﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  23 
  

  

  rather 
  flows 
  across 
  a 
  broad, 
  low, 
  hilly 
  region 
  of 
  very 
  moderate 
  

   relief 
  thus 
  allowing 
  the 
  low 
  rocky 
  hills 
  to 
  stand 
  out 
  as 
  islands. 
  

  

  The 
  rocks 
  are 
  chiefly 
  sandstones 
  and 
  limestones 
  of 
  Cambric 
  and 
  

   Ordovicic 
  ages, 
  though, 
  in 
  the 
  vicinity 
  of 
  the 
  Thousand 
  Islands 
  

   numerous 
  patches 
  of 
  the 
  underlying 
  Precambric 
  (Adirondack) 
  

   rocks 
  are 
  exposed 
  as 
  on 
  many 
  of 
  the 
  islands 
  themselves. 
  Folds, 
  

   faults 
  and 
  igneous 
  rock 
  are 
  not 
  present 
  except 
  in 
  the 
  Precambric 
  

   rocks, 
  and 
  the 
  strata 
  may 
  be 
  regarded 
  as 
  a 
  comparatively 
  thin 
  

   mantle 
  of 
  nearly 
  horizontal 
  layers 
  overlying 
  the 
  Precambric 
  rocks. 
  

  

  CHAMPLAIN 
  VALLEY 
  PROVINCE 
  

  

  The 
  Champlain 
  valley 
  bounds 
  the 
  Adirondacks 
  on 
  the 
  east 
  and 
  

   the 
  province 
  should 
  be 
  regarded 
  as 
  a 
  great 
  depression 
  separating 
  the 
  

   Adirondacks 
  on 
  the 
  west 
  from 
  the 
  Green 
  mountains 
  on 
  the 
  east. 
  

   Much 
  of 
  the 
  valley 
  bottom 
  is 
  filled 
  by 
  the 
  waters 
  of 
  Lake 
  Cham- 
  

   plain 
  (elevation 
  101 
  feet). 
  Along 
  the 
  western 
  shores 
  of 
  the 
  lake 
  

   the 
  topography 
  is 
  characteristically 
  hilly, 
  though 
  seldom 
  above 
  500 
  

   feet 
  in 
  elevation. 
  The 
  transition 
  to 
  the 
  higher 
  and 
  rugged 
  Adiron- 
  

   dacks 
  is 
  generally 
  rapid. 
  

  

  The 
  rocks 
  occupying 
  the 
  valley 
  bottom 
  are 
  sandstones, 
  limestones 
  

   and 
  shales 
  of 
  Cambric 
  and 
  Ordovicic 
  ages. 
  These 
  formations 
  are 
  

   much 
  disturbed 
  by 
  numerous 
  faults, 
  often 
  of 
  considerable 
  magni- 
  

   tude, 
  and 
  in 
  fact 
  there 
  is 
  good 
  reason 
  to 
  think 
  that 
  the 
  whole 
  

   Champlain 
  valley 
  is 
  of 
  the 
  nature 
  of 
  a 
  great 
  fault-trough 
  or 
  

   depression. 
  

  

  HUDSON 
  VALLEY 
  PROVINCE 
  

  

  General 
  description. 
  Looked 
  upon 
  in 
  a 
  broad 
  way, 
  the 
  Hudson 
  

   valley 
  province 
  is 
  a 
  depression 
  lying 
  between 
  the 
  western 
  high- 
  

   lands 
  of 
  New 
  England 
  and 
  the 
  eastern 
  highlands 
  of 
  New 
  York. 
  

   Well 
  toward 
  the 
  south 
  the 
  true 
  valley 
  feature 
  is 
  somewhat 
  inter- 
  

   fered 
  with 
  by 
  the 
  presence 
  of 
  such 
  elevated 
  masses 
  as 
  Shawangunk 
  

   mountain 
  and 
  the 
  Highlands-of-the-Hudson. 
  A 
  very 
  detailed 
  

   classification 
  of 
  topographic 
  features 
  would 
  call 
  for 
  four 
  or 
  five 
  

   provinces 
  instead 
  of 
  the 
  one 
  here 
  called 
  the 
  Hudson 
  valley 
  province. 
  

   Since 
  even 
  this 
  southern 
  part, 
  however, 
  is 
  lowland 
  compared 
  with 
  

   the 
  Catskill 
  mountains 
  immediately 
  westward 
  and 
  since 
  the 
  rock 
  

   structures 
  are 
  so 
  similar 
  and 
  characteristic 
  throughout 
  the 
  region, 
  

   though 
  the 
  kinds 
  of 
  rocks 
  vary 
  considerably, 
  it 
  seems 
  best 
  for 
  our 
  

   purpose 
  to 
  treat 
  all 
  together 
  as 
  the 
  Hudson 
  valley 
  province 
  and 
  

   then 
  very 
  briefly 
  describe 
  each 
  of 
  the 
  minor 
  subdivisions 
  of 
  the 
  

   province. 
  

  

  