﻿324 
  H. 
  L. 
  Smyth 
  — 
  Geology 
  of 
  Steep 
  Rock 
  Lake, 
  Out. 
  

  

  distributed, 
  and 
  is 
  nearly 
  if 
  not 
  quite 
  coextensive 
  with 
  the 
  

   limestone. 
  The 
  total 
  thickness 
  of 
  the 
  lower 
  limestone 
  cannot 
  

   be 
  determined 
  precisely, 
  as 
  it 
  is 
  nowhere 
  seen 
  in 
  contact 
  with 
  

   the 
  overlying 
  Formation 
  III, 
  but 
  quite 
  surely 
  is 
  not 
  less 
  than 
  

   500 
  nor 
  more 
  than 
  700 
  feet. 
  A 
  much 
  greater 
  thickness 
  is 
  ex- 
  

   posed 
  in 
  the 
  north 
  side 
  of 
  Conglomerate 
  Bay, 
  in 
  part 
  resulting 
  

   from 
  duplication 
  by 
  faulting. 
  On 
  the 
  eastern 
  arm, 
  where 
  the 
  

   rocks 
  are 
  comparatively 
  undisturbed 
  the 
  limits 
  indicated 
  are 
  

   those 
  given 
  above. 
  

  

  Formation 
  III 
  is 
  found 
  only 
  on 
  the 
  south 
  shore 
  of 
  the 
  

   eastern 
  arm 
  which 
  it 
  fringes 
  from 
  the 
  Point 
  N.W. 
  of 
  Lake 
  

   Margaret 
  Portage 
  to 
  Falls 
  Bay, 
  in 
  much 
  the 
  same 
  way 
  that 
  

   the 
  limestone 
  fringes 
  the 
  north 
  shore. 
  As 
  a 
  whole 
  the 
  forma- 
  

   tion 
  consists 
  of 
  an 
  extremely 
  soft, 
  fissile 
  dull 
  green, 
  very 
  pyrit- 
  

   iferous 
  rock, 
  which 
  carries 
  in 
  some 
  localities 
  many 
  pebbles 
  

   of 
  limestone 
  and 
  a 
  few 
  of 
  trap. 
  In 
  the 
  lower 
  parts 
  of 
  the 
  

   formation 
  the 
  limestone 
  fragments, 
  which 
  are 
  identical 
  with 
  

   the 
  rock 
  of 
  Formation 
  II, 
  are 
  rather 
  numerous, 
  and 
  some 
  are 
  

   large, 
  one, 
  angular 
  in 
  shape, 
  being 
  over 
  two 
  feet 
  in 
  diameter. 
  

   Others 
  are 
  apparently 
  rounded 
  and 
  waterworn. 
  In 
  other 
  

   localities 
  pebbles 
  are 
  not 
  found 
  at 
  all. 
  For 
  the 
  most 
  part 
  the 
  

   only 
  structure 
  observable 
  is 
  the 
  regional 
  cleavage 
  which 
  is 
  

   very 
  perfectly 
  developed. 
  At 
  two 
  localities 
  a 
  fine 
  banding 
  

   parallel 
  to 
  the 
  strike 
  of 
  the 
  rock 
  was 
  observed. 
  At 
  loc. 
  27, 
  

   south 
  of 
  trap 
  bluff 
  this 
  banding 
  is 
  very 
  prettily 
  shown. 
  The 
  

   rock 
  carries 
  a 
  few 
  rounded 
  pebbles 
  of 
  limestone. 
  The 
  banded 
  

   structure 
  is 
  thrown 
  into 
  little 
  compressed 
  S.W. 
  pitching 
  folds 
  

   the 
  tangent 
  plane 
  to 
  which 
  is 
  parallel 
  to 
  the 
  plane 
  of 
  the 
  dip 
  

   in 
  the 
  limestone 
  across 
  the 
  bay. 
  Apart 
  from 
  the 
  limestone 
  

   inclusions 
  and 
  this 
  banding 
  the 
  rock 
  shows 
  no 
  trace 
  of 
  sedi- 
  

   mentary 
  origin. 
  Under 
  the 
  microscope 
  it 
  is 
  seen 
  to 
  contain 
  no 
  

   clastic 
  material 
  and 
  all 
  the 
  evidence, 
  which 
  is 
  uot 
  however 
  

   conclusive, 
  seems 
  to 
  point 
  to 
  its 
  having 
  been 
  originally 
  a 
  vol- 
  

   canic 
  ash. 
  At 
  two 
  localities 
  a 
  bed 
  of 
  banded 
  jasper 
  and 
  iron 
  

   ore, 
  generally 
  magnetite, 
  is 
  found, 
  which 
  belongs 
  near 
  the 
  base 
  

   of 
  the 
  horizon. 
  A 
  high 
  bluff 
  of 
  trap 
  in 
  East 
  Bay, 
  probably 
  a 
  

   lenticular 
  intrusion, 
  must 
  also 
  be 
  included 
  in 
  it. 
  Except 
  on 
  

   this 
  south 
  shore 
  of 
  the 
  eastern 
  arm 
  Formation 
  III 
  is 
  everywhere 
  

   covered 
  by 
  the 
  waters 
  of 
  the 
  lake, 
  within 
  the 
  area 
  studied. 
  

   Sufficient 
  evidence 
  of 
  its 
  continuity 
  is 
  afforded 
  however 
  by 
  

   the 
  presence 
  of 
  bowlders 
  from 
  the 
  characteristic 
  iron 
  ore 
  hori- 
  

   zon 
  at 
  several 
  widely 
  distant 
  points. 
  The 
  thickness 
  varies 
  

   considerably 
  but 
  may 
  be 
  taken 
  at 
  a 
  maximum 
  of 
  600 
  feet. 
  

  

  Formation 
  IV 
  consists 
  of 
  interbedded 
  ernptives, 
  which 
  may 
  

   reach 
  a 
  maximum 
  thickness 
  of 
  1000 
  feet. 
  The 
  rock 
  is 
  very 
  

   uniform 
  in 
  character, 
  the 
  variations 
  occurring 
  being 
  mainly 
  .in 
  

   texture. 
  It 
  is 
  normally 
  a 
  massive, 
  rather 
  coarsely 
  crystalline 
  

  

  