LAKE    SUPERIOR   REGION. 
169 
Descending    succession    of   formations    in    the    Marquette,    Crystal    Falls,    and, 
Menominee  districts. 
Marquette. 
Crystal  Falls. 
Menominee. 
Upper  Marquette: 
Upper  Uuronian: 
Upper  Menominee: 
1.  Michigamme  formation,   bear- 
1. Michigamme     formation, 
1.  Great     Slate     forma- 
ing a  short  distance  above  its 
bearing  a  short  distance 
tion. 
base  an    iron-bearing   horizon, 
above   its    base   an   iron-^ 
and  being  replaced  in  much  of 
the  district  by  the  Clarksburg 
bearing  horizon. 
volcanic  formation. 
2.  Ishpeming     formation,     being 
2.  Quartzite  in  eastern  part 
composed      of     the      Goodrich 
of  the  district. 
quartzite  in  the  eastern  part  of 
the  district,  and  of  the  Good- 
rich   quartzite   and    the    Bijiki 
schists  in  the  western  part  of 
the  district. 
Unconformity. 
Unconformity. 
Unconformity. 
Lower  Marquette: 
Lower  TTuronian: 
Lower  Menominee: 
1.  Negaunee  iron  fonnation,  1,000 
1.  The     Groveland     forma- 
1. Vulcan    iron    forma- 
to 1,500  feet  thick. 
tion,  about  500  feet  thick. 
tion  containing  slates. 
2.  Siamo  slate,  in  places  includ- 
2. Hemlock  volcanic  forma- 
ing interstratified  amygdaloids, 
tion,    1,000    to    10,000  feet 
200  to  625  feet  thick. 
thick. 
3.  Ajibik  quartzite,  700  to  900  feet 
In  western  part  of  district 
thick. 
4.  We  we  slate,   550  to   1,050  feet 
also  occupies  place  of  (1) 
and  (3). 
2.  Antoine  dolomite. 
thick. 
3.  Mansfield  formation,  100 
to  1,900  feet  thick. 
5.  Kona  dolomite,  550  to  1,375  feet 
4.  Randville    dolomite,    500 
thick. 
to  1,500  feet  thick. 
6.  Mesnard  quartzite,  100  to  670 
5.  Sturgeon    quartzite,    100 
3.  Sturgeon  quartzite. 
feet  thick. 
to  1,000  feet  thick. 
Unconformity. 
Unconformity. 
Unconformity. 
Archean. 
Archean. 
Archean. 
Seaman,83  in  1899,  gives  a  summary  of  the  geological  history  of  the 
Keweenawan  copper  range  in  Michigan,  Wisconsin,  and  Minnesota. 
No  new  facts  on  the  geology  of  the  region  are  added  to  those  already 
recorded. 
Duparc,84  in  1900,  describes  the  copper-bearing  (Keweenawan) 
rocks  of  the  northwest  extremity  of  Keweenaw  Point,  Michigan.  The 
article  is  throughout  merely  a  summary  of  previous  reports  on  this 
area  by  the  geologists  of  the  Michigan  and  United  States  surveys, 
and  this,  moreover,  without  a  single  reference  to  such  reports. 
Van  TTlse  and  Bayley,85  in  1900,  describe  and  map  the  geology 
of  a  portion  of  the  Menominee  iron  district  of  Michigan. 
