212  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
Ogishki  Lake  there  is  a  slate  conglomerate  similar  to  that  on  the 
north  shore  of  Lake  Huron.  This  conglomerate  is  not  the  same  as 
the  afirelomerates  of  the  Keewatin,  such  as  those  on  Stuntz  Island,  at 
Vermilion  Lake,  and  at  Ely.  The  Keewatin  is  always  nearly  vertical, 
while  (he  dip  of  the  Taconic  rarely  exceeds  15°.  The  iron-ore  beds 
of  the  Taconic  are  the  quartzose,  hornblendic,  magnetitic  group  of  the 
Pewabic  quartzite;  an  impure  jaspilite,  hematite,  and  limonite  group; 
a  carbonated  iron  group;  and  a  gabbro  titanic  iron  group.  The  jas- 
pilitic  hematite  group  has  the  same  lithological  peculiarities  as  the 
jaspilite  beds  of  the  Vermilion  range.  The  gabbro  in  which  the 
titanic  iron  occurs  constitutes  the  Mesabi  range.  This  has  been 
before  regarded  as  the  base  of  the  Keweenawan,  into  which  it  fades 
upwardly,  but  it  has  been  found  that  this  great  gabbro  flow  was  out- 
poured at  an  earlier  date,  and  it  is  placed  at  or  near  the  bottom  of  the 
Animikie. 
Winchell  (H.  V.),172  in  1891,  states  that  the  syenite  of  Saganaga 
Lake  is  conglomeratic  in  places  and  contains  pebbles  which  are  simi- 
lar to  one  another,  being  mostly  composed  of  lamellar  augite,  with  or 
without  grains  of  feldspar,  but  there  are  no  pebbles  of  syenite  or 
jasper,  such  as  occur  in  the  Keewatin  conglomerates.  In  the  Saga- 
naga granite,  at  the  end  of  the  portage  on  Granite  River,  is  a  band  of 
silica  1|  inches  in  diameter  and  3  feet  in  length.  North  of  Saganaga 
Lake  the  syenite  grades  into  chloritic  syenite  gneiss,  and  this  into 
thick-bedded  to  massive  Keewatin  rocks.  From  these  facts  it  is  con- 
cluded that  the  syenite  is  simply  a  result  of  locally  intense 
metamorphism. 
Bayley,173  in  1892,  concludes,  after  a  microscopic  examination  of 
the  specimens  obtained  in  the  neighborhood  of  Akeley  Lake,  from  the 
formation  designated  Pewabic  quartzite  by  the  Minnesota  geologists, 
that  they  are  granulitic  and  quartzose  phases  of  the  gabbro,  and  that 
none  of  them  are  sedimentary  rocks.  These  granulitic  and  quartzose 
gabbros  are  traced  into  ordinary  gabbros;  consequently  the  Pewabic 
quartzite  is  a  part  of  the  gabbro.  The  ore  beds  of  the  Akeley  Lake 
series,  interstratified  with  these  granulitic  gabbros,  also  belong  with 
the  overlying  gabbro  and  not  with  the  Animikie.  This  conclusion 
agrees  with  that  reached  by  Chauvenet  in  1883  and  1884.  This  iron- 
bearing  silicified  gabbro  has  been  traced  by  Bayley  southwestward 
through  sees.  25,  35,  34,  T.  65  N.,  R.  5  W.,  to  Michigamme  Lake.  The 
same  silicified  gabbro  belt  has  been  found  by  Merriam  at  Lake  Gob- 
bemichigomog. 
Grant,174  in  1892,  states  that  the  Animikie  rests  unconformably 
upon  the  Saganaga  granite,  that  the  Ogishki  conglomerate  is  intruded 
by  the  Saganaga  granite,  and  therefore  that  the  Ogishki  conglomer- 
ate is  earlier  than  and  separated  by  a  great  structural  break  from 
the  Saganaga  granite.     As  the  Keewatin  has  the  same  relations  to 
