﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  65 
  

  

  ing, 
  of 
  the 
  coastal 
  lands 
  to 
  allow 
  deposition 
  of 
  sediments 
  over 
  

   much 
  of 
  the 
  region 
  now 
  known 
  as 
  the 
  Atlantic 
  Coastal 
  plain. 
  That 
  

   but 
  little 
  downwarping 
  of 
  the 
  surface 
  was 
  necessary 
  in 
  order 
  to 
  

   produce 
  proper 
  conditions 
  for 
  sedimentation 
  is 
  evident 
  because 
  the 
  

   coastal 
  lands, 
  just 
  prior 
  to 
  the 
  Cretacic, 
  were 
  already 
  low-lying 
  as 
  a 
  

   result 
  of 
  the 
  long 
  Jurassic 
  erosion 
  period. 
  There 
  was 
  just 
  enough 
  

   warping 
  of 
  these 
  low 
  coastal 
  lands 
  to 
  produce 
  wide 
  flats, 
  flood 
  

   plains, 
  shallow 
  lakes, 
  and 
  marshes 
  back 
  from 
  the 
  real 
  coast 
  line 
  and 
  

   in 
  which 
  were 
  deposited 
  the 
  sediments 
  derived 
  from 
  the 
  Piedmont 
  

   plateau 
  and 
  Appalachian 
  areas. 
  The 
  early 
  Cretacic 
  deposits 
  thus 
  

   formed 
  are 
  known 
  as 
  the 
  Potomac 
  series, 
  and 
  consist 
  of 
  very 
  

   irregular 
  layers 
  of 
  sand, 
  gravel 
  and 
  clay. 
  The 
  very 
  irregular 
  ar- 
  

   rangement 
  of 
  these 
  beds 
  and 
  their 
  rich 
  content 
  of 
  fossil 
  land 
  plants, 
  

   afford 
  conclusive 
  evidence 
  that 
  the 
  sediments 
  were 
  not 
  accumulated 
  

   under 
  marine 
  conditions. 
  The 
  Potomac 
  series 
  outcrops 
  at 
  the 
  

   western 
  margin 
  of 
  the 
  present 
  Coastal 
  plain 
  and 
  has 
  been 
  traced 
  

   from 
  Martha's 
  Vineyard, 
  through 
  Nantucket, 
  Long 
  Island, 
  Staten 
  

   island, 
  Northern 
  New 
  Jersey, 
  and 
  southward 
  into 
  Georgia. 
  Passing 
  

   seaward 
  the 
  strata 
  dip 
  under 
  those 
  of 
  later 
  age 
  (see 
  figure 
  22). 
  

   On 
  Long 
  Island, 
  Potomac 
  outcrops 
  occur 
  only 
  along 
  the 
  north- 
  

   western 
  border 
  but 
  these 
  beds 
  no 
  doubt 
  dip 
  under 
  the 
  more 
  recent 
  

   deposits 
  of 
  the 
  rest 
  of 
  the 
  island. 
  The 
  maximum 
  thickness 
  of 
  the 
  

   Potomac 
  series 
  is 
  only 
  about 
  700 
  feet. 
  

  

  Along 
  the 
  Atlantic 
  coast 
  certain 
  deposits 
  which 
  should 
  come 
  

   between 
  the 
  Lower 
  and 
  Upper 
  Cretacic 
  are 
  missing, 
  and 
  the 
  Upper 
  

   Cretacic 
  beds 
  rest 
  upon 
  the 
  eroded 
  surface 
  of 
  the 
  otherwise 
  undis- 
  

   turbed 
  Lower 
  Cretacic. 
  Thus 
  we 
  know 
  that 
  there 
  was 
  a 
  gentle 
  

   upward 
  oscillation 
  of 
  the 
  land 
  toward 
  the 
  # 
  end 
  of 
  the 
  Lower, 
  or 
  

   beginning 
  of 
  the 
  Upper, 
  Cretacic, 
  after 
  which 
  a 
  moderate 
  amount 
  

   of 
  erosion 
  of 
  the 
  Lower 
  Cretacic 
  beds 
  took 
  place. 
  

  

  Then 
  came 
  another 
  gentle 
  submergence 
  of 
  the 
  coastal 
  lands 
  when 
  

   the 
  Upper 
  Cretacic 
  strata 
  were 
  formed. 
  The 
  character 
  and 
  present 
  

   extent 
  of 
  these 
  deposits, 
  and 
  the 
  fact 
  that 
  they 
  are 
  of 
  marine 
  origin, 
  

   prove 
  that 
  this 
  subsidence 
  allowed 
  a 
  shallow 
  sea 
  to 
  spread 
  over 
  

   practically 
  all 
  of 
  what 
  is 
  now 
  called 
  the 
  Atlantic 
  Coastal 
  plain 
  in- 
  

   cluding 
  most 
  of 
  Long 
  and 
  Staten 
  islands 
  in 
  New 
  York. 
  Accordingly 
  

   we 
  learn 
  that, 
  for 
  the 
  first 
  time 
  since 
  the 
  close 
  of 
  the 
  Paleozoic, 
  

   did 
  truly 
  marine 
  conditions 
  prevail 
  over 
  any 
  portion 
  of 
  New 
  York 
  

   State, 
  and 
  also 
  that 
  Appalachia, 
  the 
  great 
  land 
  mass 
  of 
  the 
  east, 
  

   winch 
  had 
  persisted 
  through 
  the 
  many 
  million 
  years 
  of 
  the 
  Paleozoic 
  

   and 
  most 
  of 
  the 
  Medozoic, 
  now 
  disappeared 
  under 
  the 
  Cretacic 
  sea. 
  

  

  