﻿PLEISTOCENE 
  GEOLOGY 
  OF 
  NASSAU 
  CO. 
  AND 
  BOROUGH 
  OF 
  QUEENS 
  621 
  

  

  The 
  main 
  topograpliic 
  features 
  thus 
  set 
  fortli 
  are 
  traceable 
  , 
  east- 
  

   ward 
  for 
  200 
  miles, 
  one 
  or 
  more 
  elements 
  appearing 
  either 
  on 
  the 
  

   islands 
  off 
  the 
  south 
  coast 
  of 
  New 
  England 
  or 
  on 
  the 
  adjacent 
  main- 
  

   land, 
  the 
  essential 
  elements 
  of 
  tlie 
  topography 
  being 
  two 
  ridges 
  each 
  

   one 
  of 
  which 
  rises 
  rather 
  abruptly 
  above 
  a 
  plain 
  sloping 
  southward 
  

   from 
  it 
  toward 
  tlie 
  sea. 
  If 
  tlie 
  plain 
  is 
  absent, 
  the 
  sea 
  covers 
  the 
  

   space 
  where 
  we 
  should 
  expect 
  it 
  to 
  occur. 
  Westward, 
  the 
  main 
  

   ridge 
  here 
  described 
  abuts 
  on 
  lower 
  JSTew 
  York 
  bay 
  at 
  the 
  JS'arrows, 
  

   reappearing 
  on 
  Staten 
  Island 
  and 
  continuing 
  to 
  be 
  recognizable 
  far 
  

   inland 
  over 
  tlie 
  continent 
  as 
  a 
  topographic 
  feature, 
  often 
  imposed 
  

   -on 
  the 
  rocky 
  profile 
  of 
  valleys 
  and 
  high 
  ridges 
  alike. 
  

  

  GEOLOGY 
  

  

  The 
  topographic 
  features 
  above 
  described 
  have 
  long 
  been 
  known 
  

   to 
  constitute 
  a 
  group 
  of 
  drift 
  materials 
  laid 
  down 
  along 
  the 
  margin 
  

   of 
  an 
  ice 
  sheet 
  or 
  a 
  successive 
  series 
  of 
  such 
  glaciers 
  in 
  the 
  Quater- 
  

   nary 
  or, 
  as 
  it 
  is 
  now 
  usually 
  denominated, 
  the 
  Pleistocene 
  period, 
  

   a 
  time 
  defined 
  as 
  beginning 
  in 
  this 
  hemisphere 
  with 
  the 
  iirst 
  of 
  

   these 
  ice 
  invasions 
  on 
  the 
  coast 
  plain 
  and 
  closing 
  with 
  the 
  final 
  dis- 
  

   appearance 
  of 
  the 
  ice 
  from 
  eastern 
  America. 
  The 
  time 
  since 
  this 
  

   disappearance 
  of 
  the 
  ice, 
  variously 
  estimated 
  at 
  from 
  7000 
  to 
  10,000 
  

   years, 
  is 
  frequently 
  denominated 
  the 
  post-glacial 
  epoch. 
  With 
  the 
  

   deposits 
  made 
  during 
  this 
  Pleistocene 
  period, 
  the 
  present 
  report 
  has 
  

   mainly 
  to 
  do. 
  

  

  Pre-Pleistocene 
  formations 
  

  

  The 
  basement 
  on 
  which 
  these 
  Pleistocene 
  drift 
  materials 
  repose 
  in 
  

   this 
  part 
  of 
  Long 
  Island 
  has 
  but 
  a 
  small 
  exposure 
  above 
  sealevel, 
  

   and 
  that 
  is 
  mainly 
  limited 
  to 
  the 
  northern 
  coast 
  north 
  of 
  the 
  main 
  

   ridge, 
  or 
  moraine. 
  These 
  older 
  materials 
  are 
  clays 
  and 
  sands, 
  evi- 
  

   dently 
  an 
  eastward 
  extension 
  of 
  the 
  nearly 
  horizontal 
  clays 
  and 
  sands 
  

   largely 
  of 
  Cretaceous 
  and 
  late 
  Jurassic 
  age 
  which 
  constitute 
  a 
  large 
  

   part 
  of 
  the 
  coastal 
  plain 
  from 
  ]S"ew 
  Jersey 
  southward. 
  Little 
  is 
  

   known 
  of 
  the 
  attitude 
  of 
  these 
  beds 
  in 
  this 
  region, 
  prior 
  to 
  the 
  

   earliest 
  ice 
  invasion, 
  farther 
  than 
  the 
  reasonable 
  presumption 
  that 
  

   they 
  lapped 
  over 
  on 
  the 
  underlying 
  gneisses 
  and 
  igneous 
  rocks 
  of 
  

   the 
  mainland 
  and 
  the 
  extreme 
  western 
  end 
  of 
  the 
  island, 
  gently 
  

   sloping 
  from 
  their 
  inner 
  margin 
  seaward, 
  as 
  they 
  still 
  do 
  in 
  the 
  

   coastal 
  plain 
  south 
  of 
  the 
  glacial 
  district. 
  

  

  