vANiiisE.l  LAKE    SUPERIOR    REGION.  65 
is  reached  that  they  have  been  laid  down  and  folded  within  a  trough 
in  the  Laurentian  formation. 
Herrick,  Tight,  and  Jones,33  in  1886,  find  on  the  north  shore  of 
lake  Superior  three  distinct  groups  of  rocks  with  their  respective  in- 
trusives,  granitic,  schistose,  and  conglomeratic*  The  granites  are  found 
underlying  the  schists  in  such  a  way  as  to  suggest  that  they  have  been 
intruded  beneath  them,  although  similar  granites  constitute  the  peb- 
bles of  the  basement  conglomerates  in  the  schists.  The  schists  are  met- 
amorphosed at  contacts  with  the  granites j  the  schists  and  schist-con- 
glomerates especially,  in  several  places,  have  been  altered  to  porphyry 
and  felsite-porphyry  by  contact  with  the  eruptives.  The  third  group 
consists  of  basement  conglomerates,  consisting  of  fragments  of  all  the 
varieties  of  rock  included  in  the  other  two  series.  Periodic  overflows  of 
igneous  matter  have  left  vast  sheets  of  diabase,  and  there  is  a  strong 
interaction  between  the  sedimentary  and  eruptive  rocks. 
MoKellar,34  in  1888,  describes  the  Animikie  on  the  north  shore  of 
lake  Superior  as  always  resting  uneonformabby  upon  the  crystalline 
and  schistose  rocks  to  which  the  term  Huronian  is  applied,  the  con- 
tacts being  found  at  many  points.  In  lithoiogical  characteristics  these 
two  series  are  fundamentally  different.  The  original  Huronian  and 
the  schists  underlying  the  Animikie  are  compared,  and  it  is  concluded 
that  they  are  the  equivalent  of  these  rocks  rather  than  of  the  Ani- 
mikie series;  therefore  the  latter  is  later  than  the  Huronian.  The  con- 
tacts of  the  Animikie  and  Keweenawan  formations  show  that  there  is 
an  unconformity  by  erosion  between  the  two. 
Lawson,  35  in  1888,  reports  on  the  geology  of  the  Rainy  lake  region. 
The  pre-Cambriau  rocks  are  divided  into  an  upper  and  lower  Archean, 
as  at  the  lake  of  the  Woods.  The,  upper  is  a  bedded  schistose  and 
metaniorphic  series,  while  the  lower  is  granitic,  gneissic  or  syenitic  in 
character.  In  the  upper  division  two  groups  are  recognized,  one  the 
Keewatiil  of  the  lake  of  the  Woods,  and  the  other,  inferior  in  position, 
is  given  the  name  Coutchiching.  In  the  lower  division  distinctions  of 
stratigraphieal  sequence  and  relationship,  if  any  such  ever  existed, 
have  been  obliterated,  and  for  this  the  term  Laurentian  is  retained. 
These  rocks  can  be  classified  only  on  a  petrographical  basis.  The  con- 
tacts of  the  Keewatin  with  the  Coutchiching  and  Laurentian  are  very 
frequent.  The  relations  between  the  Keewatin  and  Laurentian  are 
exactly  like  those  described  as  maintaining  upon  the  lake  of  the 
Woods.  The  schists  are  intruded  by  the  granite,-  fragments  of  the 
former  being  included  in  the  latter,  and  they  are  sometimes  fused  at 
the  contact.  Very  frequently  near  the  point  of  junction  the  Keewatin 
rocks  become  more  crystalline  and  are  glistening  hornblende-schists. 
At  two  localities  basal  conglomerates  are  found  between  the  Keewa- 
tin and  Coutchiching.    At  the  first  of  these,  Bat-root  bay,  Keewatin 
conglomerate  rests  upon  Coutchiching  schists,  the  conglomerates  con- 
taining water-worn  fragments  of  quartz  and  bowlders  of  granite.    The 
Bull.  86—5 
