﻿Dakota 
  Strata 
  of 
  Kansas. 
  285 
  

  

  The 
  Spring 
  Creek 
  beds 
  consist 
  of 
  bluish, 
  greenish 
  and 
  

   yellowish 
  clays 
  containing 
  nodules 
  of 
  clayey 
  limonite. 
  

   They 
  contain 
  about 
  half 
  a 
  dozen 
  species 
  of 
  invertebrates 
  

   of 
  which 
  all 
  that 
  have 
  been 
  identified 
  are 
  also 
  present 
  

   below 
  in 
  the 
  Kiowa 
  shales. 
  The 
  thickness 
  of 
  the 
  beds 
  

   varies 
  up 
  to 
  about 
  50 
  feet 
  and 
  in 
  some 
  places 
  they 
  are 
  

   not 
  present 
  at 
  all 
  because 
  of 
  subsequent 
  erosion, 
  the 
  

   Tertiary 
  resting 
  directly 
  on 
  the 
  Kiowa. 
  The 
  member 
  is 
  

   of 
  shallow-water 
  marine 
  origin. 
  12 
  

  

  The 
  Greenleaf 
  member 
  is 
  composed 
  of 
  light 
  gray 
  to 
  

   light 
  brown 
  massive-bedded 
  and 
  occasionally 
  cross-lami- 
  

   nated 
  sandstone. 
  Less 
  than 
  half 
  a 
  dozen 
  species 
  of 
  

   marine 
  invertebrates 
  have 
  been 
  identified 
  from 
  this 
  mem- 
  

   ber 
  and 
  all 
  of 
  these 
  are 
  present 
  in 
  the 
  Kiowa 
  shales. 
  

   The 
  member 
  carries 
  the 
  record 
  of 
  a 
  retreat 
  of 
  the 
  

   Comanchean 
  sea, 
  but 
  whether 
  this 
  was 
  the 
  final 
  retreat 
  

   or 
  an 
  intermediate 
  one 
  can 
  not 
  be 
  stated. 
  The 
  thickness 
  

   varies 
  from 
  nothing 
  up 
  to 
  about 
  50 
  feet. 
  

  

  The 
  Kirby 
  clays 
  consist 
  of 
  reddish 
  sandy 
  clays 
  inter- 
  

   bedded 
  with 
  yellow 
  sandstones. 
  They 
  rest 
  conformably 
  

   on 
  the 
  Greenleaf 
  sandstones 
  and 
  are 
  the 
  coastal 
  plain 
  

   terrestrial 
  deposits 
  laid 
  down 
  by 
  streams 
  which 
  pushed 
  

   their 
  channels 
  and 
  spread 
  their 
  burdens 
  over 
  the 
  terri- 
  

   tory 
  uncovered 
  by 
  the 
  retreating 
  sea. 
  Possibly 
  the 
  

   streams 
  played 
  a 
  part 
  in 
  repelling 
  the 
  marine 
  waters. 
  

   The 
  only 
  fossils 
  which 
  have 
  been 
  seen 
  in 
  this 
  formation 
  

   are 
  fragments 
  of 
  leaves 
  of 
  dicotyledons. 
  The 
  thickness 
  

   varies 
  from 
  nothing 
  up 
  to 
  about 
  50 
  feet. 
  

  

  The 
  Reeder 
  member 
  consists 
  of 
  dark 
  brown 
  massive 
  

   sandstones 
  which 
  are 
  greatly 
  cross-laminated 
  more 
  or 
  

   less 
  throughout 
  and 
  contain 
  many 
  small 
  pebbles 
  of 
  

   quartz 
  and 
  chert 
  and 
  large 
  nodular 
  concretions. 
  The 
  

   sandstones 
  contain 
  fossil 
  leaves 
  of 
  dicotyledons 
  belong- 
  

   ing 
  to 
  species 
  which 
  are 
  characteristic 
  of 
  the 
  " 
  Dakota.' 
  r 
  

   This 
  member 
  is 
  of 
  terrestrial 
  origin. 
  The 
  thickness 
  

   varies 
  from 
  nothing 
  to 
  more 
  than 
  20 
  feet. 
  

  

  The 
  sequence 
  of 
  events 
  occurring 
  in 
  the 
  deposition 
  of 
  

   these 
  southern 
  deposits 
  was 
  as 
  follows. 
  At 
  first 
  the 
  

   region 
  was 
  part 
  of 
  a 
  coastal 
  plain 
  over 
  which 
  streams 
  of 
  

   low 
  gradient 
  deposited 
  sands 
  and 
  clays. 
  The 
  climate 
  

   was 
  probably 
  not 
  greatly 
  dissimilar 
  from 
  the 
  present 
  

  

  12 
  This 
  and 
  the 
  two 
  succeeding 
  members 
  were 
  differentiated 
  by 
  Gould 
  

   (op. 
  cit.) 
  and 
  the 
  descriptions, 
  except 
  where 
  modified, 
  are 
  based 
  on 
  those 
  

   given 
  by 
  him. 
  

  

  