GREAT    NORTHERN    INTERIOR   OF    CANADA.  539 
and  schists,  conglomerate,  halleflinta,  ferruginous  chlorite  schists,  and 
other  green  schists. 
The  Laurentian  and  Huronian  are  unconformable  overlain  by 
horizontal  sandstones  and  conglomerates,  called  the  Athabaska  sand- 
stone, which  is  placed  in  the  Cambrian.  However,  these  sandstones 
are  similar  to  the  sandstones  found  to  the  north  associated  with 
quartz  porphyries,  diabases,  etc.,  like  those  of  the  Keweenawan  of 
Lake  Superior,  and  there  is  little  doubt  that  the  tAvo  sets  of  rocks 
belong  to  the  same  horizon. 
Low,51  in  1898,  reports  on  a  traverse  of  the  northern  part  of  the 
Labrador  Peninsula,  from  Richmond  Gulf  to  Ungava  Bay.  Lauren- 
tian rocks  occupy  the  greater  part  of  the  area.  These  are  chiefly 
granites,  more  or  less  foliated.  They  are  of  different  ages,  but,  ex- 
cept in  a  few  cases,  they  can  not  be  discriminated.  Cutting  them  are 
intrusive  diabases. 
Intimately  associated  with  the  granites  is  a  series  of  more  or  less 
quartzose  mica  gneisses  and  mica  schists,  interbanded  with  horn- 
blende schists  and  hornblende  gneisses,  and  at  times  with  quartz 
magnetite  gneiss.  These  gneisses  and  schists  are  supposed  to  repre- 
sent a  bedded  series  of  rocks  somewhat  similar  to  the  Grenville  series. 
While  most  of  the  schists  are  thus  probably  very  ancient,  others  may 
be  of  the  same  age  as  the  so-called  Cambrian. 
So-called  Cambrian  rocks  were  met  with  along  the. east  coast  of 
Hudson  Bay,  to  the  north  of  Cape  Johns,  and  on  Larch  River  from 
its  junction  with  the  Kaniapiskau  upward  for  30  miles.  A  section 
examined  on  the  east  side  of  Castle  Peninsula*  on  the  north  side  of  the 
outlet  of  Richmond  Gulf,  presents  rocks  closely  resembling  the  Mes- 
nard  quartzites  and  the  Kona  dolomites  of  the  Lower  Marquette  series 
of  the  south  shore  of  Lake  Superior,  capped  by  a  later  outflow  of  trap, 
classed  as  Algonkian  by  Van  Hise. 
Tyrrell,52  in  1898,  reports  on  an  exploration  of  Doobaunt,  Kazan, 
and  Ferguson  rivers  northwest  of  Hudson  Bay,  the  northwest  coast 
of  Hudson  Bay,  and  on  two  overland  routes  from  Hudson  Bay  to 
Lake  Winnipeg. 
Laurentian  rocks,  including  granites,  diorites,  and  granite  and 
diorite  gneisses,  occupy  a  large  part  of  the  region  crossed  by  the 
three  main  lines  of  travel — Doobaunt  River  and  Chesterfield  Inlet, 
Kazan  and  Ferguson  rivers,  and  the  west  coast  of  Hudson  Bay— 
although  their  precise  extent  is  unknown. 
The  Huronian  rocks  include  three  more  or  less  distinct   groups 
the  Marble  Island  quartzites,  the  greenish  quartzites  and  graywackes, 
and  the  more  or  less  highly  altered  and  often  schistose  diabases  and 
gabbros.     The  largest  area  of  Huronian  is  found  along  the  coast  of 
Hudson  Bay  from  Bakers  Foreland  south  to  a  point  4.o  miles  north 
