﻿442 
  J. 
  Barrell 
  — 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  

  

  is 
  very 
  even, 
  lamination 
  is 
  well 
  developed, 
  and 
  strata 
  of 
  sand- 
  

   stone 
  from 
  one 
  inch 
  to 
  three 
  or 
  four 
  feet 
  in 
  thickness 
  are 
  sepa- 
  

   rated 
  by 
  shale 
  layers. 
  The 
  proportion 
  of 
  sand 
  to 
  shale 
  in 
  the 
  

   same 
  formation 
  is, 
  however, 
  by 
  no 
  means 
  constant 
  from 
  place 
  

   to 
  place. 
  

  

  Marine 
  fossils 
  are 
  abundant, 
  but 
  the 
  water 
  was 
  commonly 
  

   shallow. 
  Ripple-marks 
  occur 
  and 
  more 
  rarely 
  examples 
  of 
  

   cutting 
  and 
  tilling 
  during 
  deposition. 
  Certain 
  parallel 
  lines 
  on 
  

   shale 
  surfaces 
  suggest 
  the 
  marks 
  made 
  by 
  the 
  dragging 
  of 
  

   floating 
  vegetation 
  over 
  soft 
  mud. 
  The 
  water 
  cover 
  was 
  not, 
  

   however, 
  universal, 
  for 
  certain 
  horizons 
  in 
  southwestern 
  New 
  

   York 
  show 
  abundant 
  mud 
  cracking 
  and 
  rainprints 
  in 
  what 
  was 
  

   at 
  the 
  time 
  a 
  smooth, 
  soft 
  mud. 
  

  

  The 
  CatsJcill. 
  

  

  This 
  formation, 
  of 
  variable 
  thickness 
  but 
  measured 
  in 
  thou- 
  

   sands 
  of 
  feet, 
  extends 
  on 
  the 
  eastern 
  side 
  of 
  the 
  Appalachian 
  

   geosyncline 
  from 
  the 
  Catskill 
  Mountains 
  of 
  New 
  York 
  into 
  

   Virginia. 
  Its 
  deposition 
  extended 
  over 
  Chemung 
  time, 
  the 
  

   uppermost 
  Devonian. 
  On 
  the 
  northeast 
  the 
  Catskill 
  rests 
  

   directly 
  upon 
  the 
  Oneonta 
  and 
  differs 
  from 
  it 
  on 
  this 
  eastern 
  

   side 
  in 
  the 
  great 
  development 
  of 
  hard, 
  coarse, 
  cross-bedded, 
  

   gray 
  sandstones. 
  Among 
  these 
  are 
  intercalated 
  red 
  shales 
  and 
  

   gray 
  flags. 
  Not 
  more 
  than 
  ten 
  miles 
  west, 
  however, 
  of 
  the 
  

   eastern 
  edge 
  of 
  the 
  Catskills, 
  the 
  basal 
  Catskill 
  beds 
  pass 
  into 
  

   basal 
  Chemung. 
  The 
  higher 
  beds 
  of 
  the 
  Catskill 
  progressively 
  

   advance 
  westward 
  and 
  southwestward 
  at 
  the 
  expense 
  of 
  the 
  

   Chemung, 
  but 
  do 
  not 
  reach 
  the 
  western 
  boundaries 
  of 
  New 
  

   York 
  and 
  Pennsylvania. 
  Southward 
  the 
  Catskill 
  and 
  Chemung 
  

   disappear 
  in 
  Virginia, 
  the 
  whole 
  section 
  thinning 
  out, 
  but 
  the 
  

   Catskill 
  not 
  reaching 
  as 
  far 
  as 
  the 
  Chemung. 
  It 
  thus 
  appears 
  

   that 
  the 
  Catskill 
  phase, 
  consisting 
  typically 
  of 
  greenish 
  gray 
  sand- 
  

   stones 
  and 
  red 
  sandy 
  shales, 
  is 
  a 
  marginal 
  type 
  of 
  sedimenta- 
  

   tion 
  passing 
  into 
  the 
  distal 
  type 
  of 
  gray, 
  flaggy 
  sandstones, 
  and 
  

   gray 
  or 
  olive 
  shales. 
  The 
  transition 
  is 
  gradual 
  and 
  the 
  line 
  of 
  

   separation 
  oscillated 
  widely, 
  the 
  marginal 
  type, 
  on 
  the 
  whole, 
  

   however, 
  dispelling 
  the 
  distal 
  type. 
  The 
  oscillation 
  is 
  well 
  

   shown 
  on 
  a 
  large 
  scale 
  by 
  the 
  wedge 
  of 
  basal 
  Chemung 
  which 
  

   penetrates 
  nearly 
  to 
  the 
  eastern 
  outcrops 
  between 
  the 
  Oneonta 
  

   and 
  Catskill 
  and 
  on 
  a 
  smaller 
  scale 
  by 
  the 
  occurrence 
  of 
  red 
  

   shale 
  members 
  hundreds 
  of 
  feet 
  below 
  the 
  highest 
  Chemung 
  

   horizons, 
  the 
  beds 
  of 
  passage 
  commonly 
  covering 
  as 
  much 
  as 
  

   five 
  hundred 
  feet. 
  

  

  In 
  turning 
  attention 
  to 
  the 
  character 
  of 
  the 
  stratigraphy, 
  it 
  

   is 
  noted 
  that 
  the 
  Catskill 
  formation 
  consists 
  typically 
  of 
  thick 
  

   members 
  tens 
  of 
  feet 
  in 
  thickness, 
  alternately 
  of 
  shale, 
  red 
  and 
  

  

  