﻿320 
  H. 
  L. 
  Smyth 
  — 
  Geology 
  of 
  Steep 
  Rock 
  Lake, 
  Out. 
  

  

  N". 
  55 
  to 
  65 
  E., 
  which 
  pass 
  upward, 
  in 
  going 
  south 
  across 
  the 
  

   strike, 
  into 
  the 
  schists 
  of 
  the 
  Aticokan 
  River. 
  These 
  will 
  be 
  

   termed 
  the 
  Aticokan 
  Series. 
  

  

  Basement 
  Complex. 
  — 
  The 
  granites 
  were 
  very 
  hastily 
  exam- 
  

   ined 
  in 
  the 
  narrow 
  fringe 
  in 
  which 
  they 
  are 
  exposed 
  along 
  

   certain 
  shores 
  of 
  the 
  lake. 
  They 
  were 
  studied 
  mainly 
  with 
  

   reference 
  to 
  their 
  distribution 
  and 
  structural 
  relations 
  to 
  the 
  

   overlying 
  Steep 
  Rock 
  series 
  ; 
  no 
  attempt 
  can 
  now 
  be 
  made 
  to 
  

   separate 
  geographically 
  the 
  various 
  kinds 
  of 
  rocks 
  which 
  are 
  

   included 
  in 
  the 
  basement 
  series, 
  or 
  to 
  indicate 
  their 
  relations 
  

   to 
  one 
  another. 
  

  

  The 
  predominant 
  rock 
  in 
  the 
  basement 
  series 
  is 
  a 
  hornblende 
  

   muscovite 
  granite 
  of 
  medium 
  grain, 
  composed 
  of 
  clear 
  to 
  

   bluish 
  quartz, 
  feldspar, 
  a 
  green 
  hornblendic 
  mineral, 
  and 
  

   muscovite. 
  The 
  color 
  on 
  the 
  weathered 
  surface 
  is 
  white, 
  

   slightly 
  tinged 
  with 
  green, 
  and 
  on 
  the 
  fresh 
  fracture 
  a 
  darker 
  

   well 
  marked 
  green. 
  This 
  is 
  the 
  usual 
  type. 
  Occasionally 
  a 
  

   red 
  granite 
  carrying 
  biotite 
  is 
  seen, 
  which 
  owes 
  its 
  color 
  to 
  

   flesh-colored 
  feldspar. 
  True 
  gneisses 
  are 
  rare, 
  but 
  they 
  are 
  

   occasionally 
  found 
  as 
  at 
  locality 
  50 
  on 
  the 
  ridge 
  north 
  

   of 
  the 
  mouth 
  of 
  the 
  creek 
  emptying 
  into 
  the 
  bay 
  north 
  

   of 
  Lake 
  Margaret 
  portage, 
  and 
  in 
  the 
  peninsula 
  east 
  of 
  North- 
  

   west 
  Bay, 
  at 
  locality 
  125. 
  At 
  both 
  localities 
  the 
  rock 
  is 
  a 
  

   coarse 
  hornblende 
  gneiss, 
  exhibiting 
  a 
  parallel 
  arrangement 
  of 
  

   the 
  con 
  stitu 
  tent 
  minerals, 
  and 
  pegmatization. 
  At 
  locality 
  

   125 
  the 
  coarse 
  gneiss 
  carries 
  angular 
  inclusions, 
  which 
  are 
  finer 
  

   grained 
  and 
  darker 
  than 
  the 
  mass 
  of 
  the 
  rock, 
  but 
  similar 
  in 
  

   composition. 
  

  

  Distinguishable 
  from 
  these 
  gneisses 
  in 
  which 
  the 
  origin 
  of 
  

   the 
  gneissic 
  foliation 
  is 
  unknown 
  is 
  a 
  great 
  body 
  of 
  chloritic 
  

   gneisses 
  which 
  have 
  unquestionably 
  been 
  derived 
  from 
  the 
  

   hornblende 
  granite 
  by 
  crushing. 
  These 
  are 
  found 
  at 
  and 
  

   near 
  the 
  turn 
  of 
  folds 
  ; 
  for 
  example, 
  at 
  the 
  head 
  of 
  Falls 
  Bay, 
  

   north 
  of 
  the 
  Elbow, 
  and 
  along 
  the 
  north 
  and 
  west 
  shores 
  of 
  

   North 
  west. 
  Bay. 
  Good 
  examples 
  are 
  seen 
  on 
  the 
  west 
  shore 
  

   from 
  the 
  head 
  of 
  Falls 
  Bay 
  to 
  the 
  Elbow 
  where 
  the 
  whole 
  

   series 
  has 
  been 
  forced 
  round 
  through 
  an 
  angle 
  of 
  more 
  than 
  

   120°. 
  All 
  stages 
  in 
  the 
  process 
  are 
  seen. 
  At 
  one 
  end 
  of 
  the 
  

   series 
  is 
  found 
  the 
  typical 
  hornblende 
  granite, 
  traversed 
  by 
  

   little 
  wavy 
  fissures, 
  generally 
  parallel 
  to 
  the 
  regional 
  direction 
  

   of 
  cleavage, 
  JS". 
  43° 
  E., 
  along 
  which 
  part 
  of 
  the 
  hornblende 
  is 
  

   represented 
  by 
  thin 
  leaves 
  of 
  fresh 
  chlorite. 
  At 
  the 
  other 
  end 
  

   of 
  the 
  series 
  the 
  quartz 
  and 
  feldspar 
  are 
  greatly 
  granulated, 
  

   and 
  the 
  hornblende 
  has 
  entirely 
  disappeared 
  ; 
  the 
  chlorite 
  is 
  

   arranged 
  in 
  parallel 
  bands, 
  and 
  the 
  rock 
  has 
  developed 
  in 
  it 
  a 
  

   highly 
  perfect 
  schistose 
  structure. 
  

  

  