vanhise.]  THE    CORDILLERAS.  277 
gneisses  were,  regarded  by  Hayden  as  eruptive,  and  they  were  believed 
to  have  intruded  and  metamorphosed  the  overlying  Paleozoic  lime- 
stones. King  and  Hague,  on  the  other  hand,  regard  all  of  the  mate- 
rial of  the  three  ranges  as  metamorphic,  with  the  exception  of  the  basic 
dikes  and  possibly  some  small  areas  and  dikes  of  a  later  granite.  That 
the  horizontal  sedimentary  rocks  were  deposited  unconformably  upon 
and  against  these  ranges  is  now  admitted  by  all;  so  that  the  truth  of 
the  observations  of  Hayden  must  be  considered  doubtful,  unless  he 
found  some  place  where  there  is  actually  present  later  important  masses 
of  intrusive  granite. 
At  the  present  time  many  would  doubt  the  conclusions  of  King  and 
Hague,  that  because  the  structureless  granite  of  the  center  of  the 
ridges  vary  gradually  in  passing  outward  into  well  laminated  gneisses 
and  schists,  therefore  the  whole  is  of  sedimentary  origin,  the  inte- 
rior parts  being  more  completely  metamorphosed  than  the  exteriors. 
These  relations  might  equally  well  be  produced  by  the  increasing  ef- 
fects of  dynamic  action  upon  the  outer  borders  of  once  massive  ranges. 
The  variation  of  massive  or  nearly  massive  core  rocks  into  laminated 
gneisses  and  crystalline  schists  on  the  outer  borders,  which  occur  in 
many  other  mountain  regions,  are  thus  explained  by  numerous  later 
observers,  the  whole  being  regarded  as  igneous.  The  lamination  is 
explained  equally  as  well  by  one  theory  as  by  the  other ;  for  in  cither  case 
the  central  axes  are  the  parts  which  are  most  deeply  buried,  and  which, 
even  if  composed  of  material  originally  sedimentary,  have  become  re- 
crystallized.  On  either  hypothesis  it  is  probable  that  in  the  region 
under  discussion  are  two  fundamentally  different  series,  the  very  an- 
cient crystallines  and  the  pre-Oambrian  elastics.  The  presence  of 
abundant  granite  debris  in  the  lower  members  of  the  Medicine  peak 
series  certainly  shows  the  existence  of  a  granite  earlier  than  this  time. 
That  the  elastics  are  later  than  the  ciystallines  is  perhaps  further  in- 
dicated by  the  numerous  dikes  of  granite  which  are  found  in  the  main 
granite  area,  but  have  not  been  noted  as  cutting  the  elastics.  It  can 
not  be  said  whether  many  of  the  mica  schists  and  other  intermediate 
kinds  of  rocks  such  as  occur  in  the  Medicine  bow  and  Park  ranges 
belong  with  the  Archean  or  the  Algonkian.  It  is  wholly  among  the 
possibilities  that  schist  series  exist  which  are  older  than  the  granite; 
these  together  forming  a  basement  complex  upon  which  the  readily 
recognizable  elastics  were  deposited. 
SECTION  II.   CENTRAL  AND  WESTERN  WYOMING. 
LITERATURE    OF   THE    BIG   HORN   MOUNTAINS. 
Hayden,10  in  1861,  states  that  red  feldspathic  granites,  with  meta- 
norphic  slates  and  schists,  constitute  the  nucleus  of  the  Big  Horn 
nountains.  As  these  are  surrounded  by  strata  as  recent  as  the  Cre- 
taceous, this  uplift  is  subsequent  to  this  time. 
