﻿44 
  A: 
  C. 
  Lane 
  — 
  Lawsorts 
  Correlation 
  of 
  

  

  But 
  if 
  there 
  was 
  the 
  wide 
  continental 
  glaciation 
  for 
  which 
  

   Coleman 
  and 
  Howe 
  have 
  argued, 
  or 
  if 
  there 
  was 
  a 
  progressive 
  

   change 
  in 
  the 
  composition 
  of 
  the 
  atmosphere 
  and 
  the 
  ocean 
  

   recognizable 
  in 
  the 
  character 
  of 
  the 
  rocks 
  as 
  I 
  have 
  argued, 
  

   these 
  are 
  of 
  as 
  wide 
  range 
  as 
  his 
  granites 
  can 
  be. 
  

  

  Let 
  me 
  then 
  call 
  attention 
  to 
  certain 
  features 
  of 
  Lawson's 
  

   correlation 
  table. 
  

  

  (1) 
  Outside 
  the 
  Couchiching 
  (which 
  occurs 
  in 
  only 
  one 
  of 
  

   the 
  15 
  columns, 
  and 
  part 
  of 
  which 
  as 
  originally 
  defined 
  he 
  no 
  

   longer 
  so 
  classes) 
  the 
  oldest 
  formation 
  is 
  the 
  Keewatin, 
  a 
  

   formation 
  largely 
  of 
  volcanics 
  and 
  volcanic 
  sediments, 
  and 
  

   markedly 
  devoid 
  of 
  rocks 
  that 
  show 
  primary 
  oxidation 
  (red) 
  or 
  

   carbonaceous 
  slates, 
  or 
  that 
  concentration 
  of 
  certain 
  elements 
  

   which 
  Russell 
  has 
  emphasized 
  as 
  one 
  of 
  the 
  great 
  processes 
  

   of 
  geology 
  and 
  weathering 
  under 
  present 
  conditions. 
  On 
  the 
  

   whole 
  they 
  deserve 
  the 
  name 
  " 
  Greenstone 
  schists 
  " 
  applied 
  to 
  

   them 
  by 
  Irving 
  and 
  Williams. 
  

  

  (2) 
  The 
  next 
  formation 
  above 
  does 
  show 
  such 
  concentrated 
  

   rocks, 
  — 
  quartzites 
  largely 
  composed 
  of 
  Si0 
  2 
  , 
  and 
  limestone 
  in 
  

   which 
  Ca 
  and 
  Mg 
  are 
  concentrated. 
  

  

  (3) 
  The 
  Grenville 
  limestone 
  formation 
  or 
  dolomite, 
  before 
  

   his 
  first 
  " 
  Laurentian 
  granite 
  gneiss," 
  never 
  occurs 
  in 
  the 
  same 
  

   column 
  with 
  the 
  eo-Huronian 
  series 
  (or 
  as 
  he 
  calls 
  it, 
  Bruce 
  

   limestone 
  and 
  dolomite) 
  which 
  comes 
  just 
  after. 
  

  

  There 
  is, 
  therefore, 
  no 
  apparent 
  reason 
  why 
  they 
  might 
  not 
  

   be 
  the 
  same, 
  if 
  his 
  Laurentian 
  granite 
  is 
  not 
  all 
  of 
  the 
  same 
  

   time 
  of 
  intrusion, 
  and 
  the 
  Grenville 
  limestones 
  might 
  then 
  be 
  

   the 
  metamorphic 
  or 
  " 
  granitized 
  " 
  Kona 
  and 
  Bruce 
  dolomites. 
  

  

  (4) 
  Similarly 
  in 
  but 
  two 
  of 
  his 
  15 
  columns, 
  Vermilion 
  Lake 
  

   and 
  Marquette, 
  do 
  we 
  find 
  " 
  Iron 
  Formation 
  " 
  before 
  and 
  after 
  

   the 
  Algoman 
  granite. 
  And 
  as 
  I 
  have 
  said, 
  to 
  my 
  knowledge, 
  

   granite 
  does 
  cut 
  the 
  slates 
  he 
  classes 
  as 
  Animikian, 
  in 
  the 
  

   Thunder 
  Bay 
  and 
  Mesabi 
  ranges. 
  Therefore 
  we 
  are 
  compelled 
  

   to 
  ask 
  if 
  the 
  separation, 
  for 
  the 
  sake 
  of 
  his 
  theory, 
  of 
  the 
  

   Virginia 
  and 
  Tyler 
  slate, 
  which 
  all 
  the 
  rest 
  of 
  us 
  correlate, 
  and 
  

   which 
  seem 
  lithologically 
  and 
  structurally 
  to 
  be 
  two 
  sides 
  of 
  

   a 
  synclinal, 
  is 
  not 
  an 
  unwarranted 
  divorce. 
  

  

  (5) 
  In 
  all 
  cases 
  there 
  is 
  an 
  extensive 
  slate 
  formation 
  at 
  the 
  

   very 
  top 
  just 
  under 
  the 
  Keweenaw 
  formation. 
  

  

  (6) 
  Widespread 
  through 
  the 
  region 
  are 
  intrusives 
  or 
  

   effusives 
  of 
  basaltic 
  magma. 
  And 
  these 
  volcanics 
  except 
  

   toward 
  the 
  Adirondacks 
  are 
  the 
  latest 
  to 
  occur, 
  and 
  do 
  not 
  cut 
  

   any 
  rocks 
  that 
  contain 
  any 
  characteristic 
  fossils 
  of 
  the 
  Paleozoic. 
  

   But 
  these 
  first 
  Paleozoic 
  fossils 
  are 
  Upper 
  Cambrian. 
  

  

  These 
  Keweenawan 
  volcanics 
  appear, 
  therefore, 
  to 
  be 
  de- 
  

   posited 
  during 
  a 
  period 
  of 
  uplift 
  that 
  may 
  have 
  begun 
  before 
  

   the 
  Olenellus 
  fauna, 
  but 
  certainly 
  lasted 
  (here 
  I 
  am 
  glad 
  to 
  

   agree 
  with 
  Lawson) 
  into 
  the 
  Paleozoic. 
  

  

  