﻿H. 
  S. 
  Williams 
  — 
  Southern 
  Devonian 
  formations. 
  399 
  

  

  tains 
  corals 
  which 
  appear 
  to 
  be 
  of 
  Corniferous 
  age, 
  and 
  below 
  

   is 
  a 
  sandstone 
  capping 
  the 
  Helderberg 
  limestone. 
  At 
  a 
  single 
  

   locality, 
  under 
  the 
  woollen 
  mill 
  on 
  the 
  bank 
  of 
  the 
  east 
  branch 
  

   of 
  Powell 
  river 
  east 
  of 
  Big 
  Stone 
  Gap, 
  in 
  the 
  place 
  of 
  the 
  ore 
  

   the 
  limestone 
  is 
  quite 
  filled 
  with 
  corals 
  in 
  place, 
  followed 
  

   immediately 
  by 
  the 
  black 
  shales 
  with 
  no 
  intervening 
  iron 
  ore. 
  

   This 
  seems 
  to 
  fix 
  the 
  date 
  of 
  the 
  beginning 
  of 
  the 
  black 
  shales 
  

   for 
  this 
  region 
  at 
  an 
  horizon 
  closely 
  corresponding 
  to 
  that 
  of 
  

   the 
  Marcellus 
  shale 
  in 
  the 
  New 
  York 
  section. 
  

  

  Hence 
  it 
  may 
  be 
  safe 
  to 
  conclude 
  that 
  in 
  Tennessee, 
  Ala- 
  

   bama, 
  southern 
  Kentucky 
  and 
  probably 
  Arkansas, 
  whenever 
  

   the 
  black 
  shales 
  rest 
  on 
  some 
  formation 
  lower 
  than 
  the 
  Lower 
  

   Helderberg 
  limestone 
  (for 
  the 
  absence 
  of 
  Oriskany 
  will 
  be 
  

   explained 
  in 
  another 
  way 
  beyond) 
  that 
  either 
  there 
  had 
  been 
  

   elevation 
  and 
  therefore 
  no 
  sedimentation, 
  or 
  that 
  the 
  rocks 
  had 
  

   been 
  eroded 
  away 
  before 
  the 
  black 
  shales 
  were 
  laid 
  down. 
  

   The 
  erosion 
  may 
  have 
  been 
  partly 
  done 
  under 
  water, 
  by 
  the 
  

   scouring 
  action 
  of 
  a 
  strong 
  ocean 
  current 
  washing 
  in 
  from 
  the 
  

   west 
  between 
  the 
  Missouri 
  island 
  and 
  the 
  land 
  areas 
  in 
  southern 
  

   Arkansas 
  (between 
  M 
  and 
  K, 
  see 
  chart). 
  The 
  fact 
  of 
  the 
  inter- 
  

   val 
  containing 
  the 
  black 
  shale 
  over 
  much 
  of 
  this 
  region, 
  an 
  inter- 
  

   val 
  reaching, 
  often, 
  to 
  the 
  Ordovician 
  and 
  even 
  lower, 
  together 
  

   with 
  the 
  presence 
  of 
  a 
  low 
  anticlinal 
  of 
  the 
  Cincinnati 
  plateau 
  

   extending 
  farther 
  north, 
  suggests 
  the 
  probability 
  of 
  land 
  sur- 
  

   face 
  more 
  or 
  less 
  continuously 
  connecting 
  the 
  southern 
  end 
  of 
  

   Appalachia 
  with 
  the 
  Texas 
  area.* 
  

  

  An 
  examination 
  of 
  the 
  chart 
  will 
  at 
  once 
  make 
  evident 
  that 
  

   in 
  case 
  there 
  was, 
  as 
  we 
  should 
  expect, 
  an 
  ocean 
  current 
  flow- 
  

   ing 
  southward 
  through 
  the 
  Dakota 
  channel, 
  the 
  effect 
  of 
  rais- 
  

   ing 
  the 
  bottom 
  above 
  tide 
  level 
  along 
  the 
  gulf 
  border 
  states 
  

   (along 
  T 
  and 
  K), 
  would 
  be 
  the 
  deflecting 
  of 
  the 
  current 
  with 
  a 
  

   powerful 
  swirl 
  into 
  the 
  southern 
  part 
  of 
  the 
  interior 
  conti- 
  

   nental 
  basin. 
  Even 
  if 
  the 
  elevation 
  were 
  only 
  to 
  make 
  a 
  string 
  

   of 
  islands 
  in 
  this 
  region, 
  a 
  part 
  of 
  the 
  current 
  would 
  enter 
  the 
  

   basin 
  and 
  wash 
  across 
  the 
  northern 
  Arkansas, 
  Tennessee, 
  Ala- 
  

   bama 
  surfaces, 
  and 
  would 
  tend 
  to 
  move 
  the 
  bulk 
  of 
  the 
  muds 
  

   of 
  the 
  bottom 
  into 
  the 
  Cumberland 
  channel 
  and 
  thence 
  north- 
  

   ward. 
  As 
  a 
  working 
  hypothesis, 
  this 
  is 
  supposed 
  to 
  have 
  taken 
  

   place 
  ; 
  and 
  what 
  we 
  know 
  of 
  the 
  general 
  distribution 
  of 
  the 
  

   black 
  shales 
  is 
  consistent 
  with 
  such 
  an 
  hypothesis. 
  

  

  The 
  presence 
  of 
  polished 
  sand 
  grains, 
  with 
  nodules 
  of 
  black 
  

   shale 
  mud, 
  and 
  rolled 
  and 
  polished 
  fragments 
  of 
  large 
  fish 
  

   bones, 
  some 
  of 
  them 
  from 
  J 
  to 
  f 
  of 
  an 
  inch 
  in 
  thickness, 
  asso- 
  

   ciated 
  with 
  more 
  or 
  less 
  phosphate 
  of 
  lime, 
  at 
  the 
  bottom 
  of 
  

   the 
  shales, 
  over 
  the 
  southern 
  extension 
  of 
  the 
  Cincinnati 
  

  

  * 
  In 
  the 
  discussion 
  which 
  followed 
  the 
  reading 
  of 
  this 
  paper 
  Mr. 
  Hayes 
  

   informed 
  us 
  that 
  the 
  black 
  shale 
  thickens 
  in 
  central 
  Alabama, 
  thus 
  confirming 
  the 
  

   probability 
  of 
  land 
  in 
  that 
  direction 
  during 
  Devonian 
  time. 
  

  

  