﻿Chapter 
  3 
  

   PRECAMBRIC 
  HISTORY 
  

  

  THE 
  GRENVILLE 
  FORMATION 
  

  

  In 
  the 
  Adirondack 
  mountains, 
  and 
  also 
  probably 
  in 
  the 
  Highlands- 
  

   of-the-Hudson, 
  we 
  have 
  the 
  earliest 
  known 
  records 
  of 
  the 
  physical 
  

   history 
  of 
  New 
  York 
  State. 
  These 
  records 
  are 
  written 
  in 
  a 
  series 
  

   of 
  rocks 
  named 
  the 
  Grenville, 
  so 
  called 
  from 
  a 
  town 
  in 
  Canada 
  

   where 
  the 
  rocks 
  were 
  first 
  well 
  known. 
  The 
  Grenville 
  is 
  of 
  in- 
  

   terest, 
  not 
  only 
  because 
  it 
  is 
  the 
  most 
  ancient 
  rock 
  formation 
  so 
  far 
  

   discovered 
  in 
  New 
  York, 
  but 
  also 
  because 
  it 
  takes 
  rank 
  among 
  the 
  

   very 
  oldest 
  rock 
  formations 
  of 
  the 
  earth. 
  

  

  Until 
  about 
  fifteen 
  or 
  twenty 
  years 
  ago 
  the 
  real 
  significance 
  of 
  the 
  

   Grenville 
  and 
  its 
  closely 
  associated 
  rocks 
  in 
  the 
  Adirondacks 
  was 
  

   not 
  recognized, 
  but 
  now 
  many 
  of 
  the 
  leading 
  events 
  of 
  that 
  very 
  

   early 
  history 
  are 
  established. 
  As 
  in 
  human 
  history, 
  "so 
  in 
  earth 
  

   history, 
  the 
  earliest 
  records 
  are 
  the 
  most 
  obscure 
  and 
  difficult 
  to 
  

   read 
  and, 
  in 
  the 
  one 
  as 
  in 
  the 
  other, 
  it 
  is 
  easy 
  to 
  pass 
  from 
  con- 
  

   clusions 
  properly 
  based 
  upon 
  facts 
  to 
  mere 
  speculations. 
  Many 
  

   problems 
  regarding 
  the 
  Precambric 
  history 
  of 
  our 
  State 
  yet 
  remain 
  

   to 
  be 
  solved, 
  but 
  in 
  these 
  pages 
  it 
  is 
  rather 
  the 
  purpose 
  to 
  describe 
  

   only 
  those 
  historical 
  eventsi 
  which 
  have 
  been 
  well 
  established. 
  

  

  The 
  Grenville 
  consists 
  of 
  a 
  great 
  series 
  of 
  marine 
  water-laid 
  rocks 
  

   which 
  are 
  clearly 
  older 
  than 
  the 
  Paleozoic 
  because 
  these 
  latter 
  rest 
  

   upon 
  the 
  Grenville 
  in 
  many 
  places. 
  As 
  will 
  be 
  shown 
  below, 
  the 
  

   Grenville 
  strata 
  have 
  been 
  so 
  profoundly 
  changed 
  from 
  their 
  origi- 
  

   nal 
  condition 
  that 
  certain 
  of 
  the 
  highly 
  sedimentary 
  features 
  have 
  

   been 
  obliterated. 
  Thus 
  the 
  absence 
  of 
  water-worn 
  particles 
  and 
  

   fossil 
  shells, 
  both 
  of 
  which 
  are 
  so 
  characteristic 
  of 
  sedimentary 
  de- 
  

   posits, 
  is 
  due 
  to 
  complete 
  crystallization 
  (metamorphism) 
  of 
  the 
  

   Grenville 
  strata 
  since 
  their 
  formation. 
  Nevertheless 
  we 
  have 
  cer- 
  

   tain 
  proofs 
  of 
  the 
  sedimentary 
  origin 
  of 
  the 
  Grenville. 
  The 
  fact 
  

   that 
  these 
  rocks 
  commonly 
  occur 
  in 
  alternating 
  layers, 
  which 
  stand 
  

   out 
  in 
  sharp 
  contrast 
  because 
  of 
  marked 
  difference 
  in 
  composition 
  

   and 
  color, 
  furnishes 
  strong 
  evidence 
  that 
  this 
  distinct 
  banded 
  effect 
  

   is 
  due 
  to 
  differences 
  in 
  original 
  sedimentation. 
  A 
  great 
  mass 
  of 
  

   igneous 
  rock 
  is 
  generally 
  characterized 
  Iby 
  homogeneity 
  throughout 
  ; 
  

   a 
  mass 
  of 
  typical 
  sediments, 
  on 
  the 
  other 
  hand, 
  is 
  arranged 
  in 
  dis- 
  

   tinct 
  layers, 
  such 
  as 
  shale, 
  sandstone, 
  or 
  limestone 
  which 
  show 
  fre- 
  

   quent 
  differences 
  in 
  composition. 
  In 
  the 
  Grenville, 
  especially 
  of 
  

  

  [29] 
  

  

  