188        PRE-CAMBRIAN  KOCKS  OK  NORTH  AMERICA.     [bull.-86: 
rolled  and  are  mostly  of  chert,  but  arc  sometimes  jasper;  This  chert  and 
jasper,  whatever  their  origin,  were  in  their  present  -condition  before 
the  deposition  of  the  Penokee  series  proper. 
Further,  the  relative  geographical  positions  of  the  Penokee,  the 
Upper  Marquette,  and  the  Chippewa  quartzite  districts  are  such  as  to 
strongly  suggest  that  they  were  once  connected.  The  Penokee  series 
at  the  east  is  cut  off  by  the  unconformable  overlying  lake  Superior 
sandstone:  but  east  of  the  south  end  of  Gogebic  lake  there  are  here 
and  there  outcrops  of  slate  which  are  like  the  Upper  Slate  member  of 
the  Penokee  district,  and  a  short  distance  to  the  east  the  narrow  belt 
spreads  out  into  the  broad  area  of  upper  fragmental  rocks,  of  which 
the  Marquette  and  Menominee  districts  are  arms.  At  the  west  the 
Penokee  series  has  been  entirely  swept  away  by  erosion,  the  copper- 
bearing  rocks  coming  in  contact  with  the  underlying  gneisses  and 
granites;  but  to  the  southwest  ward  appear  the  fragmental  quartzites 
of  the  Chippewa  valley,  which  are  believed  to  be  its  continuation. 
The  equivalency  of  the  Penokee  series  with  the  Animikie  is  as  plain 
as  the  equivalency  of  any  two  areas  of  detached  rocks  in  a  single  geo- 
logical basin  can  possibly  be  in  which  is  lacking  clear  paleontological 
evidence.  It  has  been  seen  that  above  the  cherty  limestone  of  the  Pen- 
okee series  is  an  erosion  interval.  In  the  Animikie  series  proper  we 
know  of  no  equivalent  to  this  member,  and  in  what  follows  it  is  excluded 
from  the  discussion.  The  Penokee  and  the  Animikie  rocks  have  a  par- 
allelism in  lithological  characters  which  is  most  remarkable.  Not  only 
is  there  a  general  likeness  between  the  specimens  from  the  two  regions, 
but  almost-  every  phase  of  rock  from  the  Animikie  series  can  be  matched 
by  specimens  from  the  Penokee  series.  In  the  Animikie  district  the 
formations  underlying  the  iron-bearing  belt  are  not  extensively  exposed, 
and  consequently  little  is  known  of  the  Animikie  equivalent  of  the 
Quartz- Slate  of  the  Penokee  series.  But  along  the  Lower  Current 
river,  near  port  Arthur,  Ontario,  quartz-slates  underlying  the  iron- 
bearing  member  are  found  which  resemble  certain  phases  of  the  Peno- 
kee quartz  slate.  Beginning  with  the  iron  formations,  the  parallelism 
between  the  two  series  is  almost  exact.  The  irony  beds  upon  Gunflint 
lake,  where  are  found  the  best  known  exposures  of  the  formation,  are 
in  their  lower  parts  jasper,  magnetite-actinolite-schist,  and  cherty  ferru- 
ginous rocks  containing  more  or  less  iron  carbonate.  Higher  up  are 
thick  layers  of  thinly  bedded  cherty  iron  carbonate.  All  these  varie- 
ties of  rock  are  found  in  the  iron  formation  of  the  Penokee  series,  and 
at  many  places  the  order  of  succession  is  the  same.  Above  the  iron- 
bearing  belt  in  both  districts  is  a  great  thickness  of  fragmental  clay- 
slates  and  graywacke-slates  which  are  again  practically  identical  in 
character  in  both  districts.  It  is  true  that  in  the  western  part  of  the 
Penokee  district  mica-schists  have  developed  from  these  slates,  but  the 
original  condition  of  these  rocks  was  essentially  like  that  of  the  unal- 
tered phases. 
