kanhise.]  LAKE    SUPERIOR    REGION.  165 
lance  of  the  later  gra nil e  gneisses,  but  ctoes  not  emphasize  the  presence 
M the granite-gneiss-schist  complex;  Irving,  on  the  other  hand,  reverses 
the  emphasis;  while  Brooks  occupies  an  intermediate  position.  It  is 
most  significant  that  these  three  men,  starting  with  different  views, 
Lave  finally  reached  like  conclusions.  For  a  long  time  Eominger  denied 
the  existence  of  the  basement  granite-gneiss- schist  complex.  Irving 
was  slow  to  recognize  the  presence  of  later  intrusive  granite.  In 
Brooks's  earlier  work  in  the  Marquette  district  he  did  not  find  the 
evidence  of  intrusive  granite-gneiss  which  he  found  later  in  the  Menomi- 
nee district. 
Lawson  recognizes  a  physical  break  at  the  base  of  the  Keweenaw  an 
and  a  great  break  at  the  base  of  the  Animikie,  and  divides  the  under- 
lying complex  about  the  lake  of  the  Woods  and  Rainy  lake,  Ontario, 
into  Keewatin,  Coutchiching,  and  Laurentian,  this  being  the  order  of 
occurrence  downward,  but  in  age  the  granitic  and  gneissic  rocks  are 
later  than  and  intrusive  in  the  schistose  rocks.  In  this  matter  Lawson 
agrees  with  the  earlier  work  of  Bigsby  upon  Rainy  lake  and  that  of 
Dawson  upon  the  lake  of  the  Woods,  except  that  Dawson  did  not  re- 
gard all  of  the  granite-gneiss  of  the  lake  of  the  Woods  as  later  igne- 
>us  material.  These  relations  are  the  same  as  those  described  by 
Foster  and  Whitney,  and  by  Wadsworth  between  the  granite  gneisses 
and  the  Azoic  slates  on  the  south  shore.  With  Dawson,  Lawson  agrees 
iiat  the  Laurentian  gneiss  and  granite  and  the  overlying  schists  are 
jonformable.  By  Loth  of  these  writers  the  schistose  rocks  of  the  lake 
)f  the  W'oods  are  regarded  as  sedimentary  and  largely  of  volcanic  ori- 
gin. There  is  the  further  agreement  between  Lawson  and  Dawson  on 
jhe  north  shore  and  Foster  and  Whitney,  Wadsworth,  Irving,  and 
Williams  on  the  south  shore  that  they  regard  the  greenstone  slates 
is  largely  in  the  nature  of  volcanic  ash.  Lawson  gives  the  schistose 
x>cks  about  Rainy  lake  a  twofold  division,  both  series  being  regarded 
fcs  sedimentary  and  in  apparent  conformity,  but  there  are  great  differ- 
ences in  the  materials  of  which  the  series  are  composed  as  well  as  in 
legree  of  crystallization,  and  basal  conglomerates  are  found  at  the 
iottom  of  the  upper  series.  Between  the  two  there  is  believed  to  be 
i  considerable  geological  break.  The  upper  is  the  equivalent  of  the 
schistose  series  of  the  lake  of  the  Woods.  To  cover  the  two  series  is 
H-oposed  the  system  name  Ontarian.  Lawson's  succession  is  therefore 
Keweenawan,  unconformity,  Animikie,  unconformity,  Keewatin,  uncon- 
formity, Coutchiching,  irruptive  unconformity,  Laurentian  cutting  both 
Keewatin  and  Coutchiching. 
I  It  is  of  interest  to  note  that  Rominger's  early  conclusions  as  to  the 
general  relations  of  the  rock  series  on  the  south  shore  were  almost  iden- 
ical  with  those  reached  by  Lawson  as  to  the  relations  of  the  different 
series  on  the  north  shore;  that  is,  the  dioritic  group,  the  lowest  Huron 
[an,  is  regarded  as  remelted  metamorphosed  Iluronian  sediments,  the 
uore  crystalline  character  of  the  rocks  being  due  to  their  closer  prox- 
