﻿EXDLicH.] 
  SANGEE 
  DE 
  CRISTO 
  CARBONIFEROUS. 
  115 
  

  

  flanks 
  the 
  metamorphic 
  center 
  of 
  tbe 
  range 
  on 
  either 
  side, 
  dipping 
  with 
  

   the 
  slope 
  of 
  the 
  mountains. 
  There 
  it 
  reaches 
  a 
  very 
  considerable 
  ver- 
  

   tical 
  development, 
  which 
  lets 
  the 
  foot-hills 
  composed 
  of 
  it 
  appear 
  like 
  

   small 
  mountains. 
  On 
  the 
  west 
  side 
  of 
  the 
  range 
  we 
  find 
  it 
  lor 
  the 
  last 
  

   time 
  opposite 
  station 
  113, 
  but 
  isolated 
  patches 
  occur 
  nearly 
  as 
  far 
  south 
  

   as 
  Costilla 
  Peak. 
  East 
  of 
  the 
  range 
  its 
  horizontal 
  distribution 
  is 
  greater. 
  

   Extending 
  toward 
  the 
  southeast 
  from 
  station 
  5 
  it 
  underlies, 
  although 
  in 
  

   an 
  abnormal 
  position, 
  the 
  volcanic 
  rocks 
  of 
  the 
  Spanish 
  Peaks, 
  confining 
  

   itself 
  farther 
  on 
  to 
  the 
  eastern 
  slope 
  of 
  the 
  range, 
  however. 
  

  

  Commencing 
  on 
  the 
  west 
  side 
  of 
  the 
  Sangre 
  de 
  Cristo 
  Eange, 
  south 
  of 
  

   Mosco 
  Pass, 
  the 
  first 
  outcrop 
  of 
  this 
  sandstone 
  occurs 
  on 
  Ute 
  Creek, 
  

   near 
  the 
  base 
  of 
  the 
  Blauca 
  group. 
  It 
  is 
  but 
  an 
  isolated 
  patch, 
  resting 
  

   on 
  the 
  metamorphic 
  rocks 
  of 
  these 
  mountains. 
  Northwest 
  from 
  that 
  

   point, 
  in 
  Greyback 
  Gulch, 
  we 
  first 
  find 
  it 
  again, 
  this 
  time 
  as 
  a 
  spur 
  of 
  

   the 
  large 
  mass 
  that 
  runs 
  to 
  the 
  summit 
  of 
  the 
  Sangre 
  de 
  Cristo 
  Pass. 
  

   Eiding 
  to 
  this 
  summit 
  from 
  the 
  east 
  side, 
  we 
  travel 
  over 
  Lower 
  Creta- 
  

   ceous 
  until 
  the 
  pass 
  is 
  reached. 
  There 
  suddenly 
  the 
  yellow 
  color 
  of 
  

   the 
  sandstones 
  changes 
  to 
  deep 
  red, 
  and 
  interstrata 
  of 
  argillaceous 
  shale 
  

   appear. 
  The 
  first 
  view 
  presenting 
  itself, 
  after 
  crossing 
  the 
  summit, 
  is 
  

   that 
  of 
  vertical 
  walls 
  standing 
  /out 
  prominently 
  from 
  the 
  steep 
  slope 
  of 
  

   the 
  mountains 
  on 
  the 
  north 
  side. 
  At 
  first 
  sight 
  they 
  appear 
  like 
  dikes. 
  

   They 
  are 
  dark 
  in 
  color, 
  and 
  weathered 
  partly 
  in 
  grotesque 
  forms. 
  

   Small 
  cavities 
  eroded 
  into 
  the 
  rock 
  are 
  suggestive 
  also 
  of 
  volcanic 
  ma- 
  

   terial, 
  but 
  upon 
  examination 
  these 
  walls 
  prove 
  to 
  be 
  composed 
  of 
  sand- 
  

   stone. 
  Descending 
  farther 
  along 
  the 
  road 
  toward 
  Fort 
  Garland, 
  the 
  

   best 
  exposures 
  will 
  be 
  found 
  on 
  the 
  north 
  side. 
  The 
  vertical 
  dip 
  grad- 
  

   ually 
  changes 
  into 
  an 
  easterly 
  one, 
  steep 
  at 
  first, 
  but 
  sloping 
  more 
  

   gently 
  as 
  we 
  proceed. 
  Trachyte, 
  of 
  almost 
  white 
  color, 
  very 
  com- 
  

   pact, 
  and 
  closely 
  resembling 
  that 
  of 
  station 
  4, 
  forms 
  a 
  basis 
  for 
  the 
  

   strata 
  to 
  rest 
  upon. 
  This 
  trachyte, 
  a 
  spur 
  of 
  the 
  large 
  mass 
  imme- 
  

   diately 
  south, 
  continues 
  northward, 
  forming 
  the 
  highest 
  portion 
  of 
  a 
  

   ridge 
  leading 
  up 
  to 
  station 
  6. 
  Mention 
  has 
  been 
  made 
  of 
  this 
  fact, 
  

   because 
  immediately 
  after 
  passing 
  through 
  this 
  volcanic 
  rock 
  we 
  find 
  

   ourselves 
  again 
  in 
  the 
  sandstone 
  area, 
  the 
  strata 
  of 
  which 
  this 
  time, 
  

   however, 
  are 
  dipping 
  toward 
  the 
  west. 
  We 
  have, 
  therefore, 
  in 
  this 
  

   instance 
  an 
  anticlinal 
  fold, 
  the 
  apex 
  of 
  which 
  has 
  either 
  been 
  broken 
  

   by 
  the 
  eruptive 
  material, 
  or 
  has 
  been 
  gradually 
  eroded 
  away. 
  A 
  

   small, 
  synclinal 
  fold 
  now 
  occurs 
  in 
  the 
  sandstones 
  and 
  shales, 
  in 
  which 
  

   the 
  interstrata 
  of 
  limestone 
  participate. 
  Dipping 
  steeply 
  from 
  both 
  

   sides, 
  a 
  small 
  trough 
  is 
  formed 
  in 
  the 
  sandstone, 
  the 
  more 
  westerly 
  

   strata 
  of 
  which 
  dip 
  eastward 
  at 
  an 
  angle 
  of 
  about 
  45°. 
  Soon, 
  how- 
  

   ever, 
  (farther 
  west,) 
  the 
  prevailing 
  dip 
  asserts 
  itself, 
  and 
  it 
  assumes 
  

   the 
  westerly 
  direction, 
  until 
  the 
  sandstones 
  and 
  limestones 
  come 
  in 
  

   contact 
  with 
  the 
  metamorphic 
  granite. 
  This 
  continues 
  for 
  some 
  dis- 
  

   tance 
  ; 
  then 
  the 
  sandstone 
  is 
  covered 
  by 
  trachytic 
  rock, 
  which 
  in 
  turn 
  

   finally, 
  below 
  station 
  7, 
  disappears 
  under 
  the 
  prevalent 
  drift 
  of 
  San 
  

   Luis 
  Yalley. 
  

  

  So 
  as 
  to 
  give 
  a 
  more 
  definite 
  idea 
  of 
  the 
  strati 
  graphical 
  conditions 
  ob- 
  

   served 
  on 
  the 
  north 
  side 
  along 
  the 
  road 
  over 
  Sangre 
  de 
  Cristo 
  Pass, 
  a 
  

   section 
  (Section 
  I) 
  is 
  given. 
  In 
  it 
  the 
  various 
  beds 
  of 
  sandstone, 
  shaly 
  

   sandstone, 
  limestone, 
  and 
  the 
  metomorphic 
  and 
  volcanic 
  rocks 
  are 
  dis- 
  

   tinguished. 
  Starting 
  again 
  from 
  near 
  the 
  head 
  of 
  the 
  pass 
  we 
  observe 
  

   four 
  heavy 
  beds 
  of 
  a 
  very 
  compact 
  sandstone 
  (a), 
  separated 
  by 
  others 
  

   of 
  less 
  compact 
  structure. 
  These 
  four 
  are 
  tb.e 
  ones 
  described 
  as 
  having 
  

   the 
  dike-like 
  appearance. 
  From 
  a 
  vertical 
  dip 
  they 
  gradually 
  change 
  to 
  

   an 
  easterly 
  one, 
  which 
  is 
  continued 
  in 
  the 
  heavy 
  underlying 
  beds 
  of 
  

  

  