﻿W. 
  T. 
  Lee 
  — 
  Type 
  Section 
  of 
  Morrison 
  Formation. 
  187 
  

  

  ings 
  four 
  sandstones 
  are 
  exposed. 
  The 
  lowest 
  is 
  con- 
  

   tinuous 
  with 
  the 
  Saurian 
  conglomerate, 
  and 
  above 
  it 
  

   are 
  variegated 
  shales 
  similar 
  to 
  those 
  in 
  the 
  lower 
  part 
  

   of 
  No. 
  4 
  of 
  the 
  Morrison 
  section. 
  Above 
  the 
  shale 
  is 
  

   soft 
  sandstone, 
  the 
  so-called 
  " 
  lower. 
  Dakota' 
  ' 
  of 
  the 
  

   region 
  near 
  Golden, 
  and 
  in 
  it 
  are 
  many 
  fossil 
  plants. 
  

   On 
  this 
  sandstone 
  rests 
  the 
  lower 
  shale 
  of 
  the 
  fire-clay 
  

   pits 
  and 
  above 
  it 
  is 
  another 
  plant-bearing 
  sandstone. 
  

   Next 
  in 
  order 
  upward 
  is 
  the 
  second 
  shale 
  used 
  as 
  fire- 
  

   clay 
  and 
  above 
  it 
  the 
  "upper 
  Dakota' 
  ' 
  or 
  No. 
  1 
  of 
  the 
  

   Morrison 
  section. 
  

  

  The 
  relations 
  found 
  may 
  be 
  summarized 
  as 
  follows: 
  

   The 
  "upper 
  Dakota" 
  is 
  not 
  a 
  uniformly 
  continuous 
  

   layer 
  of 
  sandstone, 
  but 
  rather 
  an 
  intricate 
  mass 
  of 
  over- 
  

   lapping 
  lenses. 
  The 
  sandstone 
  layers 
  of 
  "lower 
  

   Dakota" 
  and 
  the 
  fire-clay 
  beds 
  also 
  are 
  variable 
  in 
  

   number 
  and 
  in 
  thickness. 
  Although 
  the 
  shale 
  is 
  gener- 
  

   ally 
  most 
  abundant 
  near 
  the 
  middle 
  of 
  what 
  I 
  suggest 
  

   should 
  be 
  called 
  the 
  Dakota 
  Group, 
  it 
  may 
  occur 
  between 
  

   any 
  two 
  layers 
  of 
  the 
  sandstone. 
  The 
  lower 
  sandstone 
  

   and 
  the 
  shale 
  have 
  been 
  referred 
  to 
  the 
  Lower 
  Creta- 
  

   ceous 
  on 
  the 
  assumption 
  that 
  they 
  are 
  continuous 
  units. 
  

   This 
  assumption 
  is 
  not 
  sustained 
  by 
  detailed 
  examina- 
  

   tion. 
  Furthermore, 
  although 
  the 
  upper 
  sandstone 
  may 
  

   contain 
  fossil 
  plants, 
  I 
  did 
  not 
  find 
  them 
  in 
  this 
  sand- 
  

   stone 
  near 
  Morrison, 
  but 
  did 
  find 
  many 
  in 
  the 
  lower 
  

   sandstones. 
  If 
  these 
  plants 
  are 
  indicative 
  of 
  Upper 
  

   Cretaceous 
  age, 
  the 
  "lower 
  Dakota" 
  must 
  be 
  included 
  

   in 
  the 
  Upper 
  Cretaceous 
  series. 
  And 
  not 
  only 
  so, 
  but 
  

   also 
  the 
  upper 
  part 
  of 
  the 
  type 
  Morrison, 
  which 
  some 
  

   geologists 
  have 
  maintained 
  is 
  Jurassic. 
  

  

  Although 
  the 
  facts 
  here 
  presented 
  may 
  seem 
  trivial 
  in 
  

   themselves, 
  they 
  have 
  far-reaching 
  significance, 
  for 
  the 
  

   boundary 
  between 
  Lower 
  and 
  Upper 
  Cretaceous 
  is 
  in- 
  

   volved. 
  The 
  Dakota 
  flora 
  as 
  now 
  understood 
  includes 
  

   not 
  only 
  plants 
  from 
  the 
  "lower 
  Dakota" 
  and 
  the 
  upper 
  

   Morrison, 
  but 
  as 
  well 
  plants 
  from 
  the 
  Cheyenne 
  sand- 
  

   stone 
  of 
  Kansas. 
  This 
  sandstone 
  underlies 
  the 
  Kiowa 
  

   shale, 
  which, 
  on 
  the 
  basis 
  of 
  marine 
  invertebrates, 
  has 
  

   been 
  referred 
  by 
  some 
  geologists 
  to 
  Lower 
  Cretaceous. 
  

   Others, 
  however, 
  as 
  pointed 
  out 
  by 
  Knowlton 
  in 
  the 
  

   accompanying 
  paper, 
  place 
  the 
  Kiowa 
  and 
  Cheyenne 
  in 
  

   the 
  Upper 
  Cretaceous 
  series. 
  This 
  is 
  done 
  on 
  the 
  corre- 
  

   lation 
  that 
  the 
  Washita 
  series 
  is 
  Cenomanian, 
  strata 
  that 
  

  

  