124  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86 
Mesabi  range  belonging  in  the  Anhnikie,  and  the  hematite  of  the  Ver 
milion  mines,  which  seems  to  be  the  equivalent  of  the  Marquette  an( 
Menominee  iron  ores. 
Winchell  (N".  H.),169  in  1885,  finds  in  the  red  quartzite  at  Pipestom 
two  fossils,  Lingula  calumet  and  Paradoxides  barberi,  which  are  takei 
as  indicative  that  this  formation,  as  well  as  the  Sioux  quartzite  of  low; 
and  Dakota,  the  Baraboo  quartzites  of  Wisconsin,  the  quartzites  o 
southwestern  Minnesota,  as  well  as  the  associated  red  gneisses,  felsites 
and  felsite-porphyries,  are  all  Primordial. 
Upham,170  in  1885,  gives  descriptions  of  the  quartzites  of  Minnehaln 
county,  Dakota.  These  are  not  infrequently  ripple-marked  and  cons 
glomeratic;  they  are  like  the  quartzites  of  Pipestone  county  in  Minne 
sota,  and,  like  them,  are  placed  in  the  Potsdam. 
Winchell  (N.  H),171  in  1885,  divides  the  crystalline  rocks  of  th( 
northwest  into  six  groups,  in  descending  order:  (1)  A  granitic  anc 
gabbro  group,  whicli  is  a  part  of  Irving's  Cupriferous,  and  is  by  Hunt 
parallelized  with  the  Montalban.  It  includes  rocks  which  have  passed 
for  typical  Laurentian;  while  the  gabbros  are  eruptive  and  are  like  the 
Upper  Laurentian  or  Norian  of  Canada.  The  granites  and  gneisses 
show  evidence  of  metamorphic  origin.  Below  the  granite  and  gabbrc 
is  (2)  a  mica-schist  group.  This  is  penetrated  by  biotite- granite.  (3; 
Is  the  black  mica-slate  group,  whicli  often  contains  graphitic  schists. 
in  which  are  such  ore  deposits  as  the  Commonwealth  mine  of  Wiscon- 
sin. (4)  Is  a  series  of  obscure  hydromicaceous  and  greenish  magnesiaii 
schists,  along  with  quartzites  and  clay  slates,  with  which  are  the  more 
important  bodies  of  hematitic  iron  ores,  including  those  at  Marquette 
and  the  magnetic  belt  at  Penokee.  (5)  Is  the  great  quartzite  and  marble 
group.  It  includes  the  marble  of  Menominee  and  marble  and  lowei 
quartzite  of  Marquette,  the  great  conglomerate  of  Ogishki  Manissi  lake 
and  the  lower  slate-conglomerates  of  Canada.  In  (6)  are  the  granites 
and  syenites  with  hornblende-schists.  This  is  the  lowest  recognized 
horizon  of  the  Laurentian.  Nos.  3,  4,  and  5  together  are  the  equivalent 
of  the  Taconic  system,  3  being  the  equivalent  of  the  Animikie,  while  5 
is  the  equivalent  of  the  Huronian  of  Canada.  This  succession  is  com- 
pared with  the  successions  of  Brooks  and  Irving  in  Michigan  and  Wis- 
consin. 
Winchell  (Alex.),172  in  1887,  gives  detailed  observations  made  on 
an  extensive  trip  in  northeastern  Minnesota.  The  region  presents  a 
series  of  schists  flanked  on  the  north  and  south  by  massive  crystalline 
rocks.  In  the  western  part  of  the  district  these  rocks  are  gneissic  on 
both  sides,  but  to  the  east  the  gneissic  rocks  on  the  south  are  replaced 
by  gabbro  and  greenstone.  The  schists  and  bedded  crystallines  stand 
in  a  nearly  vertical  attitude,  having  a  persistent  and  uniform  strike 
and  dip,  tlie  latter  oscillating  from  80°  to  the  north  to  80°  to  the  south. 
The  rocks  are  sericitic,  chloritic,  micaceous,  and  hornblendic  schists,  and 
argillites  and  graywackes.    The  schists  grade  into  the  gneissic  rocks, 
