﻿2.6 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  In 
  New 
  York 
  then 
  the 
  Keewatin 
  volcanics 
  are 
  wholly 
  absent, 
  

   except 
  for 
  the 
  possibility 
  that 
  some 
  of 
  the 
  amphibolite 
  inclusions 
  

   of 
  the 
  granite 
  gneiss 
  may 
  be 
  greenstone 
  fragments 
  considerably 
  

   metamorphosed. 
  OtherAvise 
  the 
  Grenville 
  sediments 
  are 
  the 
  

   oldest 
  recognized 
  rocks, 
  and 
  they 
  occur 
  in 
  patches 
  or 
  in 
  belts 
  of 
  

   varying 
  size 
  and 
  extent, 
  resting 
  on, 
  surrounded 
  by, 
  and 
  all 
  cut 
  

   to 
  pieces 
  by 
  the 
  granite 
  gneiss 
  and 
  the 
  yet 
  later 
  intrusions. 
  

  

  Grenville 
  rocks. 
  These 
  rocks 
  as 
  originally 
  deposited 
  con- 
  

   sisted 
  of 
  limestones, 
  shales 
  and 
  sandstones, 
  both 
  pure 
  and 
  in 
  

   their 
  various 
  transitional 
  phases. 
  In 
  all 
  probability 
  too 
  there 
  was 
  

   some 
  intermingled 
  volcanic 
  material, 
  though 
  the 
  presence 
  of 
  such 
  

   material 
  has 
  never 
  been 
  definitely 
  proved 
  for 
  the 
  New 
  York 
  

   Grenville. 
  The 
  rocks 
  have 
  been 
  profoundly 
  changed 
  in 
  char- 
  

   acter 
  since 
  their 
  formation, 
  in 
  part 
  owing 
  to 
  great 
  compressive 
  

   stresses 
  w^hich 
  operated 
  throughout 
  the 
  district, 
  and 
  in 
  part 
  

   owing 
  to 
  the 
  heat 
  and 
  pressure 
  furnished 
  by 
  the 
  great 
  igneous 
  

   intrusions, 
  and 
  also 
  to 
  the 
  mineralizing 
  agents 
  to 
  which 
  these 
  

   ^ave 
  rise. 
  These 
  changes 
  moreover 
  were 
  brought 
  about 
  early 
  in 
  

   Precambric 
  time 
  and 
  under 
  deep-seated 
  conditions. 
  As 
  found 
  

   today 
  the 
  rocks 
  are 
  wholly 
  crystalline, 
  having 
  completely 
  

   recrystallized 
  under 
  the 
  severe 
  conditions 
  to 
  which 
  they 
  Avere 
  

   subjected, 
  with 
  loss 
  of 
  all 
  traces 
  of 
  their 
  original 
  clastic 
  textures. 
  

   In 
  their 
  stead 
  there 
  has 
  been 
  developed 
  a 
  cleavage, 
  or 
  foliation, 
  

   due 
  to 
  parallel 
  arrangement 
  of 
  the 
  mineral 
  particles 
  on 
  recrystal- 
  

   lization. 
  The 
  old 
  bedding 
  planes 
  of 
  the 
  rocks 
  can 
  still 
  be 
  made 
  

   out, 
  however, 
  in 
  places 
  where 
  the 
  composition 
  of 
  the 
  original 
  

   rocks 
  changed, 
  as 
  where 
  limestone 
  was 
  succeeded 
  by 
  shale 
  or 
  

   by 
  sandstone, 
  and 
  from 
  these 
  old 
  bedding 
  planes 
  it 
  can 
  be 
  seen 
  

   that 
  the 
  development 
  of 
  the 
  foliation 
  is 
  parallel 
  in 
  direction 
  to 
  

   them. 
  The 
  original 
  limestones 
  have 
  become 
  coarse, 
  white 
  

   crystalline 
  limestone 
  or 
  marble, 
  the 
  sandstones 
  are 
  now 
  hard, 
  

   glassy 
  quartzites, 
  while 
  the 
  shales 
  and 
  impure 
  limestones 
  and 
  

   sandstones 
  have 
  become 
  schists 
  and 
  gneisses 
  of 
  many 
  types, 
  

   while 
  yet 
  other 
  varieties 
  are 
  contact 
  rocks 
  whose 
  nature 
  is 
  due 
  

   to 
  action 
  of 
  the 
  intrusives 
  upon 
  adjacent 
  sediments. 
  The 
  variety 
  

   of 
  rocks 
  is 
  so 
  great 
  that 
  it 
  would 
  be 
  a 
  hopeless 
  task 
  to 
  attempt 
  

   to 
  map 
  them 
  all 
  upon 
  any 
  such 
  scale 
  as 
  that 
  of 
  the 
  maps 
  which 
  

   accompany 
  this 
  report. 
  One 
  or 
  more 
  beds 
  of 
  very 
  thick 
  lime- 
  

   stone 
  occur, 
  such 
  as 
  that 
  along 
  the 
  Indian 
  river 
  northward 
  from 
  

   Theresa, 
  or 
  that 
  along 
  Butterfield 
  lake; 
  thick 
  quartzites 
  also 
  

   occur, 
  especially 
  on 
  Grindstone 
  and 
  Wellesley 
  islands; 
  a 
  large 
  

   thickness 
  of 
  green 
  schists 
  of 
  a 
  peculiar 
  type 
  is 
  found 
  to 
  the 
  south 
  

  

  