AREA   NORTH   AND   NORTHEAST   OF   LAKE    HURON.  439 
SUDBURY   DISTRICT. 
The  succession  is  as  follows,  from  the  base  up : 
1.  Keewatin  greenstones,  green  schists,  and  iron  formation.  These 
do  not  occur  in  the  Sudbury  district  proper,  but  are  found  bordering 
it  immediately  to  the  north.  They  are  correlated  with  the  Thessalon 
group  of  the  original  Huronian  area.  These  appear  on  the  Canadian 
maps  as  "  Lower  Huronian." 
2.  Lower  Huronian  resting  unconformably  upon  the  Keewatin 
rocks.  Conglomerates,  graywackes,  and  quartzites,  associated  with 
diorites,  hornblende  porphyrites,  norites,  and  green  schists.  In  the 
Wahnapitae  area,  immediately  east,  they  contain  limestones.  They 
might  perhaps  be  correlated  with  either  the  middle  or  the  lower 
Huronian  of  the  original  Huronian  district  proper,  but  because  of 
the  presence  of  limestone  they  are  correlated  with  the  lower  Hu- 
ronian.   On  the  Canadian  maps  they  appear  as  "  Upper  Huronian." 
3.  Granite,  diorite,  gneiss,  gabbro,  and  porphyrite,  intrusive  into 
lower  Huronian.  Part  of  the  granite  and  gneiss  is  referred  to  the 
Laurentian  by  Bell,  Barlow,  and  Coleman.  All  of  the  preceding 
sedimentary  rocks  and  part  of  the  igneous  rocks  are  folded,  meta- 
morphosed, and  eroded. 
4.  Upper  Huronian  resting  unconformably  upon  underlying  rocks, 
tuffs,  feldspathic  sandstones,  and  slates.  Correlated  with  the  Anim- 
ikie  group  of  Lake  Superior.  Mapped  by  Bell  as  "  Cambrian,"  by 
Coleman  as  "  Animikie  or  Upper  Huronian,"  and  by  Barlow  as 
doubtful  "  Upper  Huronian."  This  group  constitutes  a  boat-shaped 
basin  called  the  Sudbury  basin. 
5.  Granites,  nickel-bearing  eruptives  (quartz-hypersthene  gabbro 
or  norite,  diorite,  micropegmatite),  and  dikes  of  olivine  diabase.  In 
part  later  than  the  upper  Huronian  and  perhaps  of  Keweenawan 
age;  in  part  apparently  interbedded  with  upper  Huronian.  A  part 
of  these  lie  beneath  the  upper  Huronian  and  outcrop  around  the 
edge  of  the  upper  Huronian  basin.  The  norite  at  the  base  is  the 
nickel-bearing  eruptive.  According  to  Coleman  this  norite  grades 
upward — that  is,  toward  the  inner  edge  of  the  eruptive  belt — into  an 
acidic  rock.  According  to  Barlow  these  rocks  are  merely  intrusive 
into  the  basic  rocks. 
LAKES  TEMISCAMING  AND  TEMAGAMI   AND  WESTWARD  TO    LAKE   ONAPING. 
Throughout  this  area  may  be  observed  rocks  similar  to  those  on 
the  north  shore  of  Lake  Huron  and  the  Michipicoten  district.  At 
the  base  are  Keewatin  greenstones,  given  schists,  and  iron  formation, 
cut  by  Laurentian  granites  and  gneisses.     Lying  uncon  formably  upon 
