472  PRE-CAMBRIAN    GEOLOGY   OF    NORTH   AMERICA. 
ering  most  of  what  has  long  been  known  as  the  Original  Laurentian, 
and  summarizes  previous  work  in  this  district.  Archean  rocks,  occu- 
pying most  of  the  area  north  of  Ottawa  River,  are  mapped  as  crystal- 
line limestone,  gneiss,  quartzite,  anorthosite,  granite  gneiss,  and  por- 
phyry. In  the  text  the  limestones  with  the  quartzites  and  gneisses 
associated  with  them  are  described  as  sedimentary  and  are  classed  as 
Grenville,  and  the  underlying  gneisses  and  granite  gneisses  are  de- 
scribed as  of  igneous  origin  and  are  called  Fundamental  Complex,  the 
author  in  this  classification  following  previous  writers.  It  is  evident 
that  the  rocks  of  the  Grenville  series  are  decidedly  newer  than  those 
of  the  Fundamental  division.  As  for  the  numerous  and  often  large 
areas  of  red  granite  gneiss,  many  of  these  undoubtedly  are  of  more 
recent  date  than  either  of  the  others,  since  they  clearly  cut  both  the 
gneiss  and  the  limestone.  While  in  some  points  the  newer  granite 
gneiss  presents  features  similar  to  the  Fundamental  division,  as  in  the 
foliation  of  certain  portions,  there  is,  over  large  areas,  a  marked  dif- 
ference in  their  aspects  in  the  field. 
Osann,49  in  1902,  makes  a  detailed  petrographic  description  of  the 
crystalline  rocks  in  the  Original  Laurentian  area  of  the  Ottawa 
Valley. 
Adams,50  in  1902,  summarizes  the  present  status  of  the  geological 
mapping  of  the  Haliburton  and  Bancroft  areas,  Ontario.  The  survey 
has  shown  that  the  northern  half  of  the  area  mapped  consists  almost 
exclusively  of  granite  gneisses  of  igneous  origin,  which  would  in  all 
probabilit}^  have  been  classed  by  Logan  as  Fundamental  gneiss.  The 
southern  half  of  the  area,  on  the  other  hand,  consists  chiefly  of  a 
series  of  very  ancient  sedimentary  rocks,  largely  limestones,  which 
rests  upon  the  gneissic  series,  but  which  has  been  invaded  and  altered 
by  it.  Large  areas  of  the  sedimentary  series  have  been  so  shattered 
and  penetrated  by  the  granite  gneiss  that  a  sort  of  breccia  on  an 
enormous  scale  has  resulted.  Great  batholiths  of  the  granitic  rock 
arch  up  and  break  through  the  sedimentary  series  elsewhere,  the  lat- 
ter being  wrapped  around  the  batholiths  in  great  sweeping  curves. 
The  same  batholith  structure  is  observable  in  the  northern  gneisses 
also,  and  can  be  traced  by  the  curving  strikes  of  the  foliation  of  the 
gneiss,  but  here  the  limestones  have  been  swept  away  by  erosion. 
Graton,51  working  under  Adams,  in  1903,  describes  in  detail  the 
petrographical  relations  of  the  Grenville  limestones  and  granite  in 
the  township  of  Glamorgan,  Haliburton  County,  Ontario.  His  con- 
clusions are  of  importance  as  bearing  on  the  relations  of  limestones 
and  gneisses  over  other  extensive  areas  in  eastern  Canada,  the  Adiron- 
dacks,  and  New  Jersey.  The  writer  summarizes  his  conclusions  as 
follows : 
The  district  exhibits  a  development  of  Grenville  limestone  pierced 
by  intrusions  of  gneissic  granite,  which  contain  masses  of  dioritic 
