434  PRE-CAMBKIAN    GEOLOGY   OF    NORTH    AMERICA. 
The  rocks  of  the  basal  complex  correspond  perfectly,  in  position,  in 
lithological  character,  and  in  their  disturbed  and  metamorphosed  con- 
dition, to  the  oldest  formation  in  the  Lake  Superior  and  Lake  Huron 
districts,  which  the  international  committee  on  geological  nomencla- 
ture recommended  should  be  called  Keewatin.  The  rocks  of  the  gran- 
ite family  correspond  to  the  Laurentian  as  defined  by  this  committee, 
and  the  sedimentary  series  to  the  Lower  Huronian.  As  no  rocks 
newer  than  the  diabase  or  gabbro  were  seen,  it  can  be  classified  only 
as  post-Lower  Huronian. 
Above  the  solid  formations  are  glacial  and  postglacial  deposits 
of  clay,  sand,  and  gravel.  There  are,  then,  in  descending  order,  the 
following  formations : 
Postglacial Clays,  sands,  gravels. 
Glacial Bowlder  clay. 
Great  unconformity. 
Post-Lower  Huronian Diabase,  gabbro,  mica  lamprophyres. 
Igneous   unconformity. 
Lower  Huronian Conglomerate,  quartzite,  slate. 
Unconformity. 
Laurentian Granite,  pegmatite,   porphyry. 
Igneous   unconformity. 
Keewatin Greenstone,  lime,  silicate  rocks,  schists, 
dolomites,  cherts,  etc. 
Coleman,08  in  1908,  concludes  that  lower  Huronian  conglomerates 
of  the  Cobalt  district  show  convincing  evidence  of  glacial  action,  and 
that  the  occurrence  of  similar  rocks  at  various  localities  westward  for 
200  miles  in  Ontario  points  to  a  general  Huronian  ice  age. 
Miller,09  in  1908,  in  a  third  report  on  the  Cobalt  district,  discusses 
certain  possible  fragmental  sediments  and  jasper-magnetite  bands  of 
undoubted  sedimentary  origin.  The  writer  believes  that  these  sedi- 
mentary bands  should  be  classed  with  the  Grenville  series,  which  is 
found  in  much  greater  volume  in  southeastern  Ontario.  He  would 
place  the  Grenville  sedimentary  series  between  the  Keewatin  and 
lower  Huronian  in  age. 
Knight,70  in  1908,  discusses  the  geology  of  part  of  Montreal 
River  and  the  Temagami  Forest  Reserve,  Ontario.  The  succession  is 
as  follows: 
Glacial  and  postglacial Bowlder  clay,  sands,  gravels,  clays. 
Great  unconformity. 
Huronian  or  Keweenawan  (?) Diabase. 
Igneous  contact. 
Huronian Quartzite,  arkose,  conglomerate,  and  slate. 
Great  unconformity. 
Laurentian Granite,   syenite,   and  gneiss   intrusive  into 
Keewatin  but  not  into  Huronian. 
Igneous  contact. 
Keewatin The  series  is  an  igneous  complex,  consisting 
generally  of  highly  metamorphosed  basic 
igneous  rocks. 
