﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  I37 
  

  

  the 
  rubbing 
  and 
  grinding 
  action 
  of 
  a 
  continental 
  ice 
  sheet 
  has 
  long 
  

   been 
  recognized^ 
  and 
  now 
  it 
  seems 
  almost 
  certain 
  that 
  instead 
  of 
  

   only 
  one 
  there 
  have 
  been 
  several 
  ice 
  invasions 
  of 
  the 
  territory. 
  

   Students 
  of 
  glaciation 
  find 
  evidences 
  of 
  multiple 
  glaciation 
  in 
  the 
  

   Mississippi 
  basin, 
  in 
  Canada, 
  in 
  New 
  England 
  and 
  in 
  Pennsylvania. 
  

   It 
  seems 
  impossible 
  that 
  New 
  York 
  should 
  have 
  escaped 
  occupa- 
  

   tion 
  by 
  ice 
  sheets 
  that 
  buried 
  surrounding 
  territory. 
  In 
  the 
  Mis- 
  

   sissippi 
  basin 
  the 
  glacial 
  epochs 
  have 
  been 
  named 
  as 
  follows, 
  in 
  

   order 
  of 
  time 
  : 
  Jerseyan, 
  Kansan, 
  Illinoian, 
  lowan, 
  early 
  Wisconsin 
  

   and 
  later 
  Wisconsin. 
  While 
  there 
  is 
  some 
  doubt 
  as 
  to 
  the 
  validity 
  

   of 
  the 
  lowan 
  yet 
  the 
  multiplicity 
  of 
  the 
  glacial 
  invasions 
  seems 
  

   to 
  be 
  a 
  fact. 
  The 
  intervals 
  between 
  the 
  glacial 
  stages, 
  the 
  inter- 
  

   glacial 
  epochs, 
  are 
  believed 
  to 
  have 
  been 
  long 
  periods 
  of 
  temperate 
  

   climate. 
  It 
  seems 
  possible 
  that 
  our 
  present 
  time 
  of 
  release 
  from 
  

   glacial 
  conditions 
  may 
  be 
  only 
  a 
  warm 
  interval 
  between 
  the 
  latest 
  

   ice 
  invasion 
  and 
  another 
  invasion 
  to 
  come 
  in 
  the 
  near 
  (geologi- 
  

   cally) 
  future. 
  

  

  This 
  matter 
  of 
  multiplicity 
  of 
  ice 
  invasions 
  is 
  here 
  emphasized 
  

   for 
  the 
  reason 
  that 
  the 
  glacial 
  features 
  of 
  our 
  district 
  seem 
  to 
  re- 
  

   quire 
  for 
  satisfactory 
  explanation 
  the 
  work 
  of 
  more 
  than 
  a 
  single 
  

   ice 
  sheet. 
  The 
  glacial 
  phenomena 
  will 
  be 
  described 
  in 
  proper 
  order. 
  

  

  Submergence. 
  Lake 
  Iroquois. 
  As 
  the 
  latest 
  glacier 
  waned 
  

   and 
  the 
  front 
  receded 
  and 
  moved 
  northward 
  the 
  ice 
  was 
  replaced 
  

   by 
  a 
  body 
  of 
  water, 
  the 
  glacial 
  lake 
  Iroquois. 
  This 
  great 
  lake, 
  held 
  

   in 
  the 
  Ontario 
  basin 
  by 
  the 
  ice 
  barrier 
  blocking 
  the 
  St 
  Lawrence 
  

   valley, 
  and 
  with 
  its 
  outlet 
  at 
  Rome 
  to 
  the 
  Mohawk-Hudson, 
  laved 
  

   the 
  receding 
  ice 
  front 
  continuously 
  over 
  all 
  the 
  area 
  described 
  in 
  

   this 
  paper. 
  An 
  important 
  effect 
  of 
  this 
  condition, 
  which 
  the 
  reader 
  

   should 
  hold 
  in 
  mind, 
  is 
  that 
  all 
  the 
  materials 
  left 
  by 
  the 
  waning 
  

   ice 
  were 
  laid 
  down 
  beneath 
  the 
  Iroquois 
  waters, 
  and 
  are 
  conse- 
  

   quently 
  more 
  or 
  less 
  modified 
  by 
  the 
  water 
  action. 
  

  

  The 
  present 
  altitude 
  of 
  the 
  Iroquois 
  beach 
  east 
  of 
  Watertown 
  is 
  

   733 
  feet. 
  The 
  only 
  point 
  on 
  the 
  entire 
  area 
  covered 
  in 
  this 
  paper 
  

   which 
  is 
  sufificiently 
  elevated 
  to 
  reach 
  the 
  Iroquois 
  plane 
  is 
  the 
  ex- 
  

   treme 
  southeast 
  corner 
  of 
  the 
  area, 
  as 
  shown 
  at 
  the 
  bottom 
  of 
  the 
  

   Theresa 
  sheet, 
  [pi. 
  44]. 
  Here 
  the 
  nose 
  of 
  the 
  Rutland 
  promontory 
  

   brings 
  the 
  800 
  foot 
  contour 
  on 
  the 
  map 
  and 
  the 
  Iroquois 
  shore 
  line 
  

   is 
  a 
  steep 
  cliff 
  on 
  the 
  limestone 
  scarp. 
  On 
  account 
  of 
  the 
  postglacial 
  

   uplift 
  and 
  northward 
  tilting 
  of 
  the 
  region 
  the 
  Iroquois 
  plane, 
  and 
  all 
  

   later 
  water 
  planes, 
  rise 
  to 
  the 
  north. 
  On 
  the 
  parallel 
  of 
  Redwood 
  

   it 
  is 
  estimated 
  that 
  the 
  Iroquois 
  water 
  surface 
  was 
  about 
  800 
  feet, 
  

   and 
  at 
  Chippewa 
  Bay 
  toward 
  900 
  feet. 
  The 
  depth 
  of 
  water 
  over 
  

  

  