﻿446 
  J. 
  Barrett 
  — 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  

  

  sils 
  in 
  intercalated 
  gray 
  bands. 
  In 
  this 
  region 
  consequently 
  the 
  

   physical 
  conditions 
  of 
  the 
  Upper 
  Devonian 
  are 
  seen 
  to 
  have 
  

   persisted 
  somewhat 
  after 
  its 
  paleontological 
  close, 
  giving 
  rise 
  

   to 
  the 
  Cattaraugus 
  formation 
  similar 
  to 
  the 
  Chemung-Catskill 
  

   transition 
  beds. 
  

  

  Fossils, 
  as 
  previously 
  noted, 
  are 
  extremely 
  rare 
  in 
  the 
  Cats- 
  

   kill 
  and 
  Oneonta, 
  consisting 
  in 
  a 
  few 
  strata 
  holding 
  fish 
  scales 
  

   and 
  teeth, 
  more 
  rarely 
  bones, 
  a 
  bivalve 
  mollusc 
  (Amphigenia), 
  

   a 
  few 
  Eurypterids, 
  and 
  some 
  fragmentary 
  plants. 
  The 
  shales, 
  

   however, 
  often 
  show 
  a 
  mottled 
  effect 
  suggesting 
  numerous 
  faintly 
  

   marked 
  worm 
  burrows. 
  In 
  other 
  places 
  discontinuous, 
  thread- 
  

   like 
  markings 
  ramify 
  in 
  the 
  mudstones. 
  These 
  may 
  come 
  

   from 
  the 
  rootlets 
  of 
  what 
  was 
  at 
  the 
  time 
  a 
  sod-like 
  cover 
  of 
  

   vegetation. 
  The 
  fossils 
  show 
  that 
  the 
  fauna 
  was 
  not 
  of 
  the 
  

   open 
  sea, 
  but 
  on 
  the 
  other 
  hand 
  it 
  has 
  not 
  proved 
  to 
  paleontologists 
  

   that 
  the 
  Catskill 
  was 
  a 
  subaerial 
  formation 
  unrelated 
  to 
  the 
  sea. 
  

  

  The 
  Chemung. 
  

  

  With 
  the 
  close 
  of 
  Portage 
  time 
  the 
  character 
  of 
  the 
  sedi- 
  

   mentation 
  changed 
  somewhat 
  from 
  the 
  preceding, 
  a 
  coarsening 
  

   in 
  grain 
  and 
  a 
  greater 
  thickness 
  of 
  strata 
  suggesting 
  an 
  acceler- 
  

   ation 
  of 
  uplift 
  and 
  erosion 
  in 
  one 
  region, 
  of 
  subsidence 
  and 
  

   sedimentation 
  in 
  another. 
  On 
  the 
  east 
  more 
  dominantly 
  sandy 
  

   Catskill 
  beds 
  began 
  to 
  be 
  laid 
  down 
  upon 
  the 
  red 
  shales 
  and 
  

   gray 
  flags 
  of 
  the 
  Oneonta. 
  Farther 
  west 
  in 
  the 
  Chemung 
  beds 
  

   the 
  prevailing 
  color 
  changed 
  from 
  the 
  dark 
  bluish 
  gray 
  of 
  the 
  

   Portage 
  formation 
  to 
  light 
  tones 
  of 
  dull 
  .brownish 
  yellow 
  or 
  

   gray. 
  Greenish 
  tones 
  also 
  occur, 
  but 
  red 
  shales 
  are 
  absent. 
  

   The 
  tough 
  arenaceous 
  shale 
  of 
  the 
  Portage 
  with 
  knife-like 
  

   edges 
  was 
  succeeded 
  by 
  a 
  comparatively 
  soft 
  shale 
  cracking 
  into 
  

   blocky 
  fragments. 
  With 
  these 
  shales 
  are 
  intercalated 
  thin 
  beds 
  

   of 
  sandstone. 
  Calcareous 
  argillaceous 
  sandstone 
  bands 
  occur, 
  

   many 
  of 
  them 
  fossiliferous, 
  weathering 
  to 
  a 
  porous 
  texture. 
  

   Thin 
  bands 
  of 
  conglomerates 
  appear 
  at 
  several 
  horizons 
  and 
  

   these 
  considering 
  their 
  thinness 
  are 
  widely 
  persistent. 
  Many 
  

   horizons 
  of 
  marine 
  fossils 
  exist. 
  

  

  The 
  chief 
  distinctions 
  from 
  the 
  contemporaneous 
  Catskill 
  

   are 
  found 
  in 
  the 
  evenness 
  and 
  continuity 
  of 
  bedding, 
  the 
  more 
  

   argillaceous 
  and 
  in 
  places 
  calcareous 
  nature, 
  but 
  more 
  strik- 
  

   ingly 
  in 
  the 
  absence 
  of 
  red 
  beds 
  and 
  in 
  the 
  presence 
  of 
  marine 
  

   fossils. 
  The 
  Chemung 
  has 
  a 
  thickness 
  ranging 
  from 
  1,100 
  to 
  

   1,400 
  feet 
  in 
  western 
  Pennsylvania 
  and 
  southern 
  New 
  York. 
  

   In 
  central 
  Pennsylvania 
  it 
  reaches 
  2,000 
  to 
  3,000 
  feet, 
  but 
  has 
  

   not 
  been 
  separated 
  clearly 
  from 
  the 
  Portage. 
  Including 
  the 
  

   latter, 
  the 
  thicknesses 
  reach 
  from 
  3,000 
  to 
  4,000 
  feet. 
  The 
  

   Jennings 
  formation 
  in 
  western 
  Maryland, 
  equivalent 
  to 
  the 
  

  

  