﻿82 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Lawrence? 
  According 
  to 
  J. 
  W. 
  Spencer, 
  the 
  St 
  Lawrence 
  received 
  

   those 
  waters, 
  hut 
  in 
  the 
  light 
  of 
  what 
  we 
  have 
  said 
  about 
  Mesozoic 
  

   drainage, 
  and 
  also 
  in 
  view 
  of 
  the 
  fact 
  that 
  the 
  St 
  Lawrence 
  now, 
  

   in 
  the 
  Thousand 
  Islands 
  region, 
  does 
  not 
  flow 
  through 
  anything 
  

   like 
  a 
  distinct 
  channel 
  (see 
  plate 
  9) 
  cut 
  out 
  by 
  a 
  great 
  river, 
  we 
  

   must 
  admit 
  that 
  there 
  is 
  little 
  to 
  favor 
  such 
  northeastward 
  drainage 
  

   from 
  western 
  New 
  York. 
  The 
  St 
  Lawrence 
  is 
  almost 
  certainly 
  

   postglacial 
  in 
  its 
  course 
  at 
  the 
  Thousand 
  Islands 
  as 
  shown 
  by 
  the 
  

   lack 
  of 
  any 
  real 
  channel, 
  and 
  by 
  the 
  presence 
  of 
  a 
  belt 
  of 
  hard 
  Pre- 
  

   cambric 
  rock 
  extending 
  across 
  the 
  river 
  and 
  connecting 
  the 
  Adi- 
  

   rondacks 
  with 
  the 
  Canadian 
  Precambric 
  rocks. 
  This 
  hard 
  rock 
  

   belt 
  must 
  have 
  formed 
  a 
  preglacial 
  divide 
  until 
  the 
  recent 
  forma- 
  

   tion 
  of 
  Lake 
  Ontario 
  and 
  the 
  downwarping 
  of 
  the 
  land 
  which 
  

   allowed 
  the 
  drainage 
  to 
  pass 
  over 
  the 
  divide 
  for 
  the 
  first 
  time 
  (see 
  

   later 
  page). 
  

  

  Grabau's 
  interpretation 
  is 
  that 
  the 
  Tertiary 
  drainage 
  of 
  western 
  

   New 
  York 
  passed 
  westward 
  and 
  southwestward 
  into 
  the 
  Mississippi, 
  

   and 
  this 
  view 
  is, 
  in 
  the 
  writer's 
  belief, 
  far 
  more 
  tenable. 
  The 
  

   accompanying 
  map 
  (figure 
  27) 
  gives 
  a 
  good 
  idea 
  of 
  the 
  drainage 
  

   lines 
  according 
  to 
  this 
  view. 
  The 
  major 
  drainage 
  lines 
  were 
  no 
  

   doubt 
  inherited 
  from 
  the 
  Mesozoic, 
  the 
  southwestward 
  courses 
  hav- 
  

   ing 
  been 
  originally 
  determined 
  by 
  the 
  tilt 
  of 
  the 
  land 
  at 
  the 
  time 
  of 
  

   the 
  Appalachian 
  uplift. 
  When 
  the 
  Cretacic 
  peneplain 
  was 
  upraised, 
  

   these 
  major 
  streams 
  as, 
  for 
  example, 
  the 
  Dundas 
  river, 
  again 
  began 
  

   very 
  active 
  work 
  of 
  erosion, 
  and 
  tributary 
  streams 
  were 
  developed, 
  

   during 
  the 
  Tertiary, 
  along 
  the 
  belts 
  of 
  weak 
  rocks. 
  Thus 
  an 
  

   important 
  west-flowing 
  tributary 
  was 
  developed 
  along 
  the 
  belt 
  of 
  

   soft 
  Ordovicic 
  and 
  Medina 
  shales, 
  and 
  formed 
  a 
  channel 
  where 
  the 
  

   basin 
  of 
  Lake 
  Ontario 
  now 
  is. 
  The 
  Rome 
  river, 
  with 
  source 
  at 
  

   Little 
  Falls, 
  became 
  a 
  branch 
  of 
  this 
  stream 
  while 
  another 
  important 
  

   branch 
  had 
  its 
  source 
  on 
  the 
  Thousand 
  Islands 
  divide. 
  There 
  is 
  

   also 
  shown 
  the 
  position 
  of 
  the 
  Black 
  river, 
  which 
  by 
  late 
  Tertiary 
  

   had 
  already 
  carved 
  out 
  that 
  important 
  valley 
  and 
  flowed 
  into 
  the 
  

   Ontario 
  depression, 
  according 
  to 
  Grabau. 
  More 
  recent 
  evidence, 
  

   however 
  (see 
  later 
  page), 
  strongly 
  favors 
  the 
  passage 
  of 
  the 
  lower 
  

   end 
  of 
  the 
  Black 
  river 
  north 
  and 
  northeastward 
  into 
  the 
  precursor 
  

   o<f 
  the 
  modern 
  St 
  Lawrence, 
  and 
  which 
  had 
  its 
  source 
  on 
  the 
  

   Thousand 
  Islands 
  divide. 
  

  

  On 
  the 
  accompanying 
  map 
  the 
  three 
  south-flowing 
  streams, 
  one 
  

   heading 
  near 
  Rochester 
  and 
  the 
  other 
  two 
  flowing 
  through 
  Lakes 
  

   Seneca 
  and 
  Cayuga, 
  are, 
  in 
  the 
  writer's 
  judgment, 
  not 
  properly 
  

   shown 
  for 
  the 
  late 
  Tertiary, 
  that 
  is, 
  just 
  prior 
  to 
  the 
  great 
  Ice 
  age. 
  

  

  