﻿434 
  J. 
  Barrell 
  — 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  

  

  connection 
  especially 
  with 
  the 
  deposits 
  of 
  Pennsylvanian 
  

   age: 
  

  

  " 
  The 
  writer 
  [J. 
  J. 
  Stevenson] 
  has 
  become 
  convinced 
  that 
  one 
  

   must 
  seek 
  explanation 
  of 
  the 
  phenomena 
  of 
  the 
  Appalachian 
  

   basin 
  in 
  those 
  of 
  the 
  great 
  river 
  plains 
  of 
  modern 
  times 
  ; 
  and 
  the 
  

   phenomena 
  of 
  the 
  Appalachian 
  basin 
  are 
  those 
  of 
  coal 
  regions 
  

   elsewhere."* 
  

  

  From 
  this 
  conclusion 
  it 
  is 
  seen 
  that 
  a 
  present-day 
  review 
  of 
  

   the 
  Catskill 
  problem 
  would 
  probably 
  lead 
  Stevenson 
  to 
  con- 
  

   clusions 
  different 
  from 
  those 
  which 
  he 
  expressed 
  in 
  1891. 
  

  

  In 
  1895, 
  J. 
  D. 
  Dana, 
  reflecting 
  the 
  accepted 
  opinion 
  of 
  the 
  

   time, 
  regarded 
  the 
  Catskill 
  formation 
  as 
  a 
  shore 
  and 
  offshore 
  

   deposit 
  of 
  the 
  Interior 
  Continental 
  Sea.f 
  

  

  In 
  1900, 
  Willis} 
  states 
  : 
  

  

  " 
  The 
  unassorted 
  mingling 
  of 
  sandy 
  and 
  clayey 
  particles 
  is 
  a 
  

   result 
  of 
  rapid 
  deposition 
  at 
  the 
  mouths 
  of 
  muddy 
  streams 
  in 
  

   opposition 
  to 
  waves 
  which 
  are 
  too 
  weak 
  to 
  sort 
  and 
  distribute 
  the 
  

   volume 
  of 
  sediment. 
  This 
  is 
  a 
  condition 
  of 
  delta-building. 
  In 
  

   the 
  Devonian 
  sediments 
  as 
  they 
  are 
  now 
  exposed 
  to 
  view 
  the 
  

   typical 
  contour 
  or 
  profile 
  of 
  any 
  delta 
  may 
  not 
  be 
  observable, 
  but 
  

   the 
  stratification 
  is 
  not 
  less 
  significant. 
  The 
  frequent 
  and 
  irregu- 
  

   lar 
  interbedding 
  of 
  coarse 
  sands, 
  sandy 
  clays 
  and 
  clays 
  ; 
  the 
  cross- 
  

   stratified 
  beds, 
  the 
  ripple-marked 
  and 
  sun-cracked 
  mud 
  surfaces, 
  

   the 
  channels 
  scoured 
  by 
  transient 
  streams, 
  all 
  prove 
  the 
  abund- 
  

   ance 
  of 
  the 
  sediments, 
  the 
  shifting 
  conditions 
  of 
  deposition, 
  the 
  

   irregularity 
  of 
  currents, 
  the 
  wide 
  expanses 
  of 
  tide-flats 
  and 
  shallow 
  

   waters, 
  and 
  the 
  weakness 
  of 
  the 
  waves. 
  Shallow 
  waters 
  prevailed 
  

   over 
  an 
  area 
  several 
  hundred 
  miles 
  in 
  extent 
  along 
  the 
  coast 
  and 
  

   one 
  hundred 
  to 
  one 
  hundred 
  and 
  fifty 
  miles 
  wide 
  from 
  the 
  shore 
  

   westward." 
  

  

  From 
  these 
  statements 
  and 
  the 
  accompanying 
  map 
  it 
  is 
  seen 
  

   that 
  Willis 
  recognizes 
  the 
  presence 
  of 
  delta 
  building, 
  but 
  at 
  

   the 
  same 
  time 
  holds 
  that 
  this 
  was 
  a 
  marine 
  process 
  in 
  that 
  the 
  

   sedimentation 
  was 
  submarine. 
  Consequently 
  on 
  his 
  map 
  the 
  

   sea 
  is 
  shown 
  as 
  extending 
  eastward 
  over 
  the 
  Catskill 
  formation. 
  

  

  In 
  1901 
  J. 
  M. 
  Clarke 
  discussed 
  the 
  value 
  of 
  Amnigenia 
  as 
  

   an 
  indicator 
  of 
  freshwater 
  deposits 
  during 
  the 
  Devonic 
  of 
  New 
  

   York, 
  Ireland, 
  and 
  the 
  Rhineland.§ 
  He 
  concludes 
  that 
  this 
  

   fossil 
  of 
  the 
  Oneonta 
  sandstone, 
  from 
  the 
  associations 
  of 
  the 
  

   involving 
  sediment, 
  was 
  not 
  marine. 
  From 
  this 
  sediment 
  and 
  

   other 
  evidence, 
  Clarke 
  states 
  of 
  the 
  Oneonta 
  : 
  

  

  *Loc 
  cit., 
  p. 
  553. 
  

   f 
  Manual 
  of 
  Geology, 
  p. 
  629. 
  

  

  X 
  Paleozoic 
  Appalachia 
  or 
  the 
  History 
  of 
  Maryland 
  during 
  Paleozoic 
  time. 
  

   Maryland 
  Geol. 
  Surv., 
  iv, 
  pt. 
  1, 
  p. 
  63, 
  1900. 
  

   § 
  N. 
  Y. 
  State 
  Museum, 
  Bull. 
  49, 
  pp. 
  199-203. 
  

  

  