486  PEE-CAMBEIAN    GEOLOGY    OF    NOKTH    AMERICA. 
tary  rocks  of  Cambrian,  Cambro-Silurian,  or  even  Silurian  age  should 
not  assume  much  of  the  character  of  these  just  described.  It  is  now 
tolerably  clear  that  the  series  under  consideration  constitutes  the  low- 
est of  all  the  geological  formations  encountered  in  this  portion  of  the 
province. 
Both  plutonic  and  volcanic  rocks  occur  in  the  Eastern  Townships, 
including  granites  and  diorites,  some  of  which  are  at  least  as  late  in 
age  as  Lower  Silurian,  although  others  are  earlier,  as  is  shown  by  the 
fact  that  fragments  of  them  are  included  in  the  strata  referred  to  the 
Cambrian.  The  sedimentary  strata  are  altered  at  the  contacts  with 
these  intrusives.  These  granites  are,  however,  held  by  Selwyn  to  be 
metamorphic. 
Selwyn,7  in  1887,  states  that  at  the  Bras  Stream,  about  3  miles  from 
the  Chaudiere  River,  is  well  exposed  a  contact  of  the  crystalline  series 
with  the  black  slates,  showing  the  same  unconformable  relations  be- 
tween the  Cambrian  and  pre-Cambrian  as  on  the  Quebec  Central 
Railway.  The  granites  considered  by  Ells  as  intrusive  are  regarded  as 
more  probably  formed  in  situ  by  the  same  metamorphic  agencies  that 
have  altered  the  adjacent  strata,  and  the  so-called  dikes  are  probably 
due  to  segregation;  in  fact,  the  latter  are  rather  veins  than  dikes. 
The  granites  are  then  regarded  as  an  eifect  of  the  metamorphosing 
agencies  rather  than  the  cause  of  the  metamorphism. 
Ells,8  in  1889,  gives  a  second  report  on  the  geology  of  the  Quebec 
group.  Throughout  the  area  of  the  rocks  referred  to  the  Lower  Cam- 
brian no  fossils  have  yet  been  found,  but  they  resemble  the  lower  por- 
tion of  the  Cambrian  of  New  Brunswick.  The  most  that  can  be  said 
of  them  stratigraphically  is  that  they  are  intermediate  between  the 
chloritic  and  micaceous  schists  of  the  central  anticline  and  the  over- 
lying rocks  of  the  Sillery.  These  Cambrian  rocks  have  certain" beds 
which  closely  resemble  those  of  the  Potsdam  age  of  the  Sillery;  on 
the  other  hand,  it  is  not  easy  to  separate  them  from  the  underlying 
pre-Cambrian  schists,  although  at  certain  points  there  is  a  manifest 
unconformity  between  the  two  series,  as  is  well  shown  between 
Broughton  station  and  Harvey  Hill,  on  the  Quebec  Central  Railway ; 
the  regular  strike  of  the  underlying  chloritic  rocks  being  nearly  east- 
west,  while  the  overtying  black  slate,  with  which  are  associated  beds 
of  grayish  limestone,  at  times  strike  nearly  north-south.  The  differ- 
ence in  the  character  of  the  Cambrian  and  pre-Cambrian  strata,  to- 
gether with  the  occurrence  of  a  line  of  fault  between  the  crystalline 
schists  of  the  Sutton  Mountain  anticline  and  the  slates  and  serpentines 
to  the  east,  are  the  chief  reasons  for  the  separation  of  these  two  series 
into  pre-Cambrian  and  Cambrian.  The  pre-Cambrian  areas  found 
are  composed  mostly  of  alternations  of  chloritic  and  micaceous  schists. 
In  certain  localities,  as  at  Les  Saints  Anges,  are  found  micaceous 
black  and  gray  slates,  and  quartzites  with  crystalline  limestone,  which 
