AREA   NOETH   AND   NORTHEAST   OF   LAKE    HURON.  429 
of  800  square  miles,  but  no  attempt  was  made  to  separate  the  different 
sedimentary  series. 
Ingall,54  in  1903,  gives  a  brief  preliminary  account  of  a  resurvey 
of  the  Bruce  Mines  district,  in  the  Original  Huronian  district. 
Barlow,55  in  1904,  discusses  the  geology  of  the  Temagami  district 
in  eastern  Ontario.  Lower  and  Upper  Huronian  rocks  intruded  by 
granite  and  gabbro  are  present.  The  Lower  Huronian  consists  of 
greenstone,  green  schist,  sericite  schists,  slates,  dolomite,  and  iron 
formation,  with  intrusive  granites.  The  Upper  Huronian  consists 
of  breccia  or  slate  conglomerate,  slate,  and  quartzite.  The  iron 
ranges,  with  accompanying  green  schists,  slates,  dolomites,  and  schis- 
tose eruptives,  and  intruded  by  granites,  belong  to  a  series  which  had 
been  intensely  folded,  metamorphosed,  and  "considerably  eroded  before 
the  deposition  of  the  overlying  conglomerate  hitherto  described  as 
the  basal  member  of  the  Huronian  system  in  this  region.  The  larger 
fragments  in  the  conglomerate  are  principally  pebbles  of  granite  and 
greenstone  derived  from  the  degradation  of  this  underlying  series. 
The  immediate  junction  between  this  older  series  and  the  unconform- 
ably  overlying  conglomerate  is  well  seen  at  a  point  on  the  south  shore 
of  the  northeast  arm  about  15  chains  west  of  the  portage  into  Cariboo 
Lake.  The  occurrence  of  the  ores  is  believed  to  be  similar  to  that  of 
the  Vermilion  district  of  Minnesota,  and  their  origin  is  believed  to 
be  similar  to  that  described  by  Van  Hise  for  the  Lake  Superior  ores. 
Adams,  Bell,  Lane,  Miller,  and  Van  Hise,50  in  1904,  visited  vari- 
ous points  in  the  Original  Huronian  district  of  the  north  shore  of 
Lake  Huron.  At  the  old  limestone  quarry  at  Garden  River  it  was 
found,  further,  that  the  conglomerate  to  the  north  of  the  lime- 
stone, mapped  as  lower  slate  conglomerate  by  Logan  and  Murray, 
contains  fragments  of  limestone  and  is  unconformably  above  it,  thus 
being  the  same  in  age  as  the  conglomerate  south  of  the  limestone — 
that  is,  upper  slate  conglomerate.  The  limestone  thus  forms  an  anti- 
cline. This  observation  tends  to  confirm  the  conclusions  reached  two 
years  previous  by  Van  Hise  and  Leith,  that  the  limestone  at  Root 
River  to  the  west  is  anticlinal  and  that  the  conglomerate  both  to  the 
north  and  south  of  it,  as  well  as  conglomerate  farther  to  the  west, 
resting  against  the  granite,  is  the  upper  slate  conglomerate,  uncon- 
formably above  the  limestone. 
It  was  concluded  that  there  is  a  structural  break  in  the  Huronian. 
The  upper  series  includes,  in  descending  order:  (1)  White  quartzite, 
chert,  and  limestone;  (2)  yellow  chert  and  limestone:  (3)  white 
quartzite;  (4)  red  jasper  conglomerate;  (5)  red  quartzite;  (6) 
upper  slate  conglomerate.  The  lower  series  includes :  (1)  Limestone; 
(2)  lower  slate  conglomerate ;  (3)  white  quartzite:  (I)  gray  quartz- 
ite. It  was  recommended  that  these  series  be  called  the  Upper  and 
Lower  Huronian  series. 
