﻿T. 
  E. 
  Savage 
  — 
  Devonian 
  Formation 
  of 
  Illinois. 
  179 
  

  

  Upper 
  Devonian 
  Rocks 
  of 
  the 
  Northern 
  or 
  Interior 
  Conti- 
  

   nental 
  Province. 
  

  

  The 
  Devonian 
  rocks 
  of 
  the 
  northern 
  or 
  Interior 
  Con- 
  

   tinental 
  province 
  are 
  best 
  exposed 
  in 
  Illinois 
  in 
  the 
  

   vicinity 
  of 
  Rock 
  Island, 
  where 
  their 
  thickness 
  reaches 
  

   150 
  feet. 
  They 
  are 
  not 
  known 
  sonth 
  of 
  the 
  latitude 
  of 
  

   Alton, 
  Illinois, 
  or 
  east 
  of 
  the 
  city 
  of 
  Springfield. 
  These 
  

   rocks 
  are 
  clearly 
  an 
  eastward 
  extension 
  of 
  corresponding 
  

   strata 
  in 
  Iowa 
  and 
  northern 
  Missouri, 
  and 
  these 
  Devo- 
  

   nian 
  formations 
  in 
  northwest 
  Illinois 
  are 
  designated 
  by 
  

   the 
  names 
  by 
  which 
  they 
  are 
  known 
  in 
  Iowa, 
  viz., 
  Wap- 
  

   sipinicon 
  limestone 
  at 
  the 
  base, 
  Cedar 
  Valley 
  limestone, 
  

   and 
  Sweetland 
  Creek 
  shale. 
  All 
  of 
  these 
  rocks 
  should 
  

   probably 
  be 
  considered 
  of 
  Upper 
  Devonian 
  age, 
  as 
  

   shown 
  on 
  a 
  later 
  page. 
  

  

  Wapsipinicon 
  Limestone. 
  — 
  The 
  Wapsipinicon 
  lime- 
  

   stone 
  in 
  Illinois 
  consists 
  for 
  the 
  most 
  part 
  of 
  light 
  gray, 
  

   rather 
  fine-grained, 
  brecciated 
  limestone, 
  60 
  to 
  75 
  feet 
  

   thick. 
  The 
  basal 
  layers 
  which 
  probably 
  represent 
  the 
  

   Otis 
  beds 
  of 
  Norton 
  are 
  well 
  exposed 
  on 
  Campbells 
  

   island, 
  above 
  Moline. 
  They 
  are 
  only 
  slightly 
  brecciated, 
  

   and 
  contain 
  numerous 
  shells 
  of 
  Spirifer 
  subumbonus. 
  

   The 
  middle, 
  profoundly 
  brecciated 
  portion 
  of 
  the 
  forma- 
  

   tion 
  is 
  well 
  exposed 
  in 
  the 
  railroad 
  cut 
  near 
  Fayette, 
  

   Iowa, 
  and 
  was 
  called 
  by 
  McGee 
  the 
  Fayette 
  breccia. 
  It 
  

   is 
  also 
  exposed 
  in 
  the 
  old 
  Cady 
  quarry 
  in 
  Moline, 
  Illi- 
  

   nois. 
  The 
  rock 
  fragments 
  are 
  fine 
  grained, 
  in 
  places 
  

   laminated, 
  and 
  range 
  from 
  a 
  few 
  inches 
  to 
  2 
  or 
  3 
  feet 
  

   in 
  length. 
  The 
  smaller 
  pieces 
  are 
  mostly 
  shattered 
  and 
  

   displaced; 
  but 
  some 
  of 
  the 
  larger 
  masses 
  have 
  only 
  been 
  

   broken 
  and 
  tilted 
  so 
  that 
  they 
  are 
  inclined 
  at 
  different 
  

   angles 
  with 
  one 
  another, 
  but 
  in 
  some 
  places 
  the 
  original 
  

   beds 
  can 
  be 
  traced 
  for 
  several 
  feet. 
  The 
  upper 
  layers, 
  

   which 
  are 
  less 
  brecciated 
  than 
  those 
  in 
  the 
  middle 
  por- 
  

   tion, 
  contain 
  such 
  fossils 
  as 
  Product 
  ell 
  a 
  subalata, 
  Schizo- 
  

   phoria 
  iowensis, 
  S. 
  macfarlanei, 
  Gypidula 
  comis, 
  

   Hypothyris 
  intermedia 
  (=H. 
  cuboides), 
  Spirifer 
  ioiven- 
  

   sis, 
  and 
  Atrypa 
  hystrix. 
  

  

  In 
  Iowa 
  the 
  lower 
  strata 
  of 
  the 
  Devonian 
  are 
  usually 
  

   similar 
  to 
  those 
  in 
  Illinois, 
  except 
  possibly 
  in 
  Buchanan 
  

   County 
  where 
  Calvin 
  has 
  described 
  a 
  dark 
  shale 
  member, 
  

   the 
  Independence 
  shale, 
  underlying 
  the 
  Wapsipinicon 
  

   formation. 
  The 
  Independence 
  shale 
  contains 
  many 
  spe- 
  

  

  