NEW    BRUNSWICK,    NOVA    SCOTIA,    NEWFOUNDLAND,    ETC.       517 
part  of  Avalon.  Dikes  of  various  kind  intersect  the  formation,  and 
the  strata  are  in  places  volcanic  conglomerates,  volcanic  ashes,  etc. 
The  rocks  of  Brigue,  described  in  the  report  for  1808,  are  found  to 
contain  several  beds  which  are  crowded  with  Aspidella. 
Murray,78  in  1873,  finds  gneissic  rocks  at  several  localities  in  St. 
Georges  Bay.  Associated  with  these  are  labradorite  and  other 
anorthosite  rocks  wThich  belong  to  the  upper  Laurentian  system. 
Also,  on  Great  Codroy  River  is  found  white  crystalline  limestone 
with  graphite,  which  is  regarded  as  a  further  indication  of  the 
presence  of  this  division  of  the  Laurentian. 
Murray,79  in  1875,  finds  on  Gander  Lake  micaceous  slate,  fine- 
grained granite,  and  gneiss,  which  are  correlated  with  the  Lauren- 
tian gneiss  of  Bonavista  Bay. 
Howley,80  in  1877,  further  examines  Gander  Lake  and  River  and 
finds  chlorite  slates,  diorites,  and  mica  slates  which  contain  no  or- 
ganic remains,  and  which  on  account  of  their  lithological  character 
and  the  serpentine  they  contain  are  provisionally  placed  with  the 
Quebec  group.  At  Upper  Gambo  Pond  and  along  Riverhead  Brook 
are  found  sandstones  and  quartzites  which  at  some  places  pass  almost 
imperceptibly  into  gneiss,  which  rocks,  with  the  associated  micaceous 
slates,  are  provisionally  placed  with  the  Huronian. 
Howley,81  in  1882,  further  describes  the  intermediate  system  of 
Huronian  rocks.  These  metamorphic  rocks  occupy  the  greater  part 
of  the  peninsula  of  Avalon.  They  rest  upon  a  nucleus  of  Laurentian 
gneiss  and  are  succeeded  by  fossiliferous  beds  of  the  Primordial  age 
which  skirt  the  shores  of  the  bays  and  are  found  to  rest  unconform- 
ably  on  the  basset  edges  of  the  upturned  and  altered  Huronian,  and 
occasionally  in  contact  with  the  still  older  Laurentian.  The  inter- 
mediate rocks  are  found  to  be  gently  folded,  so  that  the  same  strata 
are  rejueated  several  times.  Associated  with  these  Huronian  rocks 
are  trappean  beds  and  volcanic  ash.  Contained  in  them  are  found 
two  fossils,  Aspidella  terranovica  and  Arenicolites  spirales.  The 
last-named  fossil  is  said  to  occur  in  the  Primordial  rocks  of  Sweden. 
These  fossils  give  important  assistance  in  the  ready  recognition  of 
the  Huronian.  The  gneissic  rocks  which  have  been  described  as 
being  members  of  the  Laurentian  system  protrude  through  the  Hu- 
ronian strata  by  which  they  are  surrounded.  Cutting  the  Huronian 
rocks  is  found  a  series  of  granitoid  and  other  plutonic  rock-  which 
obliquely  intersect  the  eastern  part  of  the  peninsula,  including  the 
Laurentian  gneiss.  A  second  great  igneous  intrusion  cuts  all  of  the 
rocks  of  the  western  part  of  the  peninsula,  including  the  Potsdam 
sandstone.  The  intrusions  of  the  eastern  peninsula  are  taken  to  be 
of  older  date  than  the  trap  of  the  western  peninsula,  although  prob- 
ably later  than  Huronian,  as  the  former  is  never  found  Lo  cut  the 
Potsdam  sandstone. 
