LAKE    SUPERIOR   REGION.  275 
been  folded  into  a  southwestward-dipping  monocline,  which,  under 
the  action  of  the  cleavage-producing  force  in  a  northeast-southwest 
direction,  caused  the  present  fluted  outcrop  of  the  formations  of  the 
Steep  Eock  series.  That  the  Basement  Complex  itself  yielded  to  this 
latter  force  is  shown  by  the  irregular  outcrops  of  the  dikes  cutting  it. 
As  a  result  of  the  study  the  following  general  conclusions  are 
reached :  The  contact  of  the  lowest  horizon  of  the  Steep  Rock  series 
with  the  Basement  Complex  is  one  of  erosion.  The  complex  at  the 
time  of  the  deposition  of  the  Steep  Rock  series  was  made  up  of  con- 
solidated crystalline  rocks,  and  there  is  no  evidence  whatever  that  it 
has  since  undergone  fusion  or  recurred  to  the  condition  of  a  magma. 
The  rocks  of  the  Steep  Rock  series  have  been  subjected  at  two  periods, 
more  or  less  distant  from  each  other,  to  great  orotechnic  forces, 
which  acted,  the  first  in  a  northeast-southwest  direction  and  the 
second  in  a  northwest-southeast  direction.  The  latter  force  has  im- 
posed upon  all  the  rocks  of  the  region  a  northeast  structure  which 
has  largely,  but  not  entirely,  obliterated  preexisting  lamination  in  the 
sediments  and  schists  of  the  Steep  Rock  series.  The  two  orotechnic 
actions  have  produced  great  developments  of  autoclastic  schists, 
both  in  the  granites  and  in  the  rocks  of  the  Steep  Rock  series,  the 
present  structure  of  which  was  induced  and  determined  in  direction 
by  the  later  force. 
Smith,-"'7  in  1892,  reports  on  the  Archean  rocks  of  Hunters  Island 
and  adjacent  country.  The  rocks  are  divided  into  Laurentian  and 
Huronian,  and  the  latter  are  subdivided  into  Coutchiching  and 
Keewatin.  The  main  occurrences  of  the  Laurentian  rocks  are  the 
Kawagansikok,  Poo-Bah,  Hunters  Island,  and  Saganaga  areas.  The 
Kawagansikok  granite  is  in  places  fine  grained  and  nearly  devoid  of 
mica  and  hornblende ;  in  other  places,  a  muscovite  granite ;  in  others, 
garnetiferous  granite  gneiss.  The  rock  is  in  many  places  cut  by 
coarse  pegmatite  veins.  The  Poo-Bah  area  is  usually  a  coarse  horn- 
blende syenite,  but  in  places  it  merges  into  a  finer  grained  hornblende 
granite.  The  Hunters  Island  rocks  are  usually  biotite  granites,  but 
the  biotite  is  often  replaced  by  or  associated  with  muscovite,  horn- 
blende, or  chlorite.  At  Agnes  Lake  angular  fragments  of  mica 
schist  or  gneiss  are  found  in  the  granite.  At  various  places  occur 
hornblende  granites.  There  are  other  isolated  areas  of  granite  which 
break  through  the  Coutchiching  rocks  which  can  not  certainly  be  said 
to  be  of  Laurentian  age.  The  granites  as  a  whole  usually  have  a 
foliated  character. 
The  Coutchiching  series  covers  a  large  area  in  the  northwestern 
part  of  the  district,  and  several  small  areas  are  found  to  the  east. 
The  Coutchiching  rocks  are  usually  mica  schists.  In  general  their 
schistosity  is  parallel  to  that  of  the  granites,  but  at  Conmee  Lake 
there  is  a  discrepancy  between  the  two  which  may  indicate  a  structural 
