﻿398 
  H. 
  S. 
  Williams 
  — 
  /Southern 
  Devonian 
  formations. 
  

  

  types, 
  because 
  of 
  the 
  great 
  thickness 
  of 
  the 
  black 
  " 
  Chatta- 
  

   nooga 
  shales 
  " 
  at 
  Big 
  Stone 
  Gap 
  and 
  the 
  great 
  thickness 
  of 
  the 
  

   following 
  "Grainger 
  shales" 
  which 
  were 
  called 
  Devonian, 
  

   though 
  with 
  some 
  hesitation, 
  as 
  Mr. 
  Campbell 
  stated, 
  on 
  

   account 
  of 
  lack 
  of 
  fossils. 
  An 
  examination 
  of 
  the 
  black 
  shale 
  

   at 
  Big 
  Stone 
  Gap, 
  which 
  is 
  at 
  least 
  500 
  feet 
  thick, 
  revealed 
  not 
  

   the 
  least 
  addition 
  to 
  the 
  meagre 
  Lingula 
  fauna, 
  but 
  made 
  clear 
  

   that 
  the 
  following 
  arenaceous 
  shales 
  and 
  sandstones 
  began 
  as 
  

   very 
  thin 
  intercalated 
  sheets, 
  thin 
  as 
  paper 
  at 
  first, 
  far 
  down 
  

   in 
  what, 
  to 
  the 
  casual 
  observer, 
  appeared 
  to 
  be 
  pure 
  black 
  shale. 
  

   This 
  led 
  to 
  the 
  expectation 
  that 
  the 
  section 
  farther 
  east 
  (i. 
  e. 
  

   nearer 
  to 
  the 
  ancient 
  shore 
  line) 
  would 
  show 
  the 
  shore-derived 
  

   sediments 
  earlier 
  in 
  the 
  section. 
  This 
  expectation 
  was 
  con- 
  

   firmed 
  by 
  following 
  the 
  section 
  eastward 
  to 
  Moccasin 
  Gap, 
  

   where 
  in 
  the 
  arenaceous 
  shales 
  well 
  above 
  the 
  pure 
  black 
  shale, 
  

   in 
  what 
  was 
  mapped 
  as 
  Grainger 
  shale, 
  a 
  distinct 
  Carboniferous 
  

   fauna 
  (the 
  Syringothyris 
  fauna 
  of 
  the 
  Kinderhook 
  age) 
  was 
  

   discovered. 
  These 
  observations 
  confirmed 
  the 
  belief 
  that 
  the 
  

   black 
  shale 
  material 
  was 
  derived 
  from 
  a 
  different 
  direction 
  

   from 
  the 
  other 
  clastic 
  sediments 
  making 
  up 
  the 
  section. 
  

  

  Examination 
  of 
  the 
  sections 
  at 
  Irvine, 
  Kentucky, 
  the 
  other 
  

   side 
  of 
  the 
  Cumberland 
  channel 
  (the 
  name 
  which 
  may 
  be 
  given 
  

   to 
  the 
  southern 
  part 
  of 
  the 
  Devonian 
  intercontinental 
  sea 
  lying 
  

   between 
  the 
  Cincinnati 
  plateau 
  and 
  Appalachia) 
  revealed 
  the 
  

   fact 
  that 
  there 
  the 
  black 
  shales 
  were 
  thinner 
  but 
  held 
  on 
  in 
  

   their 
  purity 
  well 
  up 
  into 
  Carboniferous 
  time. 
  The 
  intercala- 
  

   tions 
  consist 
  of 
  calcareous 
  and 
  ferruginous, 
  concretionary 
  sheets 
  

   and 
  carry 
  undoubted 
  Carboniferous 
  fossils 
  and 
  occur 
  in 
  the 
  

   sections 
  before 
  the 
  black 
  shale 
  loses 
  its 
  characteristic 
  expres- 
  

   sion. 
  This 
  settled 
  the 
  suspicion 
  that 
  the 
  black 
  shale 
  materials 
  

   were 
  derived 
  from 
  the 
  direction 
  of 
  the 
  Cincinnati 
  plateau 
  and 
  

   not 
  from 
  the 
  Appalachia 
  side 
  of 
  the 
  channel, 
  since 
  on 
  the 
  

   plateau 
  side 
  of 
  the 
  channel 
  they 
  were 
  pure 
  and 
  continued 
  later 
  

   in 
  the 
  section, 
  and 
  on 
  the 
  Appalachia 
  side, 
  where 
  there 
  were 
  

   other 
  clastic 
  sediments 
  following, 
  these 
  sediments 
  from 
  the 
  

   Archaean 
  land-wash 
  increased 
  and 
  were 
  found 
  lower 
  down 
  in 
  

   the 
  section 
  on 
  approaching 
  the 
  land 
  edge. 
  

  

  Thus 
  the 
  conclusion 
  was 
  reached 
  that 
  the 
  Cincinnati 
  plateau 
  

   was 
  the 
  source 
  of 
  the 
  black 
  shale 
  muds, 
  and 
  to 
  account 
  for 
  

   their 
  distribution 
  the 
  agency 
  of 
  an 
  ocean 
  current, 
  such 
  as 
  the 
  

   Florida 
  current 
  of 
  the 
  Gulf 
  stream 
  is 
  at 
  present 
  in 
  the 
  

   Atlantic, 
  was 
  introduced. 
  

  

  The 
  next 
  question 
  arising 
  was 
  as 
  to 
  the 
  age 
  of 
  the 
  base 
  of 
  

   the 
  black 
  shale. 
  The 
  study 
  of 
  the 
  Big 
  Stone 
  Gap 
  sections 
  also 
  

   threw 
  light 
  on 
  this 
  problem. 
  On 
  the 
  Kentucky 
  side 
  of 
  the 
  

   Cumberland 
  channel, 
  as 
  well 
  as 
  on 
  the 
  Appalachia 
  side, 
  there 
  

   are 
  frequently 
  represented 
  at 
  the 
  base 
  of 
  the 
  black 
  shales 
  beds 
  

   of 
  brown 
  iron 
  ore. 
  About 
  Big 
  Stone 
  Gap 
  this 
  brown 
  ore 
  con- 
  

  

  

  