GREAT    NORTHERN    INTERIOR   OF   CANADA.  543 
crystalline  rocks  and  of  their  relations  to  one  another  has  changed 
the  views  of  the*  writer,  and  he  now  considers  the  unaltered,  so-called 
Cambrian  rocks  to  be  the  equivalents  of  many  of  the  gneisses  and 
schists  classed  as  Laurentian  (Grenville  series),  and  the  Huronian 
areas  of  the  Labrador  Peninsula  to  represent  a  portion  of  the  un- 
altered rocks  and  their  associated  basic  eruptives  (traps,  trap  ash, 
etc.)  altered  by  the  irruption  of  granite  and  rendered  schistose  by 
pressure.  The  granites  which  have  been  classed  as  typical  Lauren- 
tian always  cut  and  alter  the  bedded  rocks  wherever  seen  in  direct 
contact  with  them,  and  are  consequently  newer  than  the  latter. 
During  the  last  season  (1899)  very  thin  layers  of  carbon  with  some 
resemblance  to  organic  forms  were  found  in  the  sandstones  of  Cotter 
Island;  these  have  the  appearance  of  lowly  organized  plant  life,  lower 
than  the  known  fossils  from  the  lowest  beds  of  the  Cambrian,  and 
consequently  this  formation  is  older  than  the  Cambrian.  It  is  pro- 
posed, therefore,  to  class  these  so-called  Cambrian  unaltered  rocks  as 
Laurentian,  as  they  represent  the  oldest  known  sedimentary  rocks  in 
northeastern  America  and  probably  in  the  world. 
Low,62  in  1903,  describes  and  maps  the  geology  of  the  east  coast 
of  Hudson  Bay.  All  the  rocks  except  those  which  form  the  chains  of 
islands  along  shore  between  Portland  Promontory  and  Cape  Jones, 
and  also  a  narrow  margin  on  part  of  the  coast  in  the  same  region, 
have  been  cut  by  granite,  which  has  not  only  intimately  penetrated 
them  but  by  its  heat  and  pressure  has  so  changed  them  to  crystalline 
schists  and  gneisses  that  only  in  a  few  places  can  any  trace  of  an 
original  sedimentary  origin  be  found.  The  unaltered  sedimentary 
rocks  with  their  associated  sheets  of  trap  and  diabase  bear  a  remark- 
ably close  resemblance  not  only  to  the  so-called  Cambrian  rocks  of 
other  parts  of  the  Labrador  Peninsula  but  also  to  the  iron-bearing 
rocks  of  the  southern  shores  of  Lake  Superior  and  the  Animikie  and 
Nipigon  rocks  to  the  north  of  Lake  Superior.  In  all  likelihood  they 
are  of  pre-Cambrian  age  and,  in  the  opinion  of  the  writer,  are  the 
oldest  known  sedimentary  rocks  of  Canada.  Notwithstanding  this 
opinion  they  will  continue  to  be  classed  as  Cambrian  in  order  to  cor- 
respond with  the  areas  of  similar  rocks  of  Labrador  which  have  al- 
ready been  so  classed.  The  series  comprises,  from  the  base  up :  Coarse 
arkose,  banded  arkose,  sandstone,  and  graywacke,  chert  impregnated 
with  oxide  of  iron  and  red  jasper,  cherty  carbonate,  carbonaceous 
shales,  and*  sandstone.  Included  in  this  series  are  sheets  or  laccoliths 
of  dark-green  trap.  This  rock  also  flowed  out  to  the  surface.  The 
basement  rock  from  which  this  series  is  derived  has  not  been  recog- 
nized in  the  region  under  discussion. 
Bell,63  in  1903,  describes  and  maps  the  geology  of  the  basin  of 
Nottaway  River.  Granites  and  gneisses  referred  to  the  Laurentian 
occupy  the  larger  portion  of  the  area.     They  are  for  the  most  part 
