﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  7I 
  

  

  succeed 
  alternations 
  of 
  blue 
  limestone 
  and 
  gray, 
  magnesian 
  lime- 
  

   stone, 
  with 
  occasional 
  white, 
  earthy 
  beds, 
  and 
  with 
  thin 
  recur- 
  

   rences 
  of 
  the 
  blackish 
  limestones 
  with 
  traces 
  of 
  the 
  marine 
  fauna; 
  

   in 
  the 
  other 
  beds 
  the 
  fossils 
  are 
  chiefly, 
  or 
  exclusively, 
  ostracods. 
  

   As 
  the 
  formation 
  thins 
  to 
  the 
  east 
  and 
  west 
  the 
  lower 
  gray 
  beds 
  

   disappear, 
  bringing 
  the 
  basail 
  sands 
  up 
  under 
  the 
  black 
  limestones 
  

   with 
  further 
  thinning 
  this 
  disappears 
  in 
  its 
  turn, 
  but 
  at 
  the 
  same 
  

   time 
  the 
  higher 
  black 
  layers 
  seem 
  to 
  show 
  increased 
  thickness 
  and 
  

   prominence, 
  so 
  that 
  where 
  the 
  lower 
  division 
  has 
  been 
  thinned 
  to 
  

   a 
  few 
  feet, 
  as 
  it 
  has 
  over 
  much 
  of 
  the 
  region, 
  it 
  is 
  still 
  character- 
  

   ized 
  by 
  black, 
  fossiliferous 
  limestone. 
  

  

  This 
  lower 
  division 
  has 
  a 
  measured 
  thickness 
  of 
  70 
  feet 
  in 
  a 
  

   nearly 
  complete 
  section 
  by 
  Perch 
  lake. 
  It 
  is 
  likely 
  somewhat 
  

   thicker 
  to 
  the 
  west 
  but 
  probably 
  does 
  not 
  exceed 
  this 
  more 
  than 
  

   15 
  or 
  20 
  feet. 
  A 
  weill 
  near 
  Stone 
  Mills 
  was 
  drilled 
  125 
  feet 
  in 
  

   the 
  formation 
  without 
  reaching 
  the 
  base, 
  but 
  drilling 
  commenced 
  

   in 
  the 
  upper 
  division 
  and 
  how 
  large 
  a 
  part 
  of 
  that 
  is 
  involved 
  is 
  

   not 
  known, 
  though 
  likely 
  50 
  feet 
  must 
  be 
  allotted 
  to 
  it. 
  

  

  The 
  upper 
  division 
  consists 
  of 
  alternations 
  of 
  white 
  earthy 
  lime- 
  

   stone, 
  and 
  of 
  dove 
  limestone, 
  with 
  occasional 
  beds 
  of 
  gray, 
  and 
  of 
  

   blue, 
  hard, 
  subgranular 
  or 
  subcrystalline 
  limestone 
  ; 
  there 
  is 
  also 
  

   some 
  yellow, 
  earthy 
  limestone, 
  and 
  a 
  horizon 
  where 
  a 
  reddish 
  tinge 
  

   is 
  likely 
  to 
  prevail. 
  The 
  summit 
  is 
  chiefly 
  of 
  dove 
  limestone. 
  The 
  

   earthy 
  limestones 
  hold 
  numerous 
  nodules 
  of 
  coarsely 
  crystalline 
  

   calcite, 
  which 
  attain 
  quite 
  large 
  size 
  in 
  some 
  of 
  the 
  upper 
  layers, 
  

   with 
  diameters 
  of 
  from 
  3 
  to 
  5 
  inches. 
  Celestite 
  nodules 
  also 
  occur, 
  

   but 
  much 
  less 
  frequently. 
  Much 
  of 
  the 
  upper 
  division 
  is 
  thin 
  

   bedded, 
  weathering 
  into 
  small, 
  yellow 
  stained 
  slabs 
  an 
  inch 
  or 
  two 
  

   in 
  thickness 
  ; 
  and 
  the 
  stone 
  walls 
  of 
  this 
  thin 
  material 
  which 
  line 
  

   the 
  roadsides 
  and 
  separate 
  the 
  fields 
  everywhere 
  characterize 
  the 
  

   upper 
  Pamelia 
  country. 
  

  

  The 
  surfaces 
  of 
  many 
  of 
  the 
  layers 
  are 
  covered 
  with 
  shrinkage 
  

   cracks, 
  especially 
  in 
  the 
  upper 
  part 
  of 
  the 
  division. 
  Sand 
  grains 
  

   also 
  appear 
  in 
  some 
  of 
  the 
  white, 
  earthy 
  beds. 
  Abundant 
  Stylio- 
  

   lites 
  occur 
  at 
  certain 
  horizons 
  in 
  the 
  upper 
  dove 
  limestones. 
  The 
  

   evidence 
  of 
  estuarine, 
  or 
  lagoon 
  deposition, 
  ■ 
  with 
  evaporating 
  

   waters, 
  occasional 
  exposure 
  of 
  broad 
  mud 
  flats, 
  and 
  from 
  time 
  to 
  

   time 
  replenishment 
  of 
  the 
  water 
  from 
  the 
  sea 
  outside, 
  freshening 
  

   it 
  and 
  bringing 
  in 
  traces 
  of 
  the 
  outer 
  marine 
  fauna 
  to 
  mingle 
  with 
  

   the 
  ostracod 
  fauna 
  of 
  the 
  lagoon, 
  is 
  very 
  plain 
  and 
  conclusive; 
  

   prevalence 
  of 
  somewhat 
  arid 
  climate 
  is 
  also 
  suggested. 
  The 
  rock 
  

   is 
  very 
  like, 
  and 
  the 
  climatic 
  and 
  depositional 
  conditions 
  very 
  simi- 
  

  

  