328  PRE-CAMBRJAN   GEOLOGY   OF    NORTH   AMERICA. 
Correlation  of  pre- Cambrian  rocks 
Series. 
Mesabi  district. 
Penokee-Gogebic 
district. 
Vermilion  district. 
Marquette  dis- 
trict. 
Keweenaw  a  ii 
series  (copper 
bearing). 
Great  basal  gab- 
bro   and   gran- 
ite. 
Gabbros,    dia- 
bases, etc. 
Gabbro. 
a 
3 
a 
o 
< 
(A 
CD 
i 
2 
*3 
o 
3 
Upper    Hii- 
ro n  i  a  n 
(iron  bear- 
ing). 
Virginia  slate. 
Biwabik    forma- 
t  i  o  n     (iron 
bearing    and 
productive). 
Pokegama 
quartzite. 
Tyler  slate. 
Iron  wood     for- 
mation    (iron 
bearing    and 
productive). 
Palms     forma- 
tion   (quartz 
slate). 
Rove  slate. 
Gunflint     forma- 
tion (iron  bear- 
ing, b  u  t   non- 
productive). 
Michigamme 
slate  (locally 
replaced  by 
Clarksburg  for- 
mation). 
Bijiki  schist 
(iron  bear- 
ing). 
Goodrich  quartz- 
ite, containing 
productive  de- 
trital  ores  at 
its  base. 
Middle  Hu- 
roni an 
(iron  bear- 
ing). 
Lower-middle 
Huronion. 
Granite  inclusive 
in  lower  forma- 
tions. 
Slate    gray- 
wacke     con- 
glomerate   for- 
mation. 
Lower-mi  ddle 
Huronian: 
Intrusives. 
Knife  Lake 
slate. 
Agawa    forma- 
tion     (iron 
bearing,    but 
nonproduct- 
ive). 
Ogishke   con- 
glomerate. 
Negaunee  for- 
mation (iron 
bearing  and 
productive). 
Siamo  slate. 
Ajibik  quartzite. 
Lower    Hu- 
ronian. 
Limestone     of 
Bad  River. 
Quartzite. 
Wewe    slate. 
Kona     dolomite. 
Mesnard    quartz- 
ite. 
ft 
s 
o 
Laurentian  series     Granitea     „   n  d 
Granite    and 
granitoid 
gneiss. 
Intrusive     gran- 
ites, porphy- 
ries, and  green- 
stones. 
G  r  a  n  i  t  e,    sye- 
nite, peridotite. 
Palmer  gneiss. 
s 
I 
CO 
Tt 
M 
O 
-■ 
Keewatin    series 
(iron  bearing) . 
Greenstones, 
green   schists, 
and  porphyries. 
Greenstones, 
green  schists, 
and     fine- 
grained gneiss. 
Soudan      forma- 
tion    (iron 
bearing        and 
productive). 
Ely     greenstone, 
an        ellipsoid- 
ally  parted 
basic      igneous 
and    largely 
volcanic  rock. 
K  i  t  c  h  i     schist 
and      M  o  n  a 
schist,  the  lat- 
ter   banded, 
and    in    a    few 
places   con- 
taining       nar- 
row   bands    of 
n  onproductive 
iron   -   bearing 
formation. 
