﻿PLEISTOCENE 
  GEOLOGY 
  OF 
  NASSAU 
  CO. 
  AND 
  BOROUGH 
  OF 
  QUEENS 
  661 
  

  

  report 
  were 
  made 
  before 
  the 
  ice 
  liad 
  melted 
  back 
  5 
  miles 
  from 
  its 
  

   extreme 
  prolongation. 
  They 
  clearly 
  belong 
  however 
  to 
  the 
  period 
  

   of 
  retreat 
  ; 
  but 
  the 
  mainland 
  on 
  the 
  north 
  was 
  still 
  actively 
  glaciated. 
  

  

  POST-GIiACIAIi 
  CHANGES 
  AND 
  PBOCSSSES 
  NOW 
  IN 
  ACTION 
  

  

  The 
  disappearance 
  of 
  the 
  ice 
  from 
  a 
  glaciated 
  district 
  of 
  itself 
  

   induces 
  certain 
  changes 
  which 
  are 
  not 
  wanting 
  in 
  this 
  part 
  of 
  Long 
  

   Island. 
  The 
  melting 
  out 
  of 
  remnants 
  of 
  the 
  glacier 
  or 
  those 
  parts 
  

   of 
  its 
  base 
  which 
  filled 
  depressions 
  has 
  in 
  many 
  instances 
  given 
  rise 
  

   to 
  small 
  lakes 
  and 
  tarns. 
  A 
  number 
  of 
  these 
  small 
  lakes 
  exist 
  in 
  

   the 
  moraine 
  west 
  of 
  Roslyn. 
  Of 
  these, 
  Lake 
  Surprise 
  is 
  the 
  best 
  

   and 
  largest 
  example. 
  It 
  lies 
  at 
  an 
  elevation 
  of 
  about 
  200 
  feet 
  above 
  

   the 
  uea 
  in 
  a 
  basin 
  w^hose 
  sides 
  are 
  gravelly 
  till. 
  Presumably 
  the 
  

   bottom 
  is 
  clay 
  rather 
  than 
  gravel, 
  as 
  the 
  waters 
  would 
  escape 
  

   through 
  the 
  latter. 
  Such 
  lakelets 
  depend 
  on 
  the 
  percolation 
  of 
  the 
  

   ground 
  waters 
  through 
  the 
  relatively 
  gravelly 
  or 
  sandy 
  materials 
  of 
  

   the 
  superficial 
  deposits, 
  the 
  water 
  standing 
  in 
  the 
  pond 
  at 
  the 
  level 
  

   of 
  the 
  ground 
  water 
  in 
  the 
  gravels. 
  Other 
  small 
  lakelets 
  lie 
  in 
  

   depressions 
  in 
  the 
  outwash 
  plain, 
  as 
  at 
  Plattsdale. 
  Westbury 
  pond 
  

   is 
  one 
  of 
  this 
  class 
  named 
  on 
  the 
  map. 
  

  

  The 
  streams 
  of 
  the 
  plain 
  flow, 
  as 
  has 
  been 
  indicated, 
  in 
  courses 
  

   which 
  were 
  carved 
  out 
  by 
  the 
  once 
  more 
  vigorous 
  glacial 
  streams 
  or 
  

   in 
  still 
  older 
  channels 
  on 
  the 
  north 
  side 
  of 
  the 
  moraine. 
  Owing 
  to 
  

   the 
  porosity 
  of 
  the 
  glacial 
  gravels, 
  much 
  of 
  the 
  rainfall 
  soaks 
  into 
  the 
  

   ground 
  and 
  issues 
  near 
  sealevel 
  in 
  the 
  form 
  of 
  springs, 
  hence, 
  since 
  

   the 
  run-off 
  is 
  small, 
  little 
  erosive 
  work 
  has 
  been 
  accomplished 
  in 
  the 
  

   post-glacial 
  epoch. 
  Yet 
  the 
  streams 
  wdiicli 
  converge 
  into 
  Oyster 
  

   bay 
  have 
  contributed 
  enough 
  gravel 
  and 
  sand 
  to 
  form 
  a 
  narrow 
  

   flat, 
  modified 
  by 
  wave 
  action 
  where 
  the 
  village 
  of 
  that 
  name 
  

   stands.^ 
  

  

  Marine 
  action 
  at 
  the 
  present 
  sealevel 
  has 
  cut 
  back 
  the 
  outwash 
  

   plain 
  on 
  the 
  south 
  coast 
  as 
  well 
  as 
  the 
  Far 
  Rockaway 
  ridge, 
  so 
  that 
  

   the 
  outermost 
  extent 
  of 
  both 
  of 
  these 
  formations 
  is 
  now 
  destroyed, 
  

  

  ' 
  la 
  June 
  1900 
  a 
  well 
  bored 
  by 
  means 
  of 
  a 
  drill 
  on 
  the 
  north 
  side 
  of 
  Main 
  st. 
  

   760 
  feet 
  distant 
  from 
  the 
  beach 
  met 
  at 
  the 
  depth 
  of 
  45 
  feet 
  (35 
  feet 
  below 
  sealevel) 
  

   a 
  marl 
  containing 
  oyster 
  shells 
  (Ostrea 
  sp). 
  Above 
  this 
  bed 
  were 
  gravels, 
  

   below 
  light 
  yellowish 
  sand. 
  

  

  