844  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
which  towers  high  above  all  later  rock  formations.  In  the  Absaroka 
Range,  stretching  along  the  entire  east  side  of  the  park  and  formed 
mainly  of  igneous  rocks,  granite  and  schists  are  exposed  at  the  north- 
ern end.  The  Snowy  Range,  which  shuts  in  the  park  to  the  north,  is 
largely  made  up  of  Archean  schists,  gneisses,  and  granites,  associated 
with  the  more  recent  outbursts  of  lava.  In  the  Gallatin  Range,  on 
the  West,  a  body  of  crumpled  gneisses  and  schists  forms  the  nucleus 
of  the  mass.  The  Archean  masses  formed  either  a  part  of  a  broad 
continental  mass  or  a  group  of  closely  related  islands.  Resting  un- 
conformably  upon  the  Archean  are  great  thicknesses  of  Paleozoic  and 
Mesozoic  rocks. 
Hague,121  in  1899,  describes  the  Archean  rocks  of  the  Absaroka 
quadrangle,  in  the  northwestern  part  of  Wyoming.  These  consist  of 
crystalline  schists  and  gneisses,  mainly  mica  gneiss,  amphibolites,  and 
schists  distinctly  light  colored,  which  are  found  only  in  the  north- 
eastern part  of  the  Crandall  quadrangle. 
Sedimentary  rocks  of  middle  Cambrian  age  overlie  the  Archean 
rocks  unconformably. 
WYOMING,    GENERAL. 
Newton,122  in  1880,  describes  the  Rawhide  Butte,  a  ridge  consist- 
ing of  a  series  of  black  micaceous  schists  or  gneisses,  with  alternating 
strata  of  a  coarse,  very  feldspathic  granite  dipping  70°  to  75°  E., 
with  a  strike  N.  40°  W.  On  the  extreme  southeast  corner  of  the  butte 
is  a  bed  of  graphic  granite  similar  to  that  found  in  many  places  in 
the  Harney  Peak  region  of  the  Black  Hills. 
Eldridge,123  in  1894,  from  a  geological  reconnaissance  in  northwest 
W}^oming,  finds  that  Archean  granites,  gneisses,  and  schists  of  various 
types  form  the  crest  of  the  Bighorn,  Wind  River,  Absaroka,  and  Owl- 
Rattlesnake  ranges.  In  the  Wind  River  and  Absaroka  ranges  the 
Archean  areas  are  extensive.  Resting  upon  the  Archean  rocks  and 
in  many  places  deriving  material  from  them  are  the  rocks  of  the 
Cambrian  system. 
Knight,124  in  1900,  in  connection  with  the  discussion  of  the  artesian 
basins  of  Wyoming,  gives  a  brief  description,  accompanied  by  a  map, 
of  the  geology  of  the  State.  Algonkian  and  Archean  rocks  are 
present.  The  Archean  rocks  consist  mainly  of  granite,  in  places  cut 
by  dikes  of  porphyry  containing  mineral  ores,  which  can  be  seen  in 
typical  exposure  at  Sherman,  Laramie  Peak,  east  of  Whalen  Canyon, 
along  the  Bighorn,  Wind  River,  Gros  Ventre,  Medicine  Bow,  Ferris, 
Scminoe,  and  Owl  Creek  ranges,  along  the  Sweetwater  River,  a  few 
miles  northwest  of  Rawlings,  and  north  of  Clarks  Fork,  in  Bighorn 
County. 
The  Algonkian  rocks  are  for  the  first  time  separated  from  the 
Archean.     They  consist  of  schists  in  great  profusion,  marbles,  and 
