﻿52 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  stone. 
  In 
  southeastern 
  New 
  York 
  (for 
  example, 
  the 
  Shawangunk 
  

   mountain) 
  the 
  first 
  Siluric 
  deposit 
  to 
  he 
  laid 
  down 
  upon 
  the 
  eroded 
  

   Ordovicic 
  shales 
  was 
  the 
  Shawangunk 
  conglomerate. 
  This 
  latter 
  

   formation, 
  as 
  determined 
  by 
  its 
  fossils, 
  belongs 
  with 
  the 
  Salina 
  divi- 
  

   sion 
  and 
  is 
  therefore 
  much 
  younger 
  than 
  the 
  Oneida 
  conglomerate 
  

   which 
  belongs 
  with 
  the 
  Medina 
  division 
  (see 
  table 
  in 
  chapter 
  i). 
  

   Also 
  the 
  whole 
  of 
  the. 
  Clinton 
  and 
  Niagara 
  formations, 
  which 
  are 
  

   SO' 
  well 
  developed 
  in 
  central 
  and 
  western 
  New 
  York, 
  were 
  never 
  

   formed 
  in 
  eastern 
  or 
  southeastern 
  New 
  York. 
  Thus 
  the 
  Siluric 
  sea, 
  

   due 
  to 
  subsidence 
  of 
  the 
  land, 
  overspread 
  central 
  and 
  western 
  New 
  

   York 
  long 
  before 
  it 
  reached 
  the 
  Hudson 
  valley 
  region. 
  In 
  fact 
  it 
  

   was 
  not 
  until 
  late 
  in 
  the 
  period 
  that 
  the 
  sea 
  encroached 
  upon 
  the 
  

   Hudson 
  valley 
  area, 
  and 
  then 
  it 
  did 
  not 
  occupy 
  all 
  that 
  area 
  because 
  

   the 
  shore 
  of 
  the 
  Siluric 
  sea 
  extended 
  only 
  as 
  far 
  east 
  as 
  the 
  western 
  

   slope 
  of 
  the 
  Taconics. 
  Western 
  New 
  York, 
  during 
  the 
  late 
  Siluric, 
  

   was 
  a 
  more 
  or 
  less 
  cut 
  off 
  basin 
  or 
  arm 
  of 
  the 
  sea 
  in 
  which 
  the 
  salt 
  

   beds 
  were 
  deposited. 
  

  

  How 
  much, 
  if 
  any, 
  of 
  the 
  Adirondack 
  region 
  was 
  covered 
  by 
  the 
  

   Siluric 
  sea? 
  The 
  total 
  absence 
  of 
  any 
  formation 
  later 
  than 
  the 
  

   Ordovicic 
  shales 
  around 
  the 
  northern 
  Adirondacks 
  and 
  across 
  the 
  

   line 
  in 
  Canada 
  strongly 
  suggests 
  that 
  this 
  region 
  was 
  upraised 
  

   toward 
  the 
  close 
  of 
  the 
  Ordovicic 
  period, 
  perhaps 
  at 
  the 
  same 
  time 
  

   as 
  the 
  Taconic 
  revolution, 
  and 
  continued 
  as 
  dry 
  land 
  not 
  only 
  

   during 
  the 
  Siluric 
  but 
  also 
  during 
  all 
  the 
  ages 
  up 
  to 
  the 
  present, 
  

   except 
  for 
  a 
  very 
  brief 
  local 
  submergence 
  during 
  the 
  Quaternary 
  

   (see 
  figure 
  34). 
  In 
  the 
  southern 
  Adirondack 
  area 
  the 
  case 
  is 
  some- 
  

   what 
  different. 
  The 
  outcrops 
  of 
  Siluric 
  strata 
  beneath 
  the 
  steep 
  

   front 
  of 
  the 
  Devonic 
  Helderberg 
  escarpment 
  immediately 
  south 
  of 
  

   the 
  Adirondacks, 
  makes 
  it 
  certain 
  that 
  these 
  strata 
  and 
  the 
  Siluric 
  

   sea 
  formerly 
  extended 
  farther 
  north. 
  The 
  difficulty 
  comes 
  in 
  trying 
  

   to 
  decide 
  how 
  far 
  northward 
  these 
  rocks 
  once 
  extended, 
  because 
  

   there 
  is 
  now 
  not 
  a 
  single 
  scrap 
  of 
  Siluric 
  rocks 
  north 
  of 
  the 
  

   Mohawk 
  river, 
  though 
  the 
  cap 
  rock 
  (Oswego 
  sandstone) 
  of 
  the 
  

   Tug 
  Hill 
  plateau 
  is 
  probably 
  of 
  Siluric 
  age. 
  All 
  we 
  can 
  say 
  is 
  

   that 
  the 
  Silurian 
  sea 
  probably 
  overspread 
  the 
  southern 
  border 
  of 
  

   the 
  Adirondacks 
  and 
  that 
  the 
  sediments 
  which 
  were 
  deposited 
  there 
  

   have 
  since 
  been 
  removed 
  by 
  erosion. 
  To 
  summarize: 
  During 
  the 
  

   early 
  Siluric 
  the 
  sea 
  had 
  spread 
  over 
  only 
  central 
  and 
  western 
  New 
  

   York, 
  while 
  during 
  the 
  late 
  Siluric 
  it 
  had 
  extended 
  over 
  practically 
  

   all 
  the 
  State 
  west 
  and 
  south 
  of 
  the 
  Adirondack 
  region. 
  

  

  The 
  strata 
  of 
  Siluric 
  age 
  were 
  deposited 
  sheet 
  upon 
  sheet 
  in 
  the 
  

   usual 
  manner 
  upon 
  the 
  sea 
  bottom. 
  For 
  our 
  purpose 
  we 
  may 
  con- 
  

  

  