﻿436 
  J. 
  Barrell 
  — 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  

  

  sediment,* 
  the 
  same 
  argument 
  applying 
  to 
  the 
  Mississippian 
  

   and 
  Pennsylvanian 
  formations 
  on 
  the 
  eastern 
  side 
  of 
  the 
  geo- 
  

   syncline. 
  

  

  In 
  1909, 
  H. 
  S. 
  Williams 
  speaks 
  of 
  the 
  brackish, 
  water 
  sedi- 
  

   mentation 
  of 
  the 
  Catskill 
  formation. 
  f 
  

  

  Stose, 
  in 
  1909, 
  states 
  of 
  the 
  Catskill 
  in 
  Fulton 
  County, 
  

   Pennsylvania, 
  — 
  

  

  "It 
  is 
  undoubtedly 
  a 
  land 
  or 
  fresh-water 
  deposit 
  replacing 
  the 
  

   upper 
  part 
  of 
  the 
  marine 
  Chemung. 
  Fresh-water 
  conditions 
  

   apparently 
  originated 
  in 
  the 
  east 
  and 
  were 
  caused 
  possibly 
  by 
  

   vast 
  floods 
  from 
  the 
  land, 
  which 
  changed 
  the 
  shallow 
  seas 
  from 
  

   salt 
  to 
  fresh, 
  and 
  brought 
  detritus 
  from 
  deeply 
  weathered 
  areas."J 
  

  

  Schuchert, 
  in 
  1909, 
  shows 
  a 
  marine 
  strait 
  in 
  the 
  Ithaca-Che- 
  

   mung 
  epoch 
  crossing 
  northern 
  ISTew 
  Jersey 
  over 
  the 
  syncline 
  

   of 
  the 
  Skunnemunk 
  conglomerate. 
  In 
  the 
  region 
  of 
  the 
  Cats- 
  

   kill 
  mountains 
  continental 
  deposits 
  are 
  shown 
  but 
  not 
  on 
  the 
  

   eastern 
  margin 
  of 
  the 
  sea 
  in 
  Pennsylvania. 
  In 
  the 
  text 
  it 
  is 
  

   stated 
  that 
  in 
  the 
  northeastern 
  end 
  of 
  the 
  trough 
  the 
  normal 
  

   marine 
  conditions 
  gave 
  way 
  to 
  vast 
  estuarine 
  flats 
  of 
  red 
  muds.§ 
  

  

  In 
  1912, 
  Schwartz 
  writes 
  of 
  the 
  Catskill 
  on 
  the 
  Potomac 
  

   River, 
  that 
  

  

  "The 
  surfaces 
  of 
  many 
  beds 
  are 
  rippled-marked 
  and 
  the 
  shales 
  

   display 
  mud 
  cracks. 
  The 
  sandstones 
  are 
  usually 
  cross-bedded 
  

   and 
  numerous 
  local 
  unconformities 
  are 
  observable. 
  The 
  features 
  

   of 
  the 
  rocks 
  of 
  this 
  formation 
  show 
  that 
  they 
  were 
  laid 
  down 
  in 
  

   shallow 
  terrestrial 
  waters 
  and 
  not 
  in 
  the 
  open 
  sea."|| 
  

  

  Criteria 
  for 
  Separation 
  of 
  Subaerial 
  and 
  Subaqueous 
  

   Delta 
  Deposits. 
  

  

  The 
  opinions 
  which 
  have 
  been 
  quoted 
  regarding 
  the 
  condi- 
  

   tions 
  of 
  origin 
  of 
  the 
  Catskill 
  and 
  associated 
  formations 
  show 
  

   the 
  opposite 
  points 
  of 
  view 
  which 
  may 
  be 
  entertained, 
  each 
  

   based 
  ultimately 
  upon 
  facts 
  of 
  stratigraphy, 
  but 
  logically 
  

   divergent 
  because 
  of 
  different 
  bases 
  of 
  interpretation. 
  They 
  

   make 
  it 
  clear 
  that, 
  before 
  describing 
  the 
  details 
  of 
  the 
  forma- 
  

   tions 
  concerned, 
  or 
  going 
  forward 
  to 
  their 
  interpretations, 
  a 
  

   summary 
  must 
  be 
  given 
  of 
  the 
  criteria 
  which 
  are 
  here 
  relied 
  

   upon 
  to 
  interpret 
  those 
  features. 
  The 
  writer 
  has 
  discussed 
  

   elsewhere 
  somewhat 
  extensively 
  the 
  conditions 
  controlling 
  the 
  

  

  * 
  Types 
  of 
  sedimentary 
  overlap. 
  Geo]. 
  Soc. 
  Am., 
  Bull., 
  xvii, 
  1906, 
  pp 
  

   629-632. 
  Presented 
  before 
  the 
  Geological 
  Society 
  of 
  America, 
  Dec. 
  1905. 
  

  

  fU. 
  S. 
  Geol. 
  Surv., 
  Watkins 
  Glen-Catatonk 
  Folio, 
  p. 
  11. 
  

  

  % 
  Mercersburg-Chambersburg 
  Folio, 
  U. 
  S. 
  Geol. 
  Surv., 
  pp. 
  12, 
  16. 
  

  

  § 
  Paleogeography 
  of 
  North 
  America, 
  Geol. 
  Soc. 
  Am., 
  Bull., 
  xx, 
  p. 
  545, 
  pi. 
  

   77, 
  1910. 
  

  

  || 
  Stose 
  and 
  Schwartz, 
  Pawpaw-Hancock 
  Folio, 
  U. 
  S. 
  Geol. 
  Surv., 
  p. 
  13. 
  

  

  