﻿Report 
  of 
  the 
  State 
  Geologist, 
  431 
  

  

  This 
  section 
  shows 
  a 
  great 
  succession 
  of 
  beds 
  of 
  various 
  rocks 
  

   dipping 
  gently 
  to 
  the 
  southwestward, 
  excepting 
  in 
  the 
  vicinity 
  

   of 
  the 
  Hudson 
  where 
  there 
  is 
  much 
  disturbance. 
  The 
  wide 
  plain 
  

   of 
  sand 
  and 
  clay 
  extending 
  west 
  from 
  the 
  Hudson 
  river 
  is 
  under- 
  

   laid 
  at 
  a 
  greater 
  or 
  less 
  depth 
  by 
  the 
  members 
  of 
  the 
  Hudson 
  

   river 
  formation. 
  The 
  great 
  cliffs 
  of 
  the 
  Helderberg 
  escarpment 
  

   are 
  due 
  to 
  the 
  overlying 
  Helderberg 
  limestones, 
  notably 
  a 
  medial 
  

   member 
  of 
  the 
  series, 
  and 
  the 
  terraces 
  and 
  plateaus 
  beyond, 
  to 
  

   alternations 
  of 
  limestones, 
  shales 
  and 
  sandstones. 
  A 
  great 
  series 
  

   of 
  overlying 
  shales 
  and 
  flags 
  constitute 
  the 
  high 
  region 
  which 
  

   rises 
  abruptly 
  to 
  the 
  south 
  and 
  west 
  and 
  extends 
  to 
  the 
  foot 
  hills 
  

   of 
  the 
  Catskills. 
  In 
  this 
  wide 
  area 
  of 
  highlands, 
  higher 
  beds 
  

   come 
  in 
  succession 
  to 
  the 
  southwestward. 
  

  

  There 
  is 
  considerable 
  variation 
  in 
  the 
  relations 
  of 
  the 
  terraces 
  

   and 
  plateaus 
  behind 
  the 
  crest 
  of 
  the 
  Helderberg 
  escarpment 
  and 
  

   in 
  the 
  nature 
  of 
  this 
  escarpment, 
  but 
  they 
  are 
  all 
  clearly 
  shown 
  

   on 
  the 
  geologic 
  map 
  and 
  described 
  in 
  the 
  following 
  pages. 
  In 
  

   the 
  northwestern 
  corner 
  of 
  the 
  county 
  the 
  Hudson 
  river 
  mem- 
  

   bers 
  of 
  the 
  series 
  rise 
  into 
  high 
  hills 
  which 
  extend 
  to 
  the 
  Helder- 
  

   berg 
  escarpment 
  southward, 
  a 
  feature 
  which 
  is 
  general 
  for 
  many 
  

   miles 
  west 
  of 
  Albany 
  county 
  but 
  ends 
  abruptly 
  in 
  the 
  northern 
  

   part 
  of 
  the 
  Helderberg 
  mountain. 
  

  

  In 
  the 
  southeastern 
  corner 
  of 
  the 
  county 
  the 
  Helderberg 
  and 
  

  

  overlying 
  formations 
  extend 
  into 
  the 
  disturbed 
  belt 
  adjoining 
  

  

  the 
  Hudson 
  river, 
  and 
  are 
  flexed 
  and 
  faulted 
  to 
  a 
  considerable 
  

  

  degree. 
  

  

  Stratigraphy. 
  

  

  The 
  stratigraphy 
  of 
  Albany 
  county 
  has 
  been 
  comparatively 
  

   well 
  known 
  for 
  over 
  half 
  a 
  century. 
  In 
  1820 
  Prof. 
  Eaton* 
  pub- 
  

   lished 
  a 
  report 
  in 
  which 
  the 
  more 
  prominent 
  features 
  were 
  out- 
  

   lined, 
  and 
  the 
  later 
  studies 
  by 
  Matherf 
  and 
  Hall;j: 
  of 
  the 
  Geo- 
  

   logical 
  Survey, 
  have 
  afforded 
  knowledge 
  as 
  to 
  the 
  character, 
  age, 
  

   palaeontology 
  and 
  relations 
  of 
  the 
  principal 
  formations. 
  

  

  In 
  the 
  following 
  descriptions 
  I 
  shall 
  give 
  a 
  resume 
  of 
  the 
  

   principal 
  characters 
  of 
  the 
  formations 
  extended 
  somewhat 
  by 
  

   new 
  inform 
  ition 
  regarding 
  local 
  features 
  and 
  distribution. 
  

  

  * 
  Amos 
  Eaton 
  and 
  T. 
  R. 
  Beck. 
  A 
  geological 
  survey 
  of 
  the 
  county 
  of 
  Albany, 
  56 
  pages, 
  8vo 
  

   Albany, 
  1820. 
  

  

  t 
  Geology 
  of 
  New 
  York. 
  Part 
  I. 
  Comprising 
  the 
  geology 
  of 
  the 
  First 
  Geological 
  District. 
  

   Albany, 
  1843. 
  

  

  X 
  Palaeontology 
  of 
  New 
  York, 
  and 
  many 
  papers 
  on 
  New 
  York 
  geology. 
  

  

  