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  W. 
  H. 
  Twenhofel 
  — 
  The 
  Comanchean 
  and 
  

  

  Washita 
  — 
  the 
  uppermost 
  division 
  of 
  the 
  Comanchean 
  or 
  

   Lower 
  Cretaceous 
  as 
  defined 
  in 
  the 
  United 
  States 
  — 
  

   affords 
  the 
  basis 
  for 
  an 
  inquiry 
  into 
  the 
  validity 
  of 
  inter- 
  

   continental 
  limitation 
  of 
  periods. 
  

  

  Previous 
  Views. 
  

  

  It 
  has 
  been 
  generally 
  assumed 
  that 
  the 
  Dakota 
  is 
  the 
  

   initial 
  formation 
  of 
  the 
  Upper 
  Cretaceous. 
  This 
  view 
  

   has 
  been 
  repeatedly 
  challenged 
  by 
  stratigraphers, 
  among 
  

   whom 
  Professor 
  L. 
  F. 
  Ward 
  appears 
  to 
  have 
  been 
  the 
  

   pioneer 
  as 
  shown 
  in 
  his 
  statement 
  that 
  "It 
  would 
  seem 
  

   probable 
  that 
  a 
  considerable 
  portion 
  of 
  the 
  deposits 
  

   underlying 
  the 
  marine 
  Cretaceous 
  of 
  the 
  Eocky 
  Moun- 
  

   tain 
  region 
  which 
  have 
  heretofore 
  been 
  referred 
  to 
  the 
  

   Dakota 
  Group 
  on 
  purely 
  stratigraphical 
  evidence 
  may 
  

   really 
  be 
  much 
  older." 
  2 
  In 
  his 
  article 
  on 
  "Types 
  of 
  

   Sedimentary 
  Overlap," 
  Grabau 
  strongly 
  insisted 
  on 
  the 
  

   Comanchean 
  age 
  of 
  at 
  least 
  a 
  part 
  of 
  the 
  Dakota 
  and 
  

   also 
  maintained 
  that 
  the 
  formation 
  is 
  probably 
  of 
  dif- 
  

   ferent 
  ages 
  in 
  different 
  parts 
  of 
  its 
  distribution. 
  3 
  In 
  

   Scott's 
  "Introduction 
  to 
  Geology," 
  the 
  Dakota 
  is 
  placed 
  

   in 
  the 
  Lower 
  Cretaceous. 
  In 
  this 
  assignment 
  he 
  stands 
  

   alone 
  among 
  authors 
  of 
  American 
  text-books. 
  4 
  A 
  sum- 
  

   mary 
  of 
  the 
  conclusions 
  of 
  American 
  students 
  on 
  this 
  

   subject 
  has 
  been 
  made 
  by 
  Todd 
  and 
  as 
  a 
  result 
  of 
  his 
  

   examination 
  of 
  the 
  literature 
  he 
  concluded 
  that 
  the 
  

   Dakota 
  is 
  Lower 
  Cretaceous. 
  5 
  

  

  The 
  Cheyenne-Kiowa-Medicine 
  Sequence. 
  

  

  The 
  strata 
  belonging 
  to 
  this 
  sequence 
  occur 
  near 
  the 
  

   southern 
  border 
  of 
  the 
  state, 
  extending 
  as 
  a 
  narrow 
  

   irregular 
  band 
  from 
  near 
  the 
  town 
  of 
  Medicine 
  Lodge 
  in 
  

   Barber 
  Co. 
  to 
  just 
  south 
  of 
  the 
  town 
  of 
  Meade 
  in 
  Meade 
  

   Co. 
  South 
  of 
  about 
  the 
  middle 
  of 
  the 
  distribution 
  

   there 
  is 
  an 
  outlier 
  on 
  the 
  Oklahoma 
  line. 
  The 
  orienta- 
  

   tion 
  of 
  the 
  band 
  is 
  conditioned 
  by 
  the 
  topography, 
  and 
  

   as 
  a 
  consequence 
  is 
  extremely 
  irregular. 
  Northward 
  the 
  

   Comanchean 
  strata 
  are 
  overlain 
  by 
  the 
  terrestrial 
  

   deposits 
  of 
  the 
  Plains 
  Tertiary, 
  which 
  on 
  the 
  eastern 
  and 
  

  

  2 
  L. 
  F. 
  Ward, 
  Jour. 
  Geol., 
  2, 
  265, 
  1894. 
  

  

  3 
  A. 
  Grabau, 
  Bull. 
  Geol. 
  Soc. 
  Am., 
  17, 
  620-627, 
  1906. 
  

  

  4 
  W. 
  B. 
  Scott, 
  Introduction 
  to 
  Geology, 
  2d 
  edition, 
  p. 
  702, 
  1907. 
  

  

  s 
  J. 
  E. 
  Todd, 
  Trans. 
  Kansas 
  Acad. 
  Sci., 
  23 
  and 
  24, 
  65-69, 
  1917. 
  

  

  