494  PRE-CAMBRIAN    GEOLOGY    OF   NORTH   AMERICA. 
ciated  with  beds  of  grit  and  conglomerate,  which  are  regarded  as 
probably  of  Huronian  age. 
Ells,17  in  1879,  finds  in  Albert,  eastern  Kings,  and  St.  Johns  coun- 
ties pre-Silurian  rocks,  which  are  placed  in  the  Huronian  and  Lauren- 
tian.  The  older  series  is  said  to  consist  of  syenite,  felsites,  feld- 
spathic  quartzites,  and  limestones.  In  many  places  are  transitions 
from  the  slates,  through  schists,  felsites,  and  gneisses,  to  syenites. 
The  newer  series  consists  of  felsitic,  siliceous,  brecciated,  and  ash 
rocks  at  the  base,,  with  talcose,  chloritic,  and  older  schists,  ash 
rocks  and  purple  grits,  and  conglomerates.  The  second  group  lies 
unconformable  upon  the  rocks  of  the  first. 
Bailey,18  in  1879,  divides  the  pre-Silurian  rocks  of  southern  New 
Brunswick  into  four  divisions  on  lithological  grounds.  The  first  are 
syenitic,  feldspathic,  and  gneissic  rocks;  the  second,  limestones  and 
dolomites,  with  others.  These  two  divisions  are  regarded  as  belong- 
ing to  the  Laurentian.  The  third  is  a  felsite-petrosilex  group  which 
comprises  sandstones  and  conglomerates,  as  well  as  amygdaloidal  ash 
rocks  and  ash  conglomerates.  This  is  the  Coldbrook  group  of  the 
earlier  reports  and  is  regarded  as  a  lower  member  of  the  Huronian 
system.  The  fourth  division  is  a  schistose,  chloritic,  and  micaceous 
group,  comprising  among  other  rocks  conglomerates,  clay  slates, 
quartzites,  ash  rocks,  amygdaloids,  etc.,  and  is  regarded  as  the  upper 
member  of  the  Huronian  system.  The  passage  from  division  2  to 
division  3 — that  is,  from  the  Laurentian  to  the  Huronian — is  a  grad- 
ual one,  as  the  two  groups  are  intimately  associated. 
Placing  the  Upper  Coldbrook  group  as  pre-Silurian,  the  uncon- 
formity of  this  group  with  the  Silurian  is  in  general  marked.  The 
Primordial  beds  sometimes  rest  upon  division  3  and  sometimes  upon 
division  4;  they  contain  in  places  coarse  basal  conglomerates,  and  ap- 
pear to  have  been  originally  deposited  among  the  hollows  of  the 
Huronian  series.  South  of  Bloomsbury  Mountain,  and  on  the  main 
stream  of  Black  River  and  the  adjacent  region,  the  Huronian  rocks 
are  associated  with  the  Devonian,  and  the  two  formations  accord 
almost  exactly  both  in  strike  and  in  dip,  the  Devonian  being  included 
among  the  Huronian  rocks.  But  in  addition  to  the  fact  that  the  con- 
glomerates of  the  former  are  largely  made  up  of  the  debris  of  the  lat- 
ter, there  are  points  in  which  this  accordance  is  clearly  wanting.  The 
discordance  is  pretty  well  seen  at  the  east  branch  of  Black  River. 
Matthew,19  in  1879,  finds  the  Kingston  series  to  exhibit  a  strong 
resemblance  to  the  Huronian  formation  of  St.  John  County,  but  it  is 
regarded  as  Silurian  on  paleontological  grounds. 
Bailey,  Matthew,  and  Ells,20  in  1880,  give  a  general  review  of 
their  work  in  southern  New  Brunswick,  which  covers  an  area  of  about 
6,000  square  miles.  The  rocks  comprised  under  the  pre-Cambrian 
include  the  Laurentian  of  1871  and  the  three  former  divisions  of  the 
