PIEDMONT  PLATEAU  AND  PORTIONS  OF  THE  APPALACHIANS.       687 
in  composition  as  the  Thunderhead  conglomerate,  except  that  in  the 
Clingman  conglomerate  there  is  smaller  development  of  slate  beds. 
The  age  of  the  Ocoee  rocks  is  undetermined,  and  they  are  there- 
fore mapped  as  of  unknown  age. 
Hayes,85  in  1895,  maps  and  describes  the  geology  of  the  Cleveland 
quadrangle,  in  Tennessee.  Ocoee  rocks  occupy  the  southeastern  part 
of  the  quadrangle,  forming  Big  Frog  Mountain  and  the  plateau 
along  its  western  base.  No  fossils  have  yet  been  found  in  these  rocks, 
and  they  are  separated  by  a  great  fault  from  rocks  of  known  age,  so 
that  their  position  in  the  stratigraphic  column  can  not  be  fixed  with 
certainty,  but  since  they  bear  the  marks  of  extreme  age  they  are  con- 
sidered as  probably  Algonkian.  The  Ocoee  series  comprises  in  this 
area  the  following  formations,  from  the  base  upward:  Wilhite  slate, 
Citico  conglomerate,  Pigeon  slate,  and  Thunderhead  conglomerate 
and  slate.  Their  correlation  with  formations  bearing  the  same  names 
in  the  Knoxville  quadrangle  to  the  northeast,  described  by  Keith,  is 
only  approximate.  The  Wilhite  slate  consists  in  the  main  of  dark- 
blue  or  black  slate.  The  Citico  conglomerate  varies  from  a  coarse, 
massive  conglomerate  to  fine-grained  sandstone  or  quartzite  in  sandy 
shale.  The  thickness  varies  from  500  to  1,150  or  more  feet.  The 
Pigeon  slate  resembles  the  Wilhite  slate,  the  chief  difference  being  a 
frequently  observed  banding  and  an  abundance  of  interbedded  gray 
schistose  sandstones  and  graywackes,  and  occasional  conglomerates. 
The  Thunderhead  conglomerate  and  slate  can  be  separated  into  three 
divisions.  The  lowest  of  these,  from  800  to  1,000  feet  thick,  is  a 
massively  bedded  conglomerate,  made  up  largely  of  blue  quartz  and 
feldspar  pebbles.  The  middle  division  consists  of  interbedded  black 
slate  and  schistose  conglomerate  or  sandstone,  the  slate  apparently 
predominating.  The  upper  division  is  also  composed  of  conglomerate 
and  slate,  but  the  slate  is  comparatively  unimportant. 
SECTION  7.     SOUTH  CAROLINA. 
SUMMARY   OF  LITERATURE. 
Ruffin,86  in  1843,  describes  as  Primitive  the  limestones  which  enter 
South  Carolina  at  York,  west  of  Kings  Mountain,  and  run  to  Spartan- 
burg. Embracing  nearly  all  the  country  above  the  loAver  falls  of  tin1 
river  is  a  granitic  region. 
Tuomey,  87  in  1848,  gives  a  report  of  the  geology  of  South  Carolina. 
The  unstratified  or  igneous  rocks  underlie  the  stratified  rocks,  or  are 
pushed  up  through  them,  and  include  granitic  and  basaltic  rocks, 
being  generally  found  in  the  form  of  dikes.  Discordances  between 
slaty  cleavage  and  bedding  are  found.  The  crystalline  structure  of  the 
Primary  stratified  rocks  is  supposed  to  be  due  to  heat  which  comes 
