vanhise.]  LAKE    SUPERIOR    REGION.  57 
and  trappean  bowlders,  and  is.  followed  by  thin  bedded  sandstones,  and 
these  by  thin  shaly  layers. 
Macfarlane,13  in  1868,  describes  the  rocks  of  the  north  and  east 
shore  of  lake  Superior.  He  here  finds  four  formations — the  Laurentian, 
Huronian,  Upper  Copper-bearing  rocks,  and  St.  Mary  sandstone.  The 
most  prevalent  rocks  of  the  Laurentian  series  are  of  a  massive  crystal- 
line' character,  more  of  a  granitic  than  of  a  gneissic  nature.  Almost 
equally  frequent  with  the  granitic  and  gneissic  rocks  are  aggregates  of 
rocks  which  can  be  described  as  brecciated  and  intrusive,  gneissic, 
granitic,  and  syenitic  rocks.  In  these  the  order  of  age  is  always  from 
basic  to  acidic.  In  one  case  fragments  of  hornblende-schists  are  found 
inclosed  in  syenitic  granite,  which  is  cut  by  granite  dikes  of  different 
ages.  It  is  believed  that  these  rocks  are  wholly  of  igneous  origin,  rep- 
resenting a  single  period  of  time — the  basic  rock  first  solidified;  they 
were  then  rent  off,  broken  up,  and  the  crevices  filled  with  more  siliceous 
material,  which  gradually  solidified,  after  which  occurred  another  gen- 
eral movement  with  further  intrusion  of  the  most  siliceous  materials. 
In  the  Huronian  series  is  placed  diabase,  augite-porphyry,  calcareous 
diabase,  diabase  schist,  greenstone  and  greenstone  slate,  chlorite- schist, 
quartzite,  hematite,  greenstone  breccia,  and  slate-conglomerate.  The 
slate  conglomerates  frequently  contains  granite  pebbles  which  are  in 
roundish,  lenticular,  bent,  long-drawn  out  masses,  with  a  diabase-schist 
or  greenstone- slate  matrix.  These  rocks  locally  have  a  sedimentary 
appearance,  but  are  believed  to  be  due  to  the  subsequent  intrusion  of  the 
Huronian  rocks,  which  have  caught  granite  fragments  in  them,  and,  by 
movement  and  heat,  have  softened  and  much  distorted  the  contained 
fragments.  It  follows  that  far  the  greater  number  of  the  Huronian 
rocks  are  regarded  as  purely  igneous. 
In  the  Upper  Copper-bearing  series  are  distinguished  melaphyre  of 
various  kinds — melaphyre  breccia,  porphyrite,  porphyritic  con  glomerate, 
felsite-tuff,  polygenous  conglomerate,  and  sandstone.  The  polygenous 
conglomerate  contains,  at  Mamainse,  fragments  chiefly  of  granite,  gneiss, 
quartzite,  greenstone  and  slate,  while  some  of  the  newer  contain  abun- 
dant bowlders  of  melaphyre  and  amygdaloid.  The  igneous  rocks  and 
sandstones  are  regularly  inter  stratified  with  each  other.  In  many  places 
the  trap  lies  unconformably  upon  the  upturned  and  contorted  edges  of 
the  sandstone. 
Along  the  coast  and  upon  many  islands  is  found  an  almost  horizontal 
red  sandstone,  which  is  supposed  to  be  a  continuation  of  the  Sault  Ste. 
Marie  sandstone.  Its  relations  to  the  copper-bearing  rocks  are  not 
clearly  made  out,  but  the  lowest  members  of  the  Mamainse  series,  are 
unconformably  overlain  by  sandstones  which  may  be  the  equivalent  of 
the  horizontal  red  sandstones,  but  their  lithological  character  is  differ- 
ent. It  is  suggested,  on  lithological  grounds,  that  this  red  sandstone 
may  be  of  Permian  age. 
