416  PRE-CAMBRIAN    GEOLOGY   OF    NORTH   AMERICA. 
River,  Lot  2,  Conn.  III.  In  the  township  of  Hyman  is  an  augen  gneiss 
which  is  evidently  a  metamorphosed  clastic,  as  it  forms  a  part  of  the 
quartzite  and  graywacke  series.  The  line  of  junction  between  the  Lau- 
rentian  and  the  Hnronian  is  unusually  straight.  West  of  Lake  Wah- 
napitae,  along  the  contact,  there  is  evidence  of  great  disturbance  and 
crushing,  the  rocks  of  the  two  series  being  much  broken  up  and  inter- 
mixed. It  is  not  improbable  that  at  the  junction  line  is  a  considerable 
fault. 
The  third  division  is  less  altered,  and  is  in  a  distinct  basin  running 
from  the  township  of  Trill  northeastward  to  near  the  South  Bay  of 
Lake  Wahnapitae,  a  distance  of  3C>  miles,  with  a  breadth  of  8  miles 
in  its  central  portion.  These  rocks  are  perhaps  unconformable  to  the 
older  Hnronian  rocks  on  which  they  rest,  and  may  be  Upper  Huro- 
nian,  or  possibly  lower  Cambrian. 
Along  Onaping  Lake  and  River  and  Straight  Lake  are  Huronian 
outliers.  The  principal  kinds  of  rocks  in  the  first  basin  are  slate  con- 
glomerates, with  well-rounded  pebbles  and  bowlders,  mostly  of  binary 
granite,  quartz,  quartzite,  and  schists;  and  coarse  arenaceous  or  gray- 
wacke conglomerate,  together  with  some  pale-pink  quartzites  and  blu- 
ish and  greenish-gray  felsites,  argillites,  and  slates.  The  principal 
rocks  of  the  second  basin  are  graywacke  schists,  quartzites,  quartzite 
or  graywacke  conglomerates,  green  schists,  hard  sandstones,  green- 
stones, and  some  dolomites.  In  the  conglomerates  are  pebbles  of  gray- 
wacke and  hornblende  granites  like  the  prevailing  varieties  found  in 
situ  in  the  region,  black  slates,  and  black  and  white  quartz.  On  Lot  4, 
Con.  Ill,  Moncrieff,  is  the  junction  of  the  Laurentian  red  hornblende 
granite  and  the  graywacke. 
It  is  concluded  that  the  Huronian  rocks  of  the  Sudbury  district  are 
largely  of  volcanic  nature,  although  many  of  them  have  been  rear- 
ranged by  water;  hence  they  may  be  termed  pyroclastic.  The  gray- 
wackes  consist  of  granite  debris  more  or  less  comminuted  by  the  modi- 
fying action  of  water.  Under  this  name  are  included  many  varieties 
of  rocks,  ranging  from  those  which  approach  quartzites  to  others 
approaching  argillites.  The  largest  fragments  are  usually  of  red  or 
gray  aplite.  As  a  general  rule  the  different  divisions  of  the  Huronian 
rocks  do  not  maintain  their  thickness  very  far  on  the  strike,  but 
diminish  more  or  less  rapidly,  their  place  at  the  same  time  being  filled 
by  a  corresponding  thickening  of  other  members  of  the  series. 
The  trappean  rocks  of  the  district  consist  of  (1)  extensive  masses, 
together  with  many  of  smaller  size,  incorporated  with  the  other 
Huronian  rocks,  and  probably  contemporaneous  with  them;  and  (2) 
dikes  which  cut  through  all  the  members  of  the  series.  There  are 
nearly  50  areas  of  diorite,  two  principal  belts  of  diabase,  and  a  belt 
of  slaty,  greenish  diorite,  which  in  places  becomes  brecciated  and 
includes  fragments,  from  large  bowlders  down  to  small  pebbles,  con- 
sisting principally  of  quartzites,  granites,  and  syenites. 
