206  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
granulitic  veins,  as  well  as  dikes  of  diabase.  The  gneisses  and  gran- 
ites are  flanked  by  vertical  crystalline  schists  of  the  Vermilion  group. 
The  transition  from  the  gneisses  to  the  crystalline  schists  is  never 
abrupt,  but  is  a  structural  gradation,  near  the  line  of  junction  the 
beds  of  gneisses  and  schists  occurring  in  many  alternations.  Above 
the  Vermilion  group  are  the  Keewatin  semicrystalline  schists,  the  two 
series  being  everywhere  conformable ;  but  there  is  a  somewhat  abrupt 
change  from  one  group  to  the  other,  and  there  is  a  possibility  that 
the  original  unconformity  has  been  destroyed  by  lateral  pressure, 
although  such  an  unconformity  is  thought  improbable.  There  has 
been  no  actual  connection  traced  between  the  Keewatin  schists  north 
of  Gunflint  Lake  and  those  of  Knife  Lake.  The  Keewatin  schists 
are  almost  everywhere  vertically  bedded.  When  the  bedding  is  ob- 
scure this  is  sometimes  due  to  the  action  of  erupted  masses,  but  more 
often  the  metamorphosed  condition  of  the  strata  is  not  ascribable  to 
any  visible  cause.  The  Keewatin  schists  include  graywacke,  argil- 
lite,  sericite  schist,  chlorite  schist,  porphyrellyte  schist,  and  hematite. 
The  Ogishki  conglomerate  is  placed  as  a  part  of  the  Keewatin 
system,  as  it  is  traced  by  actual  gradations  into  the  adjoining  argil- 
lites.  These  argillites  and  associated  schists  are  in  continuity  with 
the  argillites  and  schists  of  Vermilion  Lake,  while  in  the  conglom- 
erate itself  are  local  developments  of  sericite  schist.  The  bedding  of 
the  conglomerate  is  nearly  vertical;  its  pebbles  are  metamorphosed; 
they  include  numerous  varieties,  among  which  are  syenite  resembling 
the  Saganaga  syenite,  greenstone,  porphyry,  red  jasper,  flint,  quartz, 
petrosilex,  ordinary  syenite,  diorite,  porphyroid,  siliceous  schist,  and 
carbonaceous  siliceous  argillite.  On  structural  as  well  as  lithological 
grounds  the  Ogishki  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  im- 
probable. 
The  Animikie  series,  resting  unconformably  upon  the  Keewatin, 
stretches  from  Thunder  Bay  past  Duluth  to  Mississippi  River,  and 
perhaps  includes  the  slates  as  far  west  and  north  as  Knife  Lake. 
The  Animikie  formation  is  generally  in  a  nearly  horizontal  posi- 
tion, the  dip  not  being  more  than  from  5°  to  15°.  The  formation  is 
essentially  an  argillite,  which  embraces  jaspery,  magnetitic,  hematitic, 
and  sideritic  beds.  At  Gobbemichigomog  Lake  the  Animikie,  repre- 
sented by  the  "  muscovado,"  is  in  its  characteristic  horizontal  posi- 
tion, 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  pro- 
posed. The  succession  of  terranes  in  northeastern  Minnesota  is, 
then,  in  descending  order,  as  follows:  (1)  Huronian  system,  more 
than  4,082  feet  thick,  including  the  magnetitic  group,  siliceous  group, 
