GENERAL   ACCOUNT    OF    THE    PRE-CAMBRIAN    ROCKS.  63 
Irving  had  proposed  "Agnotozoic  "  or  "  Eparchean."  This  involved 
the  restriction  of  the  term  Archean  to  the  pre- Algonkian  complex. 
In  the  previous  edition  of  this  bulletin  (Bulletin  No.  8(3)  Algonkian 
and  Archean  were  thus  used  and  Proterozoic  was  favored  as  the 
"  zoic  "  term  equivalent  to  Algonkian.  Cambrian  was  defined  as  ex- 
tending downward  to  the  base  of  the  beds  carrying  the  Olenelltis 
fauna. 
In  the  late  nineties  work  in  the  Lake  Superior  region  showed  that 
the  rocks  of  the  Archean  complex  are  in  small  part  of  sedimentary 
origin.  The  retention  of  these  sedimentary  rocks  in  the  Archean 
marked  a  departure  from  the  usage  of  this  term  as  originally  defined 
by  the  Survey.  The  terms  as  used  in  the  present  bulletin  are  ap- 
plied essentially  to  the  same  rock  divisions  as  before,  but  the  defini- 
tions have  been  modified.  The  reasons  for  redefining  the  terms 
Archean  and  Algonkian  rather  than  taking  the  sedimentary  rocks 
out  of  the  Archean  are  discussed  on  pages  19-24. 
In  1905  the  international  geological  committee  recognized  and 
adopted  the  following  succession  and  names  for  the  Lake  Superior 
region : 
Cambrian :  Upper  sandstones,  etc.,  of  Lake  Superior  region. 
Unconformity. 
Pre-Cambrian  : 
Keweenawan    (Nipigon).a 
Unconformity. 
Upper    (Animikie). 
Unconformity, 
[uronian  \  Middle. 
Unconformity. 
Lower. 
Unconformity. 
Keewatin. 
Eruptive  contact. 
Laurentian. 
a  Lane   dissents  as  to  the  position  of   the  Keweenawan  as   follows  :   "  The  use  of  pre- 
Cambrian   above   does    not    imply    unanimity    in    the   committee   with    regard    to    the  pre- 
Cambrian    correlation    of    the    Keweenawan. — a    topic    the    committee    as    such    did  not 
investigate." 
