﻿Report 
  of 
  the 
  State 
  Geologist. 
  443 
  

  

  The 
  Hudson 
  river 
  formation. 
  — 
  The 
  Hudson 
  river 
  formation 
  

   consists 
  of 
  dark 
  shales 
  with 
  interbedded, 
  very 
  fine-grained, 
  

   massively-bedded 
  sandstones, 
  which 
  are 
  frequent 
  in 
  the 
  upper 
  

   members 
  but 
  thinner 
  and 
  less 
  frequent 
  below. 
  In 
  the 
  lowest 
  

   beds 
  there 
  are 
  intercalations 
  of 
  black 
  carbonaceous 
  slates 
  contain- 
  

   ing 
  a 
  well-known 
  graptolite 
  fauna. 
  

  

  A 
  greater 
  part 
  of 
  the 
  wide 
  area 
  occupied 
  by 
  this 
  formation 
  is 
  

   overlaid 
  by 
  Champlain 
  deposits, 
  and 
  it 
  constitutes 
  the 
  surface 
  

   only 
  in 
  the 
  hills 
  west 
  of 
  Altamont, 
  along 
  the 
  lower 
  slopes 
  of 
  the 
  

   Helderberg 
  escarpment 
  and 
  along 
  or 
  near 
  the 
  Hudson 
  and 
  

   Mohawk 
  rivers. 
  There" 
  are 
  fine 
  exposures 
  above 
  Altamont 
  where 
  

   the 
  Boxen 
  Kill 
  has 
  cut 
  a 
  ravine 
  through 
  the 
  formation 
  ; 
  and 
  there 
  

   are 
  extensive 
  outcrops 
  in 
  " 
  gulfs 
  " 
  in 
  the 
  Indian 
  Ladder 
  region. 
  

   In 
  the 
  banks 
  of 
  the 
  Ho 
  hawk 
  there 
  are 
  frequent 
  exposures, 
  

   notably 
  at 
  the 
  great 
  falls 
  at 
  Cohoes. 
  Along 
  and 
  near 
  the 
  Hudson 
  

   there 
  are 
  scattered 
  outcrops 
  of 
  which 
  the 
  most 
  extensive 
  are 
  on 
  

   the 
  lower 
  Norman's 
  Kill 
  at 
  Kenwood 
  and 
  on 
  the 
  West 
  Shore 
  rail- 
  

   way 
  along 
  the 
  scarp 
  of 
  the 
  second 
  terraces 
  from 
  " 
  The 
  Abbey 
  " 
  

   to 
  Wemple. 
  Within 
  the 
  area 
  of 
  the 
  great 
  plain 
  of 
  Champlain 
  

   deposits 
  exposures 
  are 
  rare, 
  for 
  the 
  streams 
  seldom 
  cut 
  through 
  

   to 
  the 
  slates. 
  The 
  exposures 
  along 
  the 
  Spraytkill, 
  southwest 
  of 
  

   South 
  Bethlehem, 
  are 
  the 
  best 
  that 
  I 
  observed. 
  They 
  extend 
  

   from 
  the 
  fault 
  to 
  the 
  vicinity 
  of 
  the 
  road-metal 
  quarry. 
  

  

  The 
  graptolitic 
  beds 
  are 
  exposed 
  at 
  Kenwood 
  and 
  along 
  the 
  

   railroad 
  a 
  short 
  distance 
  south 
  of 
  " 
  The 
  Abbey." 
  They 
  appear 
  

   to 
  constitute 
  the 
  lowest 
  members 
  in 
  Albany 
  county, 
  but 
  the 
  

   structure 
  in 
  this 
  region 
  is 
  so 
  complicated 
  by 
  intense 
  folding, 
  

   accompanied 
  by 
  crushing 
  and 
  faulting, 
  that 
  the 
  relations 
  were 
  

   not 
  apparent. 
  The 
  black 
  graptolitic 
  slates, 
  gray 
  slates 
  and 
  

   shales 
  and 
  sandstones 
  are 
  intermingled 
  in 
  the 
  most 
  complex 
  

   manner 
  and 
  extended 
  observations 
  will 
  be 
  necessary 
  to 
  unravel 
  

   the 
  relations. 
  

  

  The 
  thickness 
  of 
  the 
  Hudson 
  river 
  formation 
  is 
  not 
  less 
  than 
  

   3480 
  feet, 
  at 
  least 
  in 
  the 
  region 
  near 
  Altamont. 
  This 
  estimate 
  

   is 
  based 
  on 
  the 
  record 
  of 
  the 
  gas 
  wells 
  bored 
  near 
  Altamont 
  in 
  

   1886, 
  which, 
  according 
  to 
  Ashburner,* 
  penetrated 
  2880 
  feet 
  to 
  

   the 
  Trenton 
  limestone. 
  I 
  find 
  that 
  there 
  are 
  about 
  600 
  feet 
  more 
  

  

  * 
  Petroleum 
  and 
  natural 
  gas 
  in 
  New 
  York 
  State; 
  Am. 
  Inst. 
  Mining 
  Engineers. 
  Trans., 
  vol. 
  18 
  

   pp. 
  906-953, 
  plates. 
  1889. 
  

  

  