﻿EXDLicn,] 
  TRINIDAD 
  REGION 
  GEOLOGY. 
  193 
  

  

  both 
  flowing 
  northeast. 
  All 
  the 
  country 
  containing 
  this 
  drainage 
  pre- 
  

   sents 
  a 
  uniform 
  appearance. 
  The 
  streams 
  flow 
  in 
  narrow, 
  iirassy 
  valleys, 
  

   some 
  of 
  which 
  are 
  cultivated, 
  and 
  are 
  inclosed 
  by 
  steep 
  walls 
  of 
  yellow 
  

   sandstones 
  and 
  Shales. 
  At 
  times 
  the 
  water 
  has 
  cut 
  a 
  passage 
  through 
  

   these 
  sandstones 
  sufiiciently 
  narrow 
  to 
  be 
  inaccessible. 
  Vertical 
  bluffs, 
  

   though 
  often 
  not 
  very 
  high, 
  greatly 
  impede 
  the 
  travel 
  " 
  across 
  coun- 
  

   try." 
  An 
  almost 
  equal 
  level 
  is 
  maintained 
  by 
  the 
  summits 
  of 
  the 
  bluffs 
  

   and 
  plateau-like 
  ridges, 
  varied 
  only 
  occasionally 
  by 
  a 
  prominent 
  point 
  

   that 
  may 
  be 
  utilized 
  as 
  a 
  topographical 
  or 
  geological 
  station. 
  These 
  

   conditions 
  remain 
  constant 
  until 
  we 
  reach, 
  on 
  the 
  Arapahoe, 
  the 
  under- 
  

   lying 
  Cretaceous 
  strata, 
  and 
  then 
  the 
  beds 
  of 
  the 
  Lignitic 
  group 
  disap- 
  

   pear. 
  Facing 
  toward 
  the 
  great 
  plains 
  on 
  the 
  east, 
  we 
  find 
  a 
  long 
  con- 
  

   tinued 
  row 
  of 
  bluffs, 
  with 
  steep 
  slopes 
  to 
  the 
  eastward. 
  But 
  littlo 
  

   variation 
  can 
  be 
  observed 
  in 
  the 
  stratigraphical 
  relations, 
  although 
  the 
  

   beds 
  are 
  mostly 
  well 
  exposed. 
  Features 
  in 
  detail 
  that 
  have 
  been 
  noticed 
  

   in 
  the 
  group, 
  will 
  be 
  discussed 
  below. 
  A 
  number 
  of 
  settlements 
  have 
  

   been 
  made 
  along 
  the 
  western 
  edge 
  of 
  the 
  plains, 
  just 
  within 
  the 
  limits 
  

   of 
  the 
  bluff 
  region. 
  Several 
  small 
  towns 
  have 
  started 
  into 
  life, 
  and 
  

   with 
  the 
  vitality 
  of 
  young 
  western 
  colonies 
  have 
  a 
  comparatively 
  flour- 
  

   ishing 
  existence. 
  

  

  In 
  this 
  region 
  the 
  coal, 
  that 
  has 
  given 
  rise 
  to 
  so 
  many 
  able 
  arguments 
  

   regarding 
  its 
  age 
  and 
  geological 
  position, 
  is 
  found. 
  It 
  occurs 
  at 
  a 
  num- 
  

   ber 
  of 
  points, 
  is 
  mined 
  at 
  some 
  of 
  them, 
  neglected 
  for 
  the 
  present 
  at 
  

   others. 
  Evidences 
  of 
  it 
  have 
  been 
  found 
  in 
  the 
  accustomed 
  horizon, 
  

   over 
  almost 
  the 
  entire 
  area, 
  but 
  it 
  is 
  mined 
  only 
  at 
  those 
  points 
  where 
  

   facilities 
  for 
  transportation 
  insure 
  a 
  market. 
  Its 
  character 
  and 
  geo- 
  

   logical 
  relations 
  will 
  be 
  discussed 
  in 
  the 
  following 
  pages, 
  and 
  it 
  may 
  be 
  

   hoped 
  that 
  the 
  result 
  obtained 
  will 
  tend 
  to 
  throw 
  some 
  additional 
  light 
  

   upon 
  the 
  questions 
  at 
  issue. 
  Special 
  attention 
  has 
  been 
  given 
  to 
  the 
  

   coal-beds, 
  and 
  more 
  particularly 
  the 
  immediate 
  vicinity 
  of 
  Trinidad 
  has 
  

   been 
  examined 
  as 
  carefully 
  and 
  as 
  much 
  in 
  detail 
  as 
  the 
  time 
  at 
  my 
  com- 
  

   mand 
  would 
  permit. 
  Inasmuch 
  as 
  I 
  had 
  the 
  opportunity 
  of 
  examining 
  

   not 
  only 
  the 
  strata 
  inclosing 
  the 
  coal 
  at 
  Trinidad, 
  but 
  westward 
  to 
  the 
  

   terminus 
  of 
  their 
  outcrop, 
  and 
  there 
  to 
  observe 
  the 
  underlying 
  forma- 
  

   tions, 
  and 
  to 
  note 
  the 
  stratigraphical 
  relations 
  to 
  each 
  other, 
  I 
  shall 
  en- 
  

   deavor 
  to 
  present 
  a 
  synopsis 
  of 
  everything 
  observed 
  as 
  clearly 
  as 
  pos- 
  

   sible, 
  and 
  one 
  affording 
  material 
  for 
  future 
  comparison. 
  

  

  GENERAL 
  ARRANGEMENT 
  OF 
  STRATA.' 
  

  

  Mention 
  has 
  been 
  made 
  in 
  Chapter 
  I 
  of 
  the 
  Cretaceous 
  strata 
  belong- 
  

   ing 
  to 
  the 
  Dakota 
  and 
  Colorado 
  groups, 
  which 
  flank 
  the 
  eastern 
  slope 
  

   of 
  the 
  Sangre 
  de 
  Cristo 
  Range 
  south 
  of 
  Trinchera 
  Peak. 
  It 
  will 
  be 
  re- 
  

   membered 
  that 
  there 
  we 
  find 
  the 
  white 
  Dakota 
  sandstone, 
  either 
  stand- 
  

   ing 
  on 
  edge 
  or 
  covered 
  by 
  Carboniferous 
  strata, 
  that 
  have 
  been 
  over- 
  

   turned. 
  The 
  younger 
  shales 
  of 
  the 
  Colorado 
  group, 
  east 
  of 
  the 
  sand- 
  

   stone, 
  are, 
  so 
  far 
  as 
  could 
  be 
  observed, 
  conformable 
  with 
  it, 
  but 
  the 
  dip 
  

   is 
  vei\y 
  much 
  obscured. 
  They 
  weather 
  readily, 
  form 
  soil, 
  and 
  in 
  addi- 
  

   tion 
  to 
  this 
  feature 
  the 
  debris 
  and 
  drift 
  from 
  the 
  adjoining 
  mountains 
  

   succeeded 
  very 
  effectually 
  in 
  hiding 
  from 
  sight 
  nearly 
  every 
  otherwise 
  

   available 
  outcrop. 
  Very 
  imperfect 
  data, 
  therefore, 
  were 
  obtained 
  as 
  

   regards 
  this 
  point, 
  and 
  the 
  thorough 
  discussion 
  of 
  the 
  stratigraphical 
  

   relations 
  of 
  the 
  Colorado 
  shales 
  must 
  necessarily 
  suffer. 
  Dikes 
  pene- 
  

   trating 
  them 
  have 
  furnished, 
  through 
  their 
  preserving 
  influence, 
  the 
  only 
  

   data 
  from 
  which 
  anything 
  could 
  be 
  learned. 
  Owing 
  to 
  the 
  changes, 
  

   however, 
  to 
  which 
  the 
  shales 
  have 
  been 
  subjected, 
  by 
  the 
  passage 
  of 
  

   13 
  G 
  s 
  

  

  