﻿114 
  EEPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  CARBONIFEROUS. 
  

  

  A 
  group 
  that 
  I 
  refer 
  to 
  the 
  Lower 
  Carboniferous 
  occurs 
  uear 
  Trin- 
  

   chera 
  Peak. 
  At 
  the 
  time 
  we 
  were 
  examining 
  that 
  region, 
  the 
  ground 
  

   was 
  covered 
  with 
  more 
  than 
  a 
  foot 
  of 
  snow, 
  so 
  the 
  result 
  of 
  the 
  inves- 
  

   tigations 
  was 
  not 
  quite 
  as 
  satisfactory 
  as 
  might 
  have 
  been. 
  It 
  was 
  

   found, 
  however, 
  that 
  a 
  greyish-brown, 
  compact 
  shale, 
  sandy 
  in 
  part, 
  

   was 
  underlying 
  the 
  red 
  Carboniferous 
  sandstones 
  conformably, 
  and 
  

   formed 
  the 
  summit 
  of 
  Trinchera 
  as 
  well 
  as 
  the 
  highest 
  peaks 
  immedi- 
  

   ately 
  south. 
  Blue 
  limestones 
  occurred 
  with 
  it. 
  So 
  far 
  as 
  could 
  be 
  de- 
  

   termined, 
  the 
  dip 
  of 
  these 
  strata 
  is 
  to 
  the 
  east, 
  at 
  an 
  angle 
  of 
  60° 
  to 
  

   70°. 
  1 
  consider 
  this 
  group, 
  of 
  which 
  I 
  have 
  seen 
  too 
  little, 
  however, 
  

   to 
  be 
  positive, 
  analogous 
  to 
  the 
  well-established 
  gypsiferous 
  strata 
  of 
  

   other 
  localities 
  and 
  the 
  members 
  below 
  it. 
  Its 
  horizontal 
  extent 
  is 
  

   small, 
  but 
  even 
  from 
  considerable 
  distance 
  the 
  change 
  in 
  the 
  formation 
  

   can 
  be 
  noticed. 
  This 
  is 
  the 
  only 
  outcrop 
  of 
  older 
  Carboniferous 
  form- 
  

   ations 
  that 
  occurs 
  throughout 
  the 
  district. 
  Taking 
  into 
  consideration 
  

   the 
  extensive 
  area 
  surveyed, 
  the 
  numerous 
  exposures 
  of 
  strata, 
  and 
  

   masses 
  in 
  caiions 
  and 
  on 
  the 
  slopes 
  of 
  hills, 
  it 
  is 
  surprising 
  that 
  during 
  

   1874 
  and 
  1875, 
  not 
  more 
  of 
  the 
  Palaeozoic 
  formations 
  have 
  been 
  found. 
  

   The 
  only 
  conclusion 
  possible 
  to 
  arrive 
  at 
  is, 
  that 
  they 
  do 
  not 
  exist 
  in 
  

   the 
  regions 
  examined. 
  Whether 
  the 
  material 
  that 
  coojposed 
  them 
  has 
  

   been 
  metamorphosed, 
  or 
  whether 
  they 
  never 
  were 
  deposited 
  there, 
  are 
  

   questions 
  that 
  will 
  require 
  a 
  long 
  time 
  to 
  solve. 
  Certain 
  it 
  is, 
  that 
  the 
  

   volcanic 
  action 
  having 
  occurred 
  in 
  the 
  two 
  districts 
  mentioned, 
  is 
  of 
  

   enormous 
  extent, 
  but 
  at 
  the 
  same 
  time 
  we 
  have 
  evidence 
  that 
  much 
  of 
  

   the 
  metamorphosing 
  process 
  must 
  have 
  occurred 
  at 
  a 
  comparatively 
  

   old 
  geological 
  period, 
  while, 
  on 
  the 
  otber 
  hand, 
  we 
  have 
  but 
  little 
  

   I)roof 
  of 
  volcanic 
  or 
  Plutonic 
  eruption 
  that 
  may 
  have 
  occurred 
  at 
  the 
  

   same 
  time. 
  

  

  Bed 
  Carboniferous 
  sandstone. 
  — 
  In 
  the 
  report 
  of 
  1873, 
  p. 
  349, 
  the 
  heavy 
  

   beds 
  of 
  red 
  sandstone 
  north 
  of 
  Arkansas 
  Eiver 
  have 
  been 
  referred 
  to 
  

   the 
  Carboniferous. 
  The 
  same 
  view 
  has 
  been 
  held 
  as 
  regards 
  the 
  region 
  

   near 
  Eio 
  Animas, 
  explored 
  in 
  1874. 
  As 
  will 
  be 
  observed, 
  however, 
  no 
  

   positive 
  palseoutological 
  evidence 
  indicating 
  beyond 
  a 
  doubt 
  the 
  age 
  of 
  

   this 
  group 
  was 
  obtained 
  during 
  those 
  two 
  years, 
  and 
  the 
  position 
  of 
  the 
  

   same 
  was 
  mainly 
  based 
  upon 
  stratigraphical 
  evidence. 
  In 
  1875 
  the 
  

   necessary 
  evidence 
  was 
  found, 
  however, 
  as 
  will 
  be 
  seen 
  in 
  the 
  subjoined 
  

   pages, 
  and 
  it 
  is 
  without 
  reserve, 
  therefore, 
  that 
  this 
  sandstone 
  is 
  

   placed 
  in 
  its 
  present 
  position. 
  Had 
  it 
  been 
  possible 
  to 
  make 
  more 
  de- 
  

   tailed 
  examinations 
  at 
  the 
  localities 
  that 
  furnished 
  this 
  proof, 
  no 
  doubt 
  

   a 
  large 
  number 
  of 
  interesting 
  fossil 
  species 
  could 
  have 
  been 
  collected. 
  

   As 
  it 
  was, 
  a 
  sufficiency 
  of 
  material 
  was 
  obtained 
  to 
  warrant 
  a 
  positive 
  

   assertion. 
  Besides 
  the 
  observations 
  made 
  by 
  myself, 
  I 
  have 
  incident- 
  

   ally 
  heard 
  of 
  others 
  corroborating 
  them. 
  I 
  regret 
  that 
  I 
  have 
  been 
  un- 
  

   able 
  to 
  receive 
  the 
  material 
  from 
  others 
  in 
  such 
  shape 
  that 
  it 
  could 
  herein 
  

   be 
  presented, 
  so 
  merely 
  mention 
  the 
  fact. 
  The 
  distribution 
  of 
  this 
  red 
  

   Carboniferous 
  or 
  "Arkansas" 
  sandstone 
  is 
  a 
  very 
  wide 
  one. 
  It 
  forms 
  a 
  

   large 
  portion 
  of 
  the 
  Sangre 
  de 
  Cristo 
  range, 
  north 
  of 
  Mosco 
  Pass, 
  and 
  

   continues 
  from 
  there 
  nearly 
  to 
  the 
  southern 
  border 
  of 
  the 
  1875 
  district. 
  

   Station 
  G2 
  of 
  1874 
  is 
  located 
  upon 
  this 
  sandstone, 
  and 
  from 
  there 
  its 
  east- 
  

   ern 
  limit 
  runs 
  in 
  a 
  southwesterly 
  direction 
  toward 
  the 
  Blanca 
  group, 
  near 
  

   the 
  Sheep 
  Mountains, 
  upon 
  one 
  of 
  which 
  station 
  4 
  was 
  made 
  ; 
  it 
  again 
  

   spreads 
  farther 
  toward 
  the 
  east, 
  appearmg 
  on 
  the 
  summit 
  of 
  Sangre 
  de 
  

   Cristo 
  Pass. 
  The 
  larger 
  portion 
  of 
  Veta 
  Pass 
  runs 
  in 
  it, 
  and 
  farther 
  

   south 
  ludian 
  Creek 
  ji?ass 
  is 
  in 
  it 
  entirely. 
  _ 
  Continuing 
  southward 
  it 
  

  

  