﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  79 
  

  

  entirely 
  without 
  reference 
  to 
  the 
  underlying 
  rock 
  character 
  and 
  

   structures. 
  Such 
  streams 
  are 
  said 
  to 
  be 
  superimposed 
  because 
  they 
  

   have, 
  so 
  to 
  speak, 
  been 
  let 
  down 
  upon 
  the 
  underlying 
  rock 
  masses. 
  

   To 
  quote 
  Professor 
  Berkey 
  : 
  " 
  The 
  larger 
  rivers, 
  the 
  great 
  master 
  

   streams, 
  of 
  the 
  superimposed 
  drainage 
  system, 
  in 
  some 
  cases 
  were 
  

   so 
  efficient 
  in 
  the 
  corrasion 
  of 
  their 
  channels 
  that 
  the 
  discovery 
  of 
  

   discordant 
  structures 
  (in 
  the 
  underlying 
  rocks) 
  has 
  not 
  been 
  of 
  

   sufficient 
  influence 
  to 
  displace 
  them, 
  or 
  reverse 
  them, 
  or 
  even 
  to 
  

   shift 
  them 
  very 
  far 
  from 
  their 
  original 
  direct 
  course 
  to 
  the 
  sea. 
  

   They 
  cut 
  directly 
  across 
  mountain 
  ridges 
  because 
  they 
  flowed 
  over 
  

   the 
  plain 
  out 
  of 
  which 
  these 
  ridges 
  have 
  been 
  carved 
  and 
  because 
  

   their 
  own 
  erosive 
  and 
  transporting 
  power 
  have 
  exceeded 
  those 
  of 
  

   any 
  of 
  their 
  tributaries 
  or 
  neighbors." 
  1 
  Fine 
  examples 
  of 
  such 
  

   superimposed 
  streams 
  which 
  are 
  now 
  entirely 
  out 
  of 
  harmony 
  with 
  

   the 
  structure 
  of 
  the 
  regions 
  over 
  which 
  they 
  flow 
  are 
  the 
  Susque- 
  

   hanna, 
  Delaware, 
  and 
  Hudson. 
  Thus 
  the 
  Susquehanna 
  cuts 
  across 
  

   a 
  whole 
  succession 
  of 
  Appalachian 
  ridges 
  while, 
  in 
  accordance 
  with 
  

   the 
  same 
  explanation, 
  the 
  Delaware 
  cuts 
  through 
  the 
  Kittatinny 
  

   ra*nge 
  at 
  the 
  famous 
  Delaware 
  Water 
  Gap. 
  The 
  lower 
  Hudson 
  

   pursues 
  a 
  course 
  no 
  less 
  out 
  of 
  harmony 
  with 
  the 
  structure 
  of 
  the 
  

   country 
  through 
  which 
  it 
  passes. 
  Thus 
  it 
  flows 
  at 
  a 
  considerable 
  

   angle 
  across 
  the 
  Taconic 
  folds 
  above 
  the 
  Highlands, 
  after 
  which 
  

   it 
  passes 
  through 
  a 
  deep 
  gorge 
  which 
  it 
  has 
  cut 
  through 
  the 
  hard 
  

   granites 
  and 
  other 
  rocks 
  of 
  the 
  Highlands. 
  The 
  simple 
  explanation 
  

   is 
  that 
  the 
  Hudson 
  had 
  its 
  course 
  determined 
  upon 
  the 
  surface 
  of 
  

   the 
  upraised 
  Cretacic 
  peneplain, 
  and 
  that 
  it 
  has 
  been 
  able 
  to 
  keep 
  

   that 
  course 
  in 
  spite 
  of 
  the 
  discordant 
  structures 
  of 
  the 
  underlying 
  

   rocks. 
  

  

  But 
  while 
  the 
  great 
  master 
  streams 
  were 
  thus 
  cutting 
  deep 
  

   trenches 
  in 
  hard 
  and 
  soft 
  rock 
  alike, 
  numerous 
  side 
  streams 
  or 
  

   tributaries 
  came 
  into 
  existence 
  and 
  naturally 
  developed 
  along 
  the 
  

   belts 
  of 
  weak 
  rock 
  and 
  in 
  harmony 
  with 
  the 
  geologic 
  structures. 
  

   This 
  is 
  true 
  of 
  all 
  the 
  streams 
  now 
  occupying 
  the 
  valleys 
  between 
  

   the 
  Appalachian 
  ridges. 
  In 
  southeastern 
  New 
  York 
  two 
  remark- 
  

   able 
  cases 
  are 
  presented 
  by 
  the 
  Wallkill 
  river 
  and 
  Rondout 
  creek 
  

   which 
  flow 
  many 
  miles 
  northeastwardly 
  and 
  in 
  a 
  direction 
  almost 
  

   the 
  reverse 
  of 
  that 
  of 
  the 
  Hudson 
  to 
  which 
  they 
  are 
  tributary. 
  As 
  

   the 
  master 
  superimposed 
  Hudson 
  cut 
  its 
  channel 
  deeper 
  and. 
  deeper, 
  

   the 
  Wallkill 
  and 
  Rondout 
  side 
  streams 
  were 
  enabled 
  to 
  cut 
  their 
  

   valleys 
  deeper 
  and 
  deeper 
  while 
  they 
  increased 
  in 
  length 
  by 
  pushing 
  

  

  1 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  146, 
  p. 
  69. 
  

  

  