﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  27 
  

  

  and 
  southwest 
  of 
  Alexandria 
  Bay. 
  But 
  the 
  bulk 
  of 
  the 
  Grenville 
  

   of 
  the 
  district 
  occurs 
  as 
  a 
  great 
  schist 
  series, 
  with 
  rather 
  rapid 
  

   alterations 
  of 
  varying 
  types 
  in 
  bands 
  of 
  no 
  great 
  thickness, 
  and 
  

   interbanded 
  with 
  these 
  are 
  thin 
  limestones 
  and 
  quartzites. 
  After 
  

   trial 
  of 
  various 
  methods 
  it 
  was 
  found 
  that, 
  on 
  a 
  map 
  of 
  this 
  scale, 
  

   and 
  with 
  rocks 
  of 
  this 
  rapidly 
  varying 
  character, 
  no 
  further 
  

   subdivision 
  of 
  the 
  Grenville 
  was 
  possible 
  than 
  a 
  separate 
  map- 
  

   ping 
  of 
  the 
  thicker 
  limestone 
  and 
  quartzite 
  beds, 
  the 
  entire 
  

   remainder 
  being 
  mapped 
  singly 
  as 
  a 
  schist 
  formation. 
  It 
  is 
  

   feared 
  that 
  even 
  this 
  amount 
  of 
  subdivision 
  has 
  resulted 
  in 
  a 
  

   map 
  too 
  complicated 
  for 
  easy 
  use. 
  

  

  It 
  was 
  hoped 
  that 
  the 
  careful, 
  detailed 
  mapping 
  attempted 
  

   might 
  solve 
  the 
  problem 
  of 
  the 
  order 
  of 
  superposition 
  of 
  the 
  rocks 
  

   and 
  give 
  some 
  definite 
  idea 
  of 
  the 
  thickness 
  of 
  the 
  whole. 
  The 
  

   outcome 
  was 
  disappointing 
  and 
  neither 
  hope 
  distinctly 
  fulfilled, 
  

   though 
  some 
  results 
  were 
  obtained. 
  The 
  mapping 
  therefore 
  is 
  

   purely 
  lithological 
  and 
  not 
  on 
  a 
  structural 
  basis, 
  as 
  it 
  was 
  

   endeavored 
  to 
  make 
  it.^ 
  

  

  The 
  average 
  trend, 
  or 
  strike, 
  of 
  the 
  Grenville 
  rocks 
  is 
  to 
  the 
  

   northeast. 
  The 
  direction 
  to 
  be 
  sure 
  varies 
  considerably, 
  swinging 
  

   around 
  to 
  the 
  north 
  on 
  the 
  one 
  hand, 
  and 
  to 
  the 
  east 
  or 
  even 
  some- 
  

   what 
  to 
  the 
  south 
  of 
  east 
  on 
  the 
  other, 
  yet 
  these 
  variations 
  are 
  not 
  

   sufficiently' 
  frequent 
  to 
  offset 
  the 
  general 
  statement. 
  The 
  dips 
  are 
  

   usually 
  high, 
  seldom 
  less 
  than 
  45° 
  and 
  frequently 
  very 
  steep 
  or 
  

   even 
  vertical 
  [pi. 
  i, 
  2]. 
  Over 
  the 
  greater 
  part 
  of 
  the 
  area 
  north 
  

   dips 
  prevail, 
  but 
  are 
  replaced 
  by 
  south 
  dips 
  throughout 
  a 
  belt 
  of 
  

   country 
  from 
  2 
  to 
  3 
  miles 
  broad 
  across 
  the 
  Alexandria 
  quadrangle. 
  

   This 
  is 
  certainly 
  indicative 
  of 
  folding 
  of 
  large 
  magnitude, 
  and 
  is 
  

   corroborated 
  by 
  the 
  fact 
  that 
  in 
  many 
  localities 
  minor 
  folds 
  are 
  

   clearly 
  to 
  be 
  made 
  out, 
  and 
  intricate 
  minor 
  puckering 
  and 
  corruga- 
  

   tion. 
  Of 
  the 
  two 
  broad 
  limestone 
  belts 
  within 
  the 
  map 
  limits, 
  the 
  

   one 
  along 
  the 
  Indian 
  river 
  north 
  of 
  Theresa, 
  and 
  the 
  one 
  about 
  

   Butterfield 
  lake, 
  the 
  former 
  has 
  a 
  north, 
  and 
  the 
  latter 
  a 
  south 
  dip, 
  

   and 
  in 
  each 
  case 
  the 
  breadth 
  of 
  outcrop 
  across 
  the 
  strike 
  is 
  about 
  

   a 
  mile. 
  With 
  the 
  steep 
  dips 
  a 
  thickness 
  of 
  about 
  4000 
  feet 
  is 
  in- 
  

   dicated 
  for 
  this 
  limestone 
  in 
  each 
  case, 
  and 
  it 
  is 
  therefore 
  conjec- 
  

   tured 
  to 
  be 
  the 
  same 
  thick 
  stratum, 
  with 
  the 
  structure 
  synclinal. 
  If 
  

   this 
  be 
  the 
  true 
  interpretation 
  then 
  the 
  complex 
  of 
  quartzite 
  and 
  

  

  1 
  Though 
  the 
  work 
  was 
  of 
  vastly 
  more 
  detailed 
  character 
  than 
  the 
  earlier 
  

   work 
  of 
  Smyth 
  on 
  the 
  same 
  rocks, 
  it 
  will 
  be 
  seen 
  by 
  any 
  one 
  who 
  will 
  take 
  

   the 
  trouble 
  to 
  compare 
  the 
  two 
  maps 
  that 
  the 
  basis 
  for 
  the 
  subdivision 
  of 
  

   the 
  Grenville 
  is 
  sulDstantially 
  the 
  same 
  in 
  each 
  case. 
  No 
  more 
  convincing 
  

   testimony 
  could 
  be 
  given 
  as 
  to 
  the 
  high 
  class 
  character 
  of 
  Smyth's 
  work. 
  

  

  