﻿112 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  structure 
  here 
  is 
  definitely 
  anticHnal, 
  though 
  that 
  is 
  no 
  indica- 
  

   tion 
  of 
  similar 
  structure 
  in 
  the 
  main 
  fold, 
  since 
  minor 
  folds 
  on 
  

   its 
  flanks 
  must 
  consist 
  of 
  both 
  anticlines 
  and 
  synclines. 
  It 
  will 
  

   serve, 
  however, 
  as 
  a 
  sample 
  of 
  many 
  similar 
  exposures 
  in 
  the 
  district 
  

   which 
  show 
  clearly 
  that 
  the 
  series 
  is 
  folded, 
  and 
  that 
  it 
  is 
  closely 
  

   folded. 
  It 
  also 
  well 
  illustrates 
  the 
  closely 
  compressed 
  conditions, 
  

   steep 
  dips, 
  and 
  minor 
  folds 
  which 
  prevail 
  in 
  the 
  vicinity 
  of 
  the 
  

   axis 
  of 
  the 
  supposed 
  fold. 
  

  

  The 
  writer's 
  opinion 
  is 
  that 
  the 
  structure 
  here 
  presented 
  is 
  syn- 
  

   clinal, 
  similar 
  to 
  that 
  depicted 
  in 
  figure 
  7. 
  The 
  discussion, 
  how- 
  

   ever, 
  serves 
  to 
  present 
  the 
  lack 
  of 
  certainty 
  which 
  prevails, 
  and 
  the 
  

   possibility 
  that 
  the 
  structure 
  is 
  of 
  precisely 
  opposite 
  character. 
  

   Either 
  one 
  indicates 
  folding, 
  but 
  one 
  precisely 
  reverses 
  the 
  order 
  

   of 
  rock 
  succession 
  of 
  the 
  other. 
  

  

  It 
  is 
  also 
  thought 
  probable 
  that 
  the 
  heavy 
  quartzite 
  along 
  the 
  

   axis 
  of 
  the 
  supposed 
  fold 
  is 
  the 
  same 
  stratum 
  as 
  the 
  even 
  more 
  

   massive 
  looking 
  quartzite 
  of 
  Grindstone 
  and 
  Wellesley 
  islands. 
  If 
  

   the 
  structure, 
  be 
  synclinal, 
  as 
  supposed, 
  this 
  quartzite 
  is 
  the 
  youngest 
  

   Grenville 
  formation 
  of 
  the 
  mapped 
  district, 
  but 
  if 
  anticlinal 
  it 
  is 
  

   the 
  oldest. 
  If 
  these 
  two 
  quartzite 
  belts 
  do 
  represent 
  lines 
  of 
  out- 
  

   crop 
  of 
  the 
  same 
  quartzite 
  formation, 
  there 
  should 
  be 
  an 
  addi- 
  

   tional 
  line 
  of 
  outcrop 
  of 
  the 
  thick 
  limestone 
  somewhere 
  between 
  the 
  

   two, 
  in 
  the 
  near 
  vicinity 
  of 
  the 
  river. 
  This 
  does 
  not 
  appear 
  but 
  

   its 
  absence 
  is 
  not 
  a 
  fatal 
  objection 
  to 
  this 
  interpretation 
  of 
  the 
  

   structure, 
  since 
  the 
  Grenville 
  rocks 
  there 
  have 
  been 
  completely 
  cut 
  

   out 
  by 
  the 
  granite 
  of 
  the 
  Alexandria 
  bathylith, 
  and 
  it 
  is 
  impossible 
  

   to 
  say 
  what 
  may 
  have 
  originally 
  been 
  there. 
  

  

  In 
  summation 
  it 
  may 
  be 
  said 
  that 
  the 
  Grenville 
  rocks 
  are 
  greatly 
  

   tilted, 
  suggesting 
  strongly 
  compressive 
  folding, 
  and 
  frequent 
  small 
  

   folds 
  occur. 
  Two 
  belts 
  of 
  thick 
  limestone 
  and 
  two 
  of 
  thick 
  quart- 
  

   zite 
  suggest 
  a 
  single 
  formation 
  of 
  each 
  in 
  folded 
  condition. 
  Study 
  

   of 
  the 
  dips 
  suggests 
  that 
  this 
  folding 
  is 
  of 
  a 
  certain 
  type, 
  but 
  it 
  is 
  

   possible 
  that, 
  owing 
  to 
  very 
  intense 
  compression, 
  the 
  structure 
  is 
  

   just 
  the 
  reverse 
  of 
  that 
  suggested. 
  It 
  has 
  not 
  proved 
  possible 
  to 
  

   determine 
  the 
  order 
  of 
  succession 
  of 
  the 
  various 
  formations 
  com- 
  

   posing 
  the 
  Grenville, 
  and 
  to 
  use 
  that 
  succession 
  a^ 
  the 
  key 
  for 
  un- 
  

   raveling 
  the 
  structure, 
  as 
  is 
  .the 
  usual 
  method 
  in 
  folded 
  rocks. 
  

   Instead 
  the 
  attempt 
  has 
  been- 
  made 
  to 
  decipher 
  the 
  structure 
  and 
  

   from 
  that 
  to 
  determine 
  the 
  order 
  of 
  succession, 
  but 
  with 
  only 
  

   indifferent 
  success. 
  . 
  

  

  Paleozoic 
  folding. 
  While 
  the 
  Paleozoic 
  rocks 
  of 
  the 
  -district 
  

   show 
  but 
  a 
  trifling 
  amount 
  of 
  folding, 
  it 
  is 
  of 
  interesting 
  nature 
  

  

  