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  Spencer 
  — 
  Devonian 
  Strata 
  in 
  Colorado. 
  

  

  investigation 
  has 
  been 
  to 
  confirm 
  Meek's 
  opinion 
  of 
  the 
  

   Devonian 
  age 
  of 
  the 
  fossils 
  which 
  were 
  found 
  by 
  Endlich, 
  and 
  

   to 
  establish 
  the 
  basis 
  for 
  a 
  correlation 
  of 
  the 
  Devonian 
  of 
  the 
  

   San 
  Juan 
  region 
  with 
  strata 
  in 
  other 
  parts 
  of 
  the 
  State 
  which 
  

   have 
  hitherto 
  been 
  included 
  in 
  the 
  Lower 
  Carboniferous. 
  

  

  Devonian 
  in 
  Southwestern 
  Colorado. 
  — 
  The 
  Devonian 
  rocks 
  

   are 
  at 
  present 
  the 
  oldest 
  formations 
  which 
  are 
  well 
  authen- 
  

   ticated 
  in 
  the 
  San 
  Juan 
  region 
  of 
  Southwestern 
  Colorado. 
  

   Silurian 
  was 
  represented 
  upon 
  the 
  Hayden 
  map 
  in 
  End- 
  

   lich's 
  area, 
  and 
  though 
  the 
  areal 
  distribution 
  of 
  the 
  lower 
  

   formations, 
  as 
  there 
  shown, 
  is 
  very 
  incorrect 
  and 
  gives 
  no 
  basis 
  

   for 
  a 
  conclusion, 
  it 
  is 
  thought 
  from 
  the 
  text* 
  that 
  his 
  Silurian 
  

   is 
  the 
  basal 
  quartzite 
  of 
  our 
  section. 
  The 
  quartzite 
  is 
  wanting 
  

   or 
  of 
  very 
  limited 
  development 
  on 
  the 
  east 
  side 
  of 
  the 
  Animas 
  

   river, 
  where 
  the 
  Devonian 
  was 
  first 
  discovered 
  by 
  Endlich,. 
  

   while 
  it 
  is 
  very 
  prominent 
  in 
  the 
  vicinity 
  of 
  Cascade 
  creek 
  

   where 
  his 
  Silurian 
  is 
  indicated. 
  The 
  incompleteness 
  of 
  the 
  

   Hayden 
  map 
  in 
  regard 
  to 
  the 
  basal 
  portion 
  of 
  the 
  sedimentary 
  

   section 
  is 
  to 
  be 
  wondered 
  at, 
  since 
  at 
  no 
  place 
  where 
  it 
  has 
  

   thus 
  far 
  been 
  studied 
  by 
  us 
  is 
  the 
  Devonian 
  limestone 
  absent 
  

   between 
  the 
  crystalline 
  basement 
  and 
  the 
  rocks 
  of 
  well-recog- 
  

   nized 
  Carboniferous 
  age. 
  

  

  The 
  series 
  below 
  the 
  Carboniferous 
  consists 
  typically 
  of 
  

   three 
  members, 
  a 
  sandstone 
  or 
  quartzite 
  at 
  the 
  base, 
  a 
  shale 
  

   series, 
  and 
  a 
  massive 
  limestone. 
  Of 
  these, 
  the 
  lowest 
  is 
  fre- 
  

   quently 
  wanting 
  through 
  non-deposition, 
  and 
  the 
  middle 
  mem- 
  

   ber 
  is 
  also 
  sometimes 
  very 
  thin 
  or 
  entirely 
  absent. 
  The 
  

   formation 
  name, 
  Ouray 
  limestone, 
  is 
  proposed 
  for 
  the 
  only 
  

   member 
  of 
  the 
  section 
  which 
  is 
  definitely 
  shown 
  by 
  its 
  fossils 
  

   to 
  be 
  of 
  Devonian 
  age, 
  from 
  the 
  prominent 
  occurrence 
  in 
  the 
  

   vicinity 
  of 
  Ouray 
  at 
  the 
  junction 
  of 
  Canon 
  creek 
  with 
  the 
  

   Uncompaghre 
  river. 
  No 
  names 
  will 
  be 
  proposed 
  for 
  the 
  lower 
  

   formations 
  at 
  present, 
  since, 
  for 
  purposes 
  of 
  mapping, 
  it 
  may 
  

   prove 
  necessary 
  to 
  include 
  them 
  under 
  a 
  single 
  name. 
  

  

  Above 
  the 
  Devonian 
  there 
  is 
  apparent 
  conformity 
  of 
  depo- 
  

   sition, 
  but 
  the 
  occurrence 
  of 
  Upper 
  Carboniferous 
  fossils 
  within 
  

   a 
  few 
  feet 
  of 
  the 
  Devonian 
  limestone, 
  and 
  the 
  absence 
  of 
  any 
  

   fauna 
  comparable 
  with 
  the 
  Lower 
  Carboniferous 
  fauna 
  from 
  

   the 
  Gunnison 
  region 
  and 
  from 
  Tourtelotte 
  park, 
  suggests 
  a 
  gap 
  

   in 
  deposition 
  which 
  represents 
  the 
  whole 
  of 
  the 
  Lower 
  Car- 
  

   boniferous. 
  There 
  is, 
  however, 
  a 
  possibility 
  that 
  there 
  may 
  be 
  

   a 
  few 
  feet 
  of 
  unfossiliferous 
  limestone 
  above 
  the 
  true 
  Devonian, 
  

   and 
  not 
  differentiated 
  from 
  it, 
  which 
  is 
  really 
  of 
  Lower 
  Car- 
  

   boniferous 
  age. 
  Such 
  a 
  lack 
  of 
  lithological 
  difference 
  would 
  

  

  * 
  Hayden 
  G-eol. 
  and 
  Geog. 
  Surv. 
  of 
  Terr., 
  Report 
  of 
  F. 
  M. 
  Endlich 
  for 
  1874, 
  

   p. 
  210. 
  

  

  