LAKE  SUPERIOR  REGION.  217 
Bayley,180  in  1893,  gives  fully  the  field  occurrences,  relations,  and 
petrography  of  the  eruptive  and  sedimentary  rocks  of  Pigeon  Point. 
The  oldest  rocks  are  interbedded  Animikie  slates  and  quartzites. 
Cutting  the  Animikie  rocks  is  an  olivine  gabbro,  which  occupies  all 
the  higher  portions  of  the  point.  It  is  in  all  probability  the  lower 
portion  of  a  large  dike  whose  upper  part  has  been  removed  by 
denudation.  Between  the  gabbro  and  the  bedded  rocks  in  many  places 
are  successively  a  coarse-grained  red  rock,  a  fine-grained  red  rock 
(quartz  keratophyre),  and  a  series  of  contact  rocks.  The  main  masses 
of  the  keratophyre  occupy  a  position  between  the  Animikie  sedi- 
mentaries  and  the  gabbro.  This  rock  has  all  the  characteristics  of 
an  eruptive  younger  than  the  gabbro.  The  coarse-grained  rocks  be- 
tween the  gabbro  and  the  keratophyre  are  intermediate  in  character 
between  the  two,  and  grade  into  them.  They  are  therefore  regarded 
as  a  contact  product  formed  by  the  intermingling  of  the  gabbro 
and  keratophyre  magmas.  The  keratophyre  also  apparently  grades 
into  the  Animikie  slates  and  quartzites,  there  being  three  zones  show- 
ing diiferent  grades  of  alteration  of  the  sedimentary  rocks  due  to  the 
contact  with  the  igneous  rock. 
From  the  peculiar  relations  it  is  regarded  as  probable  that  the 
keratophyre  is  of  contact  origin ;  that  is,  it  was  produced  by  the 
fusion  of  the  slates  and  quartzites  of  the  Animikie  through  the  action 
upon  them  of  the  gabbro.  The  magma  thus  formed  then  acted  in  all 
respects  like  any  intrusive  magma.  It  penetrated  the  surrounding 
rocks  in  the  form  of  dikes,  and  solidified  as  a  soda  granite  under  cer- 
tain circumstances,  and  under  others  as  a  quartz  keratophyre.  Cut- 
ting all  of  the  previously  mentioned  rocks  are  diabase  dikes. 
Grant,  181  in  1893,  publishes  his  note  book  made  on  a  trip  in  north- 
eastern Minnesota.  The  areas  visited  were  those  of  Kawishiwi  River, 
Snowbank  Lake,  Kekequabic  Lake,  and  Saganaga  Lake.  In  the 
study  of  these  areas  there  was  no  evidence  found  of  a  transition  from 
semicrystalline  and  crystalline  schists  into  granite.  On  the  other 
hand,  abundant  evidence  was  found  of  the  eruptive  nature  of  the 
granite  rocks  into  the  surrounding  sediments.  The  gneissic  and  so- 
called  bedded  structure  in  the  granitic  rocks  is  not  as  common  as  has 
been  supposed,  the  structure  usually  being  truly  granitic.  The 
Kawishiwi  River  and  Snowbank  Lake  massive  rocks  are  hornblende 
syenites.  The  Saganaga  rock  is  a  coarse  hornblende  granite.  That 
around  Kekequabic  Lake  is  a  pyroxene  granite,  and  associated 
with  it  is  peculiar  pyroxene  granite  porphyr}^.  The  intrusive 
character  of  the  granite  is  particularly  well  shown  between  sees.  31 
and  32,  T.  63  N.,  R.  10  W.,  near  Clearwater  Lake,  and  in  the  SE.  \ 
SW.  \  sec.  26,  T.  64  N.,  R.  9  W.,  on  the  west  shore  of  Snowbank 
Lake.    Along    Kawishiwi  River  the  rocks  mapped  comprise  gabbro, 
