﻿160 
  Keyes 
  — 
  Carboniferous 
  and 
  Devonian 
  Strata. 
  

  

  Art. 
  XVIII. 
  — 
  Marked 
  Unconformity 
  between 
  Carboniferous 
  

   and 
  Devonian 
  Strata 
  in 
  Upper 
  Mississippi 
  Valley 
  ; 
  by 
  

   Charles 
  R. 
  Keyes. 
  

  

  After 
  half 
  a 
  century's 
  controversy 
  the 
  final 
  adjudication 
  of 
  

   the 
  Chemung 
  problem 
  in 
  the 
  Upper 
  Mississippi 
  region 
  seems 
  

   at 
  hand. 
  Exact 
  determination 
  of 
  the 
  stratigraphic 
  horizon 
  

   of 
  a 
  marked 
  plane 
  of 
  unconformity 
  which 
  may 
  be 
  properly 
  

   regarded 
  as 
  delimiting 
  the 
  base 
  of 
  the 
  Carboniferous 
  rocks 
  of 
  

   this 
  province 
  gives 
  answer 
  to 
  a 
  number 
  of 
  long 
  standing 
  

   questions. 
  

  

  In 
  the 
  delimitation 
  and 
  correlation 
  of 
  geologic 
  terranes 
  the 
  

   superior 
  value 
  of 
  diastrophic, 
  or 
  orogenic, 
  criteria 
  over 
  all 
  other 
  

   lines 
  of 
  evidence 
  has 
  been 
  recently 
  urged 
  by 
  a 
  number 
  of 
  wri- 
  

   ters,* 
  notably 
  Chamberlinf 
  and 
  Willis, 
  % 
  while 
  orogenic 
  criteria 
  

   aided 
  by 
  fossils 
  are 
  urged 
  by 
  Suess,§ 
  SchuchertJ 
  and 
  Ulrich.T" 
  

   As 
  is 
  well 
  known, 
  the 
  most 
  striking 
  expression 
  of 
  orogenic 
  

   movement 
  is 
  the 
  unconformable 
  relations 
  of 
  strata. 
  

  

  Recently, 
  during 
  the 
  progress 
  of 
  certain 
  investigations 
  for 
  

   city 
  water 
  supplies 
  in 
  Iowa, 
  Missouri, 
  and 
  Illinois, 
  it 
  became 
  

   necessary 
  to 
  make 
  some 
  rather 
  nice 
  calculations 
  on 
  the 
  thick- 
  

   ness 
  and 
  extent 
  of 
  sundry 
  geologic 
  formations. 
  In 
  the 
  course 
  

   of 
  this 
  work 
  a 
  number 
  of 
  facts 
  were 
  disclosed 
  bearing 
  directly 
  

   upon 
  the 
  vexed 
  problems 
  mentioned. 
  There 
  are 
  given 
  us 
  for 
  

   the 
  first 
  time 
  definite 
  data 
  upon 
  the 
  actual 
  stratigraphic 
  rela- 
  

   tions 
  existing 
  between 
  the 
  rocks 
  of 
  the 
  two 
  distinct 
  geologic 
  

   ages. 
  

  

  The 
  general 
  geologic 
  section 
  of 
  the 
  Devono-Carboniferous 
  

   rocks 
  of 
  southeastern 
  Iowa 
  and 
  northeastern 
  Missouri 
  is 
  as 
  

   follows 
  : 
  

  

  General 
  Geologic 
  Section. 
  

  

  Feet 
  

  

  f 
  Burlington 
  limestone 
  

  

  | 
  Chouteau 
  limestone 
  _ 
  10 
  

  

  Hannibal 
  shales 
  _ 
  75 
  

  

  Louisiana 
  limestone 
  50 
  

  

  Saverton 
  (blue) 
  shales** 
  50 
  

  

  Grassy 
  (black) 
  shales 
  40 
  

  

  Unconformity. 
  

  

  -p, 
  I 
  Lime 
  Creek 
  (blue) 
  shales 
  125 
  

  

  Devonian 
  ■< 
  ^ 
  , 
  r 
  , 
  v 
  ' 
  

  

  ( 
  Cedar 
  limestone 
  _ 
  

  

  * 
  American 
  Geologist, 
  vol. 
  xviii, 
  p. 
  289, 
  1896. 
  

  

  f 
  Das 
  Antlitz 
  der 
  Erde, 
  vol. 
  ii, 
  p. 
  15, 
  1888. 
  

  

  X 
  Journal 
  of 
  Geology, 
  vol. 
  xvii, 
  p. 
  685, 
  1909. 
  

  

  § 
  Bull. 
  Geol. 
  Soc. 
  America, 
  vol. 
  xx, 
  p. 
  447, 
  1910. 
  

  

  || 
  Science, 
  N. 
  S., 
  vol. 
  xxxi, 
  p. 
  243, 
  1910. 
  

  

  "IT 
  Bull. 
  Geol. 
  Soc. 
  America, 
  vol. 
  xxii, 
  p. 
  394, 
  1911. 
  

  

  ** 
  This 
  name 
  is 
  the 
  local 
  one 
  usually 
  applied 
  to 
  the 
  blue 
  shales 
  lying 
  be- 
  

   tween 
  the 
  Grassy 
  black 
  shales 
  and 
  the 
  Louisiana 
  limestone 
  as 
  well 
  exposed 
  

   at 
  Saverton 
  station, 
  in 
  Balls 
  county, 
  Missouri. 
  The 
  formation 
  probably 
  

   attains 
  a 
  maximum 
  thickness 
  of 
  at 
  least 
  75 
  feet. 
  

  

  Caeboniferous 
  « 
  

  

  