THE    CORDILLERAS.  805 
schists  become  interlaminated  with  .gneiss,  which  becomes  more  and 
more  abundant,  and  on  Coal  Creek,  cutting  the  schists,  are  also  peg- 
matitic  granite  veins.  Nowhere  between  the  clastic  and  the  gneissoid 
series  was  any  discordance  discovered,  there  appearing  to  be  between 
them  a  gradation,  although  a  somewhat  rapid  one.  The  clastic  series 
at  South  Boulder  Creek  is  at  least  1,000  feet  thick.  The  lower 
gneissoid  series  at  times  is  in  part  quite  regularly  laminated,  at  other 
times  becomes  a  heavily  bedded  granite  gneiss,  but  for  several  miles 
toward  the  core  of  the  mountains,  as  far  as  investigated,  does  not 
become  structureless  granite. 
On  Coal  Creek,  at  one  place  within  the  clastic  series,  is  a  wedge  of 
granite  of  considerable  thickness,  and  this  does  not  grade  into  the 
clastic  rocks  as  does  the  main  granitoid  gneiss  area.  The  relations  of 
the  Trias  both  to  the  granite  gneiss  and  to  the  clastic  series  are  such 
as  to  show  that  it  is  clearly  a  later  formation,  separated  from  them  by 
a  very  great  unconformity. 
At  Kalston  Creek  the  heavily  bedded  gneisses  were  found  to  vary 
into  hornblende  gneiss  interlaminated  with  granite  veins,  and  these 
into  rather  fine-grained  schistose  rock,  but  there  was  discovered  here 
no  clear  evidence  of  a  clastic  series,  although  the  more  schistose  phases 
immediately  under  the  T*ias  may  represent  the  more  altered  clastic 
schists  of  Coal  and  South  Boulder  creeks. 
Cross,08  in  1894,  describes  and  maps  the  geology  of  the  Pikes  Peak 
quadrangle.  The  oldest  rocks  here  found  are  Algonkian  quartzites 
and  allied  rocks,  which  occur  as  fragments  included  in  the  granite. 
These  vary  in  size  from  that  shown  in  Wilson  Park  to  minor  frag- 
ments. The  Wilson  Park  mass  is  nearly  4,000  feet  in  thickness,  stands 
on  end,  and  is  exposed  along  the  strike  for  about  5  miles.  Other  im- 
portant masses  of  quartzite  are  in  Cooper  Mountain  and  Blue  Moun- 
tain. These  masses  are  cut  by  minute  dikes  and  are  entirely  sur- 
rounded by  granite.  Smaller  fragments  are  very  numerous.  Asso- 
ciated with  the  quartzites  are  certain  gneisses  and  schists  which  almost 
grade  into  the  quartzites,  and  probably  represent  metamorphosed 
Algonkian  strata.  Schists  also  occur,  especially  in  the  Cripple  Creek 
district,  and  these  seem  to  represent  earthy  metamorphosed  Algon- 
kian rocks,  and  also  the  true  Archean  gneisses  upon  which  the  Algon- 
kian beds  were  deposited.  Later  granites  and  gneissoid  granites 
occupy  much  the  larger  part  of  the  Pikes  Peak  quadrangle.  The 
more  important  granites  are  the  coarse-grained  Pikes  Peak  type  and 
a  fine-grained  granite.  The  gneissoid  granites  are  but  foliated  phases 
of  tne  granites,  and  between  the  two  there  are  gradations.  AM  the 
granites  are  cut  by  coarse  granitic  dikes  and  vein.-.  The  Silurian 
rocks  rest  unconformably  upon,  and  derived  fragments  from,  all  the 
previous  formations.  The  base  of  the  known  Paleozoic  section  in 
Colorado   is  an  Upper  Cambrian   quartzite   which    in   the   Colorado 
