266  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
In  the  Keewatin,  quartzites  are  unimportant;  there  are  no  true 
basal  conglomerates;  and  the  fragmentals  of  the  Lake  of  the  Woods 
are  of  volcanic  origin.  No  bedded  limestones  were  observed. 
Structurally,  also,  the  two  series  are  fundamentally  different.  The 
Lake  of  the  Woods  schists  are  folded  with  the  associated  granite 
gneisses,  which  are  referred  to  the  Laurentian,  while  the  Huronian 
series  has  not  partaken  of  the  folding  to  which  the  adjacent  gneisses 
have  been  subject.  Further,  the  large  areas  of  granite  are  found  to 
be  intrusive  in  both  the  Laurentian  gneiss  and  the  Keewatin  schists, 
while  in  the  Huronian  of  Logan  such  intrusions,  if  present  at  all,  are 
mentioned  at  only  one  locality.  The  slate  conglomerate  of  Dore 
River  appears  to  resemble  the  Lake  of  the  Woods  agglomerates,  but 
this  area  is  distant  from  the  typical  Huronian  region  and  the  rocks 
appear  to  differ  from  those  of  the  Huronian  lithologically,  as  well  as 
being  in  a  nearly  vertical  attitude.  These  differences  between  the 
Dore  and  Huron  areas,  with  their  geographical  separation,  may  war- 
rant the  belief  that  possibly  Logan  embraced  under  one  designation 
two  distinct  series.  As  to  Irving's  position  that  the  Animikie  series 
is  probably  the  equivalent  of  the  Huronian,  it  is  considered  exceed- 
ingly probable  that  the  flat-lying  unfolded  Animikie  is  much  later 
than  the  Lake  of  the  Woods  schists. 
The  rocks  of  the  region,  including  both  the  Laurentian  and  the 
Keewatin,  comprise  gneiss,  granite,  felsite,  schistose  hornblende 
rocks,  diabase,  diorite,  serpentine,  coarse  clastic  rocks  and  agglom- 
erates, mica  schists,  slates,  quartzites,  clay  slates,  felsitic  schists, 
hydromica  and  chlorite  schists,  carbonaceous  schists,  and  limestones. 
The  massive  granites  sometimes  grade  into  foliated  gneisses.  Dikes 
of  granite  have  sometimes  foliated  structures  parallel  to  their  sides. 
The  agglomerates  are  not  ordinan^  elastics,  but  are  of  volcanic  origin. 
Both  paste  and  included  fragments  have  evidently  had  a  common 
origin  and  been  laid  down  together,  perhaps  not  even  always  under 
water.  The  fragments  are  usually  more  or  less  elongated  or  lens 
shaped,  due  to  pressure.  The  greatest'  planes  in  the  fragments  are 
parallel  with  the  planes  of  schistosity,  which  are  usually  observably 
identical  with  those  of  bedding ;  at  times  the  agglomerates  merge  into 
mica  schists  on  the  one  hand  and  into  hornblende  schists  on  the  other. 
The  mica  schists,  micaceous  slates,  clay  slates,  and  quartzites  consti- 
tute a  natural  group  of  rocks  intimately  associated,  both  as  regards 
their  origin  and  their  present  relations  in  the  field.  They  are  all 
probably  ordinary  metamorphic  elastics.  The  felsitic,  sericitic,  and 
hydromicaceous  schists  are  probably  sediments,  the  material  of 
which  was  probably  volcanic.  The  mica  schists  frequently  pass  into 
finely  laminated  mica  gneisses.  The  limestones  are  found  only  in 
small  masses  and  seem  to  be  vein  stones  rather  than  bedded  strata. 
