. In addition to normal diabase,
gabbroic varieties composed of one-half olivine and
one-third plagioclase and dioritic diabase composed
of one-half plagioclase and one-third augite are
present.
Envioronment of Deposition
Kryniene (1950) expressed the opinion that red
color of the Triassic sediments was due to erosion of
red soils in the source area. Reinemund (1955)
essentially agreed with this, and added that the dark
brown and red colors of the Pekin and Sanford
formations indicated that the sediments were de-posited
in a non-reducing environment.
During the time of deposition of both the Pekin
and Sanford formations fluvial conditions existed in
the Deep River basin. At this time both the border
faults had well defined scraps. Talus material ac-cumulated
at the base of these scarps producing the
fanglomerates found in the Pekin formation along
the western edge of the basin and the Sanford
formation along its eastern edge.
From the edges toward the center of the basin,
sediments of both formations become progressively
finer grained. Reinemund (1955) stated that sedi-ments
of the Pekin and Sanford formations were
deposited by streams, as indicated by the cross bed-ding
and the channel like form of some of the coarse
grained sediments. Root impressions, commonly
found in the sandstones of these formations, sug-gest
that much of the area between the major stress
channels was marshland. General coarsening of the
grain size of the sediments to the southwest indicate
that drainage within the basin was in that direction.
Gradual sinking of the basin probably occurred
during sedimentation by slight movements along the
border faults, causing rejuvination from time to
time of streams flowing into the basin. During the
latter part of Pekin sedimentation the scarp of the
Western border fault in the northern part of the
county did not stand at elevations great enough to
produce talus deposits. At this time, a stream, in-cised
along the fault scarp, deposited the Millstone
Grit.
The occurrence of the Cumnock formation, with
its black shale and coal beds in the center of the
basin, represents a change from stream and shallow
marshes, with rapid sedimentation along the mar-gins
of the basin ; to a shallow lake, with slow sedi-mentation
in the center of the basin. A shallow body
of standing water could support a lush growth of
vegetation. After death the organic remains would
fall to the bottom of the lake and be protected from
oxidization. Extremely slow sedimentation would
allow accumulation of organic material of thickness
and purity to form workable coal beds.
After the basin had filled with sediments, streams
meandered over its surface depositing the unnamed,
upper gravels which overly the Sanford formation.
It is suggested that deposition of parts of the
Pekin, Cumnock and Sanford formations, as map-ped,
might have occurred simultaneously. Only in
areas of outcropping Cumnock formation can the
names Pekin and Sanford formations be used as
time-stratigraphic units. In these areas redbeds
underlying and in direct contact with the Cumnock
formation can definitely be called the Pekin forma-tion,
and inversely, the redbeds overlying the Cum-nock
formation belong to the Sanford formation.
Because grey shales and coal beds of the Cumnock
formation are limited to the center of the basin,
redbeds deposited along the eastern and western
margins of the basin during Cumnock time are most
11
likely mapped as Sanford and Pekin formations re-spectively.
As no key horizons exist along the mar-gins
of the basin, it would be best to regard what
has been mapped in these areas as Pekin and San-ford
formations as sedimentary facies rather than
time-stratigraphic units.
Structure
Folds: The Deep River basin has been described
by Campbell and Kimball (1923) and by Reinemund
(1955) as a synclinal basin. In this paper the basin
is considered a graben structure in which the beds
dip monoclinally to the south-east. The syncline
which Reinemund (1955) regarded as the axis of
the basin occurs northeast of White Hill. Another
small syncline lies along the west bank of McLen-don's
Creek, where Highway N. C. 27 crosses the
creek. Approximately eight tenths of a mile north
of this area is located the axis of a small anticline.
Folds of large magnitude have not been observed
within the Deep River basin in Moore County.
Faults: Reinemund (1955) found three ages of
faults in the Deep River basin. The oldest is the
Jonesboro fault or eastern border fault, which re-mained
active during sedimentation ; the cross faults
are next in age, developing after sedimentation had
ceased ; and the longitudinal faults are the youngest.
This is indicated by the fact that the cross faults
have displaced the Jonesboro fault, but not the longi-tudinal
faults. In turn, the longitudinal faults have
offset the cross faults, but are not offset by the cross
faults.
Border Faults
Jonesboro Fault : The Jonesboro fault was named
by Campbell and Kimball (1925) after the town of
Jonesboro. It forms the eastern contact of the basin
placing Triassic sediments against the Carolina
Slate Belt. Reinemund (1955) estimated that the
maximum vertical displacement along this fault is on
the order of 6000 to 8000 feet. The fault strikes
north 35 degrees east in the northeastern part of the
county, but changes to a more easterly direction
south of Eastwood, where it assumes a strike of
about north 60 degrees east. The fault plane dips to
the northwest at an angle of about 65 degrees.
Reinemund (1955) observed that the Jonesboro fault
is displaced by cross faults, although no displace-ment
along the fault was noted in Moore County.
Western Border Fault : The Western Border fault
forms the western contact of the basin and also
places Triassic sediments against the Carolina Slate
Belt. Campbell and Kimball (1923) did not recog-nize
the Western Border fault, and Reinemund
(1955, Plate 1) has only mapped a few discontinu-ous
faults along the western border of the basin.
Authors of both these papers suggested the sedi-ments
wedge out to the northwest. They proposed
the sediments were once more extensive in that
direction, but have been eroded away. This concept
might be true of other areas of the Deep River Basin
but could not be applied in Moore County.
If the Triassic sediments wedged out to the west,
it would be expected that streams would have eroded
through the Triassic mantle exposing rocks underly-ing
the basin, producing a scalloped contact. The
contact is not scalloped, it is an essentially straight
line, suggesting a fault contact. In addition, the
fanglomerate, exposed along the western border of
the basin in the southern part of the county, indi-cates
that the fault scarp in this area was once a
significant topographic feature.
Campbell and Kimball (1923) and Reinemund
(1955) considered the Millstone Grit a basal con-glomerate.
The buried soil under the Millstone Grit
indicates that it is not a basal conglomerate and
that Triassic sediments had been deposited and
weathered before the conglomerate was laid down.
The presence of this fault is further indicated by
a gravity survey of the Deep River-Wadesboro Basin
conducted by Mann and Zablocki (1961). They
stated that in places the basin has graben like fea-tures,
but suggest that throw of the Western Border
fault in the Deep River basin is less than that of the
Jonesboro fault.
The Western Border fault is best exposed at the
bridge across Deep River, north of Glendon, on the
Glendon-Carthage road. It strikes north 30 degrees
east and dips to the southeast at 60 degrees. North
of Eagle Springs the fault is bent to a more westerly
direction and strikes north 55 degrees east. The
vertical displacement is unknown but it is thought
to be in the same order of magnitude as that of the
Jonesboro fault during time of sedimentation. How-ever,
post depositional movement along the Jones-boro
fault exceeded that of the Western border fault
which remained stable, causing the strata to dip to
the southeast. The Western Border fault has been
displaced in numerous places by cross faults through-out
its exposed area.
Cross Faults : Northwest trending cross faults are
found throughout the Deep River basin. As pre-viously
mentioned, along the Western border some
of these faults begin in the Carolina Slate Belt and
end in Triassic sediments. The major displacement
has been parallel to the strike. Vertical displace-ment
is usually minor being on the order of a few
12
tens of feet and occasionally ranging over one-hun-dred
feet. Reinemund (1955) noted the faults ex-tend
to great depth because many of them have been
intruded by diabase dikes. In Moore County the
cross faults trend about north forty degrees west;
however, in rare instances, they trend from north
twenty degrees west to almost due north. The fault
planes are usually at high angles approaching verti-cal
and generally dip to the northeast.
Longitudinal Faults : A series of northeast trend-ing
step faults, including the Deep River, Governors
Creek, and Crawleys Creek faults, lie in a northeast
direction across the center of the Deep River basin.
These faults have repeatedly exposed the Cumnock
formation in the northeastern part of the county.
The fault planes dip to the northwest at angles
varying from 20 degrees to thirty degrees. The ver-tical
displacement varies from five-hundred to over
two-thousand feet. Displacement gradually becomes
less to the southeast and all of the faults except the
Governors Creek fault die out before they have an
opportunity to dip under Coastal Plain sediments.
It is thought that the Governors Creek fault con- -
tinues across the southern part of the basin, and is
a rotational fault with its hinge line near Carthage.
The Western block moved down northeast of the
hinge line, but up southwest of the hinge line. This
explains why, along this fault line, the Pekin forma-tion
is in direct contact with the Sanford formation
in the southern part of the county and the Cumnock
formation in the northern part of the county.
The Formation of the Deep River Basin
Campbell and Kimball (1923) concluded that the
Deep River basin was caused by downwarping of the
earth's crust. Sediments were deposited in this
trough causing it to continue to sink. After down-warping
and sedimentation ceased, the basin was
faulted.
Prouty (1931) agreed that the basin was caused
by downwarping, but believed the Jonesboro fault
developed soon after sedimentation began. He pos-tulated
that movement along this fault continued
sporadically until sedimentation ceased. This pro-duced
a wedge shaped trough, with the thickest sedi-ments
next to the fault, becoming progressively
thinner away from the fault. The last movement
along the Jonesboro fault, as well as the development
of faults in the basin occurred after deposition.
The present investigation indicates the Deep
River basin in Moore County is a rift valley caused
by downfaulting along the Jonesboro and Western
Border faults. These faults are thought to have
existed in Pre-Triassic time and were reactivated in
Triassic time producing the basin. The sequence of
event which produced the Deep River basin in
Moore County are as follows
:
1. Removement along the Pre-Triassic Jonesboro
and Western Border faults, during Newark time,
creating a graben trough.
2. Disruption of drainage and beginning of sedi-mentation.
3. Continued movement along the border faults
and possible fractional movement along the cross
faults with continued sedimentation.
4. Stabilization of the faults with cessation of
sedimentation.
5. Removement along the Jonesboro fault, drop-ping
down the eastern side of the basin and tilting
the strata to the southeast, accompanied by active
movement along cross faults.
6. Development of longitudinal tension faults in
the center of the basin.
7. Intrusion of the diabase dikes, predominately
along northwest trending cross faults in both the
Carolina Slate Belt and Deep River Triassic basin.
THE COASTAL PLAIN
Stratigraphy
Upper Cretaceous Tuscaloosa Formation: The
Tuscaloosa formation is the basal Coastal Plain unit
in Moore County. In this report it is divided into a
lower and an upper member. The Tuscaloosa forma-tion
was named by Smith and Johnson in 1887 after
the city of Tuscaloosa, Alabama. L. W. Stephenson
(1907) subdivided the Cretaceous of North Caro-lina
into three formations. He called the basal unit
the Cape Fear formation. He considered it Lower
Cretaceous in age and correlated it with the Patux-ent
formation of Virginia. He named the overlying
unit the Bladen formation, (Black Creek formation
in present terminology) and correlated it with the
Tuscaloosa formation of Alabama. In 1912 he re-named
the Cape Fear formation the Patuxent forma-tion
and correlated it, on lithology, with the Patux-ent
of Virginia and Maryland.
Sloan (1904) named the sands and clays of sup-posedly
Lower-Cretaceous age in South Carolina,
the Middendorf Formation. However, Berry (1914)
studied plant fossils from this formation and found
that they were actually of Upper Cretaceous age.
Cooke (1936) correlated the Middendorf formations
13
of South Carolina with the Tuscaloosa formation of
Alabama and extended the Tuscaloosa into North
Carolina. Horace G. Richards (1950) described the
Tuscaloosa formation in North Carolina and stated
that it occurred in southern Moore County.
W. B. Spangler (1950) from a study of cuttings
obtained from oil-test wells drilled on the North
Carolina Coast, found that the subsurface contained
both lower and upper Cretaceous beds. He applied
the name Tuscaloosa formation only to beds of Eagle
Ford-Woodbine age. P. M. Brown (1958) also
found rocks of Woodbine and Eagle Ford age in the
subsurface stratigraphy of the North Carolina
Coastal Plain. These he assigned to the Tuscaloosa
(?) formation.
S. D. Heron (1958) mapped the basal Cretaceous
outcrops between the Cape Fear River in North
Carolina and the Lynches River in South Carolina.
He returned to the Classifications of Stephenson and
Sloan, dividing the Tuscaloosa formation into the
Lower Cretaceous ( ?) Cape Fear formation and the
Upper Cretaceous Middendorf Formation. He nam-ed
the lower part of the Black Creek formation, be-low
the Snow Hill member, the Bladen member.
Heron (1960) stated, "The Middendorf is considered
the updip facies of the Bladen member of the Black
Creek formation and both of these formations have
overlapped the Cape Fear formation."
Groot, Penny and Groot (1961) collected samples
containing plant microfossils from the Tuscaloosa
formation of the Atlantic Coastal Plain, including
one sample from the basal part of the lower member
of the Tuscaloosa formation in Moore County.
They found that the Tuscaloosa formation of the
Atlantic Coastal Plain is Upper Cretaceous age, but
slightly older than Senonian, although some Senon-ian
species are present.
Lower Member: The lower member of the Tus-caloosa
formation is the basal unit of the Coastal
Plain sediments in Moore County. It rests uncon-formably
on both the Carolina Slate Belt and the
Triassic Deep River basin. This member is best
exposed in the southeastern part of the county,
where overlying younger sediments have been strip-ped
away by erosion. It is rarely exposed in the
south-central and southwestern parts of the county,
where it usually is covered by overlying sediments.
The base of the lower member is exposed in a
road cut on the west side of Highway U.S. 15-501
on the south side of Little River. At this locality
it is underlain by the Triassic Sanford formation.
The basal part of the member is a grey carbonaceous
clay containing lignitized wood. The section at this
exposure is as follows
:
Section near juunction of Highway 15-501 and Little Rixer
Top of section covered
Cretaceous (Tuscaloosa formation member) Thickness
6. Weathered reddish brown clay.— 3'
5. Dark grey plastic carbonaceous clay 3'
4. Fine greyish green sand : 1'
3. Dark grey plastic carbonaceous clay, containing
liginitized wood 4'
2. Basal gravel _
'. 6'
Unconformity
Triassic (Sanford formation)
1. Fanglomerate 3'
Base of exposure
The gray carbonaceous clay of the basal part of
the lower member is again exposed in the west bank
of a paved road on the south side of Nicks Creek,
approximately one mile north of Murdocksville. This
locality contains both wood fragments and amber.
The type locality of the lower member of the Tus-caloosa
formation is an exposure along the Seaboard
Air Line Railroad in the center of the town of Vass.
The section at this locality is as follows
:
Section at Vass
Recent Thickness
7. Soil zone, weathered and leached, being colored
sand with occasional gravel beds 6'
Cretaceous (Tuscaloosa formation lower member)
6. Oxidized, mottled light olive and red clay 4'
5. Oxidized, iron cemented, greyish-olive sandstone 1'
4. Oxidized, light olive silty clay 8'
3. Oxidized, feldspathic, micaceous clayey course
olive sand, with occasional gravel beds stained
by hematite 6'
2. Oxidized, micaceous olive clay, containing some
silt and sand 3'
1. Unoxidized, micaceous, light grass green sandy clay.. 6'
Base of exposure
A water well, located approximately one-fourth of
a mile northwest of the type locality, drilled for the
town of Vass by C. C. Hildebrand and Company,
record the following section
:
Log of Water Well at Vass
Thickness
8. White and yellow sand 4'
7. Yellow sand clay 16'
6. Light yellow and light grey sand clay.. 5'
5. Light grey sandy clay - 10'
4. Light brown sandy clay 10'
3. Water bearing sand - 35'
2. Light brown sand clay 15'
1. Basement rocks of the Carolina Slate Belt 364'
An exposure southeast of Lobelia on the south
bank of Little River at Morrison, Bridge, Hoke
County, is as follows
:
14
Section along Little River at Morrison Bridge
Cretaceous (Tuscaloosa formation, lower member)
2. Festooned cross-bedded micaceous, feldspathic, grey-ish
white and light grey, poorly consolidated sand,
containing lignitized logs, grey clay balls, and heavy
mineral streaks. (These streaks are composed of as
much as 50 percent pyrope garnet. The lignitized
logs are partly replaced by plastic grey clay in which
growth rings are preserved) 5'
1. Unoxidized light grass green, micaceous, sandy clay 1'
River level
Two exposures of well cemented coarse sandstone
occur in the county. One is located northwest of
Taylor Town on the north bank of Joes Fork Creek,
and the other on the north shore of a private lake,
just above Hog Island intersection. Judging from
the elevation of the exposure, neither of these out-crops
could be far above the base of the unit. The
two sandstones are identical in appearance and, if
they could be correlated, might be of stratigraphic
significance. These sections are as follows
:
Section along Joes Fork Oreek northwest of Taylor Town
Cretacious (Tuscaloosa formation, lower member) Thickness
3. Oxidized reddish brown clay 3'
2. Coarse grained, well cemented greyish brown
sandstone 2'
1. Oxidized light grey clay. 2'
Base of exposure
Section: at Hog Island
Cretaceous (Tuscaloosa formation, upper member) Thickness
5. Basal quartz gravel 2'
Unconformity
(Tuscaloosa formation, lower member)
4. Dark grey clay mottled with secondary hematite____ 1.5'
3. Dark grey clay 3.5'
2. Coarse to medium grained, well cemented
greyish brown sandstone 2'
1. Dark grey silty clay ...„ 3'
Base of section
A complete stratigraphic section of the lower mem-ber
of the Tuscaloosa formation in Moore County is
not available, but from what is known, it can be
stated that the basal part consists of grey carbonace-ous
clays containing lignitized plant remains and
amber, with interbedded thin, grey and olive sand
beds. Above the base, the clays become less carbon-aceous
and lighter grey in color ; finally giving way
to light olive clayey sand beds containing thin clay
beds. Some of the sands exhibit faint graded bed-ding
and cross bedding. Although a few of the clay
beds are lenticular in outline, most persist over the
exposed outcrop area. In the subsurface some beds
can be correlated on electric logs traced over wide
areas (P. M. Brown, personal communication).
Upper- Member: The upper member of the Tusca-loosa
formation unconformably overlaps the lower
member as well as segments of the Carolina Slate
Belt and Deep River basin. The outer limits of the
upper member is an irregular contact which can be
traced in a northeast-southwest direction across the
county. Typical exposures are found in the area
around Harris Crossroads; however, measure sec-tions
in this unit are of questionable value because
of the extreme variable nature of the sediments. For
this reason, a type section of the upper member of
the Tuscaloosa formation has not been established.
The base of the upper member is exposed at a
number of localities along the margin of the Coastal
Plain. It is an unconsolidated gravel composed of
rounded quartz, varying from one to six inches in
diameter. These gravels were probably derived
from quartz veins in the Carolina Slate Belt. This
basal gravel is thin, usually not over six feet thick,
and in some places is totally absent. The basal
gravels become finer grained and diminish in thick-ness
to the southeast and might completely disappear
down dip. The gravels have a bleached appearance,
and might have been subjected to intensive weather-ing,
which removed iron staining, before transporta-tion.
Though some of the cobbles show faint pink
staining, the absence of iron contrasts with both
vein quartz in the Carolina Slate Belt and Recent
terrace deposits.
The matrix of the basal gravel is composed of
kaolinitic clay and clayey sand. Small quantities of
heavy minerals are interspersed through the matrix.
Above the basal gravel, the upper member of the
Tuscaloosa formation consists of alternating uncon-solidated
beds of white clay and clayey sand. The
clay beds pinch and swell and sometimes die out.
These beds are composed of white plastic kaolinite,
which, if weathered, is often stained pink by iron
oxide. Quartz grains up to one millimeter in diam-eter
are randomly scattered throughout the clays,
and sometimes make up as much as five percent of
the deposit. These quartz grains are usually very
angular, almost glass clear, and show little or no
rounding and frosting. In addition to the quartz,
the clays also contain mica shards.
The sand beds usually are more persistent than the
clay beds, although they also tend to thicken, thin
and occasionally pinch out. Most of the sand beds
are relatively massive and are only faintly bedded.
Some are crossbedded and others exhibit graded bed-ding.
A few of these deposits contain occasional fine
gravel interbeds. Kaolinitic clay galls, varying
from one-half to one and one-half inches in diameter,
occur sparingly in the gravel beds and along promi-
15
nent bedding planes. The sands are composed of
medium to coarse, sub-rounded quartz grains with
mica shards, feldspar grains, and rare heavy min-eral
streaks along bedding planes. The sands are
bonded together by kaolinitic clay. This clay, which
is always present, at times makes up as much as
twenty-five percent of the sediment.
Thin beds of hematite up to one inch thick occur
as a precipitate from groundwater on the upper sur-faces
of many of the clay beds and along prominent
bedding planes in the sand beds.
Hematite and occasionally limonite precipitates,
have oftentimes cemented the base of the upper mem-ber
of the Tuscaloosa formation. These deposits are
as much as six inches thick.
Environment of Deposition : The lower member
of the Tuscaloosa formation was probably deposited
in a marine environment. Although marine fossils
are lacking in Moore County, they have been recover-ed
from well cuttings down dip (P. M. Brown, per-sonal
communication). The persistence of the beds
and general rarity of cross bedding suggest these
sediments were laid down under marine conditions.
The gradual change from grey carbonaceous clays
at the base to green and olive clayey sands and thin
grass green clay beds above the base, probably rep-resents
a change from lagoonal, with stagnant con-ditions,
to marine environment, brought about by
transgression of the Lower Tuscaloosa sea.
Other evidence for the marine origin of the lower
member of the Tuscaloosa formation is suggested by
Heron's (1960) study of exposed basal Cretaceous
clays of North and South Carolina. He found that
known marine sediments contain abundant montmo-rillinite,
whereas sediments regarded as non-marine
contain kaolinite. He found that the Cape Fear
formation (lower member, Tuscaloosa formation)
contained predominately montmorillinite with some
kaolinite, suggesting that it is a marine sediment.
The samples collected from the lower member of
the Tuscaloosa formation of Moore County were
X-ray analyzed by Heron at the request of the
author. These were found to contain a majority of
montmorillinite over kaolinite (S. D. Heron, writ-ten
communications). Although montmorillinite as
an indicator of marine origin is still open to question
by some authors ; the present investigation suggests
that it is applicable in this case.
The environment of deposition for the upper mem-ber
of the Tuscaloosa formation has been discussed
in the literature. L. W. Stephenson (1923) believed
the Patuxent formation to be of alluvial origin,
deposited by overloaded streams crossing the Coastal
Plain of that period, which existed between the coast
line to the east and the highlands to the west.
Veatch (1908) stated that the almost pure kaolin-ite
beds in the Tuscaloosa formation were clearly of
sedimentary origin. He postulated that these sedi-ments
were derived from deeply-weathered crystal-line
rocks of the Piedmont in which the feldspar and
other aluminus minerals had altered to kaolinite.
During Cretaceous time, these weathered rocks were
rapidly eroded and deposited along the sea as alluvial
fans and at the mouths of streams as deltas. On
these deltas fresh water lakes were formed and filled
with reworked kaolinite clay. As these lakes were
filled, others formed.
Newman (1927) agreed that the clays were de-rived
from weathered rocks of the Piedmont, but
postulated that they were leached to essentially pure
kaolin in situ in pre-Cambrian time, under the in-fluence
of mild climate with heavy rainfall, aided by
acid conditions created by decaying vegetation. This
weathered material was then eroded, transported by
streams, and deposited in a marine environment.
Kesler (1957) agreed with Veatch's deltaic origin,
but added that the sediments were derived from a
youthful erosion surface. He postulated that the
kaolins were formed by weathering of feldspars
after deposition of the sediments, and were concen-trated
by later reworking.
Heron (1960) stated "The sediments of the Mid-dendorf
formation (upper member Tuscaloosa
formation) probably represent an environment that
was dominately fluvial". He suggested that the rela-tively
pure clay bodies, having the shape of small
basins, may represent deposition in a floodplain,
such as the filling of an abandoned meander.
The upper member of the Tuscaloosa formation in
Moore County is considered unfossiliferous although
is contains marine fossils down dip (P. M. Brown,
personal communication) . This fact has led to the
development of various theories about its environ-ment
of deposition of which too little attention has
been paid the source of the sedimentary kaolin beds
in the updip facies of the upper member.
In regard to this fact, a residual clay is developed
on Carolina Slate belt rocks directly underlying the
upper member. It is felt that this residual clay is
indicative of the source of the sedimentary clay in
the upper member of the Tuscaloosa formation. If
the crystalline rocks of the southeast were blanketed
prior to Upper Tuscaloosa time, by residual kaolins,
which were eroded and deposited during Upper Tus-caloosa
time, this would explain the widespread oc-currence
of sedimentary kaolins in the upper mem-ber
of the Tuscaloosa formation.
16
Norlh Carolina State Library
Raleigh
The McKennis pit (see Plate 1, for location) is a
typical residual kaolin deposit. The stratigraphic
section exposed in this pit is as follows
:
Section of McKennis Clay Pit
Recent Thickness
5. Present day soil zone which extends down from
the surface into unweathered gravel 4'
Tertiary (Pinehurst formation)
4. Gravel ._: 1'
Unconformity
Cretaceous (Tuscaloosa formation, upper member)
3. Pink and white mottled clayey sand 3'
2. Basal gravel _._ 1'
1. Kaolinitic clay containing quartz veins, still pre-serving
the fine alternating graded bedding of the
slates. (The relic bedding strikes north 45 degrees
east and dips southeast at 30 degrees) 2'
Base of section
This locality was visited by Mr. E. F. Goldston,
North Carolina State College, Department of Soils,
at the request of the author. At the time of exami-nation,
Mr. Goldston stated the following about the
deposit
:
1. The Coastal Plain is too thick for the kaolin to
have been formed in place by weathering after depo-sition
of the Upper Tuscaloosa member and overly-ing
sediments.
2. A climate capable of producing this degree of
weathering and leaching would, of necessity, have
been warmer and had more rainfall than present.
A section exposed on the north bank of Little
River, where the Murdocksville road crosses the
river, is as follows
:
Section of Little River
Thickness
Cretaceous (Tuscaloosa formation, upper member)
4. Sandy clay 8'
3. Basal gravel composed of quartz pebbles, ranging
in diameter from 1 to 6 inches, in a mtarix of
kaolinitic sand 2' 6"
Triassic (Sanford formation)
. 2. Sandy kaolinitic clay, developed on the Sanford
formation grading downward into unweathered
red sandstone 3' 6"
1. Red sandstone 2'
Base of section
This section indicates that Triassic rocks as well
as the Carolina Slate Belt were highly weathered
and leached prior to deposition of the upper member
of the Tuscaloosa formation.
Occurrences of residual kaolin underlying the Tus-caloosa
formation in Georgia suggest that the pre-
Upper Tuscaloosa mantle was an extensive deposit
because Munyan (1938) states, "Recently the writer,
while mapping Cretaceous rocks (in Georgia) saw
a number of contacts between the Tuscaloosa and the
underlying crystalline rocks. The crystalline rocks
were weathered to primary kaolin in many instances
and could be identified as crystallines only by the
presence of thin, but continuous quartz veins. The
overlying rock could easily be identified as unaltered
sediment. In no case observed did it appear that the
weathering of the underlying crystalline rocks was
due to leaching after the deposition of the sediment".
From this evidence it is postulated that in pre-
Upper Tuscaloosa time the Carolina Slate Belt and
the Deep River Triassic basin were peneplained and
subjected to intensive weathering and leaching un-der
tropical conditions, producing a thick residual
kaolinitic mantel. In order to prevent the mantel
from being eroded away as fast as formed, the area
was, of necessity, relatively flat. If a transgressing
sea slowly inundated this peneplaned surface, it
would be expected that the upper member of the
Tuscaloosa formation would have been laid down in
a shallow environmental basin under near shore con-ditions.
Streams emptying into this basin during
flood stage, would bring in sediments ranging in sizes
from clay to gravel. As the flood subsided the
sediments would become finer grained, explaining
why some of the sediments contained graded bed-ding.
Cross bedding would be expected in such an
environment.
During times when the streams were not in flood
stage, they would be carrying colloidal clay, which
on entering the basin would slowly settle out as a
thick viscous mass. The surface of the basin floor
was probably irregular with more clay accumulating
in the depressions than elsewhere. This explains
why the clay beds pinch and swell.
The next flood would bring in another slurry of
coarse sediments which would be deposited on top
of the clay beds. The colloidal clays would then act
as highly viscous media allowing some of the sand
grains from the overlying sediments to settle into
the clay, while supporting the remainder. This ex-plains
the presence of sand grains in otherwise pure
kaolinitic clay.
The coarse basal gravel of the upper member of
the Tuscaloosa formation was probably derived from
quartz veins which intruded the Carolina Slate Belt.
The quartz could have been brought in by streams,
however, it has been noted, in many places in Moore
County, underlain by rocks of the Carolina Slate
Belt, that the surface of the ground is covered by a
lag pavement of vein quartz. If areas covered by
these lag gravels were exposed to wave action of
an advancing sea, this action could rapidly produce
17
a deposit similar to the basal conglomerate of the
Upper Tuscaloosa member. As previously noted,
the basal gravel is thin, variable in thickness, and in
places totally absent. Pettijohn (1957, p. 244) states
"blanket conglomerates . . . were deposits of gravel
spread out by an advancing or transgressive beach.
These deposits are notably thin and patchey; low
areas may collect several tens of feet of gravel
whereas the intervening high areas may be devoid
of any gravel accumulation".
the upper member of the Tuscaloosa formation. This
contact is an undulating line, indicating a rough
erosional surface developed on the upper member
of the Tuscaloosa formation before deposition of the
Pinehurst formation. This contact can be recog-nized
at numerous localities in the county ; one of the
better of these is exposed in the west bank of high-way
U.S. 15-501 at the Vass road overpass, approxi-mately
one and one-half miles southeast of Carthage.
This section is as follows
:
TERTIARY PINEHURST FORMATION
m
Gravel beds overly the upper member of the Tus-caloosa
formation in Moore County. The gravel
deposits near Lakeview were described by Stephen-son
(1912) and correlated with the Lafayette forma-tion
of Pliocene age. Bryson (1930) described a
number of gravel pits in Moore County and stated
that the exposures are of one group and probably
belong to the Lafayette formation. In the Halifax
area, Mundorf (1946) recognized graven deposits
which he called unclassified high level gravel. He
postulated they were probably of differing ages
ranging from Cretaceous to Tertiary. Richards
(1950) recognized high level gravels in Moore
County, but did not attempt to define the distribu-tion
or suggest the age. Reinemund (1955) mapped
high level gravels in Moore County and stated that
they covered almost a fifth of the area shown in his
geologic map. He considered all of the Coastal Plain
deposits high level gravel, not recognizing the upper
member of the Tuscaloosa formation which directly
underlies the gravel throughout the county.
The gravels are unfossiliferous and the exact age
is not known. In the northeastern part of the State,
similar deposits unconformably overlie the late Mio-cene
Yorktown formation (P. M. Brown, personal
communication). Although regarded as Pliocene
age by Stephens et. al. it is conceivable that these
surficial gravels could be Late Miocene, Pliocene, or
Early Pleistocene age.
Stratigraphy: During this investigation it was
found that the so-called high-level gravels could be
recognized and mapped as a stratigraphic unit in
areas covered by Coastal Plain sediments. It is
therefore proposed that this unit be called the Pine-hurst
formation after the town of Pinehurst which
is underlain by these sediments. The type section
for the formation is located in the D. H. Wilson sand
pit on the north side of Highway 211, approximately
one and one-half miles southeast of the center of the
town of West End.
The Pinehurst formation unconformably overlies
Section along Highway 15-501 at Vass Overpass
Tertiary (?) (Pinehurst formation) Thickness
2. Brown limonite stained, faintly bedded, coarse
sand; containing lenses of well rounded quartz
gravel, ranging in size from one-half to two inches
with interspersed kaolinitic clay balls 10'
Unconformity
Cretaceous (Tuscaloosa formation, upper member)
1. White kaolinitic clay, pink mottled at the top 2'
In Moore County the Pinehurst formation is a
nonfossiliferous sand and gravel which caps all of
the higher Coastal Plain hills in central and western
Moore County. It has not been observed resting
directly on sediments older than the Upper Tusca-loosa.
The Pinehurst formation is exposed on top of the
high hill at Carthage, at an elevation of over 500
feet. From this elevation it slopes to the southeast,
at first steeply, becoming more gentle down dip
until it reaches an elevation of about 350 feet in the
southern part of the county.
The gravels on the hill at Carthage range in thick-ness
from 3 to 7 feet and consist of a coarse-brown,
iron-stained sand containing lenses of quartz peb-bles,
ranging in diameter from 2 to 5 inches. Down
dip the formation gradually thickens until, in the
southern part of the county, it is over 150 feet thick.
Bedding and composition rapidly change from coarse
sands, containing pebble beds and lenses, at Car-thage
to festooned cross-bedded sands and fine grav-els
down dip.
The formation usually is brown or greyish brown
in color. It is often iron stained, and sometimes
cemented with either hematite or limonite, hematite
being the more common. Hematite concretions occur
within the formation. The outside of these struc-tures
are coated with sand grains. Although they
are usually oval or spherical in outline, some have
a stair step appearance from preservation of relic
bending planes. When broken they are oftentimes
hollow and contain hematite powder which local
folklore attributes as the source of red Indian war
paint. Sometimes this hematite occurs in lumps
18
and when a concentration is shaken emits a sound,
from the hematite hitting the walls of the structure
;
thus giving rise to the common name "rattle rock".
Hematite and occasionally limonite is precipitated at
the base of the formation in deposits varying from
a few inches to over a foot in thickness.
Kaolinitic clay balls are commonly interspersed
throughout the formation. They usually occur along
prominent bedding planes and in gravel beds. Heavy
minerals are much more common in this formation
than in the underlying Tuscaloosa, which is relatively
devoid of heavy minerals. They are concentrated
along bedding planes and are rarely dispersed
through the sediment.
The upper surface of these deposits is covered by
olive-brown silt and fine sand ranging in thickness
from one to five feet. These deposits are attributed
to wind action in the form of winnowing. The
process was probably aided in the recent past by
denudation of the area by forest fires, but is still
going on today as can be attested to by observing
sparsely vegetated areas on a windy day.
The Pleasant sand pits, between Pinehurst and
Aberdeen, contain sediments dissimilar to the other
parts of the Pinehurst formation. These deposits
consist of water laid, well-sorted, thin-bedded, fine
white sands; thin, fissle-bedded, grey silts and
plastic clays ; and occasional micro-cross bedded fine
sands. These deposits are covered by approximate-ly
four feet of wind blown silt and fine sand.
Because of the thinness of the Pinehurst forma-tion,
the major streams have cut the deposit leaving
it capping hills along stream divides and draping
down the hillsides. These sand and gravel capped
hills are commonly referred to as the "Sand Hills
Region". Many times the tops of the hills are con-cordant,
flat, and slope gradually to the southeast.
These might represent preservation of original con-structional
topography.
Environment of Deposition: Lithology and ab-sence
of fossils suggest the Pinehurst formation is
nonmarine. However, it could have, in part, been
deposited in a transition zone. In such a zone con-ditions
for preservation of fossils are poor; and, if
preserved, they could have been subsequently leach-ed
away.
The sediments were derived from a nearby source
and carried by vigorous streams in a youthful stage
of development, as indicated by the beds and lenses
of coarse gravels in the coarse sands around Car-thage.
A change of environment from stream to
deltaic is indicated by comparing these deposits with
the cross bedded, finer grained sands and gravels
down dip. This change is further suggested by the
gradient of the formation which is steepest at Car-thage,
becoming rapidly less steep, almost flat, down
dip. The beds of coarse gravel at Carthage and
change in gradient down dip also indicates that one
of the major streams emptying into the basin of
deposition was located in the general vicinity of
Carthage. As sedimentation progressed, deltas grew
outward from the mouths of streams emptying into
the basin, explaining why the formation thickens
down dip.
An interesting feature of the Pinehurst formation
is the presence of kaolinitic clay galls. Although
clay galls were occasionally observed in Upper Tus-caloosa
outcrops, they are universally present in the
Pinehurst formation. Whether the kaolinite was
derived from erosional outliers of the underlying
Tuscaloosa formation or from weathered Carolina
Slate Belt rocks is open to debate. PettiJohn (1949)
attributes the formation of clay galls to the dessica-tion
and breaking up of mud cracks. Mud cracks
could have easily formed on mud flats along deltaic
distributaries and been incorporated in the sedi-ments
when these mud flats were inundated during
flooding.
The final product of sedimentation was a series of
coalescing deltas, creating a blanket deposit of cross
bedded unconsolidated sand and gravel. The fine
sands and clays exposed in the Pleasant sand pits
were probably deposited in a small fresh water lake,
created by blocking of one of the distributaries.
Post depositional wind action in the form of win-nowing
produced the fine sands and silts which cover
the Pinehurst formation in many places.
Structure: The Coastal Plain sediments dip to
the southeast at six to eight feet per mile. This
angle of dip is somewhat steeper than the average
for the Coastal Plain, but these are deposits along
the ancient coastal margines and should dip more
steeply. No faulting has been observed in Coastal
Plain sediments even though slicken-sides were ob-served
in Upper Tuscaloosa clays in a borrow pit on
the west side of Highway U.S. 1, at the southern city
limits of Aberdeen.
Erosional unconformities occur at the base of the
lower member of the Tuscaloosa formation and at
the base of the Pinehurst formation. The existence
of an unconformity at the base of the upper member
of the Tuscaloosa formation is suggested by the pres-ence
of what appears to be a weathered zone develop-ed
on top of the underlying lower member. A basal
conglomerate in the upper member also suggests a
break in the sedimentation cycle.
19
I
Other Deposits
Terrace Gravels: Although Reinemund (1955)
mapped four levels of terrace gravels, this author
only recognized and mapped three levels in Moore
County. The lowest of the terraces (Terrace No. 1,
Plate I) is found as scattered remnants along Aber-deen
Creek, Little River, and Crane Creek. Sedi-ments
underlying this terrace level consists of iso-lated
patches of sand and gravel at elevations from
ten to fifteen feet higher than present floodplains.
It is light tan-colored coarse sand and well rounded
gravel. The gravel fraction is composed predomi-nately
of quartz with some Carolina Slate Belt frag-ments.
The gravel is somewhat variable in size,
ranging in diameter from 1 to 3 inches.
The most extensive of the terrace deposits (Ter-race
No. 2, Plate I) occurs from 20 to 30 feet above
present floodplains. It is the only terrace level
which has developed to any extent on the crystalline
rocks of the Carolina Slate Belt. This level occurs
along Cabin Creek, north of Robbins, and along the
length of Deep River. The terrace deposits consist
of yellow-brown fine sands and clayey sand with
occasional interbedded silts and fine gravel. The
gravels are one-quarter to one-half of an inch in
diameter with some ranging upward to over one
inch. These deposits are usually covered by 12 to
18 inches of coarse silt and fine sand.
The highest of the stream terraces (Terrace No.
3, Plate I) , occurs at elevations of 65 to 70 feet above
present floodplains. It is only found along Deep
River east of Glendon and Little River north of Mt.
Pleasant. Terrace deposits underlying this level are
composed almost entirely of gravel with sand and
clay filling the interstices. Rare thin interbeds of
silty clay are present in the deposit. The subangular
to rounded gravels are composed of approximately
70 per cent quartz and 30 percent Carolina Slate
Belt rocks. The sand fraction is composed mainly
of coarse, angular, quartz grains with occasional
feldspar grains.
Soils developed on these deposits have a distinc-tive
red color. The "B" soil horizon is a maroonish-red
sand loam, whereas, the "A" horizon is a red-dish-
brown silty loam.
The three levels of river terraces indicate three
periods of downcutting and stream aggradation,
followed by deposition of alluvial sediments in the
valleys. Therefore, the highest of these deposits is
the oldest ; the lowest is the youngest with each suc-cessive
period of cutting lowering the stream and
bringing it closer to the present base level. The
periods of aggradation were probably caused by a
drop in a sealevel ; the subsequent deposition by ris-ing
sealevel.
The river terrace deposits in North Carolina have
been regarded in the literature as Pleistocene age.
Successive sets of terraces were supposedly formed
due to alternating glaciation and melting producing
a rise and fall in sealevel. The terraces in Moore
County do not contain fossils and have not been
traced into known Pleistocene deposits; therefore,
their age determination is left to conjecture.
Alluvium: The alluvium filling present stream
valleys consists predominately of chocolate-brown
and greyish-brown silt with some light and lark
grey organic clays. It is conspicuously absent in
those parts of the county underlain by the Carolina
Slate Belt. However, it is usually present along
streams flowing over much of the Triassic basin
and Coastal Plain. The presence or absence of
alluvium is determined by the relative resistance to
erosion or the rocks underlying the streams.
ECONOMIC GEOLOGY
Pyrophyllite
Pyrophyllite is a hydrous alminum silicate classi-fied
as a high alumina mineral. Its formula is
Al2 3 .4 Si0o.Ho and consists of 66.7 percent
Si02 , 28.3 percent A12 3 and 5.6 percent H20. It is
used in the manufacture of ceramics, paint, rubber,
insecticides, roofing, and paper. Its major produc-tion
goes into ceramic products and mineral filler.
Moore County contains the largest pyrophyllite ore
reserves in the United States. This mineral has been
mined near Glendon for over a hundred years.
The pyrophyllite at Glendon was originally
thought to be talc, until Emmons (1856) reported
that it contained aluminum. He called it agalman-tolite,
a soft material consisting chiefly of pyro-phyllite
used in the Orient for making carvings. In
addition he described the quarry at Hancock's Mill
(Glendon) at some length. Brush (1862) analyz-ed
material from Hancock's Mill and concluded that
it was pyrophyllite. Pratt (1900) discussed the
occurrence of pyrophyllite at Glendon and described
Phillips, Womble, Rogers Creek, and other deposits.
He noted that the pyrophyllite was often silicified
and occurred in iron breccia which merges into pyro-phyllite
schist. Stuckey (1928) investigated the
pyrophyllite deposits of Moore County and discussed
their location, size, mode of occurrence, origin, and
economic possibilities.
Pyrophyllite Mines and Prospects
Pyrophyllite deposits occur in four areas in Moore
County ; namely, north of Glendon, southeast of Hal-
20
lison, southwest of Robbins, and on Cabin Creek
near the Montgomery-Moore county line. Eight
pyrophyllite mines and prospects are located on the
Glendon fault from McConnell northeast to the
county line. This area contains the largest number
of deposits in the county. Two pyrophyllite mines
are located on the Robbins fault, south of Robbins.
Both of these deposits are at present being mined.
McConnell Prospect : The McConnell prospect lies
approximately 0.5 of a mile northeast of the village
of McConnell. The pits are now grown over, but the
dumps contain sericite schist and foliated pyrophyl-lite.
Highly sheared sericitized felsic tuff, in part
silicified, is exposed along an access road, west of
the prospect. Exposures available at the time of
investigation indicate the shear zone of the Glendon
fault in this area is only about forty feet wide and
the mineralized zone approximately ten feet wide.
Jackson Prospect: The Jackson prospect lies on
the south side of Deep River approximately three
miles northeast of the McConnell prospect. The
shear zone of the Glendon fault in this area is about
200 feet wide. The deposit is located on the fault
contact between andesitic tuff to the northwest and
slates to the southeast. Two prospect pits have been
put down to a depth of about 8 feet. They expose
white foliated sericite ; however, no pyrophyllite was
observed.
Bates Mine: The Bates mine is located on the
northeast bank of Deep River approximately two
miles northeast of the Jackson prospect. Stuckey
(1928) stated that this mine was prospected in 1903
and a mill constructed in 1904. The mine was op-erated
until 1919 at which time it closed due to lack
of quality ore.
The rock is sheared and mineralized in a zone 150
feet wide, along the Glendon fault. The hanging
wall to the northwest is composed of andesite tuff;
the footwall to the southeast is composed of slate.
The pyrophyllite is developed in a band, about three
feet wide in the area of major displacement of the
fault zone and grades into sericite schist on either
side. The ore zone strikes north 70 degrees east and
dips northwest at 80 degrees.
Phillips and Womble Mines: The Phillips and
Womble mines are separated from each other by the
Siler City-Glendon road, and lie approximately two
miles northwest of Glendon. These mines were map-ped
by plane table and alidade at a scale of one inch
equals 50 feet (see Plate 2) during the field investi-gation
for this report.
The Glendon fault is exposed for approximately
1800 feet along strike in active and abandoned mine
workings. The ore body lies in the shear zone of the
fault and dips to the northwest at an average angle
of 65 degrees. The ore body is lenticular in outline
and pinches and swells, but is considerably less in
the pinches. Pyrophyllite has also been developed
along minor displacements parallel to the main fault.
White Mine : The White Mine is located on Rogers
Creek approximately 0.8 of a mile northeast of the
Womble mine. The ore body is contained between
the Glendon fault on the southeast and a secondary
reverse fault on the northwest. The ore body is
lenticular in outline and dips to the northwest at an
angle of 60 degrees. It is exposed along strike in
the pit for 375 feet. Recent investigation indicates
that the ore body continues to the southwest for a
considerable distance. To the northeast it is not
traceable beyond the mine. An exposure along the
southwest wall of the pit reveals relatively unaltered
rock overthrusting the ore body. The direction of
movement along this fault was toward the southeast,
indicating that the ore body might be overthrust to
the northeast. The country rock surrounding the
deposit is interbedded slate and andesitic lithic tuff
and is stratigraphically in the gradational contact
zone between the andesitic tuff and slate units. The
contact between mineralized rock and unaltered rock
is unusually sharp being gradational for only a few
inches or at the most a few feet.
Jones Prospect : The Jones prospect lies approxi-mately
one and four tenths miles northeast of the
White mine. Surface exposures indicate that the
rock in this area is highly sheared. Prospect pits
reveal foliated pyrophyllite and masses of sericite
schist containing chloritoid. The general size of
the deposit could not be discerned. As Stuckey
(1928) pointed out, the pyrophyllite is considerably
iron stained. This staining is probably caused by
weathering of chloritoid and might not persist with
depth.
Currie Prospect: The Currie prospect is located
almost on the northern county line, one mile east of
the Jones prospect. This prospect lies east of the
Glendon fault. The rock in this area is slate, in
places, sheared to a sericite schist. Although
Stuckey (1928) reported pyrophyllite occurred at
this deposit, none could be found during this investi-gation.
The old prospect pits are covered with over-growth
and reveal little about the deposit.
Standard Mineral Company Mine : The Standard
Mineral Company mine is situated two and one-fourth
miles southwest of Robbins. This deposit was
21
discovered in 1918, by Mr. Paul Gerhart, and min-ing
commenced soon thereafter. This operation is
the only pyrophyllite mine in the state worked under-ground.
Ore is at present being removed from the
eighth level, about 400 feet below the surface.
The pyrophyllite zone is exposed in the mine pit
for over 1300 feet continuing beyond the area map-ped
(see Plate 3). The ore body dips northwest at
50 degrees to 70 degrees and lies in a zone of compli-cated
reverse faulting. In places this faulting has
repeated the pyrophyllite zone, making the mine-able
ore body as much as 150 feet wide. The north-eastern
half of the deposit is offset to the northwest
by cross faulting. The ore body is surrounded by
slate which has been sericitized for as much as 300
to 400 feet on either side of the deposit.
Dry Creek Mine : The Dry Creek mine is located
along the strike of the Robbins fault and lies two
miles southwest of the Standard Mineral Company
mine. The ore is exposed in two pits located 500
feet apart. It has developed along two thin parallel
shear zones (see Plate 5). Ore bodies exposed in
the southern pit lie to the northwest of the strike of
the northern pit, indicating that the mineralized
zone is offset by cross faults. The ore bodies pinch
and swell along the strike of the faults, and rarely
exceed 20 feet in width. The county rock is highly
sericitized slate.
Ruff Mine : The Ruff mine is located one and one-half
miles southwest of Hallison. The ore body can
be traced for over 180 feet. It occurs in a fault zone
which strikes north 20 degrees east and dips north-west
at 80 degrees. The southeastern limb of the
ore body is displaced to the northwest by a cross
fault which strikes north 45 degrees west and dips
to the northeast at 75 degrees. The mineralized
zone averages from 6 to 15 feet wide in the center,
but narrows to the northwest and southeast, finally
dying out along strike in these directions. The coun-try
rock is an andesitic lithic tuff.
Hallison Prospect : Pyrophyllite was discovered
six tenths of a mile west of Hallison during the re-opening
of an old gold mine (Stuckey 1928). At
this locality several shallow pits have been dug along
a quartz vein. The rock in contact with the quartz
is a sericite schist containing a minor amount of
pyrophyllite. The prospect is located in the shear
zone of a north 70 degrees east trending fault, dip-ping
northwest at 55 degrees. This fault forms the
contact between felsic tuffs and slates. If any de-gree
of mineralization took place in the slates along
this fault there is a possibility of the existence of a
workable deposit in the area.
Sanders Prospect : The Sanders prospect is locat-ed
on a hill northwest of the intersection of Cotton
Creek and Cabin Creek. The top of this hill has
recently been bulldozed along strike of the deposit
for approximately 250 feet. This cut exposes seri-citized
slate which becomes sericite schist near the
zone of maximum shear of a north 35 degrees east
trending fault, dipping 70 degrees northwest. Seri-cite
developed along this fault can be traced from
Cotton Creek northeastward for about 1000 feet.
Quartz veins have been emplaced in the center of
this fault zone. Pyrophyllite is developed adjacent
to the quartz veins, and where it occurs in direct
contact with the veins, forms radiating rosettes.
The pyrophyllite zone rarely exceeds three feet in
width. Weathered pyrophyllite outcrops are highly
iron stained; unweathered pyrophyllite is relatively
free from staining but contains excessive chloritoid.
Origin of Pyrophyllite
The pyrophyllite deposits of Newfoundland (Bud-dington,
1919), North Carolina (Stuckey, 1928) and
California (Jahns and Lance, 1950) all occur in
rocks of volcanic origin. Buddington (1919), Stuck-ey
(1928), Vhay (1937), Jahns and Lance (1950),
and Broadhurst and Council (1953) have all regard-ed
the origin of pyrophyllite as hydrothermal re-placement.
Hurst (1959) from a study of the mineralogy of
Graves Mountain, Georgia believed that kyanite in
the deposit formed under water deficient conditions
at high temperature and pressure. The pyrophyllite
is thought to have formed by the ingress of water
along fractures partially converting kyanite to pyro-phyllite.
Zen (1961) from a study of samples collected from
various pyrophyllite deposits of North Carolina
tended to disregard the effect of hydrothermal re-placement
solutions on the formation of the pyro-phyllite
bodies. The presence of three phase min-eral
assemblage of the ternary system A12 3-H2
0-
SiO.„ in his estimation, indicated water acted as a
fixed component. However, he further noted that
to say water acted as a fixed component did not com-pletely
imply the absence of a free solution phase
(hydrothermal solutions), such a phase could have
existed, but certainly did not circulate freely through
the system destroying the buffering mineral assem-blages.
From a study of the occurrence of pyrophyllite in
Moore County, certain similarities among the dif-ferent
deposits became readily apparent. These de-posits
are selective to rock type, occur in shear zones
22
of major longitudinal faults, are lenticular in out-line,
have similar mineralogies, and are zoned.
Rock Types: The major pyrophyllite deposits in
the county occur in the slate unit. The wall rock
in the White mine consists of alternating beds of
slate and andesitic tuff, whereas the wall rock of the
Ruff mine is composed entirely of andesitic tuff. It
is interesting to note that both these rocks are com-posed
of easily sheared water laid, volcanic sedi-ments.
No pyrophyllite deposits have been observed
in either felsic tuffs or mafic tuffs. This is not meant
to imply that pyrophyllite does not occur in these
rocks, because it is reported in altered rhyolites in
Newfoundland (Vhay, 1937), and in felsic tuffs in
North Carolina (Stuckey, 1928) ; and Broadhurst
and Council, (1953). On the other hand, the ability
of the slates and andesitic tuffs to readily shear and
develop schistosity must have been a factor in the
formation of pyrophyllite.
Faults : Stuckey (1928) recognized that the pyro-phyllite
deposits of Moore County occurred in shear
zones. During this investigation it was found that
the pyrophyllite deposits north of Glendon and
southwest of Robbins occur in the shear zones of the
Glendon and Robbins faults. Although not studied
in as much detail, the Sanders and Ruff deposits also
occur in fault zones.
Some of the pyrophyllite pits contain as many as
four parallel northeast trending faults. The ore
bodies in the White, Standard Mineral Company, and
Dry Creek mines have all been offset by cross faults.
Pyrophyllite has not developed along these cross
faults indicating that they developed after pyrophyl-litization.
Low angle thrust faults were observed in the
hanging wall of the Womble and White pits. Cross
faults in the White pit do not offset the thrust sheet,
indicating that thrusting occurred after cross fault-ing.
Outline of Pyrophyllite Bodies : In 1928 Stuckey
noted that the pyrophillite bodies were lenticular in
outline. This investigation revealed that the ore
bodies pinch and swell along their whole length
eventually dying out along strike. It also revealed
that the bodies all trend northeast and pitch north-west,
their development being controlled by major
northeast trending, northwest dipping longitudinal
faults. Subsurface information made available dur-ing
this investigation indicates that the ore bodies
not only pinch and swell along strike, but down dip
as well.
Mineralogy : The pyrophyllite deposits all contain
the mineral pyrophyllite, sericite, kaolinite, quartz,
hematite, and chloritoid. In addition, the fault zone
at the Phillips, Womble and Snow properties contain
small augen masses composed of pyrophyllite, topaz
and diaspore. A sample of this material was col-lected
at the Phillips property. Eldon P. Allen, a
staff member of the Division of Mineral Resources,
calculated percentages of each mineral present, using
microscopic techniques, as follows : 27 percent pyro-phyllite,
36 percent diaspore, 37 percent topaz, and
1 percent fluorite. Diaspore has also been reported
at the Sanders property (Stuckey, personal com-munication).
The only crystalline radiating phyrophyllite ob-served
was in contact with vein quartz at the Sanders
Property. Fluorite crystals occur in the vein quartz
intruding the fault zone at the Phillips Property.
Pyrite cubes and chlorite masses are found in the
sericitized wall rock at this site. The pyrite cubes
are invariably coated by a tissue thin film of quartz,
even though the host rock is not silicified. The pyrite
cubes on the hanging wall side of this deposit have a
rhombic dodechedral face which is absent in the
cubic crystals of the footwall.
Silicification is prevalent at the Phillips, Wom-ble,
Snow, Dry Creek, and Standard Mineral Com-pany
mines. Solutions which brought in this silica
in places also introduced copper and gold. Silicified
rock in the hanging wall of the Womble pit is
stained with azurite and malachite. Silicified rock
in the hanging wall of the Standard Mineral Com-pany's
pit contains gold which was mined before
pyrophyllite was discovered.
Zoning : Each of the pyrophyllite deposits observ-ed
in Moore County is zoned. Zoning was first noted
by Broadhurst and Council (1953) , p. 9) who stated
:
"A large deposit can be divided into three arbitrary
units : a very siliceous footwall, a highly mineralized
zone, and a sericitic hanging wall".
The outer zone, surrounding the deposits, is a
highly sheared country rock, enriched with hematite,
chlorite, and chloritoid, which rapidly grades into
unaltered rock away from the deposit. The contact
between the outer and middle zones is sometimes
exceptionally sharp, and occasionally cuts across the
regional schistosity. The second or middle zone is
a sericite schist still exhibiting faint relic beddings
and containing minor chloritoid. This middle zone
contains silicified bodies and, in the Phillips pit,
chlorite bodies as well as abundant zones of pyrite
cubes.
The contact between the middle and inner zones
is exceedingly gradational and poorly defined. The
inner zone is always composed primarily of pyro-phyllite
with some sericite and minor chloritoid.
23
The highest grade pyrophyllite always occurs in the
center of this zone in the area of maximum shearing.
Schistosity increases toward the center of the inner
zone, which is eventually displaced by faulting.
These fault planes are almost invariably intruded by
quartz veins.
Several generalizations can be made about zoning
in the pyrophyllite bodies. These are: Shearing
increases inwardly until a zone of rupture is reached,
the amount of pyrophyllite decreases outwardly, the
amount of chloritoid increases outwardly, and seri-cite
is best developed in the middle zone and de-creases
both inwardly and outwardly. Therefore,
the zoning in these deposits may be classified as:
1. An outer magnesian and iron enriched zone; 2.
A potassium or alkali zone; and 3. A high alumina
zone.
Discussion and Conclusions : The bulk chemical
composition of the pyrophyllite deposits is essentially
the same as that of the country rock. All of the
chemical elements present in the pyrophyllite de-posits
are present in the country rock, with the ex-ception
of fluorine, copper and gold. These elements
are associated with quartz veins and silicified zones
and were obviously brought in from an outside
source. The pyrophyllite deposits could have formed
in place, with either addition or subtraction of chem-ical
elements, if the elements were properly segre-gated
and recrystallized into new minerals. A pos-sible
sequence of events in the formation of pyro-phyllite
deposits might be as follows
:
1. Intensive folding and low grade regional meta-morphism
accompanied by faulting.
2. Establishment of a temperature water pres-sure
gradient across the shear zone, with high tem-perature
and pressure in the center diminishing
toward the sides. This would cause growth of the
lower temperature and pressure minerals chlorite,
chloritoid and hematite in the outer zones; the
higher temperature and pressure mineral sericite
in the middle zone ; and the highest temperature and
pressure minerals pyrophyllite, diaspore and topaz
in the central zone. Water vapor within the system
would give the individual iron mobility to move in
or out, as the case may be, causing previously exist-ing
minerals to be replaced selectively.
3. Invasions of quartz veins, accompanied by
silicification and introduction of fluorite, copper car-bonates,
gold and pyrite as a separate event. In
addition, at the Sanders prospect, the quartz veins
caused recrystallization of the pyrophyllite in con-tact
with the veins.
4. Removement along many of the faults, accom-panied
by shearing of the quartz veins.
5. Cross faulting.
6. Minor overthrusting in the areas around the
Womble and White pits.
Gold
Mode of Occurrence : Many of the gold mines in
Moore County were originally worked as placers.
Later, as mining deleted the original stream concen-tration,
mines were opened in the primary ore veins.
The largest number of these deposits occur in highly
sheared felsic tuffs on the northwest side of the
Robbins fault along Cabin Creek.
Some of the ore occurs in rich quartz veinlets.
However, the majority is disseminated throughout
the country rock on either side of the veins. The ore
bodies usually strike northeast and dip northwest
parallel to regional schistosity.
Orthoclase feldspars have been observed in some
quartz veins suggesting that they were emplaeed at
high temperature. Pardee and Park (1948) con-sidered
the gold lodes of the southeast as high tem-perature
deposits formed at considerable depth.
They suggested that they were emplaeed during the
orogony which occurred at the close of the Carbon-iferous
period.
Gold Mines
Clegg Mine: The Clegg mine is located one and
one-half miles west of Robbins. It was originally
operated as an open cut mine, but sometime after
1900, two shafts were sunk on the ore vein. The
main or Gerhardt shaft reached a depth of 128 feet
and the second shaft reached an estimated depth of
over 110 feet. The ore was ground on Chilean mills
and the gold recovered by passing it over riffle
boxes. These boxes were eventually replaced by
copper plates.
The deposit strikes north 25 degrees east and dips
northwest at 75 degrees. The gold is disseminated
throughout an ore zone 12 feet wide. The country
rock is a felsic tuff sheared to sericite schist. The
ore body contains a network of small quartz veinlets
and is cross cut by reportedly barren quartz veins.
Wright Mine : The Wright mine lies approxi-mately
150 feet northeast of the Clegg Mine. Prior
to 1862, a shaft of unknown depth was sunk on this
property. A second shaft was completed by J. W.
Wright to a depth of 60 feet before the mine was
closed in 1912. After grinding the ore on Chilean
mills, the gold was recovered in riffle boxes.
24
The ore vein at this mine is a continuation of the
vein found at the Clegg mine, and was reported to
vary in width from 11 to 20 inches. The ore is
disseminated through, what appears to be, highly
manganese stained fault gouge.
Cagle Mine : The Cagle mine is located 1500 feet
southeast of the Clegg mine. The date this mine
was first opened is not known, but it is thought to
have been' operated in 1865 by Charley Overton.
The mine operated sporadically until about the turn
of the century, when it was closed. An attempt to
de,water the old workings was made in 1906, but
since that time the mine has laid dormant.
The first shaft, an inclined shaft, reached a depth
in excess of 171 feet ; a second shaft, approximately
50 feet southwest of the first reached a depth of
265 feet ; and a third shaft, further southwest, reach-ed
a depth of 180