﻿132 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  South 
  of 
  station 
  84 
  of 
  1873, 
  which 
  is 
  on 
  the 
  summit 
  of 
  the 
  Greenhorn 
  

   Mountains, 
  a 
  cone-shaped 
  peak 
  rises 
  to 
  an 
  elevation 
  of 
  8.897 
  feet. 
  It 
  is 
  

   very 
  prominent 
  as 
  seen 
  from 
  the 
  surrounding 
  lower 
  country, 
  and 
  has 
  

   been 
  named 
  Badito 
  Peak. 
  Upon 
  this 
  bill 
  station 
  03 
  of 
  1874 
  was 
  

   located. 
  It 
  is 
  an 
  isolated 
  eruption 
  of 
  porphyritic 
  tracbyte, 
  thnt 
  broke 
  

   through 
  the 
  red 
  beds 
  and 
  the 
  Lower 
  Cretaceous 
  sandstones, 
  covering 
  

   now 
  but 
  a 
  small 
  area. 
  On 
  the 
  north 
  the 
  trachyte 
  rests 
  on 
  meta- 
  

   morphic 
  granite, 
  which 
  forms 
  ihe 
  bulk 
  of 
  the 
  Greenhorn 
  Mountains, 
  

   while 
  on 
  its 
  other 
  sides 
  it 
  overlies 
  Cretaceous 
  No. 
  1. 
  The 
  rock 
  

   composing 
  the 
  very 
  pretty 
  hill 
  is 
  a 
  white 
  to 
  greyish 
  trachyte, 
  with 
  

   a 
  fine 
  crystalline 
  paste, 
  crystals 
  of 
  sanidite, 
  and 
  oligoclase, 
  iind 
  some 
  

   small 
  needles 
  of 
  black 
  hornblende. 
  It 
  does 
  not 
  resemble 
  the 
  tracbyte 
  

   of 
  the 
  Greenhorn 
  Mountains, 
  butismoreclosely 
  allied 
  to 
  that 
  of 
  the 
  Uuer- 
  

   fano 
  group. 
  Although 
  the 
  shape 
  of 
  the 
  hill 
  is 
  the 
  typical 
  conical 
  one 
  

   of 
  a 
  volcano, 
  no 
  crater 
  or 
  even 
  a 
  vestige 
  of 
  any 
  crater 
  could 
  be 
  obsei 
  vpd. 
  

   It 
  is 
  a 
  curious 
  fact 
  that, 
  in 
  spite 
  of 
  the 
  very 
  large 
  amount 
  of 
  volcanic 
  

   material 
  that 
  occurs 
  in 
  Southern 
  Colorado, 
  I 
  have 
  not 
  been 
  able 
  to 
  find 
  

   a 
  single 
  mountain 
  or 
  hill 
  of 
  which 
  I 
  could 
  say 
  that 
  it 
  even 
  only 
  resem- 
  

   bled 
  an 
  extinct 
  crater. 
  The 
  eruptions 
  have 
  evidently 
  not 
  been 
  accom- 
  

   panied 
  by 
  that 
  demonstration 
  of 
  force 
  which 
  we 
  observe 
  in 
  the 
  volca- 
  

   noes 
  of 
  the 
  present 
  day, 
  but 
  the 
  existence 
  of 
  the 
  dome-shaped 
  and 
  sim- 
  

   ilar 
  mountains 
  that 
  stand 
  isolated 
  is 
  due 
  merely 
  to 
  a 
  slow 
  [)rcycess 
  of 
  

   eruption, 
  comparable 
  with 
  boiling 
  ovei'. 
  Many 
  of 
  them, 
  of 
  course, 
  owe 
  

   their 
  shape 
  to 
  the 
  gradual 
  decomposition 
  of 
  the 
  rocks 
  on 
  their 
  sides. 
  

   Earely 
  will 
  a 
  better 
  instance 
  demonstrating 
  the 
  former 
  fact 
  on 
  a 
  small 
  

   scale 
  be 
  found 
  than 
  at 
  station 
  G'S 
  of 
  1874. 
  I 
  might 
  allude 
  to 
  Mount 
  Saa 
  

   Antonio 
  and 
  Ute 
  Peak, 
  in 
  the 
  southern 
  portion 
  of 
  San 
  Luis 
  Valley; 
  

   they, 
  however, 
  are 
  of 
  large 
  extent, 
  and 
  have 
  sent 
  their 
  flows 
  for 
  a 
  long 
  

   distance 
  from 
  them. 
  

  

  This 
  is 
  the 
  last 
  of 
  the 
  larger 
  flows 
  in 
  the 
  district 
  discussed 
  in 
  this 
  

   chapter. 
  Essentially 
  we 
  have 
  but 
  three 
  groups: 
  the 
  Huerfano 
  group, 
  

   comprising 
  the 
  mountains 
  upon 
  which 
  stations 
  4, 
  5, 
  141, 
  and 
  63 
  of 
  J 
  874 
  

   are 
  located; 
  the 
  Spanish 
  Peak 
  group; 
  and 
  the 
  southern 
  Sangre 
  de 
  

   Cristo 
  or 
  Venado 
  group. 
  The 
  two 
  former 
  are 
  intimately 
  related, 
  and 
  

   are 
  probably 
  posterior 
  to 
  the 
  third. 
  Not 
  from 
  any 
  deposition 
  upon 
  cer- 
  

   tain 
  formations 
  can 
  this 
  be 
  judged, 
  but 
  mainly 
  from 
  the 
  fact 
  that 
  in 
  the 
  

   former, 
  rhyolitic 
  trachytes 
  and 
  basalt 
  occur, 
  which 
  are 
  wanting 
  in 
  the 
  

   latter. 
  The 
  relative 
  age 
  of 
  volcanic 
  rocks 
  in 
  our 
  western 
  country 
  has 
  

   been 
  so 
  well 
  established, 
  after 
  much 
  observation, 
  that 
  a 
  mistake 
  will 
  

   scarcely 
  be 
  made 
  by 
  following 
  the 
  adopted 
  succession. 
  It 
  will 
  generally 
  

   be 
  found, 
  too, 
  that 
  wherever 
  this 
  succession 
  has 
  been 
  the 
  guide 
  for 
  asser- 
  

   tions, 
  either 
  contemporaneous 
  or 
  subsequent 
  discoveries 
  will 
  corroborate 
  

   them. 
  

  

  B. 
  — 
  Bilces. 
  — 
  A 
  very 
  large 
  number 
  of 
  these 
  occur 
  throughout 
  the 
  dis- 
  

   trict, 
  but 
  as 
  it 
  would 
  be 
  useless 
  to 
  enumerate 
  all 
  observed, 
  only 
  the 
  most 
  

   ])ronnnentor 
  most 
  interesting 
  ones 
  shall 
  be 
  mentioned. 
  Station 
  142, 
  7,168 
  

   feet 
  high, 
  is 
  located 
  on 
  a 
  basaltic 
  dike, 
  that 
  is 
  one 
  of 
  a 
  small 
  complex. 
  

   The 
  general 
  trend 
  of 
  the 
  dikes 
  at 
  that 
  locality 
  is 
  northeast 
  to 
  southwest, 
  

   with 
  several 
  small 
  ones 
  crossing 
  them 
  at 
  nearly 
  right 
  angles. 
  Cretace- 
  

   ous 
  shales 
  of 
  the 
  Colorado 
  group 
  are 
  the 
  material 
  through 
  which 
  the 
  

   black 
  basalt 
  projects, 
  and 
  forms 
  the 
  steep 
  walls 
  that 
  are 
  almost 
  inacces- 
  

   sible. 
  The 
  one 
  upon 
  which 
  the 
  station 
  was 
  located 
  is 
  very 
  near 
  the 
  

   junction 
  of 
  Williams 
  Creek 
  and 
  the 
  Huerfano. 
  Although 
  scarcely 
  more 
  

   than 
  400 
  I'eet 
  above 
  the 
  valley 
  it 
  affords 
  an 
  excellent 
  point 
  for 
  an 
  exten- 
  

   sive 
  view, 
  a 
  fact 
  which 
  had 
  already 
  been 
  recognized 
  by 
  the 
  Indians, 
  in- 
  

   asmuch 
  as 
  we 
  found 
  the 
  remnants 
  of 
  an 
  old 
  " 
  look-out" 
  on 
  the 
  highest 
  

  

  