﻿184 
  W. 
  T. 
  Lee 
  — 
  Type 
  Section 
  of 
  Morrison 
  Formation. 
  

  

  by 
  Beckwith 
  and 
  described 
  by 
  Lesquereux 
  as 
  

   Dakota 
  flora. 
  ("Lower 
  Dakota" 
  of 
  some 
  geol- 
  

   ogists; 
  Purgatoire 
  or 
  Lower 
  Cretaceous 
  of 
  others) 
  75 
  

   Change 
  in 
  lithology 
  and 
  possible 
  time 
  break. 
  

  

  4 
  Sandstone, 
  friable, 
  and 
  shale; 
  plant-bearing 
  near 
  

   the 
  top, 
  variegated 
  in 
  color 
  in 
  some 
  places, 
  particu- 
  

   larly 
  near 
  the 
  base 
  (upper 
  part 
  of 
  Morrison 
  forma- 
  

   tion 
  as 
  originally 
  described) 
  100 
  

  

  5 
  Sandstone, 
  conglomeratic 
  — 
  the 
  Saurian 
  conglomer- 
  

   ate 
  — 
  containing 
  dinosaur 
  bones 
  and 
  pebbles 
  of 
  

   quartz 
  and 
  jasper; 
  sharply 
  separated 
  from 
  the 
  

   underlying 
  shale 
  10 
  

  

  Probable 
  time 
  break. 
  

   Morrison 
  formation, 
  160 
  feet. 
  

  

  6 
  Shale, 
  variegated, 
  with 
  layers 
  of 
  hard 
  sandstone 
  

   and 
  limestone; 
  contains 
  Sauropod 
  and 
  other 
  dino- 
  

   saurs 
  150 
  

  

  7 
  Sandstone 
  with 
  dinosaur 
  bones 
  and 
  quartz 
  pebbles 
  

   y 
  2 
  inch 
  in 
  diameter, 
  fills 
  hollows 
  in 
  the 
  underlying 
  

   formation 
  10 
  

  

  Erosional 
  unconformity. 
  

   Sundance 
  formation, 
  17 
  feet 
  (Upper 
  Jurassic). 
  

  

  8 
  Sandstone, 
  friable, 
  light 
  colored 
  5 
  

  

  9 
  Limestone, 
  impure, 
  with 
  pink 
  concretions 
  of 
  chal- 
  

   cedony 
  2 
  

  

  10 
  Sandstone, 
  massive, 
  friable, 
  pink 
  to 
  yellow; 
  varies 
  

   in 
  short 
  distances 
  from 
  5 
  to 
  15 
  feet; 
  rests 
  with 
  

  

  uneven 
  contact 
  on 
  red 
  sandstone 
  and 
  shale 
  10 
  

  

  Lykins 
  formation 
  (Permian 
  ?) 
  

  

  Sandstone 
  and 
  shale 
  — 
  Red 
  beds. 
  

  

  According 
  to 
  Cannon's 
  statement 
  made 
  on 
  the 
  ground, 
  

   Nos. 
  1-3 
  of 
  this 
  section 
  were 
  regarded 
  as 
  the 
  two 
  sand- 
  

   stones 
  of 
  the 
  Dakota 
  and 
  the 
  shale 
  as 
  the 
  " 
  Dakota 
  fire- 
  

   clay." 
  Other 
  geologists 
  have 
  followed 
  this 
  usage 
  and 
  

   when 
  the 
  "lower 
  Dakota" 
  and 
  the 
  shale 
  above 
  it 
  a 
  few 
  

   miles 
  farther 
  south 
  2 
  were 
  correlated 
  with 
  Purgatoire, 
  

   No. 
  3 
  of 
  the 
  Morrison 
  section 
  naturally 
  was 
  regarded 
  

   as 
  Lower 
  Cretaceous. 
  There 
  are 
  numerous 
  impressions 
  

   ■of 
  leaves 
  about 
  15 
  feet 
  above 
  the 
  base 
  of 
  this 
  sandstone, 
  

   and 
  according 
  to 
  Cannon 
  it 
  was 
  from 
  this 
  horizon 
  that 
  

   Lieutenant 
  Beckwith 
  collected 
  most, 
  if 
  not 
  all, 
  of 
  his 
  so- 
  

   called 
  Dakota 
  plants. 
  The 
  lithology 
  of 
  these 
  specimens, 
  

   which 
  are 
  now 
  in 
  the 
  National 
  Museum, 
  confirms 
  this 
  

   statement. 
  

  

  2 
  Richardson, 
  G. 
  B., 
  TJ. 
  S. 
  Geol. 
  Survey 
  Geol. 
  Atlas, 
  Castle 
  Rock 
  folio 
  

   (No. 
  198), 
  1915. 
  

  

  