﻿W. 
  H. 
  Twerihofel 
  — 
  C 
  omanchean 
  and 
  Dakota 
  Strata. 
  281 
  

  

  Aet. 
  XXII. 
  — 
  The 
  C 
  omanchean 
  and 
  Dakota 
  Strata 
  of 
  

   Kansas; 
  1 
  by 
  W. 
  H. 
  Twenhofel. 
  

  

  Table 
  of 
  Contents. 
  

   Introduction. 
  

   Previous 
  views. 
  

  

  The 
  Cheyenne-Kiowa-Medicine 
  sequence. 
  

   The 
  Mentor-Dakota 
  sequence. 
  

  

  Summary 
  of 
  the 
  conditions 
  of 
  origin 
  of 
  the 
  Comanchean 
  of 
  Kansas. 
  

   Correlates 
  of 
  the 
  Kansas 
  Comanchean. 
  

   Sequence 
  of 
  events 
  for 
  the 
  Plains 
  Comanchean. 
  

   The 
  base 
  of 
  the 
  Cretaceous. 
  

  

  Introduction. 
  

  

  The 
  formations 
  in 
  Kansas 
  which 
  in 
  this 
  article 
  are 
  

   referred 
  to 
  the 
  Comanchean 
  are 
  those 
  which 
  in 
  the 
  south- 
  

   ern 
  part 
  of 
  the 
  state 
  are 
  known 
  as 
  the 
  Cheyenne 
  sand- 
  

   stone, 
  Kiowa 
  shale 
  and 
  Medicine 
  beds 
  and 
  those 
  which 
  in 
  

   central 
  and 
  northern 
  Kansas 
  have 
  been 
  called 
  the 
  Mentor 
  

   beds 
  and 
  Dakota 
  sandstone. 
  The 
  writer 
  has 
  spent 
  parts 
  

   of 
  several 
  field 
  seasons 
  in 
  the 
  study 
  of 
  these 
  formations 
  

   and 
  has 
  arrived 
  at 
  the 
  conclusion 
  that 
  the 
  marine 
  beds 
  of 
  

   the 
  southern 
  and 
  central 
  portions 
  of 
  the 
  state 
  are 
  the 
  

   stratigraphic 
  equivalents 
  of 
  the 
  Dakota 
  sandstone 
  of 
  the 
  

   central 
  and 
  northern 
  portions, 
  the 
  chief 
  evidence 
  being 
  

   that 
  the 
  former 
  dove-tail 
  into 
  the 
  latter 
  on 
  at 
  least 
  three 
  

   horizons 
  — 
  perhaps 
  five 
  — 
  which 
  are 
  disturbed 
  from 
  near 
  

   the 
  base 
  to 
  well 
  up 
  toward 
  the 
  summit. 
  Much 
  of 
  the 
  evi- 
  

   dence 
  for 
  this 
  conclusion 
  has 
  previously 
  been 
  published 
  

   in 
  separate 
  articles 
  by 
  other 
  students. 
  Because 
  this 
  

   evidence 
  is 
  as 
  yet 
  not 
  widely 
  known, 
  however, 
  it 
  and 
  such 
  

   new 
  data 
  as 
  the 
  writer 
  has 
  collected 
  are 
  brought 
  together 
  

   in 
  this 
  article 
  and 
  afford 
  the 
  basis 
  for 
  the 
  conclusion 
  

   noted 
  above. 
  

  

  Since 
  the 
  marine 
  beds 
  belong 
  to 
  the 
  Comanchean 
  or 
  

   Lower 
  Cretaceous 
  as 
  defined 
  by 
  American 
  authors, 
  it 
  fol- 
  

   lows 
  from 
  this 
  conclusion 
  that 
  the 
  Kansas 
  Dakota, 
  gen- 
  

   erally 
  assumed 
  to 
  be 
  the 
  base 
  of 
  the 
  Upper 
  Cretaceous 
  

   in 
  that 
  state, 
  is 
  of 
  Comanchean 
  age. 
  In 
  the 
  final 
  topic 
  

   of 
  the 
  article 
  there 
  is 
  considered 
  the 
  lower 
  boundary 
  of 
  

   the 
  Upper 
  Cretaceous. 
  The 
  fact 
  that 
  the 
  base 
  of 
  the 
  

   Upper 
  Cretaceous 
  of 
  Europe 
  appears 
  to 
  have 
  its 
  corre- 
  

   late 
  beneath, 
  or 
  somewhere 
  within, 
  the 
  lower 
  half 
  of 
  the 
  

  

  1 
  Published 
  by 
  permission 
  of 
  the 
  State 
  Geologist 
  of 
  Kansas. 
  

  

  