﻿PLEISTOCENE 
  GEOLOGY 
  OF 
  NASSAU 
  CO. 
  AND 
  BOROUGH 
  OF 
  QUEENS 
  637 
  

  

  deposits 
  where 
  clays 
  do 
  not 
  occur, 
  finding 
  its 
  way 
  out 
  near 
  sealevel 
  

   in 
  springs, 
  as 
  in 
  the 
  village 
  of 
  Oyster 
  Bay. 
  At 
  best, 
  surface 
  streams 
  

   would 
  have 
  cut 
  but 
  slowly 
  on 
  these 
  deposits, 
  as 
  they 
  do 
  now, 
  the 
  

   excavation 
  in 
  post-glacial 
  time 
  being 
  practically 
  nothing 
  in 
  the 
  form 
  

   of 
  mechanical 
  abrasion. 
  

  

  The 
  share 
  which 
  the 
  ice 
  and 
  the 
  subglacial 
  streams 
  may 
  have 
  had 
  

   in 
  the 
  excavation 
  of 
  the 
  harbors, 
  is 
  discussed 
  in 
  connection 
  with 
  the 
  

   moraine 
  on 
  p. 
  643. 
  

  

  Wisconsin 
  epoch. 
  Moraines 
  and 
  attendant 
  sand 
  plains. 
  

   The 
  existence 
  of 
  two 
  lines 
  of 
  moraines 
  in 
  this 
  area 
  has 
  already 
  been 
  

   set 
  forth 
  in 
  the 
  account 
  of 
  the 
  topography. 
  Both 
  of 
  these 
  deposits 
  

   are 
  largely 
  composed 
  of 
  materials 
  which 
  have 
  been 
  water-worn, 
  

   in 
  this 
  feature 
  reflecting 
  the 
  nature 
  of 
  the 
  terrane 
  from 
  which 
  the 
  

   materials 
  were 
  eroded 
  and 
  on 
  which 
  they 
  were 
  deposited. 
  The 
  ice 
  

   sheet 
  on 
  leaving 
  the 
  bed 
  rocks 
  of 
  the 
  mainland 
  and 
  the 
  north 
  shore 
  

   of 
  what 
  is 
  now 
  Long 
  Island 
  sound 
  passed 
  over 
  the 
  Columbia 
  gravels 
  

   and 
  sands, 
  gathering 
  debris 
  from 
  these 
  older 
  water-worn 
  deposits 
  ; 
  

   hence 
  the 
  water-worn 
  pebbles 
  which 
  abound 
  in 
  the 
  moraine 
  even 
  

   when 
  the 
  materials 
  are 
  truly 
  ice-laid 
  without 
  stratification. 
  True 
  

   boulder 
  clay 
  occurs 
  in 
  small 
  patches, 
  but 
  much 
  of 
  the 
  till 
  is 
  sandy, 
  

   and 
  even 
  in 
  its 
  coarser 
  phases 
  often 
  exhibits 
  traces 
  of 
  water 
  action 
  

   closely 
  followed 
  by 
  a 
  shoving 
  of 
  the 
  deposits 
  into 
  contorted 
  drift. 
  

  

  The 
  outer 
  deposits 
  consist 
  of 
  a 
  few 
  low 
  knobs 
  rising 
  like 
  kames 
  

   from 
  the 
  surrounding 
  gravels. 
  They 
  bear 
  a 
  few 
  boulders 
  on 
  their 
  

   surface 
  and 
  frequently 
  in 
  road 
  cuts 
  reveal 
  a 
  thin 
  patch 
  of 
  till. 
  

   West 
  of 
  Searington 
  rolling 
  surfaces 
  of 
  till 
  composed 
  of 
  a 
  gravelly 
  

   boulder 
  clay 
  give 
  the 
  deposit, 
  along 
  with 
  its 
  steep 
  southerly 
  front, 
  

   something 
  of 
  the 
  aspect 
  of 
  the 
  main 
  moraine 
  as 
  it 
  exists 
  southwest 
  

   of 
  Lake 
  Surprise. 
  These 
  knobs 
  and 
  their 
  rare 
  attendant 
  basins 
  have 
  

   a 
  much 
  less 
  strong 
  development 
  than 
  those 
  heavier 
  accumulations 
  

   which 
  lie 
  in 
  the 
  form 
  of 
  a 
  strong 
  ridge 
  immediately 
  north 
  of 
  them. 
  

   The 
  deposits 
  do 
  not 
  afford 
  in 
  themselves 
  precise 
  indexes 
  of 
  the 
  posi- 
  

   tion 
  of 
  the 
  ice 
  front 
  at 
  the 
  time 
  they 
  were 
  made. 
  They 
  appear 
  to 
  

   be 
  submarginal 
  deposits 
  laid 
  down 
  when 
  the 
  ice 
  front 
  lay 
  somewhat 
  

   to 
  the 
  south 
  of 
  them, 
  and 
  are 
  best 
  compared 
  with 
  the 
  kame 
  moraine 
  

   in 
  the 
  eastern 
  part 
  of 
  Nantucket. 
  

  

  The 
  inner 
  or 
  main 
  moraine 
  exhibits 
  likewise 
  the 
  two 
  phases 
  of 
  

  

  