128  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull. 86. 
as  it  is  traced  by  actual  gradations  into  the  adjoining  argillites.  These 
argillites  and  associated  schists  are  in  continuity  with  the  argillites  and 
schists  of  Vermilion  lake,  while  in  the  conglomerate  itself  are  local  de- 
velopments of  sericite- schist.  The  bedding  of  the  con  glomerate  is  nearly 
vertical ;  its  pebbles  are  metamorphosed ;  they  include  numerous  vari- 
eties, among  which  are  syenite  resembling  the  Saganaga  syenite,  green- 
stone, porphyry,  red  jasper,  flint,  quartz,  petrosilex,  ordinary  syenite, 
diorite,  porphyroid,  siliceous  schist,  and  carbonaceous  siliceous  argillite. 
On  structural  as  well  as  lithological  grounds  theOgishki  conglomerate 
seems  to  be  a  part  of  the  Keewatin,  although  there  are  some  reasons 
for  suspecting  it  to  grade  into  the  Animikie.  That  the  Keewatin  schists 
are  eruptive  is  regarded  as  improbable. 
The  Animikie  series,  resting  unconformably  upon  the  Keewatin, 
stretches  from  Thunder  bay  as  far  as  Duluth  and  still  beyond  to  the 
Mississippi  river,  and  perhaps  includes  the  slates  as  far  west  and  north 
as  Knife  lake.  The  Animikie  formation  is  generally  in  a  nearly  hori- 
zontal position,  the  dip  not  being  more  than  from  5°  to  15°.  The  forma- 
tion is  essentially  an  argillite,  which  embraces  jaspery,  magnetitic, 
hematitic,  and  sideritic  beds.  At  Gobbemichigomog  lake  the  Animikie, 
represented  by  the  "  muscovado,"  is  in  its  characteristic  horizontal 
position,  while  the  vertically  bedded  terrane  underlies  it. 
For  the  system  of  semicrystalline  schists  subjacent  to  the  Animikie, 
to  which  the  term  Keewatin  has  been  applied,  Marquettian  is  proposed. 
The  succession  of  terranes  in  northeastern  Minnesota  is,  in  descending 
order,  then  as  follows :  (1)  Huronian  system,  over  4,082  feet  thick,  in- 
cluding the  magnetic  group,  siliceous  group,  and  argillite  group;  (2) 
Marquettian  system,  27,500  feet  thick,  including  the  Ogishki  group, 
10,000  feet  thick,  the  Tower  group  (earthy  schists),  15,000  feet  thick, 
and  the  graywacke  group,  2,500  feet  thick;  (3)  Laurentian  system, 
89,500  feet  thick,  including  the  Vermilion  group,  over  1,500  feet  thick, 
and  the  gneissic  group,  over  88,000  feet  thick.  Total,  more  than 
121,082  feet. 
Winchell  (H.  V.),176  in  1888,  gives  detailed  observations  about 
many  localities  in  northeastern  Minnesota.  The  mica-schist  and  inter- 
bedded  gneiss  are  cut  by  granite  veins  at  numerous  places. 
Winchell  (N.  H.),177  in  1888,  maintains  that  there  is  a  great  Pri- 
mordial quartzite  extending  from  New  England  through  Canada,  Wis- 
consin, and  Minnesota  to  the  Black  hills  of  Dakota.  It  includes  the 
Taconic  quartzite  of  Emmons,  that  of  Sauk  and  Barron  counties  in 
Wisconsin,  the  Sioux  quartzite  of  Dakota,  the  quartzites  of  Minnesota, 
and  those  of  the  Black  hills  of  Dakota.  At  the  exhibition  in  New 
Orleans  in  1884  was  seen  a  block  of  the  Potsdam  sandstone  of  the  state 
of  New  York  exactly  similar  to  the  Pipestone  quartzite  of  Minnesota, 
and  as  the  latter  bears  Primordial  fossils  there  is  no  lack  of  evidence  to 
parallelize  these  outcrops.    An  examination  of  the  quartzites  of  the 
