﻿5& 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  As 
  shown 
  on 
  the 
  map, 
  short 
  faults 
  are 
  suggested 
  at 
  the 
  eastern 
  

   base 
  of 
  Mill 
  mountain, 
  the 
  western 
  base 
  of 
  Stockton 
  mountain, 
  and 
  

   the 
  northern 
  base 
  of 
  Wolf 
  pond 
  mountain. 
  Except 
  for 
  some 
  evi- 
  

   dence 
  of 
  shearing 
  on 
  the 
  side 
  of 
  Stockton 
  mountain, 
  the 
  only 
  evi- 
  

   dence 
  for 
  these 
  faults 
  is 
  topographic, 
  it 
  being 
  difficult 
  to 
  account 
  

   for 
  these 
  steep 
  scarps 
  except 
  on 
  the 
  basis 
  of 
  faulting. 
  

  

  The 
  writer 
  believes 
  it 
  quite 
  likely 
  that 
  other, 
  chiefly 
  minor, 
  faults 
  

   occur 
  within 
  the 
  quadrangle, 
  but 
  the 
  ones 
  above 
  described 
  are 
  the 
  

   only 
  ones 
  he 
  feels 
  justified 
  in 
  representing 
  on 
  the 
  geologic 
  map 
  as 
  

   actually 
  or 
  very 
  probably 
  present. 
  

  

  FOLIATION 
  

  

  All 
  the 
  rocks 
  except 
  the 
  diabase 
  and 
  pegmatite 
  show 
  more 
  or 
  less 
  

   of 
  the 
  foliated 
  structure. 
  It 
  is 
  best 
  seen 
  in 
  the 
  Grenville 
  gneisses 
  

   which 
  are 
  commonly 
  distinctly 
  banded 
  due 
  to 
  differences 
  in 
  the 
  

   composition 
  of 
  the 
  beds, 
  the 
  foliation 
  so 
  far 
  as 
  observed 
  always 
  

   being 
  parallel 
  to 
  the 
  bedding. 
  The 
  syenite, 
  granite, 
  and 
  granite 
  

   porphyry 
  are 
  always 
  gneissoid 
  but 
  never 
  distinctly 
  banded, 
  the 
  

   structure 
  being 
  accentuated 
  by 
  a 
  drawing 
  or 
  flattening 
  out 
  of 
  the 
  

   dark 
  colored 
  minerals 
  parallel 
  to 
  the 
  foliation. 
  The 
  more 
  basic 
  

   pyroxene 
  and 
  hornblende 
  syenites 
  are, 
  as 
  a 
  rule, 
  not 
  very 
  gneissoid, 
  

   as, 
  for 
  example, 
  the 
  Bull 
  Rock 
  mountain 
  syenite. 
  In 
  fact 
  it 
  may 
  be 
  

   stated 
  as 
  a 
  very 
  general 
  rule 
  that 
  the 
  more 
  basic, 
  even 
  and 
  medium 
  

   grained 
  rocks 
  of 
  the 
  syenite-granite 
  series 
  are 
  least 
  gneissoid 
  ; 
  while 
  

   the 
  more 
  acid 
  rocks 
  carrying 
  hornblende 
  and 
  some 
  biotite 
  are 
  

   clearly 
  gneissoid 
  ; 
  and 
  the 
  most 
  acid 
  rocks 
  rich 
  in 
  quartz 
  and 
  

   biotite 
  are 
  very 
  gneissoid. 
  In 
  these 
  last 
  named 
  rocks 
  the 
  very 
  

   presence 
  of 
  biotite 
  flakes 
  and 
  the 
  tendency 
  of 
  the 
  quartz 
  to 
  be- 
  

   come 
  flattened 
  favor 
  the 
  development 
  of 
  the 
  foliated 
  structure. 
  

   Again, 
  it 
  often 
  happens 
  that 
  when 
  members 
  of 
  the 
  great 
  intrusive 
  

   series, 
  especially 
  the 
  granites, 
  are 
  close 
  to 
  the 
  Grenville 
  the 
  rocks 
  

   are 
  more 
  gneissoid. 
  Thus, 
  at 
  the 
  top 
  of 
  Heath 
  mountain 
  the 
  pink 
  

   granite 
  is 
  rather 
  poorly 
  gneissoid 
  while 
  at 
  the 
  base 
  of 
  the 
  mountain 
  

   it 
  is 
  very 
  gneissoid. 
  

  

  The 
  typical 
  basic 
  gabbro 
  stocks 
  seldom 
  show 
  a 
  gneissoid 
  struc- 
  

   ture 
  except 
  rather 
  often 
  in 
  the 
  narrow 
  amphibolite 
  borders. 
  Some 
  

   of 
  the 
  more 
  acid 
  stocks 
  are 
  clearly 
  gneissoid. 
  

  

  An 
  interesting 
  feature 
  is 
  the 
  common 
  occurrence 
  of 
  rapid 
  changes 
  

   in 
  degree 
  of 
  foliation 
  even 
  within 
  the 
  same 
  rock 
  ledge. 
  Thus, 
  just 
  

   west 
  of 
  The 
  Glen 
  (on 
  the 
  mountain 
  side) 
  there 
  are 
  big 
  ledges 
  of 
  

  

  