﻿84 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  the 
  state 
  passed 
  southwestward 
  to 
  westward 
  into 
  the 
  Mississippi 
  

   valley 
  with 
  very 
  little, 
  if 
  any, 
  drainage 
  into 
  the 
  Atlantic. 
  But 
  by 
  

   the 
  close 
  of 
  the 
  Mesozoic, 
  or 
  the 
  beginning 
  of 
  the 
  Tertiary, 
  a 
  con- 
  

   siderable 
  south 
  to 
  southeastward 
  drainage 
  had 
  been 
  established 
  

   along 
  the 
  lines 
  of 
  the 
  Hudson, 
  Susquehanna, 
  and 
  Delaware 
  rivers. 
  

   Have 
  we 
  any 
  explanation 
  for 
  the 
  establishment 
  of 
  these 
  important 
  

   drainages 
  into 
  the 
  Atlantic? 
  One 
  view 
  is 
  that 
  the 
  courses 
  came 
  

   about 
  as 
  a 
  result 
  of 
  the 
  meandering 
  and 
  changing 
  of 
  channels 
  on 
  

   the 
  surface 
  of 
  the 
  low-lying 
  Cretacic 
  peneplain, 
  and 
  that 
  these 
  

   courses 
  were 
  maintained 
  upon 
  the 
  upraised 
  peneplain. 
  Another 
  

   view 
  which 
  the 
  writer 
  would 
  suggest 
  as 
  worthy 
  of 
  consideration 
  

   is 
  that 
  the 
  south 
  and 
  southeasterly 
  drainage 
  lines 
  were 
  established 
  

   as 
  a 
  result 
  of 
  the 
  uplift 
  of 
  the 
  peneplain. 
  Chapter 
  5 
  shows 
  

   that 
  the 
  axis 
  of 
  greatest 
  uplift 
  passed 
  through 
  northern 
  Xew 
  York 
  

   from 
  central 
  Pennsylvania, 
  the 
  region 
  of 
  southeastern 
  Xew 
  York 
  

   and 
  northern 
  New 
  Jersey 
  not 
  being 
  raised 
  so 
  high. 
  It 
  is 
  very 
  

   reasonable, 
  if 
  not 
  highly 
  probable, 
  that 
  this 
  very 
  warping 
  or 
  slow 
  

   arching 
  up 
  of 
  the 
  peneplain 
  surface 
  inaugurated 
  the 
  present 
  drain- 
  

   age 
  toward 
  the 
  Atlantic 
  because 
  the 
  streams, 
  no 
  matter 
  what 
  their 
  

   previous 
  courses, 
  then 
  naturally 
  must 
  have 
  flowed 
  down 
  that 
  initial 
  

   slope 
  toward 
  the 
  Atlantic. 
  

  

  After 
  the 
  uplift 
  of 
  the 
  peneplain 
  the 
  larger 
  streams 
  cut 
  down 
  

   their 
  channels 
  most 
  rapidly 
  and 
  would 
  be 
  the 
  first 
  to 
  reach 
  " 
  grade," 
  

   that 
  is, 
  a 
  condition 
  in 
  which, 
  because 
  of 
  low 
  velocity, 
  they 
  could 
  no 
  

   longer 
  cut 
  down 
  their 
  channels, 
  though 
  the 
  widening 
  process 
  could 
  

   continue 
  because 
  of 
  side 
  cutting 
  due 
  to 
  meandering 
  of 
  the 
  streams 
  

   back 
  and 
  forth 
  from 
  one 
  side 
  to 
  the 
  other 
  of 
  the 
  channels. 
  The 
  

   deep 
  but 
  broad-bottomed, 
  stream-cut 
  valleys 
  so 
  common 
  in 
  Xew 
  

   York 
  State 
  show 
  that 
  many 
  of 
  the 
  streams 
  had 
  reached 
  a 
  graded 
  

   or 
  nearly 
  graded 
  condition 
  even 
  by 
  the 
  close 
  of 
  the 
  Tertiary. 
  In 
  

   southeastern 
  X 
  T 
  e\v 
  York, 
  at 
  least, 
  we 
  have 
  evidence 
  to 
  show 
  that 
  

   after 
  the 
  streams 
  had 
  reached 
  grade 
  there 
  was 
  an 
  appreciable 
  

   renewed 
  uplift 
  of 
  the 
  land 
  which 
  again 
  revived 
  the 
  activity 
  of 
  the 
  

   streams. 
  Thus 
  the 
  broad 
  Hudson 
  valley, 
  with 
  minor 
  hills 
  rising 
  

   above 
  its 
  surface, 
  was 
  produced 
  when 
  the 
  Hudson 
  was 
  well 
  along 
  

   toward 
  a 
  graded 
  condition 
  and 
  then, 
  a- 
  a 
  result 
  of 
  this 
  late 
  Tertiary 
  

   uplift 
  of 
  the 
  land, 
  the 
  present 
  narrow 
  and 
  fairly 
  deep 
  inner 
  channel 
  

   (gorge) 
  of 
  the 
  Hudson 
  was 
  formed. 
  The 
  Hudson 
  did 
  not 
  reach 
  

   grade 
  in 
  this 
  inner 
  channel, 
  it^ 
  work 
  having 
  been 
  interrupted 
  by 
  

   the 
  spreading 
  of 
  the 
  great 
  ice 
  sheet 
  over 
  the 
  region. 
  It 
  is 
  not 
  known 
  

  

  