LAKE   SUPERIOR  REGION". 
iron-bearing  formation  of  the  Marquette  series,  and  the  two  are  re- 
garded as  equivalent.  If  this  be  true,  the  Lower  Marquette  quartzite 
may  represent  the  lower  quartzitic  portion  of  the  Michigamme  jasper 
formation,  in  which  case  the  whole  of  the  Lower  Marquette  scries 
would  be  represented  by  the  highest  member  of  the  Lower  Menominee. 
The  absence  in  the  Marquette  district  of  the  equivalent  of  the  great 
thickness  of  limestone,  quartzite,  and  eruptives  below  the  Michi- 
gamme jasper  in  the  Menominee  district  is  accounted  for  by  supposing 
that  the  Marquette  area  was  more  elevated,  and  that  the  transgression 
of  the  ocean  from  the  south  reached  the  Marquette  district  when  the 
lower  portion  of  the  Michigamme  jasper  was  being  deposited.  If  the 
above  correlation  be  correct  it  further  follows  that  the  principal  ore 
formation  of  the  Menominee  has  no  equivalent  in  the  Marquette  dis- 
trict. 
The  Mount  Mesnard  series  of  quartzite,  limestone,  and  slates,  as 
described  by  Wadsworth,  in  the  eastern  part  of  the  Marquette  area, 
between  the  Cascade  range  and  Lake  Superior,  has  many  points  of 
resemblance  to  that  part  of  the  Lower  Menominee  series  below  the 
Michigamme  jasper.  The  age  of  the  Mount  Mesnard  series  is  still 
in  doubt,  but  if  it  should  prove  to  underlie  the  Lower  Marquette 
(Wadsworth's  Republic  formation)  its  position  would  probably  indi- 
cate the  limit  of  the  old  Marquette  highland  on  the  eastern  side. 
Smyth  (H.  L.),70  in  1894,  describes  a  quartzite  tongue  in  the 
jasper  at  Republic.  This  tongue  branches  from  the  main  mass  of 
quartzite,  and,  after  continuing  nearly  parallel  with  it  for  a  long- 
distance, tapers  to  a  point  toward  the  north  in  a  mass  of  specular 
jasper.  The  quartzite  tongue  includes  between  itself  and  the  main 
quartzite  a  similar  jasper  tongue,  which  starts  in  the  north  from 
the  jasper  and  tapers  to  a  point  toward  the  south  in  the  quartzite. 
the  two  tongues  interlocking.  These  unusual  relations  are  explained 
as  due  to  faulting  approximately  parallel  to  the  fold  which  occurred 
during  the  folding  of  the  series. 
Hubbard,71  in  1895,  describes  the  relation  of  the  copper  vein  at  the 
Central  mine,  Keweenaw  Point,  to  the  Kearsarge  conglomerate.  The 
veins  of  Keweenaw  Point  belong  largely  to  one  system,  and  are  con- 
fined principally  between  T.  57  N.,  R.  3g  \Y..  and  the  northeast 
extremity  of  the  Point.  The  copper-bearing  formation  between  these 
limits  dips  N.  33°  E.,  at  the  first  locality,  to  south  of  east  at  the 
last,  and  the  veins  are  nearly  at  right  angles  to  the  formation.  The 
Central  mine  is  situated  in  sec.  23,  T.  58  N.,  R.  31  W.,  about  18  miles 
northeast  of  Calumet.  Here  there  has  been  a  northerly  sliding  of  the 
formations  above  the  Kearsarge  conglomerate,  as  a  result  of  which 
the  copper  vein  in  the  overlying  formations  is  found  to  stop  abruptly 
