192  PRE-CAMBR1AN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
described  which  are  taken  to  indicate  the  intrusive  character  of  the 
granite-gneiss.  Between  the  Archean  and  the  Algonkian,  as  indicated 
by  evidence  fully  given  in  another  place,  there  is  a  great  unconformity. 
On  the  north  shore  Smyth  finds  decisive  evidence  of  a  thoroughly 
crystalline  fundamental  complex  below  the  lowest  elastics  at  Steep  Rock 
lake.  As  has  been  seen,  evidence  pointing  in  this  same  direction  is  to 
be  found  in  the  reports  of  Logan,  Dawson  (Sir  William),  Selwyn,  Bell, 
Maefarlane,  Herrick,  and  Lawson,  although  several  of  these  authors  do 
not  reach  this  conclusion.  The  difficult  and  uncertain  point  in  this 
connection  is  in  reference  to  the  Goutehichirig  of  Lawson  or  the  Ver- 
milion of  Profs.  Winehell.  If,  as  believed  by  Lawson,  there  is  a  great 
time  break  between  the  Keewatin  and  Ooutchiching  and  if  the 
Ooutchiching  is  found  to  be  older  than  any  of  the  elastics,  it  belongs 
to  the  fundamental  complex  and  the  term  Ooutchiching  has  priority 
over  Marenisean,  proposed  for  the  dark  colored,  fine  grained  schistose 
part  of  the  Archean.  This  is  the  outcome  which  seems  to  the  writer, 
according  to  present  published  evidence,  to  be  most  likely;  but  it  must 
be  stated  that  this  impression  does  not  accord  with  Lawson' s  opinion, 
who  regards  the  Ooutchiching  as  a  sedimentary  series  more  nearly  con- 
nected with  the  Keewatin  than  with  the  Archean,  nor  with  the  Profs. 
Winehell,  who  regard  the  equivalent  Vermilion  as  but  a  more  meta- 
morphosed downward  extension  of  the  Keewatin. 
In  restricting  the  word  Laurentian  to  the  granite-gueiss  of  the 
Archean,  much  of  what  has  heretofore  been  denominated  Laurentian 
Avill  be  excluded.  This  usage  will  throw  out  all  of  the  granite-gneisses 
of  an  age  later  than  the  elastics,  and  therefore  much  of  the  granite- 
gneiss  which  Lawson  has  called  Laurentian.  It  must  be  recognized 
that  about  the  lake  Superior  region  there  are  granite-gneisses  of  vari- 
ous ages.  This  is  more  evident  in  the  main  granite-gneiss  areas  than 
elsewhere,  for  not  infrequently  intruding  them  are  other  large  bosses 
of  granite  or  gneiss,  which,  with  the  earlier  granite-gneiss,  may  have 
again  been  cut  by  still  later  material  of  the  same  kind.  It  is  believed 
by  some  that  there  are  in  the  lake  Superior  region  granite-gneisses  of  at 
at  least  four  different  ages.  It  will  not  do  to  conclude  that  any  certain 
granite-gneiss  is  Archean  unless  its  structural  relations  to  the  Algon- 
kian elastics  are  determined.  However,  the  granite-gneisses  which 
belong  to  the  Archean  on  the  south  shore  are  pegmatized  through  and 
through  and  banded  and  contorted  in  the  most  intricate  manner. 
Their  constituent  minerals  show  that  they  have  undergone  repeated 
dynamic  movements.  They  are  cut  by  eruptives  of  many  kinds  and  of 
different  ages.  Many  of  the  basic  eruptives  are  so  ancient  that  they 
themselves  have  become  schistose  and  have  passed  over  into  horn- 
blende-gneisses and  similar  rocks,  which  now  are  seen  as  dark  colored 
intersecting  or  parallel  layers  in  the  pink  granite-gneiss.  This  intri- 
cate complex  of  granite,  gneiss,  and  schist,  which  has  been  subjected 
to  repeated  dynamic  movements  in  various  directions,  is  very  different 
