﻿458 
  J. 
  Barrell 
  — 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  

  

  which 
  lies 
  below, 
  contained 
  in 
  a 
  calcareous 
  sandstone 
  band. 
  

   These 
  red 
  shales, 
  on 
  the 
  other 
  hand, 
  show 
  undoubted 
  rain- 
  

   prints. 
  Mud 
  cracks- 
  were 
  found 
  sparingly 
  in 
  loose 
  blocks, 
  and 
  

   possible 
  rootmarks 
  occur. 
  These 
  contrasted 
  marks 
  of 
  marine 
  

   and 
  subaerial 
  conditions 
  are 
  here 
  closely 
  related 
  to 
  the 
  change 
  

   in 
  color 
  from 
  olive 
  shales 
  to 
  red 
  shales 
  and 
  suggest 
  that 
  in 
  

   Upper 
  Devonian 
  times 
  the 
  climate 
  of 
  this 
  region 
  was 
  such 
  that 
  

   the 
  contrast 
  in 
  color 
  happens 
  to 
  offer 
  a 
  criterion 
  for 
  separating 
  

   rather 
  sharply 
  the 
  subaqueous 
  and 
  subaerial 
  phases 
  of 
  sedi- 
  

   mentation. 
  

  

  Of 
  the 
  Catskill 
  section 
  only 
  some 
  general 
  notes 
  need 
  be 
  made 
  

   to 
  supplement 
  the 
  details 
  given 
  in 
  the 
  table. 
  It 
  is 
  to 
  be 
  ob- 
  

   served 
  that 
  the 
  lower 
  portion, 
  about 
  2900 
  feet 
  thick, 
  is 
  more 
  

   argillaceous 
  and 
  less 
  resistant 
  to 
  erosion. 
  The 
  middle 
  portion, 
  

   about 
  2300 
  feet 
  thick, 
  consists 
  of 
  resistant 
  gray 
  sandstones 
  with 
  

   some 
  conglomerate 
  and 
  but 
  a 
  minor 
  amount 
  of 
  red 
  shale. 
  The 
  

   upper 
  750 
  feet 
  have 
  sufficient 
  red 
  shale 
  to 
  permit, 
  in 
  connection 
  

   with 
  the 
  vertical 
  attitude 
  of 
  the 
  strata, 
  the 
  undermining 
  of 
  the 
  

   hard 
  sandstone 
  beds 
  and 
  produces 
  a 
  saddle 
  in 
  the 
  Pocono- 
  

   Catskill 
  mountain 
  crest. 
  In 
  this 
  upper 
  portion 
  is 
  the 
  sharpest 
  

   and 
  most 
  frequent 
  oscillation 
  from 
  gray 
  sandstone 
  to 
  red 
  shale 
  

   conditions, 
  and 
  owing 
  to 
  the 
  partial 
  protection 
  from 
  erosion 
  

   given 
  by 
  the 
  sandstones, 
  the 
  most 
  favorable 
  portion 
  in 
  which 
  

   to 
  study 
  the 
  bedding 
  character 
  of 
  the 
  shales. 
  

  

  Above 
  the 
  last 
  important 
  red 
  shale 
  and 
  red 
  sandstone 
  are 
  970 
  

   feet 
  of 
  gray 
  and 
  olive 
  sandstones, 
  moderately 
  resistant 
  and 
  not 
  

   yielding 
  good 
  outcrops 
  on 
  this 
  section. 
  The 
  sandstone 
  is 
  of 
  

   the 
  Catskill 
  type 
  rather 
  than 
  that 
  of 
  the 
  coarser 
  and 
  harder 
  

   Pocono. 
  They 
  may 
  therefore 
  be 
  put 
  as 
  transition 
  beds, 
  but 
  

   their 
  affinities 
  are 
  with 
  the 
  lower 
  more 
  than 
  with 
  the 
  upper 
  

   formation. 
  

  

  The 
  Pocono 
  here 
  is 
  a 
  much 
  coarser 
  and 
  cleaner 
  grit 
  and 
  

   gravel 
  formation 
  than 
  in 
  its 
  usual 
  development 
  in 
  Pennsylva- 
  

   nia 
  and 
  indicates 
  a 
  nearer 
  relation 
  to 
  the 
  source 
  of 
  the 
  material. 
  

  

  The 
  shales 
  of 
  the 
  Catskill 
  as 
  seen 
  in 
  this 
  section 
  are 
  a 
  bright 
  

   " 
  freight 
  car" 
  red 
  ; 
  the 
  more 
  siliceous 
  red 
  sandstones 
  are, 
  strictly 
  

   speaking, 
  maroon 
  rather 
  than 
  red. 
  The 
  gray 
  standstones, 
  if 
  argil- 
  

   laceous, 
  weather 
  to 
  a 
  yellow, 
  showing 
  that 
  they 
  contained 
  iron 
  

   oxide 
  but 
  in 
  a 
  ferrous 
  state. 
  The 
  purer 
  sandstones, 
  olive-colored 
  

   on 
  fresh 
  fracture, 
  weather 
  to 
  a 
  grayish 
  white. 
  These 
  relations 
  

   show 
  there 
  was 
  a 
  tendency 
  toward 
  deoxidation 
  during 
  the 
  for- 
  

   mation 
  of 
  the 
  beds 
  of 
  sand, 
  of 
  oxidation 
  during 
  the 
  deposition 
  

   of 
  the 
  Catskill 
  muds. 
  Where 
  the 
  clay 
  and 
  iron 
  oxide 
  were 
  

   sparing 
  in 
  quantity, 
  the 
  deoxidation 
  was 
  effective. 
  The 
  con- 
  

   ditions 
  which 
  accompanied 
  the 
  deposition 
  of 
  clay 
  and 
  iron 
  

   oxide 
  also 
  permitted 
  oxidation 
  to 
  dominate 
  over 
  deoxidation. 
  

   A 
  gray 
  or 
  olive 
  sandstone 
  member 
  is 
  commonly 
  sharply 
  delim- 
  

   ited 
  at 
  bottom, 
  but 
  at 
  the 
  top 
  grades 
  first 
  into 
  maroon 
  argilla- 
  

  

  