﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  

  

  59 
  

  

  Fig. 
  3 
  A 
  nearer 
  view 
  of 
  a 
  portion 
  of 
  the 
  

   contact 
  showing 
  a 
  local 
  steep 
  slope 
  of 
  the 
  

   hill 
  and 
  projecting 
  cornice 
  of 
  an 
  extra 
  re- 
  

  

  There 
  is 
  an 
  occasional 
  quartzite 
  pebble 
  along 
  the 
  contact, 
  otherwise 
  

   the 
  sandstone 
  is 
  normal, 
  and 
  gives 
  no 
  sign 
  of 
  basal 
  conditions. 
  

  

  Around 
  to 
  the 
  left 
  the 
  slope 
  of 
  the 
  knob 
  steepens. 
  There 
  are 
  

   occasional 
  bands 
  of 
  coarsely 
  crystalline, 
  purer 
  quartzite 
  in 
  the 
  schists 
  

   which 
  are 
  far 
  more 
  resistant 
  to 
  weathering. 
  On 
  this 
  steep 
  front 
  one 
  

   such 
  layer 
  iprojects 
  as 
  a 
  cornice 
  

   with 
  the 
  sand-filling 
  beneath, 
  as 
  

   shown 
  in 
  figure 
  3. 
  Photographic 
  

   attempts 
  here 
  proved 
  wholly 
  un- 
  

   satisfactory. 
  

  

  Besides 
  the 
  contacts 
  on 
  larger 
  

   slopes, 
  of 
  which 
  the 
  preceding 
  are 
  

   instances, 
  there 
  are 
  a 
  number 
  of 
  

   minor 
  exampks 
  of 
  the 
  sort, 
  chiefly 
  ^^^^^^* 
  quartzite 
  layer, 
  

   as 
  filled 
  hollows 
  of 
  the 
  Hmestone 
  surfaces. 
  A 
  sand-filled 
  hollow 
  of 
  

   the 
  sort 
  appears 
  at 
  the 
  top 
  of 
  the 
  limestone 
  quarry 
  near 
  the 
  Theresa 
  

   boat 
  landing, 
  and 
  is 
  shown 
  in 
  plate 
  2. 
  In 
  the 
  section 
  there 
  shown 
  the 
  

   hollow 
  is 
  about 
  6 
  feet 
  deep 
  and 
  with 
  twice 
  that 
  width 
  at 
  the 
  top. 
  

   Another 
  example 
  may 
  be 
  seen 
  at 
  the 
  quarry 
  just 
  south 
  of 
  the 
  

   Theresa 
  depot, 
  though 
  the 
  overlying 
  sandstone 
  is 
  gone 
  except 
  for 
  

   the 
  small 
  residual 
  patch 
  resting 
  in 
  the 
  hollow 
  so 
  that 
  its 
  original 
  size 
  

   can 
  only 
  be 
  guessed 
  at. 
  A 
  considerable 
  number 
  of 
  other 
  examples 
  

   have 
  been 
  seen, 
  some 
  merely 
  sand-filled, 
  others 
  containing 
  rock 
  frag- 
  

   ments 
  as 
  well. 
  In 
  all 
  cases 
  the 
  cement 
  is 
  calcareous 
  and 
  the 
  rock 
  

   weak 
  and 
  easily 
  removed. 
  

  

  The 
  above 
  evidence 
  of 
  the 
  character 
  of 
  the 
  surface 
  on 
  which 
  the 
  

   Potsdam 
  was 
  deposited, 
  is 
  of 
  precisely 
  the 
  sort 
  so 
  convincingly 
  set 
  

   forth 
  by 
  Wilson 
  in 
  his 
  discussion 
  of 
  similar 
  features 
  in 
  Ontario.^ 
  

   In 
  New 
  York 
  these 
  features 
  are 
  developed 
  in 
  a 
  belt 
  of 
  considerable 
  

   breadth 
  across 
  the 
  strike, 
  showing 
  a 
  great 
  number 
  of 
  ridges 
  and 
  

   valleys, 
  with 
  patches 
  of 
  overlying 
  Potsdam, 
  and 
  with 
  the 
  relief 
  in 
  

   every 
  case 
  owing 
  to 
  differential 
  erosion 
  on 
  rocks 
  of 
  varying 
  resist- 
  

   ance, 
  and 
  in 
  no 
  case 
  to 
  subsequent 
  folding. 
  In 
  this 
  State 
  

   exposed 
  patches 
  of 
  residual 
  materials 
  resting 
  on 
  the 
  old 
  surface 
  are 
  

   more 
  numerous 
  than 
  in 
  Ontario, 
  and 
  these 
  are 
  in 
  the 
  depressions 
  in 
  

   all 
  cases, 
  showing 
  that 
  the 
  depressions 
  were 
  in 
  existence 
  and 
  served 
  

   as 
  receiving 
  pockets 
  for 
  this 
  material 
  at 
  the 
  commencement 
  of 
  sand- 
  

   stone 
  deposition. 
  The 
  evidence 
  is 
  abundant, 
  clear 
  and 
  convincing 
  

   that 
  the 
  Precambric 
  surface 
  underneath 
  the 
  sandstone 
  is 
  precisely 
  

   like 
  that 
  where 
  the 
  sandstone 
  is 
  absent, 
  and 
  that 
  the 
  present 
  topogra- 
  

   phy 
  of 
  the 
  Precambric 
  areas 
  is 
  that 
  resulting 
  from 
  recent 
  stripping 
  

  

  'Wilson, 
  A. 
  W. 
  G., 
  Can. 
  Inst. 
  Trans. 
  7:146-55. 
  

  

  