vANinsE.]  LAKE    HURON    TO    LAKE    TEMISCAMANG.  41 
Original  Huronian.  Minnesota  equivalents. 
(  Pewabic  quartzite  (?). 
Otter  Tail  quartzite N  New  Ulm^  Pokegama  aud  Waug. 
Tliessalon  quartzite (     waugoning  quartzites. 
Black  slate Animikie  black  slate. 
"Litliographic stone"  and  fine  gray  quartzite  ..Not  known. 
Red  felsite Felsites  at  Duluth  and  probably  the 
Great  palisades. 
Mississagui  quartzite Not  known. 
Slate  conglomerate Ogisbki  conglomerate. 
Chert  and  quartzite  pebbles  in  the  Tliessalon  quartzite  lead  to  the 
inference  that  this  is  unconformably  upon  the  black  slate.  The  exist- 
ence of  granite  bowlders  in  the  slate  conglomerate  indicates  another 
unconformity  between  it  and  the  granites  of  the  region.  In  this  latter 
case  the  evidence  is  conclusive,  and  in  the  former  it  is  inconsiderable. 
Winchell  (Alex.),48  in  1888,  also  gives  many  observations  upon 
the  original  Huronian.  In  the  Huronian  system  is  a  large  volume  of 
eruptive  rock  with  a  great  thickness  of  rocks  of  undoubted  sedimen- 
tary origin,  with  an  equal  volume  of  an  obscure  slaty  character.  The 
latter  appear  to  constitute  the  green  chlorite  schist  of  Logan,  which  is 
either  an  ancient  or  much  altered  eruptive  or  highly  altered  sedimen- 
tary material.  The  quartzites  contain  angular  fragments  of  such  a 
character  that  they  seem  to  be  derived  from  this  diabase  schist;  and 
this  circumstance  countenances  the  theory  that  the  latter  are  older  and 
probably  sedimentary  in  origin.  The  Huronian  of  Canada,  in  descend- 
ing order,  is  as  follows:  Otter  Tail  white  quartzite,  4,000  feet;  Thessa- 
lon red  and  gray  quartzite,  5,000  feet;  Otter  Tail  cherty  limestone,  100 
feet;  Upper  Plummer  conglomeratic  and  siliceous  argillite,  500  feet; 
red  felsite,  granulite,  and  quartzite,  100  feet;  lower  conglomeratic  and 
siliceous  argillite,  7,400  feet;  Bruce  limestone,  100  feet;  Mississagui 
vitreous  quartzite,  3,750  feet.  This  succession  includes  neither  the 
lower  nor  the  upper  limit  of  the  Huronian.  At  St.  Joseph's  island  the 
Huronian  is  immediately  overlain  by  a  fossiliferous  limestone,  appar- 
ently the  Chazy.  It  thus  appears  that  the  Huronian  is  a  system  fol- 
lowing downward  immediately  below  the  Lower  Silurian,  and  if  no 
intervening  terranes  are  wanting  it  occupies  the  position  of  the  Taconic 
of  Emmons  and  the  Lower  Cambrian  of  Sedgwick.  The  lower  limit  of 
the  Huronian  must  be  succeeded  by  a  formation  of  vitreous  quartz,  red 
jasper,  and  graywacke,  besides  greenstones,  red  granulite,  red  gneiss, 
mica-bearing  granite,  since  fragments  of  all  these  are  found  in  the 
Huronian.  It  may  be  that  the  quartzite  pebbles  are  derived  from  the 
Mississagui  quartzite,  but  the  red  jasper  and  greywaeke  must  have 
been  derived  from  a  terrane  older  than  the  Huronian  and  newer  than 
the  crystalline  masses  of  the  Lauren tian. 
.  Bonney,49  in  1888,  discusses  the  development  of  the  crystalline 
schists  in  the  neighborhood  of  Sudbury.  The  semicrystallines  can  be 
easily  separated  from  the  thoroughly  crystalline  rocks  of  the  Lauren- 
