﻿Spencer 
  — 
  Devonian 
  Strata 
  in 
  Colorado. 
  133 
  

  

  series 
  occupies 
  below 
  the 
  Devonian 
  limestone, 
  in 
  the 
  San 
  Juan 
  

   region, 
  and 
  in 
  certain 
  localities 
  in 
  Central 
  Colorado. 
  

  

  Fossils 
  from 
  the 
  limestone 
  immediately 
  above 
  the 
  "Parting 
  

   Quartzite" 
  in 
  the 
  Gunnison 
  region 
  and 
  at 
  Salida 
  are 
  found 
  to 
  

   represent 
  a 
  fauna 
  which 
  is 
  identical 
  with 
  that 
  obtained 
  from 
  

   the 
  Devonian 
  limestone 
  occurring 
  above 
  the 
  siliceous 
  series 
  in 
  

   the 
  San 
  Juan 
  region. 
  The 
  correlation 
  is 
  thus 
  firmly 
  estab- 
  

   lished, 
  both 
  as 
  regards 
  the 
  limestone 
  and 
  the 
  siliceous 
  beds 
  

   beneath 
  it. 
  It 
  must 
  be 
  borne 
  in 
  mind, 
  however, 
  that 
  in 
  the 
  

   San 
  Juan 
  region 
  the 
  lowest 
  strata 
  may 
  be 
  older 
  than 
  Devonian. 
  

   There 
  is 
  a 
  suggestion 
  of 
  this 
  in 
  the 
  poorly 
  preserved 
  plants 
  

   from 
  the 
  lower 
  part 
  of 
  the 
  quartzite, 
  but 
  the 
  unity 
  of 
  the 
  

   quartzite 
  member 
  as 
  a 
  whole 
  is 
  distinctly 
  against 
  this 
  view.* 
  

  

  Following 
  up 
  the 
  correlation 
  brought 
  out 
  by 
  Spurr 
  [between 
  

   the 
  " 
  Parting 
  Quartzite 
  " 
  of 
  Central 
  Colorado 
  and 
  the 
  Devonian 
  

   of 
  the 
  Grand 
  Caiion 
  region, 
  it 
  is 
  of 
  interest 
  to 
  note 
  that 
  the 
  

   lower 
  part 
  of 
  the 
  Red 
  Wall 
  limestone 
  of 
  the 
  Grand 
  Canon, 
  

   below 
  the 
  part 
  which 
  contains 
  the 
  well 
  recognized 
  Lower 
  

   Carboniferous 
  forms, 
  is 
  unfossiliferous. 
  It 
  was 
  suggested 
  

   by 
  Gilbertf 
  that 
  the 
  base 
  of 
  the 
  Red 
  Wall 
  Carboniferous 
  

   limestone 
  had 
  possibly 
  been 
  placed 
  so 
  low 
  that 
  it 
  might 
  include 
  

   the 
  Devonian 
  and 
  even 
  part 
  of 
  the 
  Silurian. 
  Devonian 
  rocks 
  

   have 
  since 
  been 
  found 
  below 
  it,;}; 
  and 
  if 
  the 
  sequence 
  is 
  parallel 
  

   in 
  Colorado 
  and 
  the 
  Grand 
  Canon 
  district, 
  it 
  is 
  very 
  probable 
  

   that 
  the 
  lower 
  part 
  of 
  the 
  Red 
  Wall 
  limestone 
  is 
  equivalent 
  in 
  

   age 
  as 
  well 
  as 
  in 
  position 
  to 
  the 
  Devonian 
  limestone 
  of 
  Colo- 
  

   rado. 
  

  

  If 
  the 
  correlations 
  here 
  suggested 
  are 
  correct, 
  it 
  appears 
  that 
  

   Devonian 
  and 
  associated 
  strata 
  were 
  originally 
  deposited 
  over 
  

   an 
  extensive 
  area 
  in 
  the 
  Southern 
  Rocky 
  Mountain 
  region, 
  

   the 
  boundaries 
  of 
  which 
  are 
  as 
  yet 
  entirely 
  unknown. 
  

  

  U. 
  S. 
  G-eological 
  Survey, 
  June, 
  1899. 
  

  

  * 
  "While 
  there 
  is, 
  in 
  the 
  mind 
  of 
  the 
  writer, 
  no 
  reason 
  for 
  doubting 
  the 
  equiva- 
  

   lence 
  of 
  the 
  siliceous 
  formations 
  which 
  he 
  correlates 
  with 
  the 
  " 
  Parting 
  Quartzite," 
  

   he 
  does 
  not 
  accept 
  as 
  conclusive 
  the 
  evidence 
  concerning 
  their 
  age. 
  The 
  fish 
  

   remains 
  have 
  been 
  pronounced 
  of 
  Devonian 
  types, 
  but 
  in 
  no 
  case 
  have 
  they 
  been 
  

   specifically 
  determiuable. 
  and 
  it 
  is 
  to 
  be 
  remembered 
  that 
  the 
  fishes 
  from 
  the 
  

   Lower 
  Silurian 
  near 
  Caiion 
  City 
  are 
  of 
  types 
  not 
  previously 
  known 
  to 
  occur 
  below 
  

   the 
  Devonian. 
  

  

  f 
  U. 
  S. 
  Geol. 
  Surv. 
  W. 
  of 
  100th 
  Mer., 
  iii, 
  p. 
  178. 
  

  

  X 
  C. 
  D. 
  Walcott, 
  loc. 
  cit. 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Yol. 
  IX, 
  No. 
  50.— 
  February, 
  1900. 
  

   10 
  

  

  