﻿I36 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  of 
  the 
  basal 
  portion 
  of 
  the 
  sediments 
  and 
  caused 
  the 
  complete 
  dis- 
  

   appearance 
  of 
  their 
  old 
  floor 
  of 
  deposit. 
  

  

  There 
  followed 
  a 
  very 
  long 
  period 
  of 
  erosion 
  of 
  the 
  region 
  during 
  

   which 
  it 
  was 
  above 
  sea 
  level. 
  A 
  great 
  thickness 
  of 
  rock 
  was 
  worn 
  

   away 
  from 
  the 
  surface, 
  bringing 
  to 
  daylight 
  the 
  tops 
  of 
  the 
  great 
  

   igneous 
  masses 
  which 
  originally 
  solidified 
  much 
  below 
  the 
  surface. 
  

   The 
  final 
  effect 
  of 
  the 
  long 
  erosion 
  period 
  was 
  to 
  have 
  reduced 
  the 
  

   entire 
  region 
  to 
  one 
  of 
  low 
  altitude 
  and 
  small 
  relief. 
  Toward 
  the 
  

   close 
  of 
  this 
  erosion 
  period 
  renewed 
  igneous 
  activity 
  resulted 
  in 
  

   the 
  formation 
  of 
  the 
  trap 
  dikes. 
  

  

  Paleozoic 
  history. 
  The 
  Adirondack 
  region 
  then 
  developed 
  a 
  

   tendency 
  to 
  dome 
  upwards 
  centrally 
  and 
  to 
  sag 
  at 
  the 
  margins. 
  

   These 
  sagging 
  margins 
  passed 
  from 
  time 
  to 
  time 
  beneath 
  sea 
  level 
  

   and 
  received 
  accumulations 
  of 
  deposit. 
  In 
  these 
  troughs 
  the 
  early 
  

   Paleozoic 
  sediments 
  of 
  the 
  region 
  were 
  laid 
  down. 
  Oscillations 
  

   of 
  level 
  were 
  of 
  frequent 
  occurrence, 
  accompanied 
  by 
  warping 
  of 
  

   the 
  region. 
  Submergence 
  in 
  the 
  different 
  troughs 
  alternated; 
  it 
  

   was 
  the 
  rare 
  exception 
  that 
  all 
  were 
  depressed 
  at 
  the 
  same 
  time. 
  

   In 
  this 
  report 
  the 
  deposits 
  of 
  the 
  Champlain-Hudson 
  trough 
  (the 
  

   so-called 
  " 
  Chazy 
  basin") 
  chiefly 
  concern 
  us. 
  

  

  To 
  the 
  eastward 
  of 
  the 
  Chazy 
  basin 
  downwarping 
  developed 
  

   one 
  or 
  more 
  other 
  troughs, 
  in 
  which 
  deposits 
  quite 
  different 
  from 
  

   those 
  of 
  the 
  Chazy 
  basin 
  were 
  laid 
  down. 
  Since 
  their 
  formation 
  

   these 
  rocks 
  have 
  been 
  overthrust 
  to 
  the 
  west 
  upon 
  the 
  rocks 
  of 
  the 
  

   Chazy 
  basin, 
  and 
  directly 
  adjoin 
  them 
  upon 
  the 
  east. 
  

  

  CAMBRIC 
  HISTORY 
  

  

  Chazy 
  basin 
  deposits. 
  Potsdam 
  sandstone. 
  The 
  first 
  Pale- 
  

   ozoic 
  deposit 
  of 
  the 
  Adirondack 
  margins 
  was 
  the 
  Potsdam 
  sand- 
  

   stone, 
  an 
  accumulation 
  of 
  coarse, 
  quartzose 
  sands 
  and 
  gravels. 
  The 
  

   accumulation 
  began 
  first 
  on 
  the 
  northeast, 
  in 
  Clinton 
  county, 
  and 
  

   extended 
  itself 
  progressively 
  to 
  the 
  west 
  and 
  to 
  the 
  south. 
  Only 
  

   the 
  upper 
  portion 
  of 
  the 
  formation 
  is 
  found 
  in 
  the 
  Saratoga 
  region. 
  

  

  This 
  upper 
  portion 
  contains 
  marine 
  fossils 
  and 
  must 
  have 
  been 
  

   laid 
  down 
  in 
  shallow 
  marine 
  waters. 
  But 
  marine 
  fossils 
  are 
  lacking 
  

   in 
  the 
  lower 
  half 
  of 
  the 
  formation, 
  in 
  Clinton 
  county, 
  and 
  many 
  

   of 
  its 
  characters 
  suggest 
  that 
  it 
  was 
  laid 
  down 
  above 
  sea 
  level 
  

   instead 
  of 
  below 
  it. 
  They 
  suggest 
  also 
  that 
  the 
  climate 
  was 
  arid. 
  

   But 
  whether 
  marine 
  or 
  not, 
  the 
  accumulation 
  began 
  because 
  the 
  

   district 
  sagged 
  down. 
  This 
  sagging 
  began 
  at 
  the 
  north 
  and 
  slowly 
  

  

  