LAKE   SUPERIOR   REGION.  295 
giving  as  one  reason  for  proposing  this  name  the  statement  that  there 
is  no  evidence  that  these  rocks  are  equivalent  with  the  rocks  of  Lake 
Huron  described  by  Logan  and  Murray  as  Huronian. 
The  ellipsoidal  greenstone  agglomerate  slate  series  is  cut  in  a  most 
intricate  way  by  granite  and  granitoid  gneiss,  which  constitutes  much 
of  Falcon  Island  at  the  southern  part  of  the  Lake  of  the  Woods  and  a 
great  area  north  of  the  Lake  of  the  Woods. 
Bell  (J.  M.),292  in  1905,  makes  a  report  upon  the  iron  ranges  of 
Michipicoten  West,  covering  the  northern  and  western  extensions  of 
the  producing  Michipicoten  iron-range  district,  adjacent  to  Michi- 
picoten Bay.  The  northern  range  lies  between  Magpie  River  and  the 
western  branch  of  Pucaswa  River,  being  practically  continuous  with 
the  old  Michipicoten  range.  The  western  range,  separated  from 
the  other  by  granite,  lies  between  Otter  Head  and  Bear  River,  on 
the  Lake  Superior  shore,  and  extends  but  a  short  distance  north  of 
Lake  Michi-Biju.  Coleman  and  Willmott's  report  on  the  Michipi- 
coten area  in  the  vicinity  of  the  Helen  mine  is  followed  closely. 
Their  succession  is: 
Keweenawan , Basic  eruptives. 
Post-Huronian Acidic  eruptives. 
Upper  Huronian Dore  formation. 
Unconformity. 
Helen  iron  formation. 
Lower  Huronian 
Michipicoten  schists,  etc. 
ft 
Under  the  recommendation  of  the  joint  geological  committee,  re- 
ferred to  in  a  footnote,  the  Lower  Huronian  schists  and  iron  forma- 
tion would  be  classed  as  Keewatin  and  the  Dore  formation  of  the 
Upper  Huronian  would  be  called  Lower  Huronian. 
The  Helen  formation  consists  of  sideritic  and  pyritous  cherts,  jas- 
pers, amphibolitic  schists,  siderite,  iron  ores,  quartzite,  phyllites,  and 
biotitic  and  epidotic  schists,  all  undoubtedly  sedimentary.  The 
formation  occupies  a  position  generally  close  to  the  overlying  Dore 
conglomerate,  but  sometimes  great  masses  of  green  schists  (Kee- 
watin) intervene  between  it  and  the  Dore  formation.  Pronounced 
faults  in  the  iron  formation  may  be  seen  in  several  parts  of  the  north- 
ern and  western  Michipicoten  range.-.  The  western  range  is  less 
folded  than  the  northern  range.  The  origin  and  development  of  the 
different  phases  of  the  iron  formation  are  thought  by  Bell  to  be  those 
given  by  Van  Hise  for  Lake  Superior  ores,  and  emphasis  is  laid  on 
the  similarity  of  conditions  in  the  Michipicoten  and  Vermilion 
districts. 
Glacial  erosion  seems  to  have  removed  the  upper  parts  of  the  forma- 
tions, and  ore  deposits  should  be  looked  for  only  in  deep  troughs, 
such  as  those  at  Iron  Lake,  Frances  mine,  Brotherton  Hill,  at  the 
Leach  Lake  bands  in  the  northern  range,  and  in  Laird's  claims,  Julia 
