218  PRE-CAMBRIAN   ROCKS    OF    NORTH   AMERICA.  [bull.  86. 
line  limestones,  with  associated  graphite  and  magnetite,  appears  to  in- 
dicate the  presence  of  Middle  Lanrentian.  These  rocks  occur  on  the 
southern  part  of  Baffin  land,  Frobisher  bay,  Cumberland  sound,  and 
Melville  peninsula.  The  term  Cambrian  is  made  to  include  all  rocks 
above  the  Huronian  to  the  base  of  the  Cambro-Silnrian.  Extensive 
areas  placed  in  the  Cambrian  on  the  Arctic  coast  and  in  the  vicinity  of 
Coppermine  river  are  analogous  in  character  to  those  of  the  Keweenaw 
or  Animikie  of  the  lake  Superior  region,  and  probably  represent  both 
groups  of  that  great  copper-bearing  series.  Throughout  the  northern 
part  of  the  continent  the  characteristic  Cambrian  formation,  composed 
largely  of  volcanic  rocks,  apparently  occupies  an  unconformable  position 
with  regard  to  the  underlying  Laurentian  and  Huronian  systems.  The 
present  remnants  show  that  these  rocks  have  undergone  comparatively 
little  subsequent  disturbance.  The  cape  Eawson  beds  of  Grinnell  land 
are  provisionally  referred  to  the  Cambrian,  on  account  of  their  litholog- 
ical  resemblance  to  the  rocks  of  the  Animikie,  and  also  on  account  of; 
their  similarity  to  the  Nova  Scotia  gold-bearing  series. 
In  the  above  summary,  as  the  terms  are  used  in  this  volume,  the  Mid- 
dle Laurentian,  much  of  the  Huronian,  and  the  Coppermine  andequiva-. 
lent  series,  which  are  placed  in  the  Cambrian,  are  to  be  included  in  the] 
Algonkiau ;  while  the  Lower  Laurentian  is  largely  or  wholly  Archean.  j 
SECTION  III.   THE  LOWER   ST.  LAWRENCE  RIVER  AND  WESTWARD  TO] 
LAKES   ST.   JOHN  AND  MISSTASSINI. 
LITERATURE. 
Bayfield,39  in  1840,  describes  granite  rocks  as  occupying  the  follow- j 
ing  districts:  Along  the  St.  Lawrence  from  the  Saguenay  to  pointe  del 
Monts,  a  distance  of  130  miles;  from  pointe  de  Monts  to  the  Seven \ 
islands,  a  distance  of  CO  miles,-  the  mainland  to  the  eastward  ofMingan 
islands  and  opposite  Ste.  Genevieve  island,  where  the  country  for  many 
miles  inland  is  composed  of  low  granite  mounds;  the  coast  from  Ste.  - 
Genevieve  east  to  cape  Whittle,  longitude  60°  W.,  latitude  50°  10'  ST.  | 
The  granites  are  in  part  hornblendic  and  in  part  nonhornblendic.     A 
Ste.  Genevieve  was  observed  hypersthene  and  Labrador  feldspar.    Th 
granitic  rocks  are  regarded  as  unstratified.    They  are  traversed  by 
trap  veins,  insignificant  in  size  as  compared  with  the  immense  size  offl 
the  lake  Superior  granite  masses.    Beposing  horizontally  on  the  granites  j 
on  the  east  side  of  Pillage  bay  and  mount  Ste.  Genevieve  are  limestones.  I 
The  islands  of  the  south  shore  of  the  St.  Lawrence  and  the  south  coast ' 
from  Sagnenay  to  cape  Bozier  are  composed  of  alternating  strata  of: 
graywacke  and  slate  dipping  to  the  southward  at  angles  varying  from 
30°  to  90°. 
Logan,40  in  1850,  describes  a  metamorphic  group  of  rocks  in  the, 
vicinity  of  bay  St.  Paul,  Murray  bay,  and  White  cape  on  the  St.  Law- 
rence river.     The  predominant  rocks  are  mica-gneisses  and  hornblende- 
gneisses.    No  crystalline  limestones  were  noted. 
