LAKE    SUPERIOR  REGION. 
Correlation  table  of  Laivson,  1S93. 
317 
Western  Ontario  and 
Minnesota. 
Eastern  Ontario. 
Quebec. 
Ontarian  system. 
Hastings  series. 
Grenville  series. 
In   order   of   superposi- 
tion. 
Laurentian  system. 
Ottawa  gneiss. 
Ottawa  gneiss. 
» 
Carltonian   anortho- 
sites  of  Minnesota. 
Norian. 
Carltonian    anortho- 
sites  of  Minnesota. 
Norian. 
In  order  of  chronological 
sequence,  an  irruptive 
rock  being  of  later  age 
than    the    formations 
which  it  invades. 
■Si 
O  a) 
OJ  +^ 
U    CO 
3  >> 
OS    M 
J    J 
Batholithic   gran- 
ites and  gneisses. 
Ottawa  gneiss. 
• 
Ottawa  gneiss. 
Ont 
irian  system. 
Hastings  series. 
Grenville  series. 
Winchell  (N.  H.),328  in  1893,  gives  a  review  of  the  literature  on 
the  Norian  of  the  Northwest.  Here  are  included  the  gabbros,  placed 
as  the  basement  member  of  the  Keweenawan  by  Irving,  and  the  rocks 
of  Bohemian  Mountains,  Keweenaw  Point.  It  is  suggested  that  the 
anorthosites  of  Lawson  are  but  facies  of  the  gabbro,  and  that  the  two 
belong  together  in  the  Norian. 
Van  Hise,329  in  1893,  gives  an  historical  sketch  of  the  Lake  Superior 
region  to  Cambrian  time.  The  five  divisions  of  this  region  are  the 
Basement  Complex  or  Archean,  the  Lower  Huronian,  the  Upper 
Huronian,  the  Keweenawan  (the  last  three  together  constituting  the 
Algonkian),  and  the  Lake  Superior  Cambrian  sandstone.  These 
divisions  are  separated  from  one  another  by  unconformities. 
The  Basement  Complex  consists  mainly  of  (1)  granites  and  gneis- 
soid  granites  and  (2)  finely  foliated  dark-colored  banded  gneiss  or 
schist.  The  relations  which  obtain  between  the  two  divisions  are  fre- 
quently those  of  intrusion,  the  granites  and  gneissoid  granites  being 
the  later  igneous  rocks.  There  is  no  evidence  that  any  of  the  dark- 
colored  schists  are  sedimentary,  but  it  is  certain,  if  a  massive  granular 
structure  be  proof  of  igneous  origin,  that  a  part  of  them  are  eruptive, 
for  between  the  two  are  gradations. 
The  w7ell-known  characteristic  rocks  of  the  Lower  Huronian  are 
(1)  conglomerates,  quartzites,  quartz  schists,,  and  mica  schists;  (2) 
limestones;  (3)  various  ferruginous  schists,  and  (4)  basic  and  acidic 
eruptives,  which  occur  both  as  deep-seated  and  as  effusive  rocks.  The 
order  given,  with  the  exception  of  the  eruptives,  is  the  order  of  age 
from  the  base  upward.  In  the  Lower  Huronian  are  placed  the  Lower 
Vermilion,  Lower  Marquette,  Lower  Felch  Mountain,  Lower  Me- 
