﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  5 
  1 
  

  

  being 
  older 
  than 
  the 
  Sierras 
  and 
  the 
  Coast 
  ranges. 
  Much 
  of 
  the 
  

   material 
  making 
  up 
  the 
  mass 
  of 
  the 
  Ca/tskill 
  mountains 
  was 
  derived 
  

   from 
  the 
  wear 
  of 
  the 
  Taconic 
  mountains, 
  deposited 
  in 
  the 
  sea 
  just 
  

   to 
  their 
  west 
  and 
  later 
  raised 
  high 
  above 
  sea 
  level. 
  

  

  SILURIC 
  PERIOD 
  

  

  The 
  close 
  of 
  the 
  Ordovicic 
  age 
  or 
  the 
  opening 
  "of 
  the 
  Siluric 
  

   found 
  practically 
  all 
  the 
  State 
  above 
  sea 
  level 
  and 
  undergoing 
  

   erosion. 
  Along 
  the 
  eastern 
  side 
  the 
  great 
  Taconic 
  range 
  stood 
  out 
  

   prominently, 
  but 
  over 
  the 
  rest 
  of 
  the 
  State 
  we 
  have 
  no 
  evidence 
  

   that 
  the 
  land 
  was 
  very 
  high. 
  The 
  central 
  portion 
  of 
  the 
  Adiron- 
  

   dack 
  region 
  probably 
  stood 
  out 
  somewhat 
  more 
  prominently 
  than 
  

   the 
  western 
  region. 
  

  

  As 
  shown 
  on 
  the 
  geologic 
  map 
  (figure 
  i), 
  the 
  Siluric 
  strata 
  out- 
  

   crops 
  in 
  a 
  comparatively 
  narrow 
  belt 
  which 
  runs 
  along 
  the 
  western 
  

   side 
  of 
  the 
  Hudson 
  valley 
  to 
  the 
  Helderberg 
  hills, 
  southwest 
  of 
  

   Albany, 
  where 
  it 
  swings 
  sharply 
  around 
  westward 
  to 
  follow 
  the 
  

   south 
  side 
  of 
  the 
  Mohawk 
  valley, 
  and 
  thence 
  as 
  a 
  somewhat 
  wider 
  

   belt 
  along 
  the 
  south 
  side 
  of 
  Lake 
  Ontario. 
  These 
  Siluric 
  strata 
  

   everywhere 
  dip 
  under 
  the'Devonic 
  (surface) 
  rocks 
  of 
  the 
  Catskill 
  

   and 
  Southwestern 
  plateau 
  provinces. 
  This 
  fact, 
  combined 
  with 
  the 
  

   knowledge 
  that 
  the 
  strata 
  are 
  largely 
  of 
  widespread 
  marine 
  origin 
  

   and 
  also 
  outcrop 
  abundantly 
  in 
  central 
  Pennsylvania, 
  makes 
  it 
  

   practically 
  certain 
  that 
  the 
  Siluric 
  rocks 
  underlie 
  all 
  of 
  the 
  Catskill 
  

   and 
  southwestern 
  plateau 
  regions. 
  Thus 
  we 
  must 
  conclude 
  that 
  at 
  

   least 
  during 
  much 
  of 
  Siluric 
  time 
  all 
  of 
  New 
  York 
  State 
  south 
  of 
  

   Lake 
  Ontario 
  and 
  the 
  Moliawk 
  valley 
  and 
  west 
  of 
  the 
  Hudson 
  river, 
  

   was 
  covered 
  by 
  sea 
  zvater. 
  That 
  the 
  earliest 
  Siluric 
  sea 
  did 
  not 
  

   spread 
  over 
  the 
  area 
  is 
  proved 
  by 
  the 
  absence 
  of 
  the 
  very 
  earliest 
  

   known 
  Siluric 
  deposits. 
  Furthermore, 
  we 
  know 
  that 
  the 
  sea 
  

   transgressed 
  upon 
  the 
  State 
  from 
  the 
  south 
  or 
  west, 
  the 
  Taconic 
  

   range 
  forming 
  an 
  effective 
  barrier 
  on 
  the 
  east 
  and 
  total 
  absence 
  of 
  

   Siluric 
  strata 
  in 
  the 
  St 
  Lawrence 
  and 
  Champlain 
  valleys 
  (as 
  well 
  

   as 
  in 
  Canada 
  just 
  north 
  of 
  the 
  State) 
  precluding 
  encroachment 
  of 
  

   the 
  sea 
  from 
  the 
  north. 
  

  

  This 
  encroachment 
  of 
  the 
  sea 
  over 
  so 
  much 
  of 
  the 
  State 
  was 
  due 
  

   to 
  a 
  gradual 
  sinking 
  of 
  the 
  land. 
  That 
  central 
  and 
  western 
  New 
  

   York 
  was 
  submerged 
  before 
  the 
  Hudson 
  valley 
  region 
  is 
  proved 
  

   as 
  follows: 
  In 
  central 
  New 
  York 
  (south 
  of 
  Utica) 
  the 
  first 
  deposit 
  

   to 
  form 
  upon 
  the 
  eroded 
  surface 
  of 
  the 
  Ordovicic 
  shales 
  was 
  the 
  

   Oneida 
  conglomerate 
  which 
  passes 
  westward 
  into 
  the 
  Medina 
  sand- 
  

  

  