﻿62 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  were 
  being 
  eroded. 
  The 
  sediments 
  derived 
  from 
  the 
  erosion 
  of 
  

   the 
  young 
  Appalachians 
  were 
  especially 
  abundant 
  because 
  of 
  the 
  

   vigorous 
  wearing 
  down 
  of 
  the 
  young 
  mountains. 
  A 
  thickness 
  of 
  

   thousands 
  of 
  feet 
  of 
  non-marine 
  rocks, 
  mostly 
  red 
  sandstones 
  and 
  

   shales, 
  was 
  finally 
  accumulated 
  in 
  these 
  basins, 
  and 
  is 
  known 
  as 
  the 
  

   Newark 
  series. 
  The 
  great 
  thickness 
  of 
  these 
  rocks, 
  from 
  10,000 
  to 
  

   even 
  possibly 
  15,000 
  feet, 
  strongly 
  argues 
  for 
  a 
  gradual 
  downwarp- 
  

   ing 
  of 
  the 
  basins 
  as 
  deposition 
  of 
  sediments 
  went 
  on. 
  It 
  is 
  often 
  

   stated 
  that 
  these 
  strata 
  were 
  formed 
  in 
  estuaries, 
  but 
  at 
  least 
  in 
  the 
  

   northern 
  area, 
  from 
  the 
  Connecticut 
  valley 
  to 
  Maryland, 
  many 
  of 
  

   the 
  layers 
  show 
  sun 
  cracks, 
  rain-drop 
  pits, 
  ripple 
  marks, 
  and 
  re- 
  

   mains 
  and 
  footprints 
  of 
  land 
  reptiles. 
  These 
  features 
  show 
  that 
  

   for 
  the 
  most 
  part 
  the 
  beds 
  were 
  formed 
  in 
  very 
  shallow 
  water 
  such 
  

  

  Fig. 
  20 
  Detailed 
  section 
  running 
  west-northwest 
  through 
  Pelhamville, 
  

   Yonkers 
  and 
  the 
  Palisades 
  in 
  southeastern 
  New 
  York, 
  showing 
  the 
  intense 
  

   folding 
  of 
  Taconic 
  age, 
  the 
  granite 
  dikes, 
  and 
  the 
  relation 
  of 
  the 
  Palisade 
  

   lava 
  to 
  the 
  other 
  formations. 
  Fg 
  = 
  Fordham 
  fineiss 
  (Precambric) 
  ; 
  Pq 
  — 
  

   Poughquag 
  quartzite 
  (Cambric); 
  Sd^ 
  Stockbridge 
  dolomite 
  (Cambro- 
  

   Ordovicic) 
  ; 
  Hs 
  = 
  Hudson 
  schist 
  (Ordovicic) 
  ; 
  Yg 
  = 
  Yonkers 
  gneiss; 
  Gr 
  

   = 
  granite 
  dike; 
  Ns 
  = 
  Newark 
  sandstone 
  (Jura-Trias); 
  Pd 
  — 
  Palisade 
  dia- 
  

   base 
  or 
  lava 
  (Triassic). 
  

  

  Modified 
  from 
  New 
  York 
  City 
  folio, 
  U. 
  S. 
  G. 
  S. 
  

  

  as 
  flood 
  plains 
  or 
  lakes 
  where 
  changing 
  conditions 
  frequently 
  

   allowed 
  the 
  surface 
  layers 
  to 
  lie 
  exposed 
  to 
  the 
  sun. 
  

  

  During 
  the 
  time 
  of 
  the 
  formation 
  of 
  the 
  Newark 
  beds 
  there 
  was 
  

   considerable 
  igneous 
  activity 
  as 
  shown 
  by 
  the 
  occurrence 
  of 
  sheets 
  

   of 
  igneous 
  rocks 
  within 
  the 
  mass 
  of 
  sediments. 
  In 
  some 
  cases 
  true 
  

   lava 
  flows, 
  with 
  cindery 
  tops, 
  were 
  poured 
  out 
  on 
  the 
  surface 
  and 
  

   then 
  became 
  buried 
  under 
  later 
  sediments, 
  while 
  in 
  other 
  cases 
  the 
  

   sheets 
  of 
  molten 
  rock 
  were 
  forced 
  up 
  either 
  between 
  the 
  strata 
  or 
  

   obliquely 
  through 
  them, 
  thus 
  proving 
  their 
  intrusive 
  character. 
  As 
  

   a 
  result 
  of 
  subsequent 
  erosion, 
  these 
  lava 
  intrusions 
  often 
  stand 
  

   out 
  conspicuously 
  as 
  topographic 
  features. 
  Perhaps 
  the 
  most 
  note- 
  

   worthy 
  of 
  these 
  is 
  the 
  great 
  igneous 
  rock 
  sheet, 
  part 
  of 
  which 
  out- 
  

   crops 
  to 
  form 
  the 
  famous 
  Palisades 
  of 
  the 
  Hudson 
  and 
  which 
  out- 
  

   crops 
  altogether 
  for 
  a 
  distance 
  of 
  seventy 
  miles. 
  As 
  shown 
  in 
  

  

  