﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  63 
  

  

  figure 
  20, 
  the 
  molten 
  rock 
  sheet 
  first 
  broke 
  through 
  the 
  strata 
  and 
  

   then 
  crowded 
  its 
  way 
  along 
  parallel 
  to 
  them. 
  During 
  the 
  process 
  

   of 
  cooling 
  there 
  was 
  contraction 
  which 
  expressed 
  itself 
  by 
  breaking 
  

   the 
  rock 
  mass 
  into 
  great, 
  crude, 
  vertical 
  columns, 
  and 
  hence 
  the 
  

   origin 
  of 
  the 
  name 
  " 
  Palisades 
  " 
  (see 
  plate 
  34). 
  At 
  the 
  base 
  of 
  the 
  

   Palisade 
  rock, 
  as 
  well 
  as 
  on 
  its 
  top 
  a 
  little 
  back 
  from 
  the 
  edge 
  of 
  

   the 
  cliff, 
  the 
  Newark 
  sandstone 
  outcrops. 
  The 
  steep 
  cliff 
  is 
  due 
  to 
  

   the 
  fact 
  that 
  the 
  hard 
  igneous 
  rock 
  is 
  much 
  more 
  resistant 
  to 
  erosion 
  

   and 
  weathering 
  than 
  the 
  sandstone 
  above 
  and 
  below 
  it. 
  

  

  The 
  rocks 
  of 
  the 
  Newark 
  series 
  are 
  nearly 
  everywhere 
  some- 
  

   what 
  folded, 
  tilted 
  and 
  extensively 
  fractured 
  by 
  normal 
  faults. 
  Just 
  

   when 
  this 
  deformation 
  occurred 
  is 
  not 
  exactly 
  known, 
  but 
  it 
  was 
  

   probably 
  at 
  the 
  close 
  of 
  the 
  Triassic 
  period 
  as 
  will 
  be 
  shown 
  under 
  

   the 
  next 
  heading. 
  

  

  Briefly 
  summarized, 
  the 
  Triassic 
  zvas 
  a 
  time 
  of 
  accumulation 
  of 
  

   thick 
  deposits 
  of 
  red 
  sandstone 
  and 
  shale 
  of 
  nonmarine 
  character 
  

   in 
  troughlike 
  depressions 
  along 
  the 
  Atlantic 
  slope, 
  these 
  deposits 
  

   being 
  represented 
  in 
  southeastern 
  New 
  York. 
  During 
  their 
  forma- 
  

   tion 
  there 
  was 
  considerable 
  igneous 
  activity 
  when 
  sheets 
  of 
  lava 
  

   were 
  forced 
  through 
  or 
  between 
  the 
  strata 
  as 
  is 
  well 
  shown 
  in 
  the 
  

   case 
  of 
  the 
  rock 
  of 
  the 
  Palisades. 
  

  

  JURASSIC 
  PERIOD 
  

  

  No 
  rocks 
  of 
  Jurassic 
  age 
  occur 
  within 
  New 
  York 
  State 
  nor 
  as 
  a 
  

   matter 
  of 
  fact 
  in 
  all 
  eastern 
  North 
  America, 
  except 
  possibly 
  some 
  

   fresh-water 
  deposits 
  along 
  the 
  Potomac 
  river 
  of 
  Maryland. 
  The 
  

   failure 
  of 
  such 
  strata 
  is 
  readily 
  explained 
  by 
  the 
  fact 
  that 
  the 
  

   Jurassic 
  period 
  was 
  ushered 
  in 
  by 
  a 
  slight 
  upwarping 
  (accompanied 
  

   by 
  faulting 
  and 
  tilting 
  of 
  the 
  rocks) 
  of 
  the 
  Atlantic 
  border 
  of 
  North 
  

   America 
  so 
  that 
  there 
  were 
  no 
  basins 
  of 
  deposition 
  within 
  the 
  

   present 
  eastern 
  border 
  of 
  the 
  continent. 
  That 
  this 
  uplift 
  actually 
  

   occurred 
  and 
  that 
  the 
  Jurassic 
  period 
  in 
  the 
  eastern 
  United 
  States 
  

   was 
  a 
  time 
  of 
  extensive 
  erosion, 
  is 
  well 
  established 
  because 
  the 
  

   whole 
  Atlantic 
  seaboard, 
  including 
  the 
  tilted 
  and 
  faulted 
  Triassic 
  

   strata, 
  was 
  worn 
  down 
  well 
  toward 
  the 
  condition 
  of 
  a 
  peneplain 
  

   and 
  the 
  next 
  sediments 
  (Cretacic) 
  were 
  deposited 
  upon 
  the 
  eastern 
  

   portion 
  of 
  that 
  worn-down 
  surface 
  (see 
  figure 
  22). 
  For 
  instance, 
  

   on 
  Staten 
  island 
  and 
  in 
  northern 
  New 
  Jersey, 
  the 
  Cretacic 
  beds 
  

   may 
  be 
  seen 
  resting 
  directly 
  upon 
  the 
  deeply 
  eroded 
  Triassic 
  rocks, 
  

   and 
  hence 
  the 
  proof 
  is 
  conclusive 
  that 
  during 
  much 
  if 
  not 
  all 
  of 
  the 
  

   Jurassic 
  period 
  active 
  erosion 
  was 
  taking 
  place, 
  and 
  this 
  in 
  turn 
  

   implies 
  that 
  the 
  Triassic 
  beds 
  were 
  well 
  elevated 
  in 
  the 
  early 
  

   Jurassic. 
  

  

  