﻿150 
  Williams 
  — 
  Devonian 
  Interval 
  in 
  northern 
  Arlcansas. 
  

  

  are 
  not 
  later 
  residual 
  products 
  of 
  decay 
  of 
  the 
  lower 
  lime- 
  

   stones, 
  as 
  Mr. 
  Penrose 
  explains 
  the 
  origin 
  of 
  the 
  manganese- 
  

   bearing 
  interval-material 
  in 
  Independence 
  County. 
  Again, 
  

   the 
  black 
  nodules 
  contain 
  Lingulas 
  as 
  do 
  the 
  black 
  shales, 
  and 
  

   the 
  structure 
  of 
  the 
  nodules, 
  and 
  the 
  evident 
  agglutination 
  of 
  

   some 
  of 
  them, 
  and 
  the 
  concretionary 
  nature 
  of 
  the 
  oolitic 
  

   grains 
  of 
  which 
  others 
  are 
  composed, 
  all 
  point 
  to 
  a 
  concre- 
  

   tionary 
  mode 
  of 
  formation 
  rather 
  than 
  to 
  a 
  simple 
  rounding 
  of 
  

   broken 
  fragments; 
  while 
  the 
  extreme 
  polishing 
  and 
  medium 
  

   size 
  with 
  absence 
  of 
  finer 
  grains 
  of 
  the 
  sandstone, 
  point 
  to 
  

   excessive 
  erosion. 
  Again, 
  the 
  fauna 
  appearing 
  next 
  above 
  this 
  

   interval-material 
  is 
  in 
  all 
  cases, 
  when 
  covered 
  by 
  rock, 
  of 
  Car- 
  

   boniferous 
  age 
  ; 
  the 
  species 
  indicating 
  generally 
  a 
  Chouteau 
  

   fauna, 
  in 
  some 
  cases 
  later 
  Chouteau 
  with 
  traces 
  of 
  Burlington, 
  

   or 
  Keokuk 
  species. 
  

  

  The 
  interpretation 
  of 
  these 
  facts 
  is 
  that 
  the 
  typical 
  interval- 
  

   materials, 
  the 
  green 
  shale 
  and 
  the 
  Sylamore 
  sandstone, 
  were 
  

   deposited 
  after 
  the 
  period 
  of 
  the 
  formation 
  of 
  the 
  typical 
  

   black 
  shales 
  which, 
  along 
  the 
  borders 
  of 
  the 
  Ozark 
  uplift, 
  was 
  

   terminated, 
  or 
  actually 
  driven 
  outward, 
  by 
  the 
  elevation 
  of 
  the 
  

   region 
  ; 
  that 
  these 
  particular 
  deposits 
  mark 
  the 
  stage 
  of 
  sink- 
  

   ing 
  again 
  of 
  the 
  land 
  and 
  the 
  resultant 
  erosion 
  which 
  intro- 
  

   duced 
  the 
  Carboniferous 
  formations 
  for 
  this 
  region 
  ; 
  that 
  the 
  

   time 
  was 
  at 
  the 
  very 
  close 
  of 
  the 
  Devonian 
  and 
  beginning 
  of 
  

   the 
  Carboniferous 
  eras. 
  I 
  conclude 
  that 
  the 
  explanation 
  of 
  the 
  

   varying 
  age 
  and 
  nature 
  of 
  these 
  deposits 
  is 
  due 
  to 
  the 
  sections 
  

   having 
  been 
  taken 
  at 
  places 
  at 
  lower 
  or 
  higher 
  position 
  on 
  the 
  

   gradually 
  sinking 
  land, 
  and 
  expressing 
  the 
  overlap 
  of 
  the 
  suc- 
  

   cessively 
  more 
  recent 
  deposits. 
  This 
  point, 
  however, 
  can 
  be 
  

   satisfactorily 
  determined 
  only 
  by 
  examination 
  of 
  the 
  strati- 
  

   graphical 
  relations 
  of 
  the 
  various 
  formations. 
  My 
  judgment 
  is 
  

   based 
  upon 
  the 
  relations 
  of 
  the 
  various 
  formations 
  in 
  the 
  few 
  

   sections 
  presenting 
  several 
  of 
  the 
  formations 
  in 
  succession. 
  

  

  The 
  descriptions 
  in 
  Dr. 
  Penrose's 
  Keport 
  (Ann. 
  Kept., 
  1890, 
  

   vol. 
  i) 
  stratigraphy 
  of 
  Independence 
  county 
  led 
  me 
  to 
  infer 
  a 
  

   similar 
  explanation 
  of 
  the 
  facts 
  there 
  ; 
  but 
  evidence 
  was 
  not 
  

   then 
  at 
  hand 
  to 
  disprove 
  the 
  reference 
  of 
  the 
  red 
  limestones, 
  

   lying 
  above 
  the 
  interval-accumulations, 
  to 
  the 
  Silurian 
  lime- 
  

   stone. 
  If 
  Dr. 
  Penrose 
  was 
  correct 
  in 
  his 
  reference 
  of 
  the 
  

   upper 
  limestone, 
  in 
  the 
  section 
  of 
  the 
  O'Flynn 
  mine 
  (p. 
  231, 
  

   fig. 
  14), 
  to 
  the 
  St. 
  Clair 
  limestone, 
  it 
  is 
  difficult 
  to 
  discover 
  any 
  

   relationship 
  between 
  the 
  Sylamore 
  sandstone 
  and 
  the 
  manga- 
  

   nese 
  deposit 
  which 
  would 
  be 
  included 
  in 
  the 
  midst 
  of 
  that 
  

   limestone. 
  Among 
  the 
  specimens 
  sent 
  in 
  by 
  Mr. 
  Hopkins, 
  

   there 
  is 
  no 
  evidence 
  of 
  the 
  Silurian 
  limestone 
  at 
  the 
  O'Flynn 
  

   mine, 
  but 
  there 
  does 
  appear 
  evidence 
  of 
  a 
  deposit 
  similar 
  to 
  

   the 
  Sylamore 
  sandstone 
  in 
  connection 
  with 
  the 
  so-called 
  

  

  