﻿Mississippian 
  of 
  Ohio 
  and 
  Pennsylvania. 
  303 
  

  

  ness 
  of 
  the 
  Shenango 
  sandstone 
  and 
  the 
  Shenango 
  shale 
  over- 
  

   lying 
  it. 
  Since 
  the 
  top 
  of 
  the 
  latter 
  is 
  the 
  locus 
  of 
  an 
  uncon- 
  

   formity, 
  the 
  thickness 
  is 
  variable. 
  A 
  feature 
  well 
  brought 
  out, 
  

   however, 
  is 
  the 
  gradual 
  thickening 
  of 
  the 
  sandstone 
  at 
  the 
  

   expense 
  of 
  the 
  shale 
  as 
  they 
  are 
  traced 
  eastward. 
  Toward 
  the 
  

   west 
  both 
  shale 
  and 
  sandstone 
  are 
  cut 
  out 
  by 
  the 
  unconformity, 
  

   but 
  reappear 
  in 
  the 
  longitude 
  of 
  Cleveland 
  as 
  the 
  uppermost 
  

   part 
  of 
  the 
  Royalton 
  formation. 
  The 
  formation 
  representing 
  

   the 
  Shenango 
  shale 
  and 
  sandstone 
  in 
  central 
  Ohio 
  is 
  the 
  Logan. 
  

  

  Fig. 
  2. 
  

  

  a> 
  

  

  %7- 
  

  

  Ilty 
  

  

  &f\ 
  

  

  feiv 
  

  

  3<6 
  

  

  74 
  

  

  ^R- 
  

  

  

  Bn.se. 
  

  

  rntitrrfi 
  

  

  ^^m 
  

  

  ■HI 
  

  

  jiiiijiij 
  

  

  Sharps 
  £ffj 
  

  

  

  \! 
  lllc 
  

  

  w$ 
  

  

  zsH 
  

  

  v 
  Pffifi? 
  

  

  iii'i'HW 
  

  

  3ft 
  

  

  Fig. 
  2. 
  Sections 
  showing 
  the 
  Meadville 
  and 
  Sharpsville 
  formations. 
  

  

  Meadville 
  formation 
  : 
  The 
  county 
  seat 
  of 
  Crawford 
  County, 
  

   Pa., 
  is 
  Meadville. 
  It 
  suggested 
  the 
  name 
  of 
  this 
  formation 
  to 
  

   Dr. 
  White. 
  Consisting 
  essentially 
  of 
  bluish 
  gray 
  sandy 
  shales, 
  

   it 
  would 
  appear 
  at 
  first 
  not 
  to 
  be 
  of 
  any 
  great 
  value 
  for 
  the 
  

   stratigraphic 
  geologist. 
  However, 
  two 
  layers 
  at 
  definite 
  hori- 
  

   zons 
  are 
  of 
  such 
  striking 
  lithology 
  that 
  they 
  serve 
  as 
  excellent 
  

   guides. 
  They 
  are 
  essentially 
  limestones, 
  but 
  because 
  of 
  their 
  

   high 
  silica 
  content 
  are 
  very 
  hard 
  and 
  compact 
  and 
  possess 
  a 
  

   conchoidal 
  mode 
  of 
  fracture. 
  Pieces 
  of 
  these 
  layers 
  can 
  there- 
  

   fore 
  readily 
  be 
  recognized 
  in 
  streams 
  even 
  though 
  the 
  parent 
  

   rock 
  may 
  be 
  covered. 
  

  

  In 
  1ig. 
  2 
  sections 
  have 
  been 
  platted 
  showing 
  the 
  character 
  

   and 
  thickness 
  of 
  this 
  formation 
  together 
  with 
  the 
  Sharpsville 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  XLIII, 
  No. 
  256. 
  — 
  April, 
  1917. 
  

   21 
  

  

  