﻿Report 
  of 
  the 
  State 
  Geologist. 
  395 
  

  

  through 
  the 
  State 
  and 
  turns 
  abruptly 
  southward 
  in 
  Albany 
  county 
  

   at 
  the 
  edge 
  of 
  the 
  Hudson 
  basin 
  in 
  a 
  great 
  escarpment, 
  constitut- 
  

   ing 
  the 
  eastern 
  face 
  of 
  the 
  Helderberg 
  mountains. 
  For 
  the 
  greater 
  

   part 
  of 
  its 
  course 
  this 
  shelf 
  slopes 
  back 
  for 
  several 
  miles 
  to 
  the 
  

   base 
  of 
  high 
  hills, 
  which 
  consist 
  of 
  the 
  lower 
  members 
  of 
  the 
  

   Hamilton 
  group. 
  The 
  escarpment 
  at 
  the 
  outer 
  edge 
  of 
  the 
  shelf 
  

   consists 
  of 
  north-facing 
  cliffs 
  of 
  limestone. 
  In 
  the 
  Cobleskill 
  

   and 
  Schoharie 
  region 
  it 
  is 
  deeply 
  trenched 
  by 
  the 
  Cobleskill 
  and 
  

   Schoharie 
  creeks, 
  which 
  flow 
  out 
  from 
  the 
  south 
  and 
  give 
  rise 
  to 
  

   deep 
  indentations 
  on 
  the 
  line 
  of 
  escarpment. 
  Figures 
  4 
  and 
  5 
  

   will 
  illustrate 
  the 
  general 
  structure 
  of 
  the 
  eastern 
  extension 
  of 
  

   the 
  Helderberg 
  escarpment, 
  fig. 
  4 
  showing 
  the 
  cliffs 
  and 
  slopes 
  

   on 
  the 
  west 
  side 
  of 
  the 
  gorge 
  cut 
  by 
  Schoharie 
  creek. 
  Eastward 
  

   from 
  Schoharie 
  for 
  some 
  miles 
  the 
  escarpment 
  is 
  a 
  low 
  line 
  of 
  

   cliffs 
  varying 
  from 
  ten 
  to 
  one 
  hundred 
  feet 
  in 
  height, 
  but 
  

   averaging 
  about 
  fifty 
  feet, 
  and 
  surmounting 
  a 
  long, 
  broken 
  slope 
  

   of 
  Hudson 
  slates. 
  The 
  shelf 
  extends 
  from 
  the 
  crest 
  of 
  this 
  cliff 
  

   in 
  a 
  long 
  slope 
  southward 
  to 
  the 
  Foxkill, 
  a 
  branch 
  of 
  the 
  

   Schoharie 
  creek, 
  south 
  of 
  which 
  rises 
  the 
  very 
  high 
  terraced 
  

   hills 
  of 
  the 
  Hamilton 
  rocks. 
  (See 
  fig. 
  5.) 
  Southeast 
  of 
  Alta- 
  

   mont 
  the 
  escarpment 
  attains 
  its 
  maximum 
  prominence 
  and 
  con- 
  

   stitutes 
  the 
  northern 
  end 
  of 
  the 
  Helderberg 
  mountains. 
  Here 
  it 
  

   presents 
  imposing 
  cliffs 
  surmounting 
  a 
  rocky 
  slope 
  rising 
  precip- 
  

   itously 
  from 
  500 
  to 
  600 
  feet 
  above 
  the 
  great 
  plain 
  which 
  extends 
  

   far 
  to 
  the 
  north 
  and 
  east. 
  A 
  short 
  distance 
  behind 
  the 
  crest 
  of 
  

   the 
  cliffs 
  there 
  rises 
  a 
  series 
  of 
  steep 
  terraces, 
  culminating, 
  finally 
  

   in 
  high 
  hills 
  of 
  Hamilton 
  rocks, 
  all 
  of 
  which 
  fall 
  into 
  the 
  general 
  

   slope 
  as 
  the 
  line 
  of 
  cliffs 
  trends 
  southward, 
  and 
  culminating 
  in 
  a 
  

   magnificent 
  terraced 
  escarpment 
  rising 
  steeply 
  to 
  an 
  altitude 
  of 
  

   more 
  than 
  1,200 
  feet 
  above 
  the 
  plain. 
  

  

  In 
  the 
  next 
  few 
  miles 
  to 
  the 
  eastward 
  this 
  escarpment 
  grad- 
  

   ually 
  decreases 
  in 
  prominence, 
  the 
  members 
  of 
  the 
  lower 
  terraces 
  

   widening 
  out 
  to 
  the 
  southeastward 
  into 
  a 
  rolling 
  region 
  of 
  

   moderate 
  height 
  and 
  the 
  Hamilton 
  hills 
  dropping 
  back 
  to 
  the 
  

   south 
  and 
  then 
  extending 
  to 
  the 
  southeast 
  as 
  a 
  series 
  of 
  high 
  

   north-trending 
  ridges, 
  ending 
  abruptly 
  northward 
  en 
  echelon. 
  

  

  The 
  irregular 
  eastern 
  border 
  of 
  the 
  rolling 
  region 
  in 
  which 
  the 
  

   lower 
  terraces 
  merge 
  is 
  marked 
  by 
  a 
  low, 
  but 
  distinct, 
  escarp- 
  

   ment 
  of 
  limestone 
  cliffs 
  separating 
  it 
  from 
  the 
  Hudson 
  terraces, 
  

  

  