160  PEE-CAMBRTAN    GEOLOGY    OF    NORTH    AMERICA. 
granite,  resting  with  visible  contact  upon  the  Basement  Complex 
and  composed  of  material  mainly  derived  from  it.  South  of  the  Cas- 
cade range  there  are  again  a  number  of  localities,  from  sees.  34  to  32, 
T.  47  N.,  R.  26  W.,  where  there  are  basal  conglomerates,  the  great 
bowlders  again  being  mainly  identical  with  the  adjacent  granites, 
gneisses,  and  schists  of  the  Basement  Complex.  South  of  Summit 
Mountain,  in  the  west  half  of  sec.  25,  T.  47  N.,  R.  27  W.,  is  an  ex- 
posure of  the  basal  conglomerate.  The  conglomerate  grades  down- 
ward into  a  schist  which  is  scarcely  distinguishable  from  the  Palmer 
gneiss,  with  which  it  is  in  contact.  The  next  contact  to  the  west 
is  in  sec.  28,  T.  47  N.,  R.  27  W.,  where  the  phenomena  are  similar  to 
those  south  of  Summit  Mountain.  At  the  end  of  the  Republic 
trough  a  conglomerate  hangs  with  visible  contact  upon  the  flank 
of  the  Archean  granite,  bearing  well-rounded  waterworn  bowlders 
from  the  granite. 
At  the  north  side  of  the  Lower  Marquette  series  and  near  the  east 
end  of  the  district  there  is  exposed  a  magnificent  basal  conglomerate, 
about  3  miles  west  of  Marquette,  north  of  Mud  Lake.  The  next  con- 
tacts to  the  west  are  at  the  base  of  the  quartzite  east  and  west  of  Teal 
Lake.  At  one  place  here  the  relations  are  such  that  the  layers  of  the 
conglomerate  cut  across  the  foliation  of  the  subjacent  schists  at  an 
acute  angle.  Still  farther  west,  in  sec.  30,  T  48  N.,  R  28  W.,  contacts 
are  found  in  a  number  of  places.  West  of  this  point  the  only  actual 
contact  known  is  north  of  the  Michigamme  mine. 
The  unconformity  between  the  Lower  Marquette  and  Upper  Mar- 
quette series  is  also  well  marked.  At  the  close  of  Lower  Marquette 
time  the  land  was  raised  above  the  sea  and  gently  folded  and  eroded, 
and  the  Upper  Marquette  sediments  were  later  laid  down  unconform- 
ably  upon  this  floor.  In  general  the  discordance  between  the  Lower 
Marquette  series  and  the  succeeding  series  is  not  great,  being  meas- 
ured frequently  by  5°  to  10°,  at  other  times  by  10°  to  15°,  and  it  is 
only  rarely  that  the  plications  of  the  lower  series  are  such  as  to  make 
the  beds  abut  perpendicularly  against  those  of  the  overlying  series. 
Erosion  has  cut  deeper  in  the  Lower  Marquette  series  in  some  places 
than  in  others,  so  that  the  Upper  Marquette  series  rests  upon  differ- 
ent members  of  the  lower  series.  At  the  east  end  of  the  area  it  left 
a  very  considerable  thickness  of  the  iron-bearing  formation,  but  in 
places  to  the  west  this  formation  is  quite  cut  out.  Indeed,  in  places 
erosion  cut  through  the  Siamo  slate  and  the  Ajibik  quartzite,  and  in 
some  places  even  into  the  Basement  Complex.  This  particularly 
occurs  in  the  western  and  southwestern  parts  of  the  district,  west  of 
Champion  and  along  the  Republic  trough,  where  but  few  members  of 
the  Lower  Marquette  series  were  deposited.  Even  within  a  short  dis- 
tance the  differential  erosion  was  considerable.     For  instance,  at  the 
