van  Hiss,!  LAKE    SUPERIOK    REGION.  191 
mentaries.  This  vast  area  has  been  too  little  studied  to  say  definitely 
what  part  of  the  areas  referred  to  Irvine's  mica-schist  group,  Winchell's 
Vermilion  series,  and  Lawson's  Ooutchiching  belongs  with  the  Basement 
Complex.  It  is  equally  difficult  to  say  whether  the  Keewatin  of  Law- 
son  and  Winchell  does  not  comprise  more  than  one  series.  It  is 
Lawson's  opinion  that  it  does  and  that  the  physical  break  described 
as  occurring  in  the  clastic  series  on  the  south  shore  exists  between 
the  Upper  and  Lower  Keewatin.  Our  knowledge  of  this  part  of  the 
lake  Superior  region  is  not  sufficiently  advanced  to  outline  with 
any  accuracy  the  areas  which  are  to  be  referred  to  these  main 
divisions.  It  is,  however,  tolerably  clear  that  in  this  part  of  the  region 
there  are  the  same  great  subdivisions  of  the  pre-Cambrian  rocks  as 
elsewhere;  that  a  part  of  what  has  ordinarily  been  called  Laurentian 
will  be  included  in  the  Basement  Complex;  that  a  part  of  Irving's  mica- 
schist  group,  Lawson's  Coutehiching,  and  the  Profs.  Winchell's  Vermil- 
ion also  falls  within  this  complex.  It  is  further  probable  that  a  part 
of  the  Keewatin  is  the  equivalent  of  the  Lower  Marquette,  Lower  Me- 
nominee, and  equivalent  series.  It  is  possible  that  other  parts  of  the 
series  which  have  been  designated  Keewatin  belong  rather  with  the 
Aniinikie.  If,  however,  the  break  at  the  base  of  the  Animikieis  higher 
than  that  above  the  Vermilion,  Hunter's  island,  and  Kaministiquia  iron- 
bearing  series,  aud  the  latter  break  belongs  within  the  Keewatin,  as 
now  known,  this  group  will  need  to  be  subdivided  into  two  series,  and 
the  succession  will  thus  be  expanded  at  this  point  into  Lower  Keewatin, 
unconformity,  and  Upper  Keewatin. 
NOMENCLATURE. 
There  still  remains  the  question  of  nomenclature,  In  Chapter  vm. 
the  major  taxonomy  of  the  prei-Cambrian  is  discussed  and  reasons 
are  given  for  including  under  the  term  Algonkian  all  the  pie- 
Cambrian  elastics,  for  confining  the  term  Archean  to  the  inferior  crys- 
talline complex,  for  restricting  the  term  Laurentian  to  the  coarser 
grained  light  colored  granite-gneiss  part  of  this  Complex,  and  for  pro- 
posing for  the  dark  colored  fine  grained  schistose  part  of  this  complex 
the  term  Mareniscan.  These  reasons  will  not  be  repeated  here,  but  the 
terms  with  these  definitions  will  be  applied  to  the  rock  successions  of 
different  districts  of  the  lake  Superior  region.  This  will  serve  to  illus- 
trate the  usage  of  these  terms  and  at  the  same  time  will  be  a  test  of 
the  propriety  of  the  usages  proposed,  since  the  lake  Superior  region  is 
the  one  in  America  about  which  most  has  been  written  and  which  fur- 
nishes   \e  fullest  pre-Cambrian  column. 
^Belof  ;'iag  to  the  Archean  onthesouth  shore  arethe  Southern  ( 'omplex 
of  the  U  3nokee  districts',  the  fundamental  complex  of  the  Marquette  and 
;  Menoipnee  districts,  andagreat  expanse  of  rocks  in  northern  Wisconsin. 
This  complex  is  more  largely  of  the  Laurentian   gneiss  than  of  the 
i  Mareniscan  schists.     Between  the  two  are  often  the  peculiar  gradations 
