122  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
Winchell  (N.  H.),162  in  1881,  describes  the  Cupriferous  series  of 
Minnesota  as  having'  a  wide  extent.  Iu  passing  from  the  shore  of  lake 
Superior  it  gradually  becomes  more  changed  and  crystalline.  The 
tilted  red  shales,  conglomerates,  and  sandstones  at  Fond  du  Lac  are 
the  same  as  those  associated  with  the  igneous  rocks  all  along  the  shore. 
At  Fond  du  Lac  they  lie  on  a  white  quartz  pebbly  conglomerate  a  few 
feet  in  thickness,  which  rests  unconformably  on  the  roofing  slates  of  the 
Huronian,  the  same  formation  that  succeeds  to  the  red  rock  formation 
at  Ogishki  Manissi  and  Knife  lakes,  northwest  of  Grand  Marais.  The 
Cupriferous  series  differs  from  the  Upper  Laurentian  or  Norian  only  in 
the  absence  of  beds  of  limestones,  but,  as  the  lake  Superior  Cupriferous 
is  Cambrian  or  Lower  Silurian,  it  is  inferred  that  the  so-called  Upper 
Laurentian,  containing  Eozoon  canadense,  is  really  Cambrian  or  Lower 
Silurian. 
Winchell  (N.  H.),163  in  1882,  continues  his  description  of  localities. 
At  Fond  du  Lac  the  detailed  succession  of  sandstones  and  shales  is 
given.  The  flint  and  jasper  formations  of  Gunflint  lake  appear  to  be 
in  apparent  unconformity  with  the  underlying  slates  and  syenites.  On 
Ogishki  Manissi  lake  is  found  a  great  conglomerate.  This  conglomerate 
carries  large  rounded  pieces  of  the  Saganaga  granite,  which  proves 
the  greater  age  of  that  granite  and  the  unconformability  to  it  of  the 
conglomerate.     The  conglomerate  also  contains  red  jasper. 
The  descending  succession  in  northeastern  Minnesota  is  (1)  the  horizon- 
tal quartzites  and  slates  running  from  Grand  portage  to  Gunflint  lake; 
(2)  the  conglomerate;  (3)  jaspery  and  calcareous  Gunflint  beds;  (4) 
gray  marble;  (5)  the  tilted  slaty  Ogishki  Manissi  conglomerate;  (6) 
amphibolitic  and  chloritic  slates;  (7)  mica-schists  alternating  with  syen- 
ite; (8)  syenites  and  granites  of  Saganaga  and  Gull  lakes.  As  to 
whether  the  Gunflint  beds  belong  with  the  schistose  and  tilted  slates 
and  conglomerates  of  Ogishki  Manissi  lake  is  an  open  question,  although 
there  are  several  things  which  indicate  that  they  belong  to  the  same 
series.  The  gabbro  is  found  to  have  a  widespread  extent.  It  is  sug- 
gested that  if  this  gabbro  and  the  associated  red  gneisses  belong  to  the 
Cupriferous,  the  Minnesota  and  Wisconsin  quartzites,  as  well  as  the 
red  gneisses  of  the  Upper  Mississippi  valley,  may  also  belong  to  this 
series.  The  red  syenite  of  Beaver  bay  is  a  metamorphosed  conglome- 
rate which  was  brecciated  and  mingled  with  the  trap.  This  red  rock 
was  fluidized  so  as  to  intrude  itself  in  the  form  of  belts  and  veins.  A 
conglomerate  at  Taylors  falls,  on  the  St.  Croix,  contains  water- worn 
bowlders  and  traps  of  the  region,  but  the  superposition  of  the  conglom- 
erate on  the  trap  can  not  actually  be  seen.  This  sandstone  is  fossil- 
iferous.  It  is  concluded  that  the  Potsdam  is  represented  by  the  copper- 
bearing  series,  while  the  underlying  Animikie  is  equivalent  to  the 
Taeonic  of  Emmons. 
Upham,164  in  1884,  describes  the  crystalline  rock  outcrops  in  central 
Minnesota. 
