﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  1 
  25 
  

  

  and 
  there 
  is 
  little 
  trace 
  of 
  the 
  old 
  consequent 
  streams, 
  though 
  the 
  

   streams 
  running 
  westerly, 
  out 
  of 
  the 
  Adirondacks, 
  seem 
  to 
  repre- 
  

   sent 
  the 
  old 
  heads 
  of 
  such 
  streams. 
  

  

  Tertiary 
  uplift 
  

  

  Evidence 
  derived 
  chiefly 
  from 
  without 
  the 
  district 
  indicates 
  that 
  

   our 
  region, 
  in 
  common 
  with 
  much 
  of 
  eastern 
  North 
  America, 
  was 
  

   worn 
  down 
  to 
  a 
  comparatively 
  smooth 
  surface 
  (peneplain) 
  of 
  low 
  

   altitude 
  by 
  the 
  close 
  of 
  Mesozoic 
  time. 
  It 
  then 
  experienced 
  con- 
  

   siderable 
  uplift, 
  erosion 
  was 
  renewed 
  and 
  streams 
  cut 
  and 
  widened 
  

   considerable 
  valleys 
  in 
  the 
  weaker 
  rock 
  belts, 
  while 
  the 
  more 
  

   resistant 
  rocks 
  retained 
  in 
  considerable 
  measure 
  their 
  original 
  alti- 
  

   tude, 
  and 
  give 
  us 
  the 
  remnants 
  of 
  the 
  old 
  plain. 
  Elevations 
  of 
  over 
  

   1500 
  feet 
  are 
  found 
  on 
  the 
  Watertown 
  sheet, 
  immediately 
  south 
  

   of 
  our 
  map. 
  On 
  the 
  Port 
  Ley 
  den 
  sheet, 
  next 
  south, 
  the 
  altitudes 
  

   reach 
  almost 
  2000 
  feet, 
  the 
  district 
  there 
  forming 
  a 
  low 
  plateau, 
  

   capped 
  by 
  the 
  resistant 
  Oswego 
  sandstone, 
  between 
  the 
  Ontario 
  low- 
  

   land 
  to 
  the 
  west 
  and 
  the 
  broad 
  valley 
  of 
  the 
  Black 
  river 
  to 
  the 
  

   east. 
  East 
  of 
  the 
  valley 
  the 
  levels 
  rise 
  within 
  a 
  few 
  miles 
  to 
  2000 
  

   feet, 
  in 
  the 
  westerly 
  edge 
  of 
  the 
  Adirondack 
  platform, 
  and 
  from 
  

   there 
  continue 
  to 
  slowly 
  rise 
  eastward. 
  The 
  Adirondack 
  highland, 
  

   and 
  the 
  Oswego 
  sandstone 
  plateau, 
  are 
  regarded 
  as 
  remnants 
  of 
  the 
  

   old 
  peneplain 
  surface, 
  which 
  as 
  uplifted, 
  was 
  given 
  a 
  slight 
  tilt 
  

   toward 
  the 
  west, 
  while 
  the 
  deep 
  valleys 
  of 
  the 
  region 
  have 
  been 
  cut 
  

   since 
  the 
  uplift 
  and 
  give 
  some 
  measure 
  of 
  its 
  amount. 
  Unless 
  later 
  

   rocks 
  in 
  considerable 
  thickness 
  have 
  been 
  worn 
  away 
  from 
  the 
  

   surface 
  of 
  the 
  Oswego 
  sandstone 
  plateau, 
  the 
  amount 
  of 
  wear 
  

   there 
  has 
  been 
  very 
  slight 
  ; 
  yet 
  this 
  small 
  thickness 
  of 
  removed 
  rock 
  

   represents 
  the 
  general 
  erosion 
  over 
  the 
  entire 
  region 
  from 
  the 
  close 
  

   of 
  the 
  Ordovicic 
  to 
  the 
  close 
  of 
  the 
  Cretaceous, 
  a 
  wear 
  so 
  slight 
  

   as 
  to 
  be 
  only 
  compatible 
  with 
  low 
  altitude 
  of 
  land 
  when 
  the 
  length 
  

   of 
  the 
  time 
  interval 
  is 
  considered. 
  

  

  Tertiary 
  drainage 
  

  

  The 
  Tertiary 
  uplift 
  of 
  the 
  region 
  gave 
  to 
  the 
  land 
  an 
  altitude 
  

   in 
  excess 
  of 
  that 
  of 
  the 
  present. 
  A 
  partial 
  measure 
  of 
  this 
  Ex- 
  

   cess 
  is 
  the 
  difference 
  in 
  level 
  between 
  the. 
  Tertiary 
  valley 
  bottoms 
  

   and 
  those 
  of 
  today; 
  but 
  we 
  do 
  not 
  know 
  the 
  depth 
  of 
  valley 
  filling 
  

   in 
  this 
  district 
  and 
  hence 
  can 
  not 
  state 
  the 
  excess. 
  Even 
  before 
  

   the 
  uplift 
  the 
  streams 
  had 
  likely 
  become 
  adjusted 
  to 
  much 
  their 
  

   present 
  relation, 
  namely 
  consequent 
  streams 
  flowing 
  westerly 
  

  

  