﻿M. 
  E. 
  Wilson 
  — 
  Laurentian 
  Highlands 
  of 
  Canada. 
  109 
  

  

  Art. 
  XII. 
  — 
  The 
  Banded 
  Gneisses 
  of 
  the 
  Laurentian 
  High- 
  

   lands 
  of 
  Canada 
  ; 
  by 
  Morley 
  E. 
  Wilson. 
  

  

  Introduction. 
  

  

  The 
  larger 
  part 
  of 
  the 
  Pre-Cambrian 
  oldland 
  of 
  northeastern 
  

   Canada 
  is 
  composed 
  of 
  a 
  complex 
  of 
  banded 
  gneisses, 
  which, 
  in 
  

   accordance 
  with 
  the 
  designation 
  of 
  Sir 
  William 
  Logan, 
  is 
  

   generally 
  called 
  Laurentian. 
  It 
  is 
  now 
  generally 
  believed 
  that 
  

   these 
  gneisses, 
  for 
  the 
  most 
  part, 
  originally 
  constituted 
  huge 
  

   batholithic 
  masses 
  of 
  magma 
  and 
  that 
  the 
  foliated 
  structures 
  

   which 
  they 
  possess 
  originated 
  as 
  a 
  result 
  of 
  deformation. 
  But 
  

   the 
  investigation 
  of 
  the 
  origin 
  and 
  structures 
  of 
  the 
  gneissic 
  

   complex 
  has 
  not 
  been 
  carried 
  beyond 
  these 
  generalizations. 
  

  

  During 
  the 
  summer 
  of 
  1912, 
  in 
  making 
  a 
  geological 
  recon- 
  

   naissance 
  across 
  the 
  Laurentian 
  highlands 
  of 
  Quebec, 
  an 
  

   opportunity 
  was 
  afforded 
  the 
  writer 
  to 
  study 
  the 
  Laurentian 
  

   banded 
  gneisses 
  in 
  some 
  detail, 
  and 
  to 
  collect 
  additional 
  data 
  

   bearing 
  on 
  their 
  mode 
  of 
  origin 
  and 
  their 
  relationship 
  to 
  the 
  

   structural 
  history 
  of 
  the 
  Laurentian 
  plateau. 
  In 
  the 
  following 
  

   pages 
  is 
  embodied 
  a 
  brief 
  account 
  of 
  this 
  investigation. 
  

  

  Geological 
  Relationships 
  of 
  the 
  Banded 
  Gneisses. 
  

  

  The 
  Pre-Cambrian 
  rocks 
  occurring 
  in 
  northeastern 
  Ontario 
  

   and 
  western 
  Quebec 
  may 
  be 
  divided 
  stratigraphically 
  into 
  two 
  

   strikingly 
  different 
  divisions 
  : 
  an 
  older 
  complex 
  and 
  a 
  younger 
  

   group 
  of 
  slightly 
  disturbed 
  Huronian 
  sediments 
  which 
  occur 
  as 
  

   erosion 
  remnants 
  scattered 
  here 
  and 
  there 
  over 
  the 
  surface 
  of 
  

   the 
  basement 
  upon 
  which 
  they 
  were 
  deposited. 
  Since 
  the 
  

   banded 
  gneisses 
  are 
  confined 
  entirely 
  to 
  the 
  basement 
  complex, 
  

   it 
  is 
  their 
  relationship 
  to 
  the 
  other 
  rocks 
  of 
  that 
  division 
  of 
  

   the 
  Pre-Cambrian 
  that 
  is 
  of 
  special 
  interest 
  in 
  this 
  connection. 
  

  

  Near 
  the 
  southern 
  border 
  of 
  the 
  Laurentian 
  plateau 
  the 
  

   banded 
  gneisses 
  have 
  their 
  greatest 
  development 
  in 
  a 
  wide 
  belt 
  

   which 
  extends 
  continuously 
  from 
  Georgian 
  bay 
  to 
  the 
  Gulf 
  of 
  

   St. 
  Lawrence. 
  To 
  the 
  south 
  of 
  this 
  belt, 
  the 
  gneisses 
  intrude 
  

   and 
  include 
  bands 
  and 
  masses 
  of 
  crystalline 
  limestone 
  and 
  other 
  

   sediments, 
  the 
  masses 
  and 
  bands 
  gradually 
  decreasing 
  in 
  size 
  

   and 
  number 
  towards 
  the 
  north 
  until 
  finally 
  replaced 
  entirely 
  

   by 
  the 
  banded 
  gneisses. 
  To 
  the 
  north 
  of 
  the 
  gneissic 
  belt, 
  in 
  

   the 
  vicinity 
  of 
  Lake 
  Timiskaming 
  and 
  extending 
  westward 
  to 
  

   the 
  north 
  shore 
  of 
  Lake 
  Huron 
  and 
  eastward 
  to 
  Lake 
  Mis- 
  

   tassini, 
  a 
  belt 
  of 
  volcanic 
  flows 
  and 
  sediments 
  occur 
  in 
  the 
  base- 
  

   ment 
  complex 
  which 
  like 
  the 
  sediments 
  of 
  the 
  southern 
  belt 
  

   are 
  intruded 
  by 
  granite 
  and 
  gneiss 
  and 
  like 
  the 
  sediments 
  of 
  the 
  

  

  