﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  6l 
  

  

  The 
  sharpness 
  of 
  the 
  contact 
  between 
  the 
  igneous 
  rocks 
  and 
  the 
  

   Grenville 
  and 
  the 
  altitude 
  of 
  the 
  igneous 
  masses 
  above 
  the 
  Gren- 
  

   ville 
  have 
  often 
  been 
  accentuated 
  by 
  the 
  faulting, 
  but 
  in 
  spite 
  of 
  

   this 
  some 
  idea 
  of 
  the 
  irregular 
  surface 
  of 
  the 
  great 
  intrusive 
  mass 
  

   may 
  be 
  gained. 
  Thus, 
  the 
  Grenville 
  between 
  Kelm 
  and 
  County 
  

   House 
  mountains 
  occupies 
  a 
  depression 
  fully 
  300 
  or 
  400 
  feet 
  deep 
  

   in 
  the 
  granite 
  porphyry 
  ; 
  while 
  between 
  Mill 
  and 
  Oven 
  rtiountains 
  

   the 
  Grenville 
  occupies 
  a 
  depression 
  some 
  700 
  or 
  800 
  feet 
  deep 
  in 
  

   the 
  granite. 
  Even 
  if 
  we 
  grant 
  the 
  possibility 
  of 
  some 
  faulting 
  of 
  

   the 
  Pine-Gage 
  mountain 
  mass, 
  it 
  seems 
  clear 
  that 
  this 
  igneous 
  rock 
  

   rose 
  by 
  intrusion 
  some 
  hundreds 
  of 
  feet 
  through 
  the 
  Grenville. 
  

   In 
  spite 
  of 
  the 
  accentuated 
  heights 
  of 
  the 
  igneous 
  masses 
  of 
  Hack- 
  

   ensack, 
  Moon, 
  Heath, 
  Potter, 
  Huckleberry, 
  and 
  Crane 
  mountains, 
  

   it 
  seems 
  necessary 
  to 
  regard 
  a 
  considerable 
  amount 
  of 
  the 
  eleva- 
  

   tion 
  of 
  the 
  igneous 
  rocks 
  above 
  the 
  Grenville 
  as 
  due 
  to 
  the 
  intru- 
  

   sion 
  itself. 
  The 
  only 
  other 
  alternative 
  is 
  the 
  untenable 
  view 
  that 
  

   faults 
  completely 
  surround 
  these 
  igneous 
  bodies. 
  

  

  In 
  general, 
  then, 
  we 
  see 
  that 
  the 
  great 
  intrusive 
  body 
  often 
  

   shows 
  irregularities 
  on 
  its 
  surface 
  which 
  vary 
  in 
  altitude 
  by 
  hun- 
  

   dreds 
  of 
  feet 
  within 
  from 
  1 
  to 
  3 
  or 
  4 
  miles. 
  

  

  TOPOGRAPHY 
  

  

  RELATION 
  OF 
  TOPOGRAPHY 
  TO 
  ROCK 
  CHARACTER 
  

  

  The 
  surface 
  configuration 
  of 
  the 
  North 
  Creek 
  sheet 
  is 
  almost 
  

   perfectly 
  adjusted 
  to 
  rock 
  character. 
  A 
  glance 
  at 
  the 
  geologic 
  

   map 
  will 
  show 
  that 
  the 
  Grenville 
  rocks, 
  with 
  few 
  exceptions, 
  occupy 
  

   the 
  lowlands 
  ; 
  this 
  is 
  because 
  of 
  the 
  relative 
  weakness 
  of 
  those 
  

   rocks 
  as 
  compared 
  with 
  the 
  intrusives. 
  The 
  limestone 
  areas 
  or 
  

   belts, 
  being 
  weakest 
  of 
  all, 
  are 
  invariably 
  found 
  in 
  the 
  valleys, 
  

   and 
  stream 
  courses 
  have 
  commonly 
  developed 
  along 
  such 
  belts. 
  

   Occasionally 
  the 
  more 
  resistant 
  Grenville 
  gneisses, 
  even 
  where 
  un- 
  

   affected 
  by 
  faulting, 
  have 
  stood 
  out 
  fairly 
  well 
  against 
  erosion 
  

   as, 
  for 
  example, 
  south 
  of 
  Valentine 
  pond 
  and 
  south-southwest 
  of 
  

   Thurman. 
  The 
  Grenville 
  quartzite 
  being 
  quite 
  pure 
  and 
  very 
  

   resistant 
  usually 
  stands 
  out 
  fairly 
  conspicuously 
  in 
  the 
  Grenville 
  

   areas. 
  This 
  is 
  well 
  shown 
  in 
  the 
  area 
  south 
  of 
  Warner 
  pond, 
  

   though 
  the 
  height 
  is 
  there 
  accentuated 
  by 
  faulting. 
  The 
  steep 
  

   slope 
  of 
  the 
  quartzite 
  ridge 
  east 
  of 
  Tripp 
  pond 
  appears 
  to 
  be 
  due 
  

   to 
  more 
  rapid 
  wearing 
  away 
  of 
  the 
  much 
  weaker 
  underlying 
  Gren- 
  

   ville. 
  In 
  the 
  mixed 
  gneiss 
  areas, 
  particularly 
  where 
  the 
  Grenville 
  

   is 
  abundant, 
  the 
  topographic 
  development 
  has 
  been 
  very 
  similar 
  

   to 
  that 
  of 
  the 
  Grenville 
  areas. 
  

  

  