﻿432 
  J. 
  Barrett 
  — 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  

  

  equable 
  in 
  temperature 
  but 
  subject 
  to 
  seasonal 
  rainfall. 
  The 
  

   conditions 
  over 
  the 
  great 
  delta 
  plain 
  of 
  China 
  facing 
  the 
  

   shallow, 
  muddy 
  waters 
  of 
  the 
  Yellow 
  Sea 
  may 
  offer 
  the 
  best 
  

   analogy. 
  

  

  On 
  the 
  west 
  of 
  the 
  Catskill 
  delta 
  plain 
  the 
  shore 
  line 
  oscil- 
  

   lated 
  widely 
  and 
  the 
  low 
  alluvial 
  land 
  shaded 
  off 
  through 
  

   fringing 
  lagoons 
  into 
  a 
  shallow 
  mud-bottomed 
  sea. 
  At 
  the 
  

   beginning 
  of 
  the 
  Upper 
  Devonian 
  this 
  shore 
  zone 
  was 
  near 
  the 
  

   present 
  northeastern 
  outcrops. 
  During 
  Portage 
  (Senecan) 
  

   time 
  the 
  sea 
  retreated 
  widely, 
  but 
  because 
  of 
  lack 
  of 
  deep 
  sub- 
  

   sidence 
  of 
  the 
  bottom 
  more 
  than 
  because 
  of 
  rapidity 
  of 
  sedi- 
  

   mentation. 
  At 
  the 
  beginning 
  of 
  Chemung 
  (Chatauquan) 
  time 
  

   the 
  sea 
  again 
  advanced, 
  but 
  only 
  to 
  retreat 
  slowly, 
  and 
  at 
  the 
  

   close 
  of 
  the 
  Devonian 
  the 
  shore 
  line 
  stood 
  in 
  western 
  Pennsyl- 
  

   vania, 
  passing 
  diagonally 
  northeast 
  into 
  central 
  New 
  York. 
  

   This 
  is 
  shown 
  on 
  the 
  map, 
  fig. 
  1, 
  representing 
  the 
  stage 
  pre- 
  

   vious 
  to 
  the 
  deposition 
  of 
  the 
  Cattaraugus 
  formation. 
  The 
  

   contours 
  show 
  the 
  total 
  original 
  depth 
  of 
  Upper 
  Devonian 
  

   sediments. 
  

  

  In 
  the 
  first 
  part 
  it 
  is 
  the 
  relations 
  of 
  land 
  and 
  sea 
  and 
  the 
  

   character 
  of 
  the 
  delta 
  which 
  are 
  made 
  the 
  chief 
  object 
  of 
  study. 
  

   These 
  relations 
  depend 
  for 
  their 
  elucidation 
  upon 
  observations 
  

   of 
  the 
  strata. 
  The 
  tremendous 
  erosion 
  of 
  the 
  Mesozoic 
  and 
  

   Cenozoic 
  has 
  aided, 
  not 
  hindered, 
  in 
  drawing 
  the 
  conclusions. 
  

   Toward 
  the 
  ancient 
  uplands, 
  however, 
  the 
  formations 
  have 
  been 
  

   completely 
  removed. 
  Here 
  erosion 
  has 
  destroyed 
  the 
  evidence 
  

   of 
  the 
  original 
  relations. 
  The 
  problem 
  must 
  be 
  approached 
  

   along 
  converging 
  lines 
  of 
  inferences 
  and 
  by 
  quite 
  different 
  

   principles 
  of 
  interpretation 
  than 
  those 
  used 
  in 
  the 
  first 
  part. 
  

   This 
  side 
  of 
  the 
  subject 
  is 
  reserved 
  for 
  Parts 
  II 
  and 
  III, 
  to 
  be 
  

   published 
  later. 
  Certain 
  of 
  the 
  conclusions 
  are 
  expressed, 
  

   however, 
  in 
  fig. 
  1, 
  which 
  applies 
  to 
  the 
  whole. 
  The 
  loca- 
  

   tion 
  of 
  the 
  eastern 
  limit 
  of 
  the 
  sediments 
  is 
  shown 
  as 
  modi- 
  

   fied 
  by 
  the 
  Permian 
  folding. 
  In 
  its 
  original 
  position 
  it 
  must 
  

   have 
  been 
  a 
  straighter 
  line 
  with 
  less 
  of 
  a 
  westward 
  deflec- 
  

   tion 
  in 
  the 
  south. 
  

  

  The 
  length 
  of 
  time 
  through 
  which 
  the 
  writer 
  has 
  studied 
  

   these 
  formations 
  and 
  the 
  fulness 
  with 
  which 
  they 
  are 
  here 
  dis- 
  

   cussed 
  are 
  due 
  to 
  more 
  than 
  a 
  mere 
  descriptive 
  interest 
  in 
  the 
  

   formations 
  themselves 
  ; 
  for 
  terrestrial 
  deposits 
  reflect 
  closely 
  

   the 
  topographic 
  and 
  climatic 
  environments 
  under 
  which 
  they 
  

   originate 
  and 
  thus 
  furnish 
  a 
  basis 
  for 
  the 
  discussion 
  of 
  larger 
  

   problems 
  of 
  paleogeography 
  and 
  paleoclimatology. 
  

  

  In 
  closing 
  this 
  introduction 
  the 
  writer 
  desires 
  to 
  acknowl- 
  

   edge 
  his 
  indebtedness 
  to 
  Professor 
  Schuchert 
  for 
  the 
  deter- 
  

   mination 
  of 
  fossils 
  from 
  the 
  section 
  exposed 
  on 
  the 
  Schuylkill 
  

   River 
  and 
  to 
  Mr. 
  D. 
  F. 
  Hewett 
  for 
  detailed 
  measurements 
  of 
  a 
  

   part 
  of 
  the 
  same 
  section. 
  

  

  