﻿410 
  Twenhofel 
  — 
  Wreford 
  and 
  Foraker 
  Limestones. 
  

  

  7. 
  Limestone 
  having 
  a 
  rotten 
  appearance, 
  yellow 
  when 
  

   weathered, 
  light 
  colored 
  on 
  fresh 
  fracture. 
  Contains 
  consid- 
  

   erable 
  argillaceous 
  material 
  and, 
  if 
  much 
  weathered, 
  has 
  the 
  

   appearance 
  of 
  shale. 
  Fragments 
  of 
  fossils 
  are 
  present 
  . 
  . 
  2 
  feet. 
  

  

  6. 
  Compact 
  gray 
  limestone 
  containing 
  numerous 
  silicified 
  

   (chert) 
  fossils, 
  the 
  greatest 
  number 
  being 
  those 
  of 
  Composita 
  

   suhtilita. 
  The 
  beds 
  are 
  six 
  inches 
  to 
  one 
  foot 
  thick 
  and 
  are 
  sepa- 
  

   rated 
  by 
  partings 
  of 
  thin 
  limy 
  shale. 
  In 
  some 
  exposures 
  this 
  

   zone 
  has 
  a 
  chalky 
  appearance 
  3 
  feet, 
  10 
  inches. 
  

  

  5. 
  Light 
  yellow 
  shale 
  with 
  thin, 
  compact, 
  bluish-gray 
  lime- 
  

   stone. 
  About 
  one-third 
  is 
  shale. 
  Numerous 
  Prodactus 
  nebras- 
  

   kensis, 
  together 
  with 
  other 
  fossils, 
  are 
  present. 
  The 
  fossils 
  are 
  

   not 
  silicified. 
  Base 
  of 
  the 
  Wreford 
  limestone 
  . 
  .1 
  foot, 
  8 
  inches. 
  

  

  4. 
  Light 
  yellow 
  shale 
  with 
  thin 
  gray 
  limestones 
  . 
  . 
  6 
  inches. 
  

   3*. 
  Light 
  brown 
  and 
  yellow 
  shale' 
  with 
  thin 
  (% 
  inch) 
  lenti- 
  

   cular 
  limestones 
  .» 
  8 
  inches. 
  

  

  2. 
  Light 
  blue 
  shale 
  in 
  lower 
  six 
  inches, 
  upper 
  foot 
  composed 
  

  

  of 
  yellow 
  shale 
  1 
  foot, 
  6 
  inches. 
  

  

  1. 
  Red 
  gritty 
  shale 
  4 
  feet. 
  

  

  The 
  second 
  section 
  was 
  measured 
  about 
  a 
  mile 
  north- 
  

   east 
  of 
  the 
  town 
  of 
  Dexter. 
  It 
  is 
  as 
  follows 
  : 
  

  

  10. 
  Gray 
  limestone 
  weathering 
  into 
  rounded 
  blocks 
  of 
  about 
  

   eight 
  inches 
  in 
  diameter. 
  Base 
  not 
  exposed 
  4 
  feet. 
  

  

  9. 
  Gray 
  limestone 
  which 
  on 
  exposure 
  occurs 
  as 
  large 
  slabs 
  

   on 
  the 
  slope. 
  Contains 
  many 
  round 
  vertical 
  holes 
  which 
  vary 
  

   between 
  three 
  and 
  six 
  inches 
  in 
  diameter. 
  Chert 
  occurs 
  in 
  this 
  

   zone 
  but 
  its 
  relation 
  to 
  the 
  limestone 
  has 
  not 
  been 
  deter- 
  

   mined 
  1 
  foot, 
  5 
  inches. 
  

  

  8. 
  Gray 
  limestone, 
  not 
  honej^combed. 
  Separates 
  into 
  slabs 
  

   with 
  diameters 
  of 
  from 
  three 
  to 
  four 
  feet 
  1 
  foot, 
  6 
  inches. 
  

  

  7. 
  Gray 
  limestone 
  (one 
  bed) 
  in 
  which 
  are 
  many 
  vertical 
  cir- 
  

   cular 
  holes 
  of 
  about 
  one 
  inch 
  in 
  diameter, 
  giving 
  it 
  a 
  honeycomb 
  

   appearance. 
  Fresh 
  exposures 
  show 
  that 
  these, 
  in 
  all 
  probability, 
  

   were 
  originally 
  worm 
  burrows 
  which 
  were 
  about 
  as 
  deep 
  as 
  the 
  

   rock 
  is 
  thick, 
  since 
  passing 
  nearly 
  vertically 
  through 
  the 
  fresh 
  

   rock 
  are 
  tube-like 
  structures 
  of 
  three-eighths 
  to 
  one-half 
  inch 
  

   in 
  diameter 
  which 
  are 
  composed 
  of 
  material 
  — 
  chiefly 
  mud 
  and 
  

   fragments 
  of 
  fossils 
  — 
  which 
  is 
  less 
  resistant 
  than 
  the 
  surrounding 
  

   limestone. 
  In 
  some 
  exposures 
  this 
  zone 
  is 
  united 
  to 
  the 
  over- 
  

   lying, 
  the 
  two 
  zones 
  in 
  such 
  exposures 
  making 
  a 
  single 
  bed 
  

  

  2 
  feet, 
  3 
  inches. 
  

  

  6. 
  Gray 
  limestone 
  in 
  two- 
  to 
  six-inch 
  beds 
  . 
  . 
  2 
  feet, 
  3 
  inches. 
  

  

  5. 
  Gray 
  limestone 
  with 
  little 
  chert 
  in 
  the 
  upper 
  portion, 
  but 
  

   with 
  an 
  abundance 
  of 
  large 
  brown-surfaced 
  chert 
  nodules 
  in 
  the 
  

   lower- 
  half. 
  Some 
  of 
  the 
  nodules 
  are 
  as 
  great 
  as 
  three 
  and 
  a 
  half 
  

   feet 
  in 
  their 
  greatest 
  horizontal 
  diameters. 
  The 
  vertical 
  diam- 
  

   eters 
  do 
  not 
  exceed 
  a 
  foot 
  2 
  feet, 
  4 
  inches. 
  

  

  