﻿44 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  seem 
  to 
  indicate 
  that 
  the 
  southern 
  Adirondack 
  region 
  could 
  not 
  have 
  

   been 
  completely 
  submerged 
  at 
  the 
  close 
  of 
  the 
  Lower 
  Silurian, 
  much 
  

   less 
  so 
  at 
  the 
  close 
  of 
  the 
  Trenton." 
  

  

  PLEISTOCENE 
  (GLACIAL) 
  GEOLOGY 
  

  

  From 
  the 
  standpoint 
  of 
  its 
  glacial 
  history 
  the 
  Port 
  Leyden 
  district 
  

   is 
  unusually 
  interesting 
  and 
  instructive. 
  When 
  the 
  great 
  ice 
  sheet, 
  

   which 
  covered 
  most 
  of 
  New 
  York 
  State, 
  reached 
  its 
  maximum 
  

   development 
  the 
  Black 
  river 
  valley 
  must 
  have 
  been 
  buried 
  under 
  

   several 
  thousand 
  feet 
  of 
  ice. 
  We 
  know 
  this 
  because 
  the 
  whole 
  

   Adirondack 
  region 
  is 
  glaciated 
  and 
  was 
  covered 
  by 
  the 
  ice. 
  The 
  

   advance 
  and 
  retreat 
  of 
  the 
  ice 
  across 
  the 
  Port 
  Leyden 
  quadrangle 
  

   has 
  left 
  most 
  of 
  the 
  ordinary 
  marks 
  of 
  glaciation, 
  while 
  certain 
  of 
  

   them 
  are 
  developed 
  to 
  a 
  remarkable 
  degree. 
  So 
  far 
  as 
  the 
  writer 
  

   knows 
  nothing 
  has 
  'been 
  published 
  regarding 
  the 
  Pleistocene 
  history 
  

   of 
  this 
  immediate 
  region, 
  although 
  a 
  report 
  by 
  Chamberlin^ 
  pub- 
  

   lished 
  some 
  2y 
  years 
  ago 
  has 
  an 
  indirect 
  bearing.^ 
  

  

  Direction 
  of 
  ice 
  flow 
  

  

  Chamberhn, 
  in 
  the 
  report 
  above 
  referred 
  to, 
  makes 
  the 
  tentative 
  

   statement 
  '' 
  that 
  massive 
  ice 
  currents 
  having 
  their 
  ulterior 
  channels 
  

   in 
  the 
  Champlain 
  valley, 
  on 
  the 
  one 
  hand, 
  and 
  the 
  St 
  Lawrence 
  on 
  

   the 
  other, 
  swept 
  around 
  the 
  Adirondacks 
  and 
  entered 
  the 
  Mohawk 
  

   valley 
  at 
  either 
  extremity, 
  while 
  a 
  feebler 
  current, 
  at 
  the 
  hight 
  

   of 
  glaciation, 
  probably 
  passed 
  over 
  the 
  Adirondacks 
  and 
  gave 
  to 
  the 
  

   whole 
  a 
  southerly 
  trend." 
  Observations 
  by 
  later 
  investigators 
  have 
  

   tended 
  to 
  bear 
  out 
  this 
  view 
  and 
  the 
  evidences 
  from 
  the 
  Port 
  Leyden 
  

   quadrangle 
  herewith 
  presented 
  have 
  an 
  important 
  bearing 
  upon 
  the 
  

   proposition. 
  

  

  The 
  direction 
  of 
  flow 
  is 
  best 
  shown 
  by 
  the 
  glacial 
  striae 
  which 
  

   have 
  been 
  observed 
  at 
  a 
  number 
  of 
  different 
  places 
  through 
  the 
  

   district. 
  The 
  striae 
  are 
  best 
  preserved 
  upon 
  the 
  hard 
  Precambric 
  

   rocks, 
  but 
  these 
  are 
  mostly 
  drift 
  covered 
  except 
  along 
  the 
  chief 
  

   stream 
  courses. 
  The 
  limestones 
  are 
  next 
  most 
  favorable 
  while 
  upon 
  

   the 
  shales 
  none 
  have 
  been 
  found. 
  Striae 
  are 
  present 
  only 
  upon 
  those 
  

   surfaces 
  from 
  which 
  the 
  drift 
  has 
  been 
  recently 
  removed, 
  because 
  

  

  'U. 
  S. 
  Geol. 
  Sur. 
  3d 
  An. 
  Rep't 
  1881-82. 
  p. 
  36(^-65- 
  

  

  ^ 
  Since 
  the 
  above 
  was 
  written 
  Prof. 
  H. 
  L. 
  Fairchild 
  has 
  presented 
  several 
  

   papers, 
  bearing 
  on 
  the 
  glacial 
  history 
  of 
  northern 
  and 
  central 
  New 
  York, 
  

   before 
  the 
  1908 
  meeting 
  of 
  the 
  Geological 
  Societ}^ 
  of 
  America. 
  These 
  papers 
  

   will 
  be 
  published 
  in 
  the 
  bulletin 
  of 
  the 
  society. 
  

  

  