﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  i) 
  

  

  Pregrenville 
  masses 
  were 
  either 
  engulfed 
  by 
  the 
  later 
  great 
  in- 
  

   trusions 
  or 
  that 
  they 
  were 
  changed 
  beyond 
  recognition. 
  

  

  Areal 
  distribution 
  of 
  the 
  Grenville. 
  About 
  four-ninths 
  of 
  the 
  

   surface 
  rock 
  of 
  the 
  quadrangle 
  is 
  Grenville, 
  provided 
  we 
  include 
  

   the 
  Grenville 
  which 
  makes 
  up 
  considerable 
  portions 
  of 
  the 
  areas 
  of 
  

   mixed 
  gneisses. 
  It 
  should 
  be 
  noted 
  that 
  the 
  Grenville 
  here 
  as- 
  

   sumes 
  much 
  more 
  prominence 
  than 
  is 
  usually 
  the 
  case 
  in 
  the 
  Adi- 
  

   rondacks. 
  Also, 
  as 
  the 
  accompanying 
  map 
  shows, 
  the 
  Grenville 
  

   is 
  very 
  widespread 
  in 
  its 
  distribution, 
  it 
  being 
  least 
  prominently 
  

   developed 
  in 
  the 
  central 
  and 
  northern 
  portions. 
  A 
  striking 
  feature 
  

   is 
  the 
  " 
  patchy 
  " 
  character 
  of 
  its 
  distribution, 
  this 
  being 
  due 
  to 
  

   the 
  very 
  irregular 
  manner 
  in 
  which 
  the 
  great 
  igneous 
  intrusions 
  

   broke 
  through 
  and 
  cut 
  to 
  pieces 
  the 
  Grenville 
  strata. 
  

  

  The 
  three 
  types 
  of 
  Grenville 
  which 
  are 
  sufficiently 
  different 
  to 
  

   allow 
  of 
  separate 
  representation 
  on 
  the 
  geologic 
  map 
  are: 
  

  

  i 
  Crystalline 
  limestone 
  which 
  is 
  generally 
  associated 
  with 
  dark 
  

   hornblende 
  gneiss, 
  this 
  latter 
  rock 
  often 
  being 
  garnetiferous. 
  

  

  2 
  Quartzite 
  in 
  thin 
  to 
  thick 
  beds 
  and 
  usually 
  more 
  or 
  less 
  inter- 
  

  

  bedded 
  with 
  thin 
  layers 
  of 
  biotite 
  gneiss 
  or 
  sometimes 
  a 
  little 
  

   limestone. 
  

  

  3 
  Other 
  gneisses, 
  chiefly 
  gray 
  feldspar-garnet 
  or 
  dark 
  gray 
  biotite- 
  

  

  garnet-feldspar 
  or 
  white 
  feldspar-gneiss. 
  Occasionally 
  a 
  

   little 
  limestone, 
  quartzite, 
  or 
  hornblende-gneiss 
  may 
  occur 
  

   closely 
  associated, 
  especially 
  where 
  the 
  glacial 
  drift 
  is 
  heavy. 
  

  

  The 
  largest 
  area 
  of 
  Grenville 
  occupies 
  the 
  western 
  portion 
  of 
  

   the 
  quadrangle 
  and 
  by 
  far 
  the 
  greater 
  part 
  of 
  it 
  consists 
  of 
  lime- 
  

   stone 
  and 
  its 
  associated 
  hornblende 
  gneisses. 
  A 
  considerable 
  area 
  

   of 
  quartzite 
  lies 
  south 
  of 
  Sodom 
  and 
  a 
  smaller 
  one 
  east 
  of 
  Little 
  

   mountain. 
  The 
  only 
  distinct 
  area 
  of 
  mica-feldspar 
  gneiss 
  covers 
  a 
  

   few 
  square 
  miles 
  south 
  of 
  Thurman. 
  

  

  Toward 
  the 
  southeast 
  occur 
  two 
  irregular 
  shaped 
  areas 
  of 
  Gren- 
  

   ville 
  which 
  are 
  almost 
  entirely 
  made 
  up 
  of 
  limestone 
  and 
  associated 
  

   hornblende-garnet 
  gneiss, 
  the 
  limestone 
  being 
  especially 
  thick 
  and 
  

   well 
  shown 
  in 
  outcrops 
  just 
  west 
  of 
  the 
  Potter-Birch 
  mountain 
  

   ridge. 
  

  

  The 
  large 
  and 
  very 
  irregular 
  shaped 
  area 
  along 
  the 
  eastern 
  side 
  

   of 
  the 
  sheet 
  consists 
  mostly 
  of 
  various 
  gneisses 
  with 
  one 
  consider- 
  

   able 
  area 
  of 
  quartzite 
  south 
  of 
  Pottersville 
  and 
  another 
  east 
  of 
  

   Chase 
  mountain. 
  The 
  only 
  mappable 
  limestone 
  belt 
  there 
  is 
  a 
  small 
  

   one 
  extending 
  eastward 
  from 
  Valentine 
  pond. 
  

  

  