﻿4 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  the 
  latter 
  only 
  on 
  the 
  eastern 
  slope, 
  however, 
  rest 
  against 
  the 
  metamor- 
  

   phic 
  "core" 
  of 
  the 
  rauge. 
  Volcanic 
  eruptions 
  of 
  the 
  trachytic 
  series 
  

   have 
  occurred, 
  and 
  show 
  an 
  arrangement 
  parallel 
  to 
  the 
  general 
  course 
  

   of 
  the 
  chain. 
  A 
  more 
  or 
  less 
  isolated 
  group 
  of 
  peaks 
  is 
  north 
  of 
  Fort 
  Gar- 
  

   land, 
  termed 
  the 
  Sierra 
  Blanca. 
  Passes 
  are 
  both 
  north 
  and 
  south 
  of 
  it, 
  — 
  

   Mosca 
  Pass 
  and 
  the 
  Sangre 
  de 
  Cristo 
  and 
  Abeyta 
  Passes. 
  While 
  Cre- 
  

   taceous 
  beds, 
  overlying 
  the 
  Carboniferous 
  and 
  subjected 
  to 
  considerable 
  

   disturbances, 
  slope 
  off 
  from 
  the 
  range 
  toward 
  the 
  eastward, 
  their 
  area 
  

   is 
  somewhat 
  limited, 
  as 
  the 
  Lignitic 
  group 
  there 
  again 
  makes 
  its 
  appear- 
  

   ance 
  in 
  the 
  Raton 
  Hills 
  and 
  north 
  of 
  them. 
  Lithologically, 
  this 
  is 
  iden- 
  

   tical 
  with 
  the 
  one 
  observed 
  on 
  the 
  Rio 
  San 
  Juan. 
  Comparisons 
  of 
  the 
  

   succession 
  of 
  strata 
  and 
  relative 
  thickness, 
  etc, 
  will 
  be 
  found 
  in 
  Dr. 
  

   Endlich's 
  report. 
  The 
  age 
  of 
  this 
  group 
  has 
  for 
  some 
  time 
  occupied 
  the 
  

   attention 
  of 
  geologists, 
  and 
  given 
  occasion 
  for 
  dissenting 
  views. 
  It 
  is 
  

   highly 
  probable 
  that 
  the 
  results 
  obtained 
  during 
  the 
  past 
  season 
  will 
  

   not 
  admit 
  of 
  a 
  definite 
  decision 
  with 
  regard 
  thereto. 
  They 
  will 
  at 
  least 
  

   be 
  entitled 
  to 
  more 
  consideration 
  than 
  those 
  of 
  explorers 
  having 
  merely 
  

   traveled 
  over 
  a 
  limited 
  area, 
  as 
  so 
  large 
  a 
  continuous 
  district 
  containing 
  

   the 
  formation 
  has 
  been 
  examined. 
  It 
  is 
  not 
  possible 
  at 
  present 
  to 
  state 
  

   positively 
  what 
  these 
  results 
  will 
  be; 
  but, 
  from 
  the 
  observations 
  taken 
  

   in 
  the 
  field, 
  it 
  can 
  be 
  deduced 
  that 
  the 
  age 
  of 
  the 
  Lignitic 
  group 
  near 
  

   Trinidad 
  is 
  not 
  Cretaceous. 
  A 
  full 
  discussion 
  of 
  this 
  important 
  subject 
  

   will 
  be 
  found 
  in 
  a 
  subsequent 
  portion 
  of 
  the 
  Report. 
  

  

  Upon 
  the 
  completion 
  of 
  the 
  examination 
  of 
  the 
  just-mentioned 
  group, 
  

   The 
  work 
  of 
  the 
  season 
  was 
  connected 
  to 
  the 
  nortli 
  and 
  northeast 
  \vith 
  

   that 
  of 
  1874, 
  and 
  therewith 
  finished. 
  On 
  October 
  12, 
  the 
  party 
  returned 
  

   to 
  Denver, 
  having 
  fully 
  accomplished 
  the 
  purpose 
  for 
  which 
  it 
  was 
  sent 
  

   out. 
  important 
  and 
  useful 
  information 
  has 
  been 
  obtained 
  regarding 
  

   mineral 
  and 
  agricultural 
  resources 
  of 
  the 
  district, 
  and 
  data 
  have 
  been 
  

   obtained 
  for 
  the 
  preparation 
  of 
  a 
  topographical 
  and 
  geological 
  map 
  of 
  

   the 
  area 
  surveyed. 
  

  

  The 
  southwestern 
  division 
  was 
  conducted 
  by 
  W. 
  H. 
  Holmes 
  as 
  geolo- 
  

   gist, 
  with 
  G. 
  B. 
  Chittenden 
  as 
  chief 
  topographer 
  and 
  T. 
  S. 
  Brandegee 
  

   as 
  assistant 
  topographer. 
  Mr. 
  Brandegee 
  also 
  acted 
  as 
  botanist. 
  

  

  The 
  area 
  assigned 
  to 
  this 
  division 
  is 
  bounded 
  on 
  the 
  east 
  by 
  the 
  work 
  

   done 
  by 
  Mr, 
  Wilson 
  in 
  1874, 
  or 
  a 
  line 
  about 
  on 
  the 
  meridian 
  of 
  108° 
  

   west 
  longitude 
  ; 
  on 
  the 
  south 
  by 
  the 
  parallel 
  of 
  36° 
  45'; 
  on, 
  the 
  west 
  by 
  

   meridian 
  109° 
  30' 
  ; 
  and 
  on 
  the 
  north 
  by 
  37° 
  30' 
  north 
  latitude. 
  These 
  

   boundaries 
  include 
  an 
  area 
  of 
  about 
  six 
  thousand 
  five 
  hundred 
  square 
  

   miles. 
  An 
  area 
  of 
  about 
  five 
  hundred 
  square 
  miles 
  was 
  surveyed 
  along 
  

   the 
  eastern 
  base 
  of 
  the 
  mountains 
  on 
  the 
  outward 
  march. 
  Here 
  Mr. 
  

   Chittenden 
  made 
  about 
  twelve 
  stations, 
  connecting 
  with 
  the 
  former 
  

   work 
  and 
  completing 
  the 
  sheets 
  to 
  the 
  proposed 
  eastern 
  line 
  of 
  the 
  Sur- 
  

   vey. 
  

  

  The 
  easternmost 
  line 
  of 
  the 
  district 
  assigned 
  to 
  this 
  division 
  was 
  over 
  

   four 
  hundred 
  miles 
  from 
  Denver. 
  The 
  party 
  arrived 
  there 
  on 
  the 
  30th 
  

   June, 
  and 
  commenced 
  work 
  immediately. 
  

  

  