PIEDMONT   PLATEAU  AXh   PORTIONS  OF  THE  APPALACHIANS.      697 
The  greater  part  of  the  North  Carolina  Piedmont  region  is  in- 
cluded between  the  eastern  belt  described  above  and  the  mountain 
region  in  the  western  part  of  the  State.  The  middle  belt  of  the 
Piedmont  region,  immediately  west  of  and  parallel  to  the  eastern 
belt,  is  composed  largely  of  igneous  rocks,  principally  granites,  which 
are  now  more  or  less  schistose  from  dynamo-metamorphism.  The 
mica  types  largely  predominate,  though  hornblendic  ones  are  not  un- 
common. Altered  basic  eruptives,  greenstones,  and  greenstone  schists 
are  common,  and  in  some  places  form  the  rocks  into  which  the  gran- 
ites were  intruded.  Watson  has  indicated  that  probably  the  major 
part  of  this  complex,  if  indeed  not  all  of  it,  can  reasonably  be  re- 
ferred to  a  pre-Cambrian  age. 
Excluding  several  narrow  bands  and  other  irregular  areas  of  meta- 
morphic  slates,  schists,  limestone,  quartzites,  and  conglomerates  of 
unknown  age,  probably  Cambrian  and  later  in  part,  the  western 
portion  of  the  Piedmont  region  is  composed  of  gneisses,  mapped  by 
the  North  Carolina  Geological  Survey  as  probable  Archean.  Both 
micaceous  and  hornblendic  gneisses  occur,  with  t lie  former  greatly 
predominating.  Over  parts  of  the  area  the  gneisses  are  regarded  as 
passing  into  schists  through  a  higher  development  of  lamination, 
and  include  numerous  masses  of  granitic  and  other  distinctively  ig- 
neous rocks.  The  gneisses  have  been  commonly  considered,  in  great 
part,  to  be  sedimentary  rocks,  though  a  part  of  them  are  certainly 
granites  and  other  original  igneous  rocks.  The  general  strike  of  the 
gneisses  is  about  N.  30°  E.,  with  a  prevailing  dip  at  a  high  angle 
toward  the  southeast.  Local  variations  in  both  strike  and  dip  are 
very  numerous. 
In  the  western,  and  especially  the  southwestern,  pari  of  the  gneiss 
belt  occur  numerous  small  lenticular  masses  of  basic  magnesiai) 
rocks,  chiefly  peridotites,  pyroxenites,  and  amphibolites,  the  former 
largely  predominating,  which  are  regarded  as  of  igneous  origin  and 
intrusive  in  character. 
Keith  has  recently  mapped  and  described  the  geology  of  the  Cran- 
berry, Asheville,  Mount  Mitchell,  and  Nantahala  quadrangles,  in 
North  Carolina  and  Tennessee.  These  quadrangles  are  in  the  moun- 
tain region  and  along  the  junction  of  the  Piedmont  Plateau  and  the 
Blue  Ridge.  In  the  Cranberry  quadrangle  all  but  the  northwest 
corner  in  Tennessee  is  occupied  by  rocks  of  Archean  and  doubtful 
Algonkian  ages.  The  Archean  rocks  mapped  and  described  com- 
prise the  Carolina  gneiss.  Roan  gneiss,  soapstone,  Cranberry  granite. 
Blowing  Rock  gneiss,  and  Beech  granite.  The  Carolina  gneiss  is 
the  oldest  rock  of  the  area,  and  is  of  unknown  origin.  The  five  re- 
maining formations  of  Archean  age  are  regarded  as  of  igneous  origin. 
The  format  ions  classed  as  doubtful  Algonkian  are  Linville  metadia- 
base,  Montezuma    schist.    Flattop   schist,   mid    tnetarhyolite.     The 
