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CI 


North  Carolina 

Department  of  Conservation  and  Development 

Robert  L.  Stallings,  Jr.,  Director 


Division  of  Mineral  Resources 
Jasper  L.  Stuckey,  State  Geologist 


Bulletin  75 


GEOLOGY  OF  THE  ALBEMARLE  QUADRANGLE, 

NORTH  CAROLINA 


By 
James  F.  Conley 


Raleigh 
1962 


North  Carolina 
Department  of  Conservation  and  Development 

Robert  L.  Stallings,  Jr.,  Director 


Division  of  Mineral  Resources 
Jasper  L.  Stuckey,  State  Geologist 


Bulletin  75 


GEOLOGY  OF  THE  ALBEMARLE  QUADRANGLE, 

NORTH  CAROLINA 


By 
James  F.  Conley 


Raleigh 
1962 


I 


Members  of  The  Board  of  Conservation  and  Development 

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

R.  Walker  Martin,  Vice  Chairman...  Raleigh 

John  M.  Akers  Gastonia 

Dr.  Mott  P.  Blair  Siler  City 

Robert  E.  Bryan Goldsboro 

Mrs.  B.  F.  Bullard  Raleigh 

Daniel  D.  Cameron....  Wilmington 

Mrs.  Fred  Y.  Campbell  ..  Waynesville 

Dr.  John  Dees  Burgaw 

William  P.  Elliott.  Marion 

E.  Hervey  Evans,  Jr.  Laurinburg 

E.  R.  Evans...  ..  Ahoskie 

Andrew    Gennett...  Asheville 

Luther  W.  Gurkin,  Jr.  Plymouth 

Woody  R.  Hampton  ...  Sylva 

Charles  E.  Hayworth  .High  Point 

Gordon  C.  Hunter..  Roxboro 

Roger  P.  Kavanaugh,  Jr.  __  Greensboro 

Carl  G.  McGraw  Charlotte 

Lorimer  W.  Midgett  Elizabeth  City 

Ernest  E.  Parker,  Jr.  Southport 

R.  A.  Poole  _..Clinton 

Eric  W.  Rodgers  ...Scotland  Neck 

Robert  W.  Scott  Haw  River 

James  A.  Singleton...  Red  Springs 

J.  Bernard  Stein  Fayetteville 

Paul  H.  Thompson  Fayetteville 

Charles  B.  Wade,  Jr Winston-Salem 


11 


Letter  of  Transmittal 

Raleigh,  North  Carolina 
December  14,  1962 

To  His  Excellency,  Honorable  Terry  Sanford 
Governor  of  North  Carolina 

Sir: 

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

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


Respectfully  submitted, 

Robert  L.  Stallings,  Jr. 
Director 


in 


Contents 

Page 

Introduction  1 

Location  and  description  of  the  area 1 

Purpose  and  scope 1 

Field  work  and  acknowledgments  _ 2 

General  geology  2 

Previous  investigations 3 

Stratigraphy .' 4 

Lower-volcanic  sequence:    Felsic  tuff  unit 4 

Volcanic-sedimentary  sequence 5 

Argillite  unit 5 

Tuffaceous  argillite  unit 5 

Felsic  tuffaceous  argillite—- -. 6 

Felsic  crystal  tuff 6 

Vitric  tuff  6 

Felsic  tuff  of  the  "Flatswamp  Mountain  Sequence" 7 

Mafic  tuffaceous  argillite  7 

Mafic  tuff  _ : 7 

Graywacke  unit  7 

Gray wacke  7 

Mafic  tuff 8 

Lithic  tuff  8 

Upper  volcanic  sequence 8 

Andesitic  tuffs  unit 8 

Basaltic  tuffs  unit  9 

Rhyolite  unit 9 

Intrusive  rocks 10 

Gabbro  sills 10 

Rhyolite  dikes . 11 

Diabase  dikes  , 11 


IV 


Page 
Chemical  composition  12 

Environment  of  deposition —12 

Structure    13 

Troy  anticlinorium  13 

New  London  synclinorium    13 

Angular  unconformity  14 

Shear  zones  15 

Jointing  __•_ , __  15 

Cleavage   15 

Metamorphism  .15 

Geomorphology 15 

Stage  of  development  ___15 

Drainage  pattern  and  development 15 

Erosional  surfaces 17 

Economic  geology  17 

Gold  ■. 17 

Coggins  mine  17 

Morris  Mountain  mine 17 

Worth  placer  mine 17 

Moratock  ( ?)  mine '. 17 

Parker  mine  1 8 

Cottonpatch  mine 18 

Gold  mine,  name  unknown . 1 8 

Dutchmans  Creek  and  Island  Creek  placer  mines 18 

Lead  and  zinc 18 

Quartz  18 

Crushed  stone 19 

Flagstone    19 

Brick  clay  1 19 

Lightweight  aggregate  20 

References  cited 26 


• 


Illustrations 

Page 
PLATES 

Plate  1.    Geologic  Map  of  the  Albemarle  quadrangle in  pocket 

Plate  2.    Photomicrographs  of  Typical  Volcanic  Rock Page  22 

Plate  3.    Photographs  of  Typical  Rock  Specimens Page  24 

FIGURES 

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


Yl 


GEOLOGY  OF  THE  ALBEMARLE  QUADRANGLE, 

NORTH  CAROLINA 

By 
James  F.  Conley 


INTRODUCTION 

Location  and  Description  of  Area 

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

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

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

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

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


an  average  of  200  days  per  year. 

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

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

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

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

Purpose  and  Scope 

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


VIRGINIA 


GEORGIA 


SCALE 

0        25        50         75        MOMiieS 


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


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

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

Field  Work  and  Acknowledgments 

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

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


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

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

General  Geology 

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

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

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


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

Previous  Investigations 

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

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

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

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


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

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

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

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

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

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


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

Stratigraphy 

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

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

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

Lower  Volcanic  Sequence 

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


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

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

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

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

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


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

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

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

Volcanic-Sedimentary  Sequence 

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


Argillite  Unit 

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

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

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

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

Tuffaceous  Argillite  Unit 

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


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

Felsic  Tuffaceous  Argillite 

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

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

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


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

Felsic  Crystal  Tuff 

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

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

Vitric  Tuff 

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

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

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


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

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

Felsic  Tuff  of  the  "Flatswamp  Mountain  Sequence" 

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

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

Mafic  Tuffaceous  Argillite 

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


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

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

Mafic  Tuff 

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

Graywacke  Unit 

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

Graywacke 

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


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

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

Mafic  Tuff 

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

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

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


Lithic  Tuff 

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

Upper  Volcanic  Sequence 

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

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

Andesitic  Tuffs  Unit 

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


8 


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

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

Balsatic  Tuft's  Unit 

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

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


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

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

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

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

Rhyolite  Unit 

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

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


9 


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

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

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

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

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


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

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

INTRUSIVE  ROCKS 
Gabbro  Sills 

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

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


10 


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

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

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

Rhyolite  Dikes 

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


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

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

Diabase   Dikes 

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

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

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

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


11 


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

CHEMICAL  ANALYSES  OF  CAROLINA 
SLATE  BELT  ROCKS 


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


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

TABLE  I 
Major  Constituents  of  Carolina  Slate  Belt  Rocks 

*         **  I g  n . 

Si03      R2O3  FezOs  CaO     MgO    Na-0     l<20    Loss 


Frrphyriiic    rhyoht; 
rhyolite  unit. 


rhyolite  unit. 


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


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


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


7.0       5.9       1.88       0.25 


5.07 


Graywacke, 
Graywacke  unit. 


>7.7       4.3       2.5       0.4       0.69       11.76       4.8 


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

"£  lite,  tuffaceous  argillite 

£  c  unit. 

._  ° 

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

CO  „  lite,  tuffaceous  argillite 

.2 ,?  unit. 


Vitric   tuff,  78.0 

tuffaceous  argillite  unit. 


Argillite 
Argillite   unit. 


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


:  Felsic   tuff. 


73.1         15.1       2.5       2.5       0.3       2.04       0.55       1.07 


Gabbro  .sill. 


11.1  15.5       5.0       8.9     16.3       0.60       0.10       5.61 


2§ 


•Predominantly  AI2O3  but  could  contain  amounts  of  Ti02,  M11O,  P2O5 
and  other  elements  precipitated  by  NH*OH  after  silica  dehydration. 
**Total   iron   content   reported  at  Fe202. 

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

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


Environment  of  Deposition 

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

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

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

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


12 


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

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

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

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

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

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


Structure 

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

Troy  Anticlinorium 

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

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

New  London  Synclinorium 

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


13 


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

Angular  Unconformity 

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

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

Further  indications  of  the  unconformity  are: 

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

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

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

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


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

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

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

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

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


14 


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

Shear  Zones 

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

Jointing 

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

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

Cleavage 

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

Metamorphism 

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


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

Geomorphology 

Stage  of  Development 

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

Drainage  Pattern  and  Development 

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

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

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


15 


i 


16 


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

Erosional  Surfaces 

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

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

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

ECONOMIC  GEOLOGY 

Gold 

Coggins  Mine 

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

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


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

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

Morris  Mountain  Mine 

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

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

Gold  per  ton ...  $3.61     $82.68 

Silver  per  ton.  .68       trace 


$4.29     $82.68 

Worth  Placer  Mine 

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

Moratock(?)  Mine 

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

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


17 


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

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

Parker  Mine 

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

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

1  to  214  pounds  each. 

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

Cotton  Patch  Mine 

The  Cotton  Patch  mine  is  located  approximately 

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


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

Gold  Mine,  Name  Unknown 

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

Dutchmans  Creek  and  Island  Creek  Placer  Mines 

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

Lead  and  Zinc 

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

Quartz 

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


18 


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

Crushed  Stone 

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

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

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

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


Flagstone 

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

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

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

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

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

Brick  Clay 

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


19 


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

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

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

Lightweight  Aggregate 

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


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

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

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


20 


BULLETIN  75 


PLATE  2 


»«ks«M 


Photomicrographs  of  Typical  Volcanic  Rocks 


22 


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


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


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


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

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

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

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


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


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


23 


BULLETIN  75 


PLATE  3 


24 


Photographs  of  Typical  Rock  Specimens 


1  .     Welded  crystal  flow  tuff,  felsic  tuff  unit. 

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

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

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

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


6.  Graywacke     containing     crude     graded     bedding,     graywacke 
unit. 

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

8.  Porphyritic   rhyolite,   rhyolite  unit. 

9.  Spherulitic   rhyolite,   rhyolite  unit. 

10.     Amygdaloidal   gabbro  from  a  gabbro  sill. 


25 


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26 


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