﻿62 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  igneous 
  rocks, 
  where 
  homogeneous 
  and 
  free 
  from 
  Grenville 
  

   inclusions, 
  without 
  exception 
  form 
  the 
  highest 
  mountain 
  masses. 
  

   Occasionally 
  the 
  gabbro 
  bosses 
  appear 
  to 
  be 
  slightly 
  more 
  resistant 
  

   than 
  the 
  country 
  rock 
  and 
  they 
  then 
  form 
  the 
  tops 
  of 
  low 
  mountains 
  

   or 
  hills. 
  

  

  Another 
  topographic 
  feature 
  often 
  locally 
  conspicuous 
  is 
  the 
  

   sand 
  flat 
  or 
  flat-topped 
  sand 
  terrace. 
  Among 
  the 
  best 
  examples 
  

   are: 
  in 
  the 
  vicinity 
  of 
  Warrensburg 
  and 
  Pottersville, 
  west 
  of 
  Star- 
  

   buckville, 
  southwest 
  of 
  North 
  Creek, 
  and 
  at 
  a 
  number 
  of 
  places 
  

   southwest 
  of 
  Johnsburg. 
  These 
  represent 
  delta 
  deposits 
  which 
  

   were 
  formed 
  in 
  glacial 
  lakes 
  which 
  will 
  be 
  described 
  in 
  the 
  suc- 
  

   ceeding 
  pages. 
  

  

  RELATION 
  OE 
  TOPOGRAPHY 
  TO 
  ROCK 
  STRUCTURES 
  

  

  Some 
  of 
  the 
  most 
  prominent 
  topographic 
  features 
  of 
  the 
  quad- 
  

   rangle 
  are 
  the 
  bold 
  escarpments, 
  more 
  or 
  less 
  well-defined 
  ridges, 
  

   and 
  isolated 
  mountain 
  masses 
  or 
  domes 
  of 
  igneous 
  rock. 
  These 
  

   rock 
  domes 
  will 
  be 
  especially 
  treated 
  under 
  the 
  next 
  heading. 
  

   Most 
  of 
  the 
  escarpments 
  or 
  ridges 
  are 
  due 
  to 
  faulting 
  and 
  have 
  

   already 
  been 
  described. 
  Some 
  ridges, 
  however, 
  especially 
  those 
  in 
  

   the 
  Grenville 
  areas, 
  are 
  due 
  to 
  other 
  structural 
  features 
  combined 
  

   with 
  rock 
  character. 
  Thus 
  the 
  prominent 
  ridge 
  of 
  gneiss 
  which 
  

   runs 
  several 
  miles 
  southeastward 
  from 
  North 
  Creek 
  is 
  due 
  to 
  the 
  

   fact 
  that 
  a 
  belt 
  of 
  weak 
  limestone 
  everywhere 
  dips 
  sharply 
  under 
  

   the 
  harder 
  rock 
  of 
  the 
  ridge. 
  The 
  ridge 
  south 
  of 
  Valentine 
  pond 
  

   is 
  to 
  be 
  explained 
  in 
  a 
  similar 
  manner. 
  Many 
  small 
  streams 
  in 
  the 
  

   Grenville 
  have 
  developed 
  along 
  structural 
  belts 
  of 
  weakness. 
  

  

  In 
  the 
  igneous 
  rocks, 
  too, 
  there 
  is 
  a 
  notable 
  tendency 
  for 
  local 
  

   short 
  ridges 
  and 
  valleys 
  to 
  develop 
  along 
  lines 
  parallel 
  to 
  the 
  direc- 
  

   tion 
  of 
  foliation. 
  

  

  The 
  most 
  remarkable 
  topographic 
  feature 
  in 
  the 
  whole 
  region 
  

   is 
  the 
  deep, 
  narrow 
  rift 
  between 
  Crane 
  and 
  Huckleberry 
  moun- 
  

   tains, 
  which 
  is 
  certainly 
  due 
  to 
  a 
  combination 
  of 
  faulting, 
  a 
  belt 
  of 
  

   weak 
  Grenville, 
  and 
  some 
  erosion 
  since 
  the 
  faulting. 
  

  

  EXFOLIATION 
  DOMES 
  * 
  

  

  One 
  of 
  the 
  most 
  striking 
  features 
  of 
  the 
  landscape, 
  especially 
  

   in 
  the 
  southern 
  two-thirds 
  of 
  the 
  quadrangle, 
  is 
  the 
  prevalence 
  of 
  

   distinct, 
  isolated, 
  domelike, 
  topographic 
  forms 
  which 
  rise 
  hundreds 
  

  

  1 
  For 
  a 
  fuller 
  discussion 
  of 
  this 
  subject, 
  see 
  paper 
  by 
  the 
  writer 
  in 
  N. 
  Y 
  

   State 
  Mus. 
  Bui. 
  149, 
  p. 
  187-94. 
  

  

  