vaxhi-f!  lake  superior  region.  189 
Underlying  both  the  Animikie  and  Penokee  series  is  a  complex  of 
granites  and  schists,  the  unconformity  between  which  and  these  series 
is  of  the  most  pronounced  character.  That  the  Animikie  series  istluis 
separated  from  the  underlying  rocks  has  been  seen  by  all  who  have 
studied  it.  Above  both  series  follows  the  Keweenawan.  In  both  dis- 
tricts, in  passing  at  any  place  from  the  underlying  rocks  to  the  Kewee- 
naw series  in  section,  the  two  are  in  apparent  conformity;  but,  when 
the  lines  of  contacts  between  the  iron-bearing  and  the  Keweenaw 
series  are  followed  for  some  distance,  both  with  the  Animikie  and 
Penokee  series,  this  apparent  conformity  is  found  to  be  illusory.  That 
is,  the  Keweenaw  series  is  found  to  come  in  contact  with  one  member  of 
the  underlying  series  atone  place  and  with  another  member  at  another 
place,  until  in  both  districts  at  one  or  more  places  the  entire  iron-bearing 
series  is  cut  off,  the  basal  Keweenaw  rocks  coming  directly  in  contact 
with  the  fundamental  complex.  These  relations  mean  that  between 
the  deposition  of  the  Penokee  and  Animikie  series  and  the  outflows  of 
Keweenaw  time  there  intervened  a  period  of  erosion  which  was  suffi- 
cient in  places  to  remove  the  whole  of  the  inferior  series  and  to  cut 
in  some  places  quite  deeply  into  the  fundamental  complex.  There  is 
then  an  immense  time  gap  between  these  series  and  the  Keweenawan, 
although  this  unconformity  does  not  approach  in  the  length  of  time  in- 
volved to  that  separating  the  Animikie  and  Penokee  series  from  the 
underlying  schists  and  granites. 
The  Animikie  series  in  its  most  typical  development  extends  from 
Gunflint  lake  on  the  national  boundary,  between  Minnesota  and  Ontario, 
to  Thunder  bay,  lake  Superior.  The  Penokee  series  lies  upon  the  oppo- 
site side  of  lake  Superior.  The  latter  is  a  simple  unfolded  succession 
dipping  to  the  northward  under  the  lake;  the  Animikie  is  another  such 
succession  dipping  to  the  southward  under  the  same  body  of  water. 
There  is  then  little  doubt,  considering  all  the  facts,  that  the  two  series 
represent  a  single  period  in  the  history  of  the  synclinal  trough  which 
forms  the  basin  of  lake  Superior.  The  relations  and  likeness  of  the 
Penokee  and  the  Animikie  series  have  been  repeated  at  length  as  show- 
ing the  breadth  of  the  geological  basin  in  which  the  deposition  of  like 
rocks  was  taking  place  simultaneously.  The  equivalency  here  shown 
is  a  long  step  in  understanding  the  equivalency  of  other  rocks  in  the 
lake  Superior  basin. 
SUCCESSION   ANlKEtji;i\  ALENTS    <>F   THE   MARQUETTE    DISTRICT   SERIES. 
In  the  Marquette  district,  as  the  succession  has  already  been  dis 
cussed,  it  need  here  be  only  briefly  repeated.     It  is  as  follows:  At  the 
base  is  the  Archean  gneiss-granite-schist  complex.     In  ascending  order 
follow  Che  Lower  and  Upper  Marquette,  having  the  litliological  charac- 
ters aj  J  relations  above  described. 
MiMh  work  remains  to  be  done  in  this  district  which  has  been  stud- 
ied sf  closely.     From  present  knowledge  it  is  not  even  definitely  known 
