316  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
LITERATURE   OF  THE   PARK  RANGE. 
Marvine,41  in  1874,  describes  the  northern  part  of  the  Park  range 
as  composed  of  a  very  distinctively  and  evenly  bedded  series  of  schists, 
gneisses  and  granites,  which  have  a  strike  nearly  with  the  ridge,  and 
a  dip  of  40°  or  50°  to  the  southward. 
LITERATURE   OF   THE   SAWATCH   MOUNTAINS. 
Hayden,57  in  1874,  describes  the  Sawatch  range  as  a  solid  mass  of 
granite,  80  miles  in  length  by  40  in  width,  which  has  acted  as  a  sin- 
gle wedge  thrust  upward,  and  thus  causing  the  sedimentaries  to  incline 
from  either  side. 
Peale,42  in  1874,  states  that  on  Massive  mountain  the  rocks  are 
mainly  gneissic,  with  alternations  of  porphyritic  granite  or  granite- 
porphyry,  with  seams  of  quartzite  and  hornblendic  volcanic  rock.  On 
Eagle  river,  at  the  base  of  the  section  is  gneiss,  and  above  this  is  white 
quartzite. 
Endlich,43  in  1874,  states  that  the  granite  of  the  Sawatch  on  the 
west  side  of  the  Arkansas  is  probably  post- Silurian.  This  range  has 
two  kinds  of  granite  that  are  peculiar  to  it  and  an  older  predominating 
one.  Both  of  these  are  newer  than  the  red,  middle,  and  coarse  grained 
rock  found  in  the  Wet  mountains.  The  first  of  these  varieties  composes 
the  main  part  of  the  range  and  constitutes  its  most  prominent  peak, 
mount  Princeton.  Besides  this,  there  is  protogine  and  eruptive  granite. 
Mount  Ouray  is  composed  in  large  part  of  hornblende  rock.  On  one 
side  the  hornblende  and  granite  are  interstratified,  the  granite  being 
regarded  as  intruded  between  the  strata.  The  change  from  the  granite 
to  the  hornblende  rock  is  always  abrupt. 
Endlich,48  in  1877,  states  that  at  the  southern  end  of  the  Sawatch 
range  trachyte  is  the  principal  rock. 
Emmons,  (S.  F.),58  in  1882,  states  that  in  the  Mosquito  range  are  found 
granites,  gneisses  and  anrphibolites.  The  granites  are  in  most  cases 
stratified  and  are  of  undoubted  sedimentary  origin.  In  other  cases 
the  evidence  is  less  clear  and  they  have  the  characteristics  of  eruptive 
granites.  Within  the  masses  of  the  normal  granite  occur  large  irreg- 
ular vein-like  masses  of  secondaiy  origin,  corresponding  to  pegmatite. 
The  gneiss  is  mostly  mica-gneiss.  The  amphibolite  is  less  abundant 
than  the  gneiss  and  granite  and  occurs  interstratified  with  them.  Un- 
conformably  above  these  are  quartzites  which  bear  Primordial  fossils 
belonging  to  the  Potsdam. 
Lakes,59  in  1886,  describes  the  Sawatch  range  as  consisting  of  gneiss 
and  granite  penetrated  by  volcanic  dikes,  with  patches  of  Silurian, 
Carboniferous  and  more  recent  strata  resting  on  or  up  tilted  against 
each  flank.  In  the  Aspen  region  are  two  granites,  one  the  meta- 
morphic  granite  of  the  Sawatch  and  the  other  a  diorite  and  eruptive 
lava  of  the  Elk  mountain  system.  On  the  granites  are  unconformably 
located  the  Cambrian  strata,  the  base  of  which  is  quartzite. 
