﻿Mississippian 
  of 
  Ohio 
  and 
  Pennsylvania. 
  311 
  

  

  it 
  will 
  not 
  be 
  necessary 
  to 
  have 
  any 
  warping 
  in 
  the 
  region 
  

   affected 
  by 
  the 
  unconformity. 
  

  

  On 
  the 
  other 
  hand, 
  it 
  has 
  not 
  yet 
  been 
  proved 
  that 
  the 
  

   Berea 
  nowhere 
  cuts 
  down 
  below 
  the 
  Bedford. 
  In 
  fact 
  Mr. 
  

   Burrows* 
  cites 
  one 
  example 
  in 
  Lorain 
  County, 
  where 
  a 
  channel 
  

   175 
  feet 
  wide 
  and 
  extending 
  down 
  considerably 
  into 
  the 
  Cleve- 
  

   land 
  shale 
  (which 
  underlies 
  the 
  Bedford) 
  was 
  carved 
  in 
  the 
  

   interval 
  between 
  Bedford 
  and 
  Berea 
  times. 
  It 
  is 
  quite 
  likely 
  

   that 
  further 
  search 
  will 
  reveal 
  others 
  that 
  penetrate 
  beneath 
  

   the 
  Bedford. 
  

  

  Even 
  if 
  we 
  disregard 
  this 
  evidence, 
  however, 
  and 
  look 
  at 
  the 
  

   matter 
  from 
  another 
  angle, 
  we 
  may 
  say 
  that 
  the 
  sub-Carbonifer- 
  

   ous 
  period 
  witnessed 
  the 
  inception 
  of 
  the 
  epeirogenic 
  move- 
  

   ments 
  which 
  culminated 
  in 
  the 
  formation 
  of 
  the 
  coal-swamps 
  

   of 
  the 
  upper 
  Carboniferous 
  in 
  eastern 
  United 
  States. 
  The 
  

   Lauren 
  tian 
  shield 
  has 
  always 
  been 
  a 
  positive 
  segment 
  of 
  the 
  

   continent 
  and 
  it 
  does 
  not 
  seem 
  improbable 
  that 
  one 
  of 
  its 
  pre- 
  

   liminary 
  movements 
  brought 
  a 
  section 
  three 
  hundred 
  miles 
  

   wide 
  into 
  relief 
  without 
  appreciable 
  warping. 
  Furthermore, 
  

   the 
  coal 
  measures 
  offer 
  abundant 
  testimony 
  of 
  periods 
  of 
  

   emergence 
  of 
  slight 
  relief, 
  so 
  that 
  we 
  may 
  assume 
  that 
  northern 
  

   Ohio 
  also 
  emerged 
  but 
  slightly 
  and 
  that 
  therefore 
  the 
  agents 
  

   of 
  erosion 
  consumed 
  a 
  great 
  deal 
  of 
  time 
  in 
  cutting 
  through 
  

   the 
  sandstones 
  of 
  the 
  Bedford 
  and 
  into 
  the 
  red, 
  blue, 
  and 
  

   black 
  shales 
  beneath. 
  

  

  Another 
  bit 
  of 
  evidence 
  from 
  another 
  direction 
  may 
  not 
  

   seem 
  amiss. 
  Sufficient 
  well 
  records 
  are 
  now 
  available 
  to 
  

   enable 
  one 
  to 
  trace 
  the 
  Berea 
  from 
  its 
  outcrop 
  in- 
  central 
  and 
  

   southern 
  Ohio 
  across 
  the 
  eastern 
  part 
  of 
  the 
  state 
  well 
  into 
  

   Pennsylvania. 
  In 
  a 
  similar 
  way 
  the 
  writer 
  has 
  traced 
  the 
  

   Corry 
  into 
  southern 
  Pennsylvania 
  from 
  its 
  outcrop 
  in 
  north- 
  

   western 
  Pennsylvania.f 
  By 
  this 
  method 
  it 
  will 
  be 
  found 
  to 
  

   correlate 
  pretty 
  definitely 
  with 
  the 
  base 
  of 
  the 
  Pocono. 
  Since 
  

   this 
  formation 
  is 
  universally 
  admitted 
  to 
  represent 
  the 
  base 
  of 
  

   the 
  Mississippian 
  in 
  the 
  east, 
  it 
  should 
  indicate 
  that 
  its 
  corre- 
  

   late, 
  the 
  Berea, 
  also 
  occupies 
  the 
  same 
  horizon. 
  

  

  It 
  must 
  be 
  admitted 
  that 
  the 
  problem 
  of 
  finding 
  the 
  divid- 
  

   ing 
  line 
  in 
  Ohio 
  is 
  a 
  difficult 
  one 
  and 
  that 
  the 
  evidence 
  at 
  

   present 
  available 
  is 
  insufficient 
  to 
  warrant 
  a 
  clear-cut 
  conclu- 
  

   sion 
  ; 
  still, 
  the 
  writer 
  is 
  of 
  the 
  opinion 
  that 
  further 
  evidence 
  

   will 
  place 
  it 
  at 
  the 
  base 
  of 
  the 
  Berea. 
  

  

  Summary. 
  

  

  The 
  correlation 
  of 
  the 
  Devonian 
  and 
  Mississippian 
  forma- 
  

   tions 
  in 
  northwestern 
  Pennsylvania 
  and 
  northeastern 
  Ohio 
  is 
  a 
  

  

  * 
  Burroughs, 
  W. 
  G., 
  Berea 
  Sandstone 
  in 
  Eroded 
  Cleveland 
  Shale, 
  Jour, 
  of 
  

   Geol., 
  vol. 
  xxii, 
  p. 
  766, 
  1914. 
  

  

  fThis 
  Journal, 
  vol. 
  xlii, 
  p. 
  51, 
  1916. 
  

  

  