508  PRE-CAMBKTAN    GEOLOGY   OF    NORTH   AMERICA. 
conformable  overlying  group  of  pre-Cambrian  age.  The  limestones 
in  every  case  cap  the  felsites,  with  which,  however,  they  often  seem 
to  blend  near  the  contacts  as  if  by  a  common  metamorphism.  As  evi- 
dence of  this  unconformity  are  cited  the  occurrences  of  limestone 
in  a  higher  position  than  the  syenites  and  felsites;  the  irregular 
line  of  contact  by  which  the  syenite  passes  under  the  limestone;  and 
the  absence  of  veins  and  dikes  of  syenite  in  the  limestone.  The  rocks 
are  sometimes  intricately  mingled,  as  at  Dallas  Brook,  where  layered 
felsite,  limestone,  and  slate  are  met  with,  while  on  the  top  of  the  hill 
limestone  occurs,  and  farther  back  syenite,  displaying  a  coarse  ad- 
mixture of  finely  foliated  gneiss.  In  some  localities  the  syenite  be- 
gins abruptly,  as  if  cutting  veinlike  across  the  strike  of  the  gneiss; 
in  others  the  change  from  syenite  to  gneiss  is  gradual.  The  gneiss 
is  associated  with  large  masses  of  white  quartzite.  Metamorphic 
rocks  are  described  which  are  referred  to  the  Devonian,  but  the 
evidence  is  so  slight  that  it  is  concluded  that  all  of  these  strata  may 
belong  to  an  older  period.  Between  them  and  the  pre-Cambrian 
series  there  is  a  marked  unconformity,  and  also  one  of  less  importance 
between  them  and  the  Carboniferous. 
Fletcher,58  in  1885,  finds  that  in  northern  Cape  Breton  the  sye- 
nitic,  gneissoid,  and  other  feldspathic  rocks  of  the  Lower  pre-Cam- 
brian group  are  intimately  mingled  on  Margaree  River  with  foliated 
rocks.  At  Coinneach  Brook,  Avhere  the  syenite  comes  in  contact  with 
the  contorted  mica  schist,  the  latter  is  seen  to  underlie  the  syenite. 
Higher  up  the  syenite  again  appears  and  contains  a  layer  5  feet  thick 
of  mica  schist,  which  is,  as  it  were,  intruded  among  the  syenites. 
Red  granite  overlies  unconformably  the  strata  of  the  George  River 
limestone  group  at  Fionnar  Brook. 
Gilpin,59  in  1880,  describes  the  pre-Cambrian  rocks  of  Cape  Breton 
as  including  a  felsite  series  and  a  crystalline  limestone  series,  the 
latter  unconformabhy  overlying  the  former;  both  are  referred  to 
the  Laurentian.  With  the  felsites  and  interstratified  porphyries  are 
also  syenitic  and  gneissic  rocks;  while  the  crystalline  George  River 
limestone  also  contains,  interstratified  with  the  limestones,  syenites, 
diorites,  mica  schists,  quartzites,  and  quartzose  conglomerates.  The 
limestone  area  is  limited  in  extent  as  compared  with  the  felsite  group. 
Fletcher,00  in  1887,  further  describes  the  pre-Cambrian  rocks  of 
a  part  of  northern  Nova  Scotia.  The  crystalline  rocks  here  found 
resemble  none  known  as  Cambrian  in  other  parts  of  Nova  Scotia, 
and  are  strikingly  like  those  beneath  the  Cambrian  in  Cape  Breton. 
Although  they  are  certainly  known  to  rest  unconformably  below  the 
Cambro-Silurian  strata,  a  part  or  all  of  these  rocks  may  be  Cambrian 
or  even  Cambro-Silurian.  Similar  gneisses  and  schists  in  southern 
New  Brunswick  have  been  included  by  Bailey  in  his  Cambro-Silurian 
