﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  1 
  7 
  

  

  In 
  the 
  Champlain 
  valley 
  the 
  Beekmantown 
  rocks 
  are 
  overlaid 
  

   by 
  the 
  Chazy 
  limestones. 
  There 
  is 
  evidence 
  there 
  of 
  a 
  break 
  

   between 
  the 
  two 
  formations 
  and 
  the 
  Ghazy 
  has 
  a 
  basal 
  sandstone. 
  

   The 
  Champlain 
  Chazy 
  trough 
  also 
  had 
  a 
  westerly 
  bay 
  but 
  it 
  never 
  

   extended 
  as 
  far 
  west 
  as 
  the 
  district 
  under 
  discussion. 
  During 
  the 
  

   long 
  time 
  interval 
  therefore 
  during 
  which 
  Beekmantown 
  and 
  early 
  

   Chazy 
  sedimentation 
  was 
  transpiring 
  in 
  the 
  subsiding 
  Champlain 
  

   trough, 
  the 
  district 
  here 
  was 
  above 
  sea 
  level 
  and 
  experiencing 
  wear 
  

   rather 
  than 
  receiving 
  deposit. 
  Considering 
  the 
  length 
  of 
  the 
  interval 
  

   the 
  amount 
  of 
  erosion 
  which 
  it 
  suffered 
  was 
  but 
  slight, 
  arguing 
  for 
  

   low 
  altitude 
  and 
  gentle 
  slopes 
  for 
  the 
  land. 
  Broad, 
  shallow 
  valleys 
  

   were 
  cut 
  in 
  the 
  surface 
  of 
  the 
  Theresa 
  limestone 
  but 
  the 
  depth 
  of 
  

   cutting 
  seems 
  never 
  to 
  reach 
  the 
  base 
  of 
  the 
  formation. 
  

  

  Pamelia 
  (Stones 
  River) 
  limestone. 
  The 
  Chazy 
  basin 
  of 
  the 
  

   Champlain, 
  St 
  Lawrence 
  and 
  Ottawa 
  valleys 
  was 
  landlocked 
  to 
  

   the 
  south 
  and 
  west 
  during 
  lower 
  and 
  middle 
  Chazy 
  time. 
  Dur- 
  

   ing 
  this 
  time 
  interval, 
  however, 
  other 
  and 
  larger 
  basins 
  of 
  sub- 
  

   sidence 
  and 
  deposit 
  existed 
  to 
  the 
  south 
  and 
  west 
  but 
  completely 
  

   separated 
  from 
  the 
  Chazy 
  basin. 
  Both 
  the 
  rocks 
  and 
  the 
  con- 
  

   tained 
  fossils 
  therefore 
  differ 
  from 
  the 
  Chazy 
  and 
  the 
  formation 
  

   is 
  known 
  as 
  the 
  Stones 
  River. 
  Notwithstanding 
  difference 
  of 
  

   name 
  the 
  two 
  formations 
  represent 
  substantially 
  the 
  same 
  time 
  

   interval. 
  

  

  As 
  Chazy 
  time 
  passed 
  on, 
  the 
  large 
  Stones 
  river 
  basin 
  to 
  the 
  

   southward 
  encroached 
  northwardly 
  and 
  toward 
  the 
  latter 
  part 
  of 
  

   the 
  interval 
  had 
  become 
  sufficiently 
  extended 
  to 
  submerge 
  the 
  

   immediate 
  district. 
  The 
  slow 
  warping 
  of 
  the 
  land 
  which 
  brought 
  

   about 
  this 
  subsidence 
  gave 
  the 
  district 
  a 
  wholly 
  different 
  direc- 
  

   tion 
  of 
  slope. 
  In 
  Potsdam 
  and 
  Theresa 
  times 
  it 
  had 
  sloped 
  to 
  

   the 
  northeast 
  and 
  formed 
  part 
  of 
  the 
  extreme 
  westerly 
  end 
  of 
  the 
  

   subsiding 
  trough. 
  It 
  now 
  came 
  to 
  slope 
  to 
  the 
  southwest, 
  was 
  in- 
  

   vaded 
  by 
  the 
  sea 
  from 
  that 
  direction, 
  and 
  to 
  the 
  northeast 
  lay 
  a 
  

   land 
  area 
  which 
  separated 
  it 
  from 
  the 
  Chazy 
  basin 
  beyond. 
  

   Though 
  the 
  district 
  was 
  covered 
  by 
  the 
  waters 
  of 
  both 
  marine 
  

   invasions 
  it 
  was 
  near 
  the 
  shore 
  line 
  in 
  each 
  case 
  and 
  received 
  

   only 
  comparatively 
  thin, 
  marginal 
  deposits, 
  representing 
  only 
  a 
  

   small 
  fraction 
  of 
  the 
  entire 
  thickness 
  of 
  the 
  formations 
  con- 
  

   cerned. 
  Hence 
  in 
  a 
  broad 
  way 
  it 
  is 
  true 
  that 
  what 
  had 
  been 
  the 
  

   western 
  shore 
  of 
  the 
  earlier 
  sea 
  became 
  now 
  the 
  eastern 
  shore 
  

   of 
  this 
  later 
  western 
  sea, 
  or 
  that 
  the 
  general 
  district 
  formed 
  an 
  

   axis 
  or 
  pivot 
  from 
  which 
  the 
  land 
  tipped 
  now 
  in 
  one 
  direction 
  

  

  