﻿Report 
  of 
  the 
  State 
  Geologist. 
  441 
  

  

  In 
  Knox 
  township 
  the 
  cliffs 
  of 
  Pentamerus 
  limestone 
  vary 
  

   considerably 
  in 
  elevation, 
  but 
  they 
  are 
  continuous 
  throughout. 
  

   At 
  several 
  points 
  in 
  the 
  western 
  part 
  of 
  the 
  township 
  there 
  are 
  

   heavy 
  masses 
  of 
  drift 
  piled 
  against 
  the 
  cliffs, 
  but 
  they 
  are 
  not 
  

   entirely 
  buried. 
  At 
  the 
  Indian 
  Ladder 
  the 
  cliffs 
  expose 
  the 
  entire 
  

   thickness 
  of 
  the 
  formation, 
  together 
  with 
  the 
  underlying 
  beds. 
  

   A 
  view 
  of 
  this 
  feature 
  is 
  given 
  in 
  plate 
  3. 
  

  

  In 
  the 
  ridges 
  east 
  of 
  Clarksville 
  the 
  formation 
  occupies 
  an 
  area 
  

   of 
  considerable 
  width 
  along 
  the 
  crests, 
  and 
  extending 
  down 
  their 
  

   western 
  slope 
  to 
  the 
  Oniskethau 
  creek. 
  The 
  cliffs 
  trend 
  to 
  the 
  

   eastward 
  along 
  portions 
  of 
  their 
  course 
  in 
  this 
  region, 
  and 
  the 
  

   escarpments 
  presented 
  northward 
  are 
  heavily 
  flanked 
  by 
  drift. 
  

   From 
  Feurabush 
  southward 
  the 
  Pentamerus 
  cliff 
  has 
  considera- 
  

   ble 
  prominence, 
  except 
  for 
  a 
  short 
  distance 
  west 
  of 
  South 
  Beth- 
  

   lehem, 
  where 
  it 
  is 
  crossed 
  by 
  the 
  low 
  gap 
  between 
  Oniskethau 
  

   and 
  Spray 
  t 
  creeks. 
  South 
  of 
  here 
  the 
  line 
  of 
  cliffs 
  is 
  continuous 
  

   to 
  the 
  gap 
  cut 
  by 
  the 
  Hannacrois 
  creek 
  in 
  Greene 
  county. 
  

  

  Tentaculite 
  limestones 
  — 
  These 
  are 
  thin-bedded, 
  dark-blue 
  lime- 
  

   stones 
  lying 
  below 
  the 
  Pentamerus 
  beds 
  and 
  usually 
  outcropping 
  

   in 
  the 
  base 
  of 
  the 
  Helderberg 
  escarpment 
  or 
  lying 
  beneath 
  its 
  

   talus. 
  The 
  strata 
  vary 
  in 
  thickness 
  from 
  an 
  inch 
  to 
  a 
  foot, 
  in 
  

   greater 
  part, 
  but 
  two 
  or 
  three 
  inches 
  is 
  the 
  general 
  average. 
  

   There 
  are 
  occasional 
  intercalations 
  of 
  shaly 
  beds. 
  In 
  the 
  upper 
  

   members, 
  in 
  most 
  localities 
  there 
  is 
  a 
  thin 
  bedding 
  or 
  ribboning 
  

   of 
  alternating 
  lighter 
  and 
  darker 
  tints, 
  which 
  is 
  the 
  " 
  ribbon 
  

   limestone 
  '* 
  of 
  some 
  writers. 
  Toward 
  the 
  base 
  of 
  the 
  series 
  there 
  

   is 
  usually 
  a 
  more 
  massive 
  bed 
  containing 
  Strom 
  atqpora, 
  but 
  the 
  

   member 
  is 
  not 
  conspicuous 
  in 
  Albany 
  county 
  in 
  its 
  typical 
  

   development.* 
  The 
  Tentaculite 
  beds 
  have 
  a 
  thickness 
  of 
  about 
  

   thirty 
  feet 
  along 
  the 
  eastern 
  face 
  of 
  the 
  Helderberg 
  mountain, 
  

   and 
  this 
  appears 
  to 
  be 
  the 
  average 
  thickness 
  throughout. 
  

  

  The 
  beds 
  are 
  frequently 
  exposed 
  at 
  intervals 
  along 
  the 
  Helder- 
  

   berg 
  escarpment. 
  They 
  outcrop 
  at 
  several 
  points 
  southwest 
  and 
  

   south 
  of 
  Altamont, 
  at 
  the 
  Indian 
  Ladder, 
  southwest 
  of 
  New 
  

  

  *Thia 
  Stromatopora 
  bed 
  is 
  excellently 
  exposed 
  on 
  the 
  Albany 
  and 
  Schoharie 
  plank-road 
  

   beyond 
  Altamont; 
  also 
  about 
  two 
  miles 
  west 
  of 
  the 
  road 
  from 
  Albany 
  to 
  Clarksville 
  on 
  th9 
  

   land 
  of 
  Mr. 
  Herkel, 
  and 
  on 
  the 
  same 
  road 
  two 
  miles 
  northeast 
  of 
  Clarksville. 
  There 
  is 
  also 
  a 
  

   good 
  exposure 
  on 
  the 
  slope 
  of 
  the 
  hill 
  at 
  Coeymans 
  Junction, 
  both 
  on 
  the 
  roadside 
  and 
  in 
  an 
  

   extensive 
  quarry. 
  Most 
  of 
  these 
  exposures 
  show 
  that 
  the 
  bed 
  lies 
  but 
  a 
  few 
  feet 
  below 
  the 
  

   Pentamerus 
  limestone.— 
  H. 
  

  

  56 
  

  

  