682  PRE-CAMBRIAN    GEOLOGY   OF    NORTH   AMERICA. 
been  referred  to  the  "  Ocoee  "  by  the  recent  work  of  the  United  States 
Geological  Survey. 
Emmons  was,  in  a  measure,  correct  in  calling  the  Taconic  rocks  of 
central  North  Carolina  the  bottom  sediments  and  placing  them  be- 
low the  Silurian.  The  absence  of  fossils  in  the  slates,  however,  ne- 
cessitates our  going  back  still  another  step  and  placing  them  below 
the  Cambrian  sediments,  in  the  Algonkian,  which  Van  Hise  has  de- 
fined as  including  all  recognizable  pre-Cambrian  elastics  and  their 
equivalent  crystallines,  the  base  of  the  Cambrian  being  placed  below 
the  Olenellus  fauna.  Here  the  matter  must  rest  until  we  can  find 
fossils  in"  the  rocks,  or  verify  the  organic  character  of  Emmons's 
Paleotrochis;  or  until  we  can  trace  the  rocks  into  a  terrane  of  known 
age.  So  also  the  pyroclastic  volcanics  must  be  looked  upon  as  pre- 
Cambrian. 
Keith,71  in  1903,  describes  and  maps  the  geology  of  the  Cranberry 
quadrangle  of  North  Carolina  and  Tennessee,  along  the  junction  of 
the  Piedmont  Plateau  and  the  Blue  Ridge.  Archean  and  doubtful 
Algonkian  rocks  occupy  all  but  the  northwest  corner  of  the  area. 
The  Archean  rocks  are  mapped  and  described  under  the  heads  Caro- 
lina gneiss,  Roan  gneiss,  soapstone,  Cranberry  granite,  Blowing  Rock 
gneiss,  and  Beech  granite.  The  Carolina  gneiss  is  the  oldest  rock  of 
the  region  and  consists  of  interbedded  mica  schist,  mica  gneiss,  and 
fine  granitoid  layers.  The  Roan  gneiss  consists  of  hornblende  gneiss, 
hornblende  schist,  and  diorite,  with  some  interbedded  mica  schist  and 
gneiss,  all  cutting  the  Carolina  gneiss.  Soapstone,  resulting  from  the 
alteration  of  peridotite  and  pyroxenite,  occurs  in  bodies  closely  asso- 
ciated with  the  Roan  gneiss  and  probably  of  the  same  age.  The 
Cranberry  granite  is  the  most  extensive  formation  in  the  district, 
occurring  chiefly  in  the  mountain  district.  It  consists  of  granite  and 
of  schist  derived  from  granite,  and  cuts  the  Roan  gneiss  and  the  Caro- 
lina gneiss.  All  of  the  rocks  named  are  cut  by  the  Blowing  Rock 
gneiss  and  the  Beech  granite,  which  are  considered  to  be  of  the  same 
age. 
Four  formations  are  classed  as  doubtful  Algonkian :  Linville  meta- 
diaba.se,  altered  greenish  diabase  and  gabbro;  Montezuma  schist,  in- 
cluding blue  and  green  epidotic  schist,  probably  altered  basalt,  and 
amygdaloidal  basalt;  Flattop  schist,  a  gray  and  black  schist,  proba- 
bly altered  andesitic  rocks;  metarhyolite,  grayish  metarhyolite,  and 
rhyolite  porphyry.  The  first  of  these  appears  to  be  the  lower  part  of 
a  surface  flow ;  the  last  three  are  of  surface  volcanic  nature. 
Keith,72  in  190-t,  maps  and  describes  the  geology  of  the  Asheville 
and  Greenville  quadrangles  of  Tennessee  and  North  Carolina.  Pre- 
Cambrian  rocks  occupy  all  the  southeastern  part  of  the  area.  They 
are  igneous  and  metamorphic  rocks  much  folded  and  of  complex  dis- 
tribution.    Those  referred  to  the  Archean  are,  from  the  base  up: 
