828  PRE-CAMBRTAN    GEOLOGY    OF    NORTH    AMERICA. 
is  also  provisionally  correlated  by  Ball  and  Spurr  with  certain  schists 
of  the  Cripple  Creek  region,  classed  provisionally  as  Archean  by 
Cross. 
In  the  Pikes  Peak  district  Cross  describes  numerous  masses  of 
quartzite  included  in  and  cut  by  granite.  The  largest  of  these,  in 
Wilson  Park,  is  4,000  feet  thick,  stands  on  edge,  and  is  exposed  for 
5  miles  along  the  strike.  Other  large  masses  occur  in  Cooper  and 
Blue  mountains.  These  quartzites  and  the  intersecting  granite, 
which  occupies  a  far  greater  area  than  the  quartzites,  Cross  refers  to 
the  Algonkian. 
Van  Hise  believes  that  some  of  the  gneisses  and  amphibolitic  schists 
associated  with  the  quartzites  northwest  of  Florissant,  in  the  Pikes 
Peak  quadrangle,  are  older  than  the  main  masses  of  intrusive  gran- 
ites, and  probably  belong  to  the  basement  complex  or  Archean. 
Rocks  of  a  similar  old  aspect  were  observed  by  W.  N.  Smith  in  the 
Felch  Creek  section. 
Crosby  calls  attention  to  the  general  even  character  of  the  granite 
floor  of  this  area  and  holds  that  it  marks  the  end  and  not  the  begin- 
ning of  base-leveling  processes. 
WET   AND    SANGRE    DE    CRISTO    RANGES.0 
Pre-Cambrian  rocks,  mainly  granite,  gneiss,  and  mica  schist,  form 
the  Wet  Mountains.  The  granite  is  intrusive  into  the  gneiss  and 
schist  and  is  correlated  by  Cross  with  Algonkian  granites  of  the 
Front  Range.     The  origin  of  the  mica  schists  is  not  known. 
Granite,  gneiss,  and  schist  are  also  found  in  the  axis  of  the  Sangre 
de  Cristo  Range.  Dark  amphibolite  and  other  dark  schists  occur  in 
Hunts  Peak.  Cross  concludes  that  the  "  eruptive  granite  "  of  the 
Hayden  map  is  probably  of  post- Algonkian  age.  Quartzite,  taken 
to  be  Algonkian,  has  been  observed  by  Emmons  in  the  southern  part 
of  the  range  and  by  Van  Hise  and  Leith  on  the  north  flank  south  of 
Salida.  Cross  concludes  that  the  southern  part  of  the  range  near 
Silver  Cliff  is  composed  mainly  of  Carboniferous  sandstones  and 
conglomerates. 
PARK  RANGE.0 
The  Park  Range  is  composed  of  rocks  of  pre-Cambrian  age,  con- 
sisting largely  of  granite  associated  with  gneiss  and  schist  and  amphi- 
bolites,  with  pegmatite  dikes.  The  rocks  in  general  resemble  those 
of  the  Front  Range.  The  prevailing  dips  of  secondary  structure  are 
toward  the  west.  In  the  northern  part  the  dip  is  40°  to  50°  S. 
Hague  and  King  viewed  the  range  as  representing  the  west  half  of 
an  anticline,  the  eastern  half  of  which  has  been  faulted  down.     Cam- 
a  By  the  authors. 
