﻿124 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY, 
  

  

  extend 
  along 
  Williams 
  Creek 
  until 
  lest 
  under 
  the 
  drift 
  of 
  the 
  southern 
  

   lj?ortion 
  of 
  Wet 
  Mountain 
  Valley. 
  Numerous 
  volcanic 
  dikes 
  traverse 
  both 
  

   the 
  sandstones 
  and 
  shales, 
  and 
  have 
  produced 
  many 
  alterations 
  in 
  the 
  

   physical 
  appearance 
  of 
  the 
  rocks 
  with 
  which 
  they 
  have 
  come 
  in 
  con- 
  

   tact. 
  About 
  east 
  of 
  the 
  Spanish 
  peaks 
  the 
  Cretaceous 
  strata 
  cease 
  to 
  

   be 
  exposed, 
  as 
  they 
  are 
  covered 
  by 
  the 
  younger 
  Lignitic 
  group, 
  which 
  

   extends 
  far 
  to 
  the 
  northward. 
  West 
  of 
  Spanish 
  Peaks 
  ISTo. 
  1 
  again 
  ap- 
  

   pears, 
  iu 
  an 
  abnormal 
  position, 
  however, 
  as 
  has 
  been 
  shown 
  above. 
  

   From 
  there 
  the 
  sandstones 
  and 
  shales 
  both 
  continue 
  southward 
  in 
  a 
  line 
  

   parallel 
  to 
  the 
  trend 
  of 
  the 
  Sangre 
  de 
  Cristo 
  Eange. 
  Along 
  this 
  expos- 
  

   ure 
  they 
  aiford 
  features 
  of 
  much 
  interest, 
  though 
  at 
  the 
  same 
  time 
  feat- 
  

   ures 
  that 
  require 
  careful 
  study 
  for 
  correct 
  interpretation. 
  More 
  iJar- 
  

   ticularly 
  No. 
  2 
  is 
  puzzling, 
  as 
  to 
  its 
  occurrence 
  and 
  stratigraphy. 
  

  

  Dakota 
  Group. 
  — 
  {Cretaceous 
  No. 
  1.) 
  — 
  This 
  characteristic 
  group 
  is 
  well 
  

   represented. 
  Beginning 
  east 
  and 
  south 
  of 
  station 
  63 
  of 
  1874, 
  it 
  rests 
  con- 
  

   fortuably 
  upon 
  the 
  older 
  Mesozoic 
  beds. 
  First 
  the 
  dip 
  is 
  toward 
  the 
  east 
  

   15° 
  to 
  20°; 
  then 
  it 
  veers 
  around 
  to 
  the 
  west, 
  diminishing, 
  however, 
  in 
  

   steepness 
  as 
  soon 
  as 
  it 
  is 
  due 
  west. 
  On 
  either 
  side 
  of 
  Williams 
  Creek, 
  

   the 
  white 
  and 
  yellowish 
  sandstones 
  form 
  the 
  rim 
  of 
  a 
  basin, 
  as 
  it 
  were, 
  to 
  

   the 
  younger 
  Cretaceous 
  beds 
  deposited 
  therein, 
  dipping 
  gently 
  from 
  both 
  

   sides 
  toward 
  the 
  center 
  of 
  this 
  basin. 
  Northwest 
  and 
  west 
  they 
  rest 
  

   partly 
  on 
  the 
  red 
  Carboniferous 
  sandstone, 
  frequently 
  the 
  junction 
  is 
  so 
  

   obscured 
  by 
  debris, 
  or 
  drift, 
  as 
  to 
  leave 
  its 
  precise 
  location 
  in 
  doubt. 
  

   After 
  passing 
  station 
  G2 
  of 
  1874, 
  the 
  sandstone, 
  which 
  here 
  is 
  yellow, 
  makes 
  

   a 
  sweep 
  to 
  the 
  southeast, 
  including 
  within 
  its 
  area 
  the 
  volcanic 
  mount- 
  

   ains 
  of 
  the 
  Sheep 
  Mountain 
  group 
  (stations 
  4 
  and 
  5). 
  While 
  riding 
  

   up 
  to 
  the 
  Sangre 
  de 
  Cristo 
  Pass, 
  along 
  the 
  wagon-road 
  from 
  the 
  east, 
  

   we 
  pass 
  over 
  heavy 
  beds 
  of 
  sandstone 
  belonging 
  to 
  this 
  group. 
  From 
  

   there 
  it 
  turns 
  toward 
  the 
  eastern 
  edge 
  of 
  the 
  Spanish 
  Peaks, 
  and 
  there 
  

   disappears. 
  Although 
  it 
  appears 
  to 
  crop 
  out 
  very 
  distinctly 
  in 
  that 
  

   region, 
  overlying 
  the 
  red 
  Carboniferous 
  sandstone, 
  its 
  horizontal 
  ex- 
  

   posure 
  is 
  certainly 
  very 
  small, 
  and 
  obscured 
  by 
  the 
  intense 
  color 
  pro- 
  

   duced 
  by 
  all 
  washes 
  and 
  dSbris 
  coming 
  from 
  the 
  former. 
  

  

  A 
  section 
  (Section 
  VII) 
  taken 
  from 
  station 
  03 
  of 
  1874 
  to 
  station 
  4 
  may 
  

   show 
  the 
  general 
  stratigraphical 
  arrangement, 
  which 
  is 
  simple. 
  The 
  firstr 
  

   named 
  station 
  is 
  located 
  on 
  porphyritic 
  trachyte 
  (a), 
  which 
  probably 
  oc- 
  

   curs 
  there 
  not 
  as 
  a 
  continuation 
  of 
  the 
  mass 
  on 
  the 
  summit 
  of 
  Green- 
  

   horn 
  Mountains, 
  (stations 
  83 
  and 
  84 
  of 
  1873, 
  but 
  as 
  an 
  independent 
  erup- 
  

   tion. 
  It 
  has 
  broken 
  through 
  the 
  red 
  Mesozoic 
  sandstones 
  (6), 
  which 
  

   surround 
  it 
  on 
  three 
  sides. 
  They 
  dip 
  to 
  the 
  southwest 
  at 
  an 
  angle 
  of 
  

   about 
  10° 
  to 
  15°, 
  and 
  are 
  overlaid 
  conformably 
  by 
  the 
  sandstones 
  {c) 
  of 
  

   the 
  Dakota 
  group. 
  Of 
  these, 
  the 
  lower 
  strata'are 
  white 
  to 
  light 
  yellow, 
  

   fine 
  grained 
  and 
  hard, 
  while 
  the 
  upper 
  ones 
  are 
  softer, 
  yellow, 
  and 
  de- 
  

   compose 
  more 
  readily. 
  As 
  they 
  descend 
  toward 
  the 
  valley, 
  the 
  angle 
  

   of 
  the 
  dip 
  gradually 
  diminishes, 
  so 
  as 
  to 
  become 
  almost 
  imperceptible. 
  

   Yellow 
  and 
  grayish 
  shales 
  (c?) 
  of 
  No. 
  2 
  (Colorado 
  group), 
  containing 
  the 
  

   characteristic 
  fossils 
  of 
  that 
  horizon, 
  are 
  deposited 
  on 
  the 
  sandstones, 
  

   and 
  are 
  in 
  turn 
  covered 
  by 
  a 
  yellow 
  sandstone 
  (6'), 
  which 
  has 
  mostly 
  suc- 
  

   cumbed 
  to 
  erosion. 
  Approaching 
  toward 
  station 
  4, 
  which 
  is 
  located 
  

   upon 
  trachyte 
  (/), 
  we 
  iind 
  that 
  the 
  dips 
  are 
  reversed. 
  Instead 
  of 
  an 
  

   inclination 
  toward 
  the 
  west, 
  we 
  now 
  have 
  an 
  easterly 
  one. 
  All 
  the 
  

   beds 
  above 
  given 
  are 
  recognizable 
  here, 
  and 
  generally 
  form 
  either 
  

   small 
  bluffs 
  or 
  low 
  benches, 
  according 
  to 
  the 
  lithological 
  constitu- 
  

   tion 
  of 
  the 
  rock 
  composing 
  the 
  strata. 
  This 
  section 
  gives 
  a 
  general 
  

   idea 
  of 
  the 
  condition 
  in 
  which 
  we 
  find 
  Cretaceous 
  No. 
  1 
  iu 
  Huerfano 
  Val- 
  

   ley 
  and 
  iu 
  the 
  valleys 
  of 
  its 
  main 
  tributaries. 
  Totally 
  different 
  from 
  

  

  