138  PRE-CAMBRIAN    ROCKS    OF    NORTH   AMERICA.  [bull. 86.1 
at  Bete  Grise  bay,  tbe  sandstone  dips  away  from  the  north-dippingi 
Keweenawan  diabases  at  quite  a  high  angle  near  the  contact,  whiehj 
rapidly  flattens  as  it  is  receded  from.  Finally  along  the  north  face  obi 
the  South  range  eastward  from  lake  Agogebic  the  sandstone  is  not] 
infrequently  met  in  a  flat-lying  position,  and  at  one  place  lies  directly] 
across  the  course  of  the  Keweenawan  belt. 
As  to  the  age  of  the  Eastern  sandstone,  it  is  regarded  as  demon-! 
strated  that  it  is  older  than  the  Trenton;  hence  its  Triassic  age  is  notl 
discussed.  The  Western  sandstone  is  regarded  as  the  equivalent  of  the 
Eastern  sandstone,  although  they  are  not  found  connected,  nor  is  the| 
Western  sandstone  at  any  point  connected  with  the  Mississippi  valley] 
Cambrian  sandstone.  It  has,  however,  already  been  shown  that  the 
Keweenawan  rocks  rest  unconformably  under  the  Cambrian  sandstone^ 
of  the  Mississippi  valley  in  western  Wisconsin. 
The  Animikie  series  in  the  Thunder  bay  district  is  of  great  thickness?] 
probably  uj)ward  of  10,000  feet,  comprising  quartzites,  quartz- si ates,jj 
clay-slates,  magnetitic  quartzites,  sandstones,  thin  limestone  beds,  andl 
beds  of  cherty  and  jaspery  material.  With  these  are  associated  mJ 
great  volume  both  in  interbedded  and  intersecting  masses  coarse  gab- 
bro  and  fine  grained  diabase,  like  those  well  known  in  the  Keweenaw 
series.  A  broad  examination  of  the  region  shows  that  there  is  little: 
ground  for  the  belief  in  one  crowning  overflow.  The  Animikie  series  is? 
lithologically  like  the  Penokee  range  in  Wisconsin;  both  series  bear  the! 
same  relations  to  the  newer  Keweenawan  rocks  and  the  older  gneisses,* 
and  the  two  groups  are  regarded  as  the  same. 
The  Animikie  rocks  are  also  the  equivalent  of  if  not  actually  continu-  j 
ous  with  the  Mesabi  iron  range  running  to  Pokegama  Falls  and  the? 
slates  of  the  St.  Louis  river,  although  these  latter  are  affected  by  slatyj 
cleavage. 
The  Original  Huronian  of  Logan  is  compared  with  the  Animikie^ 
slates  of  Thunder  bay  and  the  two  are  regarded  as  equivalent.    Tiny 
Marquette  and  the  Menominee  Huronian,  with  minor  exceptions  duej 
perhaps  to  metasomatic  changes,  are  lithologically  like  the  Animikie] 
and  Penokee  series,  and  are  also  regarded  as  belonging  to  the  samel 
horizon.    The  Original  Huronian,  the  Animikie  slates,  the  Penokee'; 
iron  rocks,  and  iron- bearing  rocks  of  Marquette  and  Menominee  appear  1 
then  to  belong  together  and  may  hence  properly  be  called  Huronian.: 
The  Huronian  schists  in  each  of  these  areas  are  limited  by  granite  and 
gneiss.    There  are,  however,  considerable  areas  of  crystalline  schists  ■ 
the  relations  of  which  are  doubtful,  and  it  is  suspected  that  in  several 
of  the  iron  regions  there  are  two  distinct  kinds  of  schists,  those  belong- 
ing to  the  Huronian  and  a  schistose  greenish  phase  belonging  with  an 
older  series.     It  is  also  possible  that  a  portion  of  the  granites  are  erup- 
tive and  relatively  new,  while  others,  and  especially  those  connected 
with  the  gneisses,  may  be  of  some  sort  of  metamorphic  origin  not  un- 
derstood.   The  iron-bearing  schists  of  Vermilion  lake  are,  however,  so 
