280  PRE -CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
appear  to  remain  constant  in  certain  zones.  Passing  to  the  eastward 
the  granites  disappear  and  are  replaced  by  schistose  granites  or  typical 
schists.  The  granites  are  flexed  and  contorted  in  every  possible  direc- 
tion and  contain  simple  bands  of  micaceous  and  chloritic  schists,  which 
denote  the  original  planes  of  stratification.  It  is  believed  that  by  a 
careful  examination  evidence  will  be  found  bearing  upon  the  former 
condition  of  this  metamorphic  area.  The  Wind  river  range  is  regarded 
as  a  steep  anticlinal  fold.  The  rocks  constituting  it  are  regarded  as 
representing  siliceous  shales  (schists)  and  are  more  or  less  argillaceous 
sandstones  (granites).  On  the  eastern  side  of  the  Wind  river  range  is 
found  hard  red  quartzitic  sandstones  directly  overlying  the  youngest 
metamorphic  granites.  It  extends  up  the  gently  sloping  ridges  in  a 
scalloped  line.  In  direct  contact  with  the  granites  it  is  difficult  to 
determine  where  the  granite  ends  and  the  quartzite  begins,  so  that  it 
may  be  said  that  the  quartzites  and  granites  blend  into  each  other.  It 
appears  that  the  lowest  Silurian  strata  were  deposited  before  the  thor- 
ough metamorphosis  of  the  entire  mass  took  place,  unless  the  change 
in  the  sandstone  is  caused  by  a  generation  of  heat  during  the  period  of 
mountain  elevation.  The  Archean  rocks  of  the  Wind  river,  S weetwa ter, 
and  adjacent  ranges  are  classified  into  the  Huronian,  Laurentian,  and 
Prozoic  systems.  The  first  includes  micaceous,  hornblendic,  and  chlor- 
itic granite,  30,000  feet  thick.  The  Laurentian  includes  metalliferous 
schists  composed  of  quartz,  feldspar,  hornblende,  and  mica,  18,000  feet 
thick.  The  Prozoic  includes  massive  structureless  inuscovite  granite 
of  indefinite  thickness. 
Peale,15  in  1879,  states  that  the  western  foothills  of  the  Wind  river 
mountains  and  a  few  isolated  buttes  are  composed  of  muscovite  granite, 
the  most  prominent  of  the  latter  being  Fremont's  bntte. 
St.  John,16  in  1883,  describes  the  Archean  rocks  of  the  Wind  river 
range  and  gives  a  number  of  sections  showing  the  unconformable  rela- 
tions of  these  rocks  to  the  overlying  Potsdam  and  higher  sedimenta- 
ries.  The  Archean  area  is  composed  of  granitic,  gneissic,  and  various 
schistose  rocks,  including  hornblendic,  micaceous,  talcose,  and  garnet- 
iferons  varieties. 
LITERATURE   OF   THE   GROS   VENTRE    AND   WYOMING  RANGES. 
St.  John,17  in  1879,  states  that  the  Gros  Ventre  range  has  an 
Archean  nucleus,  consisting  chiefly  of  distorted  gneissic  and  schistose 
layers,  and  forms  a  sort  of  transverse  bar  or  truss  connecting  the 
Wind  river  and  Teton  ranges.  The  Primordial  quartzite  was  seen 
lying  in  immediate  contact  unconformably  above  the  Archean  schists, 
from  which  it  is  separated  by  a  rose-colored  finely  laminated  gneissoid 
layer,  which  may  be  the  metamorphosed  basal  member  of  the  quartzite. 
St.  John,16  in  1883,  further  describes  the  Gros  Ventre  range  and 
gives  various  sections  through  it.  The  Primordial  quartzite  rests  di- 
rectly upon  the  Archean  rocks.  In  the  Wyoming,  as  in  the  Gros  Ventre- 
range,  the  Archean  is  unconformably  below  the  stratified  rocks. 
