430  PKE-CAMBIIIAN    GEOLOGY   OF    NORTH   AMERICA. 
The  "  green  chloritic  slate  "  mapped  by  Logan  and  Murray  near 
Thessalon  was  found  to  consist  of  ellipsoidal  greenstones,  amygda- 
loids,  agglomerates,  and  massive  greenstones,  collectively  referred  to 
as  the  Thessalon  series.  No  undoubted  sediments  were  observed. 
The  granite  and  gneiss,  mapped  by  Logan  as  Laurentian,  are  intrusive 
into  the  Thessalon  series.  The  conglomerate  and  quartzite  at  the  base 
of  Logan's  Huronian  series  are  found  to  rest  unconformably  upon 
the  granite  east  of  Thessalon,  and  probably  also  upon  the  Thessalon 
series,  thus  confirming  the  like  conclusions  of  Irving,  Pumpelly,  and 
Van  Hise  based  upon  earlier  observations.  Accordingly  the  Thessa- 
lon series  should  be  excluded  from  the  Huronian  and  assigned  to  the 
Keewatin  division  of  the  Basement  Complex. 
Coleman,57  in  1904,  describes  and  maps  the  northern  nickel  range 
of  the  Sudbury  district  of  Ontario.  It  constitutes  the  northern  up- 
turned edge  of  a  syncline  of  eruptive  rocks  resting  on  Laurentian 
granites  and  gneisses  and  including  within  it  a,  little-disturbed  basin 
of  Cambrian  or  Upper  Huronian  sediments  and  tuffs.  The  contacts 
with  the  rocks  above  and  below  are  eruptive.  The  eruptive  grades 
from  acidic  in  its  inner  or  upper  margin  to  basic  in  its  outer  or  lower 
margin.     The  nickel  is  concentrated  in  its  basic  edge. 
Barlow,58  in  1904,  describes  and  maps  the  geology  of  the  Sudbury 
nickel  and  copper  district  of  Ontario.  He  makes  the  succession  as 
folloAvs : 
1.  Lower  Huronian.  No  rocks  of  this  age  are  at  present  known 
in  the  nickel-bearing  area,  but  this  period  is  represented  in  part  by  the 
banded  siliceous  magnetites  and  associated  rocks  of  the  townships  of 
Hutton  and  Wissner. 
2.  Upper  Huronian.  (a)  Diorites,  hornblende  porphyrites,  and 
green  schists,  (b)  Conglomerates,  graywackes,  and  quartzites. 
(c)  Norite  and  diorite  (Worthington  mine  belt  and  areas  southeast 
of  Evans  mine  and  east  of  Sudbury). 
■  3.  Laurentian.     Granite  and  diorite  gneiss  near  Wanapitei  station. 
4.  Upper  Huronian?  Tuffs,  feldspathic  sandstones,  and  slates, 
classified  provisionally  on  previous  geological  maps  as  of  Cambrian 
age. 
5.  Post-Huronian.  (a)  Granites,  (b)  Nickel -bearing  eruptive  of 
the  main  belt  (quartz-hypersthene  gabbro  or  norite,  diorite,  with 
their  peculiar  differentiation  product,  micropegmatite).  (c)  Dikes  of 
olivine  diabase. 
On  the  maps  the  rocks  are  lithologically  separated  and  grouped 
as  Archean. 
The  nickel  is  confined  to  the  norite  and  its  altered  varieties. 
Closely  associated  with  this  is  a  rock  of  granitic  composition  and  pre- 
vailing gneissoid  texture,  which  can  not  be  sharply  separated  from 
the  basic  eruptive,  although  the  change  is  usually  sharp  enough  to 
