702  PRE-CAMBRTAN    GEOLOGY    OF    NORTH   AMERICA. 
United  States  Geological  Survey.  The  work  of  Hayes  farther  south 
shows  that  the  same  series  of  rocks  in  the  same  relations  occur  in 
Georgia  and  Alabama. 
Carolina  gneiss. — This  is  the  oldest  formation  known  in  the  south- 
ern Appalachians.  It  consists  mainly  of  mica  gneiss  and  mica  schist, 
with  varying  amounts  of  quartz,  feldspar,  muscovite,  and  biotite. 
Many  layers  are  granitoid,  others  are  fine  schists.  With  these 
major  types  there  are  also  found  cyanite,  garnet,  and  muscovite 
schists  and  gneisses.  At  several  localities  large  layers  of  marble  are 
interbedded  with  the  gneiss.  Thus  the  formation  is  in  part  of  sedi- 
mentary origin,  while  other  beds  have  a  probable  igneous  origin. 
The  nature  of  most  of  the  formation  is  entirely  unknown,  however, 
and  all  varieties  are  thoroughly  metamorphosed.  The  banded  gneisses 
and  schists  produced  during  one  metamorphism  were  folded  and 
crumpled  during  another.  The  different  layers  were  thickened  or 
thinned  and  cut  across  by  secondary  foliation. 
Roan  gneiss. — Hornblende  schist  and  gneiss  make  up  most  of  the 
formation.  With  these  are  found  bodies  of  diorite  and  gabbro,  all 
more  or  less  altered.  These  rocks  cut  the  Carolina  gneiss  in  intricate 
dikelike  forms.  In  the  Roan  gneiss  also  the  schistosity  and  gneissoid 
banding  of  one  deformation  are  folded  and  cut  by  those  of  a  second. 
Soapstone  group. — Dunite,  serpentine,  and  soapstone  are  alteration 
products  of  peridotite  and  pyroxenite  and  are  closely  associated.  A 
single  rock  mass  may  be  composed  of  all  the  varieties  or  of  one.  In 
the  great  majority  of  cases  their  association  with  the  Roan  gneiss  is 
so  distinct  as  to  show  a  close  connection  in  age,  although  they  appear 
to  cut  the  Roan  here  and  there.  The  dunite  and  serpentine  are  not 
schistose,  while  the  soapstone  and  other  varieties  are  decidedly  so. 
Cranberry  granite. — The  Carolina  and  Roan  gneisses  are  cut  by 
the  Cranberry  granite,  which  consists  of  coarse  and  fine  gray  and  red 
granite.  It  is  usually  characterized  by  biotite  and  frequently  shows 
large  orthoclase  phenocry>ts.  Much  of  the  rock  is  massive,  but  large 
parts  are  gneissoid  and  in  certain  zones  extremely  schistose  and 
striated.  The  foliation  planes  are  fairly  constant  in  dip  over  large 
areas. 
Henderson  granite. — This  formation  does  not  touch  the  other 
granites,  but  cuts  the  Carolina  and  Roan  gneisses.  It  is  characterized 
by  orthoclase  phenocrysts  and  muscovite.  This  granite  is  strongly 
schistose,  both  groundmass  and  phenocrysts  being  deformed.  The 
schistose  planes  are  remarkably  uniform  in  dip. 
Blowing  Roek  gneiss. — This  formation  cuts  the  Carolina  gneiss 
and  appears  to  cut  the  Cranberry  granite.  The  formation  con- 
sists of  a  highly  porphyritic  rock  in  which  large  orthoclase  crystals 
are  embedded  in  a  dark  groundmass  characterized  by  biotite.  The 
original  rock  was  probably  a  basic,  porphyritic  granite.     Usually  it 
