﻿12 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  ville 
  and 
  the 
  syenite. 
  The 
  more 
  resistant 
  syenite 
  here 
  forms 
  a 
  

   high, 
  steep 
  rock-wall 
  on 
  the 
  south 
  side 
  of 
  the 
  river, 
  while 
  the 
  

   less 
  resistant 
  Grenville 
  gneisses 
  have 
  been 
  deeply 
  trenched 
  by 
  

   the 
  river 
  [see 
  pi. 
  2]. 
  Moose 
  river 
  really 
  bears 
  about 
  n. 
  40° 
  e. 
  

   here 
  and 
  parallel 
  to 
  the 
  foliation 
  instead 
  of 
  nearly 
  east 
  and 
  west 
  

   as 
  shown 
  on 
  the 
  map. 
  

  

  In 
  the 
  area 
  east 
  of 
  Fowlersville 
  the 
  Grenville 
  rocks 
  are 
  chiefly 
  

   pyroxene 
  gneisses. 
  The 
  gneissic 
  structure 
  is 
  highly 
  developed 
  

   and 
  accentuated 
  by 
  the 
  alternations 
  of 
  light 
  and 
  dark 
  colored 
  

   bands 
  although 
  none 
  of 
  the 
  rocks 
  are" 
  very 
  dark 
  colored. 
  The 
  

   bands 
  are 
  seldom 
  more 
  than 
  a 
  few 
  inches 
  thick. 
  Microscopic 
  

   investigation 
  shows 
  the 
  common 
  rock 
  to 
  be 
  made 
  up 
  as 
  follows 
  : 
  

   40 
  to 
  Sofc 
  of 
  quartz; 
  25 
  to 
  30;^ 
  of 
  large, 
  bright 
  green, 
  pyroxene 
  

   crystals, 
  sometimes 
  slightly 
  pleochroic; 
  about 
  25,^ 
  of 
  feldspar, 
  

   mostly 
  orthoclase 
  together 
  with 
  a 
  little 
  acid 
  plagioclase; 
  3 
  to 
  5^ 
  

   each 
  of 
  hypersthene 
  and 
  enstatite; 
  and 
  a 
  little 
  bronzite 
  and 
  

   white 
  pyroxene. 
  Judging 
  by 
  the 
  composition 
  the 
  sediments 
  

   from 
  which 
  these 
  rocks 
  were 
  derived 
  were 
  probably 
  shales 
  or 
  

   shaly 
  sandstones 
  possibly 
  somewhat 
  calcareous. 
  These 
  gneisses 
  

   are 
  very 
  similar 
  to 
  those 
  referred 
  to 
  by 
  Smyth 
  as 
  being 
  directly 
  

   associated 
  with 
  limestone. 
  Although 
  no 
  limestone 
  is 
  here 
  seen 
  

   in 
  outcrop, 
  it 
  is 
  possible 
  that 
  some 
  does 
  occur 
  along 
  the 
  east 
  

   side 
  of 
  the 
  area 
  which 
  may 
  thus 
  account 
  for 
  the 
  distinct 
  depres- 
  

   sion 
  (now 
  drift-filled) 
  along 
  that 
  side 
  and 
  from 
  which 
  some 
  

   softer 
  or 
  less 
  resistant 
  material 
  has 
  certainly 
  been 
  removed 
  by 
  

   erosion. 
  Associated 
  with 
  these 
  gneisses 
  are 
  a 
  few 
  layers 
  rich 
  

   in 
  basic 
  plagioclase 
  feldspar 
  and 
  poor 
  in 
  pyroxenes 
  and 
  which 
  

   have 
  the 
  appearance 
  of 
  igneous 
  rocks. 
  This 
  Grenville 
  area 
  forms 
  a 
  

   long, 
  narrow 
  ridge 
  which 
  stands 
  out 
  as 
  a 
  distinct 
  topographic 
  feature. 
  

   Moose 
  river 
  has 
  cut 
  a 
  channel 
  across 
  this 
  ridge. 
  The 
  rocks 
  dip 
  at 
  

   an 
  angle 
  of 
  40° 
  or 
  50° 
  westward 
  and 
  strike 
  almost 
  due 
  north 
  and 
  

   south. 
  Outcrops 
  of 
  syenite 
  have 
  been 
  found 
  on 
  all 
  sides 
  of, 
  and 
  

   pretty 
  close 
  to 
  the 
  Grenville 
  mass. 
  There 
  are 
  no 
  sharp 
  contacts 
  

   visible 
  but 
  it 
  seems 
  certain 
  that 
  we 
  are 
  here 
  dealing 
  with 
  a 
  long, 
  

   narrow 
  inclusion 
  of 
  the 
  Grenville 
  in 
  the 
  syenite. 
  This 
  matter 
  will 
  be 
  

   further 
  discussed 
  below 
  under 
  the 
  heading 
  " 
  Syenite 
  gneiss." 
  

  

  Syenite 
  gneiss 
  

  

  As 
  indicated 
  on 
  the 
  geologic 
  map, 
  syenite 
  gneiss 
  makes 
  up 
  a 
  

   considerable 
  portion 
  of 
  the 
  known 
  Precambric 
  area. 
  From 
  the 
  

   standpoint 
  of 
  both 
  composition 
  and 
  structure 
  it 
  is 
  very 
  uniform 
  

  

  