﻿Dakota 
  Strata 
  of 
  Kansas. 
  293 
  

  

  It 
  is 
  possible 
  that 
  zone 
  2 
  is 
  the 
  equivalent 
  of 
  the 
  Chey- 
  

   enne 
  sandstone, 
  but 
  a 
  correlation 
  on 
  the 
  basis 
  of 
  lithology 
  

   and 
  stratigraphical 
  position 
  is 
  so 
  hazardous 
  that 
  it 
  is 
  

   not 
  attempted. 
  Zone 
  3 
  contains 
  species 
  which 
  are 
  pres- 
  

   ent 
  in 
  the 
  Kiowa, 
  and 
  no 
  doubt 
  whatever 
  can 
  be 
  enter- 
  

   tained 
  that 
  the 
  zone 
  is 
  contemporaneous 
  with 
  some 
  

   portion 
  of 
  the 
  Kiowa. 
  Nothing 
  equivalent 
  to 
  the 
  upper 
  

   marine 
  zones 
  of 
  the 
  Kansas 
  sequence 
  has 
  been 
  discov- 
  

   ered 
  and 
  it 
  is 
  assumed 
  that 
  the 
  Washita 
  sea 
  existed 
  in 
  

   Colorado 
  for 
  a 
  much 
  shorter 
  time 
  than 
  it 
  did 
  in 
  Kansas. 
  

  

  In 
  his 
  description 
  of 
  the 
  geology 
  of 
  the 
  Apishapa 
  

   quadrangle 
  Stose 
  18 
  differentiated 
  the 
  strata 
  containing 
  

   marine 
  fossils, 
  together 
  with 
  the 
  sandstones 
  below, 
  as 
  

   the 
  Purgatoire 
  formation 
  and 
  showed 
  that 
  in 
  some 
  of 
  the 
  

   sections 
  there 
  is 
  much 
  lateral 
  variation 
  of 
  lithology 
  in 
  

   some 
  horizons. 
  The 
  upper 
  portion 
  of 
  the 
  Purgatoire 
  is 
  

   certainly 
  of 
  Kiowa 
  age 
  and 
  the 
  lower 
  portion 
  may 
  be 
  the 
  

   equivalent 
  of 
  the 
  Cheyenne. 
  

  

  In 
  the 
  Colorado 
  Springs 
  quadrangle 
  Findlay 
  19 
  differ- 
  

   entiated 
  the 
  Purgatoire 
  formation 
  into 
  the 
  Lytle 
  sand- 
  

   stone 
  member 
  at 
  the 
  base 
  and 
  the 
  Grlencairn 
  shale 
  above. 
  

   The 
  shales 
  contain 
  a 
  few 
  fossils; 
  there 
  are 
  none 
  in 
  the 
  

   Lytle 
  sandstone. 
  

  

  The 
  important 
  consideration 
  for 
  this 
  portion 
  of 
  the 
  

   country 
  is 
  the 
  age 
  of 
  the 
  "Dakota." 
  In 
  the 
  folios 
  to 
  

   which 
  reference 
  has 
  been 
  made 
  it 
  was 
  separated 
  from 
  

   the 
  strata 
  below 
  on 
  the 
  basis 
  of 
  its 
  dicotyledonous 
  flora, 
  

   but 
  that 
  evidence 
  can 
  be 
  given 
  no 
  validity 
  since, 
  as 
  we 
  

   have 
  seen, 
  such 
  also 
  occurs 
  below 
  the 
  Washita 
  fauna. 
  It 
  

   is 
  possible 
  that 
  the 
  Colorado 
  "Dakota" 
  may 
  belong 
  to 
  

   the 
  Upper 
  Cretaceous 
  and 
  be 
  younger 
  than 
  the 
  leaf 
  -bear- 
  

   ing 
  beds 
  of 
  Kansas, 
  but 
  such 
  a 
  conclusion, 
  or, 
  in 
  fact, 
  

   any 
  conclusion, 
  must 
  wait 
  for 
  further 
  evidence. 
  

  

  Sequence 
  of 
  Events 
  for 
  the 
  Plains 
  Comanchean. 
  

  

  The 
  sequence 
  of 
  events 
  for 
  Kansas 
  and 
  adjacent 
  states 
  

   from 
  the 
  time 
  of 
  the 
  first 
  appearance 
  of 
  the 
  Comanchean 
  

   sea 
  to 
  the 
  time 
  of 
  the 
  invasion 
  of 
  the 
  Eagle 
  Ford-Benton 
  

   sea 
  was 
  something 
  as 
  follows 
  : 
  

  

  1. 
  Terrestrial 
  deposition 
  of 
  the 
  Cheyenne 
  sandstone, 
  

   by 
  streams 
  and 
  winds 
  on 
  a 
  coastal 
  plain 
  in 
  a 
  semi-arid 
  

   climate. 
  

  

  18 
  G. 
  W. 
  Stose, 
  U. 
  S. 
  Geol. 
  Surv., 
  Folio 
  186, 
  pp. 
  3-5, 
  1912. 
  

  

  19 
  G. 
  I. 
  Findlay, 
  IT. 
  S. 
  Geol. 
  Surv., 
  Folio 
  203, 
  pp. 
  7-8, 
  1916. 
  

  

  