﻿118 
  EEPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  to 
  physical 
  changes 
  in 
  the 
  underlying 
  metamorphics. 
  Near 
  station 
  113 
  

   it 
  stops, 
  however, 
  on 
  the 
  west 
  side 
  of 
  the 
  range, 
  with 
  the 
  exception 
  of 
  a 
  

   few 
  patches 
  north 
  of 
  Costilla 
  Peak 
  that 
  reach 
  from 
  the 
  east 
  over 
  on 
  the 
  

   west 
  side 
  of 
  the 
  divide. 
  Throughout 
  its 
  entire 
  occurrence 
  thus 
  far 
  de- 
  

   scribed, 
  this 
  red 
  sandstone 
  shows 
  a 
  singularly 
  uniform 
  character 
  both 
  

   in 
  its 
  stratification 
  and 
  its 
  constitution. 
  No 
  lighter 
  beds 
  occur 
  to 
  vary 
  

   it, 
  as 
  have 
  been 
  observed 
  at 
  other 
  points, 
  and 
  its 
  only 
  changes 
  appear 
  

   to 
  consist 
  in 
  the 
  varying 
  accumulation 
  of 
  argillaceous 
  material, 
  whereby 
  

   differences 
  are 
  produced. 
  The 
  granite, 
  which 
  crops 
  out 
  west 
  of 
  it 
  in 
  a 
  

   north 
  and 
  south-line 
  about 
  from 
  station 
  122 
  to 
  station 
  116, 
  was 
  probably 
  at 
  

   one 
  time 
  covered 
  by 
  it, 
  but 
  the 
  fact 
  that 
  the 
  strata 
  exposed 
  their 
  edges 
  on 
  

   account 
  of 
  the 
  dip 
  greatly 
  facilitated 
  the 
  process 
  of 
  erosion, 
  and 
  today 
  

   the 
  metamorphic 
  rock 
  is 
  left 
  entirely 
  denuded 
  at 
  the 
  immediate 
  base 
  of 
  

   the 
  mountains. 
  This 
  exhausts 
  the 
  occurrence 
  of 
  Carboniferous 
  sand- 
  

   stone 
  on 
  the 
  west 
  side 
  of 
  the 
  range. 
  

  

  Of 
  greater 
  extent 
  and 
  more 
  varied 
  in 
  occurrence 
  is 
  this 
  same 
  sand- 
  

   stone 
  on 
  the 
  eastern 
  side 
  of 
  the 
  Sangre 
  de 
  Cristo 
  Range. 
  

  

  Station 
  62 
  of 
  1874 
  is 
  located 
  on 
  the 
  red 
  sandstone, 
  near 
  Muddy 
  Creek. 
  

   At 
  that 
  locality 
  it 
  dips 
  toward 
  the 
  mountains 
  at 
  an 
  angle 
  of 
  about 
  15^. 
  

   This, 
  however, 
  is 
  sometimes 
  locally 
  increased. 
  South 
  of 
  the 
  station 
  there 
  

   are 
  a 
  few 
  low 
  remnants 
  of 
  the 
  same 
  formation, 
  that 
  show 
  a 
  steep 
  dip, 
  

   reaching 
  eO'^ 
  toward 
  the 
  east, 
  while 
  opposite 
  them 
  toward 
  the 
  range 
  

   the 
  dip 
  is 
  westward. 
  Between 
  the 
  two 
  outcrops 
  Cretaceous 
  shales 
  

   of 
  No. 
  2 
  have 
  been 
  deposited 
  nearly 
  horizontally, 
  thus 
  showing 
  a 
  very 
  

   striking 
  unconformability. 
  It 
  is 
  possible 
  that 
  these 
  isolated 
  points 
  may 
  

   be 
  but 
  iragments 
  of 
  the 
  main 
  mass 
  farther 
  west, 
  or 
  it 
  may 
  be 
  that 
  they 
  

   denote 
  an 
  anticlinal 
  fold. 
  In 
  view 
  of 
  the 
  contortions 
  and 
  plications 
  ob- 
  

   servable 
  farther 
  south, 
  I 
  am 
  inclined 
  to 
  the 
  latter 
  opinion. 
  Section 
  III 
  

   will 
  illustrate 
  the 
  relative 
  positions. 
  As 
  there 
  are 
  no 
  exposures 
  that 
  

   admit 
  of 
  any 
  idea 
  as 
  to 
  how 
  the 
  strata 
  continue 
  to 
  lower 
  depths, 
  only 
  the 
  

   appearance 
  of 
  the 
  surface 
  has 
  been 
  given. 
  Metamorphic 
  schists 
  («), 
  

   partly 
  gneissoid, 
  partly 
  micaceous, 
  and 
  partly 
  hornblendic, 
  are 
  found 
  in 
  

   Mosco 
  Pass, 
  but 
  give 
  way 
  to 
  a 
  red, 
  coarse-grained 
  granite 
  (6) 
  lower 
  

   down. 
  A 
  deposit 
  of 
  drift 
  (c) 
  originating 
  in 
  the 
  metamorphic 
  area 
  ob- 
  

   scures 
  the 
  junction 
  of 
  the 
  sandstone 
  {d) 
  with 
  the 
  granite. 
  The 
  former 
  

   is 
  stratified 
  in 
  heavy 
  beds, 
  coarse 
  to 
  middle 
  grained, 
  showing 
  a 
  variety 
  

   of 
  brown 
  and 
  red 
  shades 
  upon 
  exposure. 
  It 
  dips 
  westward 
  at 
  an 
  angle 
  

   of 
  about 
  15° 
  to 
  ISO. 
  Descending 
  over 
  the 
  rise 
  produced 
  by 
  the 
  direc- 
  

   tion 
  of 
  the 
  dip, 
  which 
  probably 
  caused 
  the 
  lodgment 
  of 
  drift 
  at 
  the 
  point 
  

   indicated, 
  we 
  traverse 
  a 
  narrow 
  valley 
  containing 
  horizontal 
  beds 
  of 
  

   Cretaceous 
  shales 
  No. 
  2 
  (e). 
  Immediately 
  beyond 
  that 
  is 
  one 
  of 
  the 
  

   isolated 
  hills 
  of 
  red 
  sandstone, 
  the 
  strata 
  composing 
  which 
  dip 
  east- 
  

   ward 
  at 
  an 
  angle 
  of 
  about 
  35°. 
  So 
  far 
  as 
  could 
  be 
  observed, 
  they 
  are 
  

   identical 
  with 
  the 
  western 
  ones, 
  but 
  all 
  or 
  nearly 
  all 
  the 
  beds 
  of 
  this 
  

   sandstone 
  are 
  so 
  much 
  alike, 
  that 
  it 
  becomes 
  a 
  matter 
  of, 
  detailed 
  re- 
  

   search 
  to 
  decide 
  any 
  question 
  of 
  that 
  kind. 
  Only 
  for 
  a 
  short 
  horizontal 
  

   distance 
  do 
  we 
  find 
  this 
  outcrop 
  ,• 
  then 
  it 
  is 
  again 
  covered 
  by 
  Cretaceous 
  

   beds 
  belonging 
  to 
  Nos. 
  2 
  and 
  3 
  (fund 
  g). 
  Judging 
  from 
  the 
  entire 
  posi- 
  

   tion 
  of 
  the 
  outcrops 
  with 
  reference 
  to 
  each 
  other, 
  the 
  acceptance 
  of 
  an 
  

   anticlinal 
  axis 
  or 
  a 
  fault 
  appears 
  to 
  be 
  the 
  more 
  reasonable. 
  It 
  is 
  

   strengthened 
  furthermore 
  by 
  the 
  approximately 
  straight 
  line 
  which 
  the 
  

   general 
  course 
  of 
  the 
  outcrops 
  shows. 
  

  

  Alittleeast 
  of 
  south 
  of 
  station 
  62of 
  1874, 
  there 
  occuranumberof 
  isolated 
  

   outcrops 
  of 
  trachytic 
  rocks, 
  forming 
  either 
  long 
  coffin-shaped 
  hills, 
  or 
  

   rounded 
  dome-like 
  ones. 
  A 
  portion 
  of 
  the 
  higher 
  land 
  near 
  the 
  head- 
  

   waters 
  of 
  Huerfano 
  drainage 
  is 
  also 
  covered 
  by 
  the 
  same 
  material. 
  

  

  