y-ANHisB.]  LAKE    SUPERIOE    REGION.  177 
in  western  Ontario,  acquiesce  in  Lawson's  conclusion  in  so  far  as  the 
uncon fosmity  is  concerned,  but  differ  from  Lawson  in  that  they  find  a 
great  structural  discordance  between  the  basal  clastic  series  easl  of 
Rainy  lake  and  a  fundamental  complex  consisting  of  granite,  gneiss, 
and  schist,  while  finding  the  superinduced  foliation  of  both  series 
parallel. 
Tn  Minnesota  the  Profs.  Winchell,  although  recognizing  the  plane 
between  the  elastics  and  crystallines  as  a  boundary  between  two  groups 
of  rocks,  maintain  conformity  and  gradations,  although  Alexander 
Winchell  suggests  that  it  is  a  possibility  that  the  apparent  conformity 
is  superinduced  by  subsequent  dynamic  action. 
The  probability  of  an  unconformity  here  follows  from  the  same  line 
of  reasoning  as  that  applied  to  the  lake  of  the  Woods  and  Rainy  lake 
districts,  and  is  further  indicated  by  the  descriptions  of  conglomerates 
at  Saganaga  and  Epsilon  lakes  in  northeastern  Minnesota  by  Alex. 
Winchell.  In  the  published  notebooks  these  conglomerates  are 
described  and  figured  as  sharply  separated  from  the  underlying  syenite 
and  containing  rounded  pebbles  of  it,  although  it  is  said  the  conglom- 
erates were  not  laid  down  on  the  solidified  syenite.  Later  these  occur- 
rences are  interpreted  to  mean  that  the  syenite  and  gneiss  are  of  sedi- 
mentary origin,  being  completely  metamorphosed.  However;,  I  am  not 
sure  that  I  understand  the  descriptions  well  enough  to  be  certain  that 
these  so  called  conglomerates  are  not  really  due  to  the  intrusion  of  the 
later  irruptive  syenite,  as  was  suggested  by  Winchell  himself.  In  the 
earlier  work  on  the  north  shore  of  lake  Superior  done  by  Bell,  no  dis- 
tinction was  made  between  the  fine  grained  elastics  and  the  crystalline 
schistose  rocks,  although  it  is  not  improbable  that  closer  work  will  make 
it  possible  to  extend  the  structural  subdivisions  of  Puinpelly  and  Smyth. 
Macfarlane  noted  that  the  squeezed  Huronian  slate  conglomerates  fre- 
quently contain  granite  fragments,  although  he  did  not  consider  them 
to  be  of  sedimentary  origin.  Herrick  found  in  his  schistose  group  on 
Michipicoten  bay  basement  conglomerates,  the  pebbles  of  which  are  like 
the  granite  below,  although  the  relations  between  the  granite  and 
schists  are  such  as  to  suggest  to  him  that  the  granite  had  been  intruded 
beneath  the  schist.  Dawson  (Sir  William),  Logan,  and  Bell  all  mention 
granite  and  gneiss  fragments  in  the  Original  Huronian  east  of  lake 
Superior,  and  Logan  clearly  believed  the  two  to  be  unconformable. 
Irving  found  additional  evidence  in  favor  of  this  unconformity.  Recent 
work  of  Puinpelly  and  myself  has  shown  that  the  lowest  member  of 
the  Original  Huronian,  as  mapped  by  Logan,  rests  with  a  great  uncon- 
formity upon  the  basement  complex,  the  Laurentian  of  Logan.  Sel  wyn, 
although  thinking  the  Huronian  and  Laurentian  conformable,  states 
that  Laureutian  pebbles  occur  in  the  Huronian. 
As  shown  in  another  place,  the  gradation  described  by  the  Profs. 
Winchell  in  northeastern  Minnesota,  and  which  appears  to  occur  in 
other  places,  is  wholly  consistent  with  a  real  structural  break  between 
Bull.  80 13 
