﻿II. 
  S. 
  Williams 
  — 
  Southern 
  Devonian 
  formations. 
  397 
  

  

  period 
  of 
  the 
  accumulation 
  of 
  these 
  varying 
  sediments, 
  includ- 
  

   ing 
  some 
  sheets 
  of 
  black 
  shale, 
  as 
  well 
  as 
  several 
  belts 
  of 
  equally 
  

   tine 
  sediments 
  which 
  do 
  not 
  carry 
  the 
  black 
  shale 
  fauna. 
  

   Also 
  the 
  geographical 
  distribution 
  of 
  the 
  black 
  shales 
  is 
  not 
  at 
  

   all 
  related 
  to 
  distance 
  from 
  these 
  shores. 
  Hence 
  it 
  has 
  been 
  

   necessary 
  to 
  give 
  to 
  the 
  geologist, 
  who 
  has 
  appealed 
  to 
  the 
  

   paleontologist 
  to 
  know 
  what 
  is 
  the 
  age 
  of 
  the 
  southern 
  black 
  

   shale, 
  the 
  same 
  kind 
  of 
  answer 
  Lonsdale 
  gave 
  regarding 
  the 
  

   original 
  rocks 
  of 
  Devonshire, 
  that 
  all 
  we 
  know 
  is 
  that 
  they 
  are 
  

   younger 
  than 
  Silurian 
  and 
  older 
  than 
  the 
  central 
  member 
  of 
  

   the 
  Mississippian 
  series 
  of 
  the 
  interior. 
  In 
  like 
  manner 
  the 
  

   sudden 
  appearance 
  of 
  the 
  coarse 
  and 
  quite 
  uniform 
  sands 
  of 
  

   the 
  Oriskany 
  epoch, 
  in 
  the 
  northeastern 
  corner 
  of 
  the 
  interior 
  

   continental 
  sea, 
  following 
  immediately 
  after 
  the 
  Helderberg, 
  

   which 
  was 
  a 
  limestone 
  with 
  its 
  center 
  of 
  distribution 
  also 
  there, 
  

   finds 
  no 
  solution 
  upon 
  the 
  theory 
  of 
  rise 
  of 
  the 
  shore, 
  especially 
  

   when 
  we 
  consider 
  that 
  its 
  distribution 
  is 
  limited 
  to 
  the 
  shores 
  

   of 
  the 
  Lauren 
  tia 
  and 
  Appalachia 
  lands 
  and 
  possibly 
  some 
  parts 
  

   of 
  the 
  Cincinnati 
  plateau. 
  Some 
  other 
  factors 
  than 
  those 
  

   usually 
  applied 
  to 
  the 
  solution 
  of 
  correlation 
  problems 
  must 
  be 
  

   brought 
  under 
  consideration. 
  It 
  is 
  necessary 
  to 
  explain 
  the 
  

   general 
  conditions 
  of 
  sedimentation 
  for 
  the 
  whole 
  basin 
  in 
  

   Devonian 
  time, 
  and 
  also 
  the 
  reasons 
  for 
  the 
  differences 
  of 
  sedi- 
  

   mentation 
  in 
  different 
  parts 
  of 
  the 
  area. 
  It 
  is 
  also 
  necessary 
  to 
  

   explain 
  the 
  almost 
  total 
  absence 
  of 
  a 
  series 
  of 
  varied 
  faunas, 
  

   abundant 
  in 
  the 
  northern 
  and 
  northeastern 
  part 
  of 
  the 
  basin, 
  

   from 
  the 
  southern 
  central 
  part. 
  To 
  reach 
  these 
  ends 
  a 
  minute 
  

   study 
  of 
  the 
  relations 
  of 
  the 
  black 
  shale 
  to 
  the 
  sediments 
  and 
  

   conditions 
  both 
  preceding 
  and 
  following 
  its 
  occurrence, 
  in 
  

   purity, 
  seemed 
  likely 
  to 
  throw 
  some 
  light. 
  The 
  studies 
  already 
  

   made 
  in 
  Arkansas 
  and 
  Tennessee 
  seemed 
  to 
  warrant 
  the 
  conclu- 
  

   sion 
  that 
  in 
  certain 
  sections 
  of 
  the 
  south 
  there 
  was 
  uncon- 
  

   formity 
  below 
  the 
  black 
  shale, 
  and 
  the 
  suspicion 
  was 
  forced 
  

   upon 
  my 
  mind 
  that 
  the 
  base 
  of 
  the 
  shales 
  themselves 
  was 
  of 
  

   varying 
  age. 
  The 
  suggestion 
  made 
  in 
  Mr, 
  Hayes' 
  paper 
  on 
  the 
  

   Tennessee 
  phosphates," 
  that 
  the 
  bottom 
  might 
  have 
  been 
  

   scoured 
  by 
  ocean 
  currents, 
  led 
  me 
  to 
  think 
  that 
  ocean 
  currents 
  

   might 
  account 
  for 
  the 
  distribution 
  of 
  the 
  black 
  muds. 
  

  

  In 
  order 
  to 
  study 
  the 
  facts 
  more 
  minutely 
  I 
  spent 
  several 
  

   weeks 
  last 
  summer 
  in 
  southern 
  Virginia, 
  Tennessee 
  and 
  Ken- 
  

   tucky. 
  The 
  Estillville 
  sheetf 
  of 
  southern 
  Virginia 
  prepared 
  

   by 
  Mr. 
  Campbell 
  offered 
  the 
  most 
  promising 
  field 
  for 
  ascertain- 
  

   ing 
  the 
  relationship 
  of 
  the 
  black 
  mud 
  sediments 
  to 
  other 
  clastic 
  

  

  * 
  The 
  Tennessee 
  Phosphates, 
  by 
  Charles 
  W. 
  Hayes, 
  11th 
  Ann. 
  Rept. 
  U. 
  S. 
  

   Geol. 
  Survey. 
  Part 
  IV. 
  pp 
  610-630. 
  1895. 
  

  

  f 
  Estillville 
  Folio, 
  Ky. 
  Ya. 
  and 
  Tenn. 
  U. 
  S 
  G. 
  S. 
  Geol., 
  by 
  M. 
  R. 
  Campbell, 
  

   1894. 
  "Geology 
  of 
  the 
  Big 
  Stone 
  Gap 
  Coal 
  field 
  of 
  Va. 
  and 
  Ky.," 
  by 
  M. 
  R. 
  

   Campbell. 
  Ball. 
  No. 
  Ill, 
  U. 
  S. 
  G. 
  S., 
  1893. 
  

  

  