QUEBEC    NORTH    AND    WEST    OF    ST.    LAWRENCE    RIVER.  461 
In  the  limestone  in  certain  places  are  masses  of  quartzose  rock  and 
crushed  gneiss,  presenting  the  aspect  of  a  true  conglomerate.  As  to 
the  thickness  of  the  gneiss,  on  Rouge  River,  the  most  favorable  place 
found  for  measurement,  the  section  gave  a  thickness  of  10,000  feet 
beneath  the  limestone,  if  there  is  no  break,  but  this  figure  may  not  be 
accurate,  as  faults  and  repetitions  of  strata  may  occur  at  several 
places. 
Intrusive  within  the  gneiss  and  limestone  are  the  anorthosite  and 
syenite  masses  of  Grenville  and  Chatham,  and  other  less  conspicuous 
masses.  No  fewer  than  six  or  seven  clearly  distinguished  periods  of 
intrusion  can  be  recognized.  The  augen  gneiss  of  Rouge  River  is 
probably  also  an  intrusive. 
The  succession  in  the  district,  as  determined,  is,  in  ascending  order : 
(1)  Reddish-gray  gneiss  without  distinct  signs  of  bedding  or  stratifi- 
cation, but  with  a  foliated  structure;  (2)  reddish  orthoclase  gneiss 
interstratified  with  hornblendic,  quartzose,  and  garnetiferous  gneiss 
and  beds  of  quartzite,  the  whole  showing  a  well-stratified  arrange- 
ment of  beds;  (3)  grayish  and  rusty  gneiss  passing  gradually  up- 
ward into  the  calcareous  portion  of  the  system,  between  the  gneiss  and 
the  limestone,  there  being  interstratifications  of  the  two;  (4)  schis- 
tose, sericitic,  chloritic,  and  micaceous  schists  of  the  Hastings  series. 
Division  4  overlies  the  crystalline  limestone,  and  is  believed  to  repre- 
sent the  lower  member  of  the  Huronian  system.  This  arrangement 
of  the  Laurentian  accords  very  closely  with  that  in  New  Brunswick 
as  given  by  Bayley  and  Matthew.  Unconformable  upon  the  Lauren- 
tian of  Ontario  is  the  Paleozoic. 
Adams,34  in  1893,  describes  the  typical  Laurentian  areas  of  Canada. 
The  basement  rock  here  found  is  the  Fundamental  gneiss.  It  is  uni- 
formly reddish  or  grayish  orthoclase-bearing  gneissoid  granite,  poor 
in  mica,  and  bisilicates.  The  foliation  is  often  due  to  movement  in  a 
plastic  condition.  Dark  bands  of  amphibolite  are  not  uncommon, 
and  hornblendic  and  pyroxenic  gneiss  appears  in  some  places.  The 
Fundamental  gneiss,  so  far  as  at  present  known,  is  a  complicated 
series  of  rocks,  for  the  most  part  of  unknown  origin,  but  comprising 
a  considerable  amount  of  intrusive  material. 
In  certain  parts  of  the  Laurentian  area,  and  notably  in  the  Gren- 
ville district,  the  Laurentian  has  a  different  character.  In  the  Gren- 
ville series  the  orthoclase  gneiss  is  still  the  predominating  rock,  al- 
though it  here  has  a  greater  variety  of  mineralogical  condition  and  is 
frequently  well  foliated.  Amphibolites,  hornblende  schists,  heavy 
beds  of  quartzite,  and  numerous  thick  bands  of  crystalline  lime- 
stones are  all  abundant  and  interstratified  with  one  another.  In  the 
series  are  ores  and  a  wide  variety  of  minerals.  In  the  limestone 
and  associated  rocks  graphite  is  often  widely  disseminated,  but  it  does 
