﻿164 
  NEW 
  YOEK 
  STATE 
  MUSEUM 
  

  

  below 
  Portage. 
  It 
  is 
  generally 
  recognized 
  by 
  its 
  black, 
  soft, 
  slaty 
  

   texture, 
  but 
  its 
  fossils 
  are 
  very 
  rare. 
  

  

  Portage 
  group 
  

  

  This 
  name 
  has 
  been 
  given 
  to 
  the 
  next 
  higher 
  portion 
  of 
  the 
  

   great 
  slaty 
  and 
  shaly 
  masses, 
  which 
  form 
  the 
  walls 
  of 
  deep 
  gorge 
  

   of 
  the 
  Genesee 
  at 
  Portage 
  and 
  cover 
  everywhere 
  on 
  the 
  south 
  

   the 
  Hamilton 
  group 
  and 
  Genesee 
  slates. 
  This 
  enormous 
  pile 
  of 
  

   sandy, 
  slaty 
  and 
  shaly 
  strata 
  is 
  in 
  some 
  parts 
  of 
  the 
  state 
  1,000 
  

   feet 
  in 
  thickness 
  : 
  it 
  was 
  divided 
  by 
  Prof. 
  Hall 
  into 
  a 
  lower 
  mass 
  

   called 
  the 
  Cashaqua 
  shale, 
  a 
  middle 
  mass 
  called 
  the 
  Gardeau 
  

   shale 
  and 
  flagstones, 
  and 
  a 
  terminal 
  mass 
  of 
  sandstones 
  seen 
  at 
  

   Portage; 
  but 
  in 
  middle 
  and 
  eastern 
  New 
  York, 
  these 
  divisions 
  

   are 
  not 
  distinct. 
  

  

  Much 
  of 
  this 
  group 
  is 
  a 
  soft 
  olive-colored 
  shale; 
  but 
  its 
  most 
  

   useful 
  portions 
  are 
  its 
  layers 
  of 
  flagstone, 
  which 
  are 
  largely 
  quar- 
  

   ried 
  near 
  Norwich 
  and 
  Ithaca, 
  on 
  the 
  hills 
  back 
  of 
  the 
  Helder- 
  

   bergs, 
  on 
  those 
  west 
  of 
  the 
  Hudson 
  river 
  as 
  far 
  down 
  as 
  Rondout; 
  

   and 
  in 
  Sullivan 
  county 
  near 
  the 
  Delaware 
  river. 
  

  

  From 
  Chenango 
  and 
  Broome 
  counties 
  eastward 
  to 
  Greene 
  

   county 
  the 
  Portage 
  is 
  represented 
  by 
  the 
  Oneonta 
  formation 
  

   which 
  forms 
  the 
  lower 
  1,000 
  feet 
  of 
  the 
  Catskill 
  mountain 
  strata. 
  

  

  The 
  soft 
  shales 
  of 
  the 
  Portage 
  group 
  contain 
  many 
  of 
  the 
  con- 
  

   cretions 
  known 
  as 
  Septaria, 
  which 
  also 
  occur 
  in 
  the 
  Marcellus 
  

   shales. 
  

  

  Chemung 
  group 
  

   To 
  the 
  Portage 
  succeeds 
  the 
  Chemung, 
  so 
  called 
  from 
  being 
  

   well 
  exhibited 
  at 
  the 
  ' 
  Narrows 
  ' 
  of 
  the 
  Chemung 
  river, 
  near 
  

   Waverly, 
  in 
  Tioga 
  county. 
  Its 
  thickness 
  of 
  1,000 
  or 
  1,500 
  feet 
  is 
  

   made 
  up 
  of 
  a 
  series 
  of 
  thin-bedded 
  sandstones 
  with 
  intervening 
  

   shales 
  and 
  occasional 
  beds 
  of 
  impure 
  limestone 
  mainly 
  formed 
  

   by 
  the 
  materials 
  of 
  fossil 
  shells. 
  In 
  many 
  places 
  it 
  abounds 
  

   with 
  fossils. 
  While 
  well 
  developed 
  in 
  central 
  and 
  western 
  New 
  

   York 
  the 
  Chemung, 
  as 
  a 
  group 
  of 
  fine 
  sediments, 
  disappears 
  to 
  

   the 
  eastward 
  and 
  is 
  represented 
  by 
  the 
  Catskill 
  formation. 
  

  

  