314  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
Endlich,48  in  1877,  states  that  metamorphics  compose  the  main  bulk 
of  the  interior  portion  of  the  lower  Sangre  de  Cristo  range,  though  at 
many  places  sedimentary  beds  and  volcanic  flows  have  obscured  the 
relations.  The  highest  peaks  of  the  range  are  as  a  rule  metamorphics 
among  which  granites  and  gneisses  are  predominant.  These  are  asso- 
ciated with  granites  and  gneissoid-schists,  associated  with  which  are 
hornblendic,  chloritic,  and  micaceous  schists.  Near  Trinchera  the  sedi- 
mentary strata  stand  nearly  on  end  and  lie  tipped  up  against  the 
granite.  At  other  places  the  granite  protrudes  through  the  Carbonifer- 
ous. It  is  concluded  that  the  metamorphics  of  the  lower  Sangre  de  Gristo 
are  altered  Silurian  rocks.  North  of  the  Arkansas  river  the  Silurian 
formation  occurs.  From  here  it  crosses  the  river  toward  the  south  and 
is  last  seen  as  such  near  the  northern  end  of  the  Sangre  de  Cristo  range. 
In  its  stratigraphical  relations  it  is  conformable  with  the  overlying 
younger  formations  wherever  it  has  been  there  seen. 
Endlich,49  in  1878,  states  that  while  in  the  Sangre  de  Cristo  the 
eruptive  granite  is  the  cause  of  the  upthrow  of  the  Carboniferous  strata, 
nowhere  in  the  sedimentary  beds  is  found  any  case  of  intrusion.  These 
granites  are  regarded  as  post-Carboniferous. 
Emmons,45  (S.  F.),  in  1890,  states  that  quartzites  have  been  noticed  con- 
nected with  the  Archean  of  the  southern  end  of  the  Sangre  de  Cristo 
range  which  maybe  assumed  to  be  the  remnants  of  some  Algonkian  beds. 
LITERATURE  OP  THE  FRONT  RANGE  OP   SOUTHERN   COLORADO  aND  NORTHERN 
NEW  MEXICO. 
Wislizenus,50  in  1848,  states  that  granitic  rocks  prevail  in  the 
mountains  about  Santa  Fe,  and  for  some  distance  to  the  south.  These 
are  associated  with  porphyry  and  trap. 
Blake,51  in  1856,  describes  ridges  of  metamorphic  slate  in  the  Santa 
Fe  mountains,  upon  the  edges  of  which  rest  horizontal  Carboniferous 
strata. 
Loew,52  in  1875,  states  that  the  mountains  between  Santa  Fe  and  Las 
Vegas  contain  Azoic  rocks  which  are  chiefly  granite  and  syenite.  At 
Santa  Fe  creek  gneiss  is  accompanied  by  primitive  clay-slate  and 
syenite.  Veins  of  fine  grained  gneisses  occur  in  a  coarse  aplite  or 
granulite  also  intersected  by  syenite  seams. 
St.  John,53  in  187G,  describes  the  Black  mountains  as  a  lofty  granite 
barrier.  The  upper  canyon  of  the  Cimarron  is  composed  of  granitic 
rocks,  with  which  are  associated  micaceous  schists  and  hard  quartzose 
rocks.  In  the  Raton  hills  are  granitic  igneous  rocks,  the  relations  of 
which  to  the  Tertiary  are  not  easy  to  make  out.  The  Vermejo  mount- 
ains have  a  nucleus  of  massive  metamorphic  rocks. 
Newberry,54  in  1876,  states  that  in  the  Santa  Fe  mountains  is  found 
coarse  red  granite,  characteristic  of  the  central  portion  of  the  Rocky 
mountain  system.  It  differs  from  the  granite  of  the  Appalachian  as 
well  as  those  of  the  Sierra  and  Cascade.  The  Carboniferous  strata 
rest  directly  upon  the  granites.    The  central  axis  of  the  Nacimiento 
