﻿110 
  M. 
  E. 
  Wilson 
  — 
  Banded 
  Gneisses 
  of 
  the 
  

  

  southern 
  belt 
  gradually 
  disappear 
  when 
  traced 
  (southward) 
  in 
  

   the 
  direction 
  of 
  the 
  central 
  belt 
  of 
  gneisses. 
  Throughout 
  

   western 
  Quebec 
  and 
  northeastern 
  Ontario, 
  therefore, 
  there 
  is 
  

   everywhere 
  a 
  basal 
  Pre-Carabrian 
  complex, 
  the 
  surface 
  rocks 
  

   of 
  which 
  (sediments 
  and 
  volcanic 
  flows) 
  may 
  be 
  divided 
  

   lithologically 
  into 
  two 
  provinces, 
  a 
  southern 
  limestone 
  belt 
  

   known 
  as 
  the 
  Grenville 
  series, 
  and 
  a 
  northern 
  belt 
  of 
  volcanic 
  

   flows 
  and 
  sediments 
  to 
  which 
  the 
  writer 
  has 
  given 
  the 
  name 
  

   Abitibi 
  group. 
  Between 
  the 
  Grenville 
  series 
  and 
  the 
  Abitibi 
  

   group 
  intervenes 
  the 
  central 
  belt 
  of 
  Lauren 
  tian 
  banded 
  

   gneisses. 
  

  

  Geological 
  investigation 
  throughout 
  the 
  world 
  has 
  shown 
  

   that 
  wherever 
  mountains 
  have 
  been 
  greatly 
  denuded, 
  batho- 
  

   lithic 
  masses 
  of 
  rock 
  are 
  generally 
  found 
  at 
  their 
  centers, 
  and 
  

   since 
  the 
  Lauren 
  tian 
  banded 
  gneisses 
  occur 
  in 
  a 
  central 
  belt 
  

   intervening 
  between 
  belts 
  of 
  folded 
  surface 
  rocks, 
  it 
  is 
  inferred 
  

   that 
  the 
  Laurentian 
  gneissic 
  complex 
  in 
  this 
  locality 
  originally 
  

   formed 
  the 
  core 
  of 
  a 
  Pre-Cambrian 
  mountain 
  chain 
  and 
  con- 
  

   stitutes 
  a 
  geanticlinal 
  axial 
  belt 
  intervening 
  between 
  geosyn- 
  

   clines 
  formed 
  by 
  the 
  rocks 
  of 
  the 
  Abitibi 
  group 
  and 
  the 
  Gren- 
  

   ville 
  series. 
  But 
  denudation 
  was 
  carried 
  to 
  so 
  profound 
  a 
  

   depth 
  in 
  Pre-Cambrian 
  time 
  that 
  not 
  only 
  were 
  all 
  the 
  roof 
  

   rocks 
  stripped 
  from 
  the 
  central 
  geanticlinal 
  mass 
  but 
  the 
  geo- 
  

   synclines 
  were 
  truncated 
  so 
  close 
  to 
  their 
  bottoms 
  that 
  they 
  also 
  

   are 
  intruded 
  by 
  batholiths 
  of 
  granite 
  and 
  gneiss. 
  Adams 
  and 
  

   Barlow 
  have 
  concluded 
  from 
  their 
  areal 
  work 
  in 
  eastern 
  

   Ontario, 
  that 
  these 
  smaller 
  batholiths 
  are. 
  anticlinal 
  in 
  their 
  

   relationship 
  to 
  the 
  Grenville 
  series.* 
  Whether 
  this 
  relation- 
  

   ship 
  also 
  holds 
  in 
  the 
  case 
  of 
  the 
  batholiths 
  intruding 
  the 
  

   Abitibi 
  group 
  is 
  as 
  yet 
  unknown. 
  

  

  It 
  is 
  of 
  historical 
  interest 
  in 
  this 
  connection 
  to 
  note 
  that 
  Logan, 
  

   in 
  his 
  report 
  on 
  the 
  geology 
  of 
  the 
  Ottawa 
  river,t 
  regarded 
  the 
  

   metamorphic 
  series, 
  which 
  he 
  afterwards 
  named 
  Laurentian, 
  

   as 
  forming 
  the 
  axis 
  of 
  an 
  anticlinal 
  arch 
  lying 
  between 
  north- 
  

   ern 
  and 
  southern 
  troughs 
  of 
  Huronian 
  and 
  Paleozoic 
  sediments; 
  

   a 
  conception 
  analogous 
  to 
  that 
  suggested 
  in 
  the 
  foregoing 
  par- 
  

   agraph. 
  The 
  two 
  conceptions 
  differ, 
  however, 
  in 
  that 
  Logan 
  

   assumed 
  the 
  anticlinal 
  relationship 
  to 
  exist 
  between 
  the 
  base- 
  

   ment 
  complex 
  (Laurentian), 
  and 
  the 
  Huronian 
  and 
  Paleozoic 
  

   rocks, 
  whereas 
  in 
  the 
  present 
  paper 
  the 
  anticlinal 
  relationship 
  

   is 
  regarded 
  as 
  existing, 
  not 
  between 
  the 
  basement 
  complex 
  and 
  

   younger 
  series, 
  but 
  within 
  the 
  basement 
  complex 
  itself. 
  

  

  Definition 
  of 
  Laurentian. 
  

  

  The 
  name 
  Laurentian 
  was 
  first 
  used 
  by 
  Sir 
  William 
  Logan 
  

   to 
  designate 
  the 
  great 
  complex 
  of 
  gneisses 
  and 
  associated 
  rocks 
  

  

  * 
  Memoir 
  No. 
  6. 
  G. 
  S. 
  Dept. 
  of 
  Mines, 
  Can., 
  p. 
  16, 
  1910. 
  

   t 
  Ann. 
  Rep. 
  G. 
  S. 
  C, 
  p. 
  40, 
  1845. 
  

  

  