﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  157 
  

  

  smooth 
  clay 
  fillings, 
  as 
  meadows 
  or 
  swamps 
  between 
  the 
  rock 
  bluffs 
  

   or 
  among 
  the 
  rock 
  knobs, 
  make 
  striking 
  contrast 
  [pi. 
  29]. 
  

  

  The 
  clay 
  is 
  evidently 
  the 
  rock 
  flour 
  of 
  the 
  glacial 
  mill, 
  sifted 
  by 
  

   the 
  standing 
  waters. 
  Its 
  glacial 
  relationship 
  is 
  shown 
  by 
  the 
  fact 
  

   that 
  in 
  some 
  localities 
  it 
  shades 
  into 
  ordinary 
  clayey 
  till; 
  by 
  its 
  in- 
  

   clusion 
  of 
  boulders 
  and 
  cobbles, 
  probably 
  ice 
  rafted; 
  and 
  by 
  its 
  

   composition 
  which 
  is 
  decidedly 
  calcareous. 
  

  

  In 
  many 
  exposures 
  the 
  clay 
  rests 
  directly 
  on 
  glaciated 
  rock 
  [pi. 
  

   57] 
  with 
  no 
  mass 
  or 
  visible 
  layer 
  of 
  till 
  or 
  stones 
  intervening. 
  In 
  

   the 
  gullies 
  or 
  storm-wash 
  hollows 
  a 
  few 
  cobbles 
  or 
  boulders 
  are 
  

   commonly 
  found, 
  derived 
  from 
  the 
  mass 
  of 
  the 
  deposit, 
  but 
  they 
  

   do 
  not 
  seem 
  perceptibly 
  more 
  common 
  at 
  the 
  base. 
  The 
  bed 
  of 
  

   the 
  creek 
  where 
  plate 
  57 
  was 
  taken 
  was 
  filled 
  with 
  cobbles 
  from 
  the 
  

   clay 
  ravine. 
  At 
  the 
  top 
  of 
  this 
  section 
  the 
  lamination 
  was 
  destroyed, 
  

   but 
  the 
  crushing 
  appears 
  to 
  be 
  very 
  localized, 
  and 
  has 
  rarely 
  been 
  

   noted 
  elsewhere. 
  However, 
  the 
  structure 
  does 
  not 
  often 
  appear, 
  as 
  

   the 
  exposed 
  clay 
  quickly 
  loses 
  its 
  lamination 
  and 
  forms 
  a 
  rough, 
  

   crackled 
  skin 
  over 
  the 
  slope, 
  as 
  shown 
  in 
  plate 
  58. 
  It 
  is 
  only 
  where 
  

   the 
  clays 
  are 
  freshly 
  exposed 
  that 
  the 
  lamination 
  becomes 
  evident. 
  

  

  In 
  plate 
  58 
  the 
  numerous 
  white 
  fragments 
  scattered 
  over 
  the 
  

   slope 
  are 
  calcareous 
  concretions, 
  discoid 
  or 
  irregular 
  in 
  form. 
  Evi- 
  

   dently 
  they 
  represent 
  concentration 
  of 
  the 
  lime 
  that 
  was 
  originally 
  

   disseminated 
  in 
  the 
  deposit, 
  but 
  the 
  clay 
  still 
  retains 
  enough 
  of 
  the 
  

   carbonate 
  to 
  effervesce 
  very 
  freely 
  in 
  weak 
  acid. 
  The 
  latter 
  is 
  

   true 
  of 
  all 
  the 
  clays 
  tested, 
  except 
  in 
  some 
  cases 
  the 
  topping 
  lay- 
  

   ers, 
  I 
  or 
  2 
  feet 
  thickness. 
  The 
  lack 
  of 
  carbonate 
  at 
  the 
  surface 
  

   may 
  be 
  due 
  to 
  postglacial 
  leaching, 
  and 
  perhaps 
  to 
  original 
  lack 
  of 
  

   carbonate 
  since 
  the 
  latest 
  beds 
  may 
  have 
  been 
  deposited 
  from 
  well 
  

   washed 
  material, 
  the 
  ice 
  being 
  far 
  removed 
  to 
  the 
  northward. 
  

  

  Some 
  sections 
  do 
  not 
  contain 
  the 
  lime 
  concretions. 
  This 
  is 
  the 
  

   case 
  with 
  a 
  great 
  exposure 
  i}4 
  miles 
  east 
  of 
  Clayton 
  where 
  the 
  

   river 
  has 
  undercut 
  the 
  bank, 
  giving 
  a 
  section 
  15 
  to 
  18 
  feet 
  high. 
  

   The 
  lower 
  part 
  is 
  beautifully 
  laminated, 
  the 
  upper 
  part 
  with 
  older 
  

   exposure 
  showing 
  the 
  characteristic 
  mottled 
  or 
  crackled 
  skin 
  and 
  

   some 
  small 
  lime 
  particles. 
  The 
  east 
  end 
  of 
  the 
  clay 
  section 
  exhibits 
  

   some 
  crumpling 
  of 
  the 
  beds. 
  All 
  these 
  clays 
  effervesce 
  freely. 
  

  

  The 
  volume 
  of 
  this 
  clay 
  over 
  the 
  area 
  increases 
  southward, 
  over 
  

   the 
  limestones, 
  but 
  the 
  total 
  seems 
  excessive 
  In 
  proportion 
  to 
  the 
  

   scanty 
  drift 
  of 
  other 
  materials. 
  It 
  is 
  possible 
  that 
  the 
  genesis 
  and 
  

   history 
  of 
  the 
  clay 
  is 
  more 
  complex 
  than 
  would 
  at 
  first 
  appear. 
  

   Apparently 
  It 
  Is 
  all 
  Postwisconsin, 
  for 
  If 
  It 
  were 
  partly 
  the 
  deposit 
  

   of 
  ice 
  of 
  earlier 
  invasion 
  we 
  should 
  expect 
  to 
  find 
  the 
  deeper 
  and 
  

  

  