186  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
Besides  the  reason  already  mentioned  for  placing  the  upper  Original 
Huronian  as  the  equivalent  of  the  Animikie  and  Upper  Marquette  rather 
than  below  these  series,  as  advocated  by  certain  geologists,  we  have  one 
characteristic  feature  already  ei ted  which  is  of  some  weight.  One  of  the 
most  peculiar  rocks  of  the  Upper  Original  Huronian  is  a  conglomerate 
which  carries  numerous  fragments  of  blood-red  jasper.  At  present  the 
source  of  these  fragments  is  unknown  unless  they  come  from  the  iron- 
bearing  formation  of  the  Lower  Huronian.  From  what  has  gone  before 
it  is  apparent  that  a  jasper  conglomerate  is  the  basal  member  of  the 
Upper  Marquette  series,  and  also  that  similar  conglomerates  occur  in  a 
like  position  in  Ontario  and  northeastern  Minnesota.  Considering  the 
widespread  character  of  this  jaspery,  cherty,  and  iron-ore  conglomer- 
ate, its  occurrence  in  the  Upper  Huronian  of  lake  Huron  suggests  that 
this  jasper  may  there  be  found  in  the  future  in  the  Lower  Huronian  in 
large  quantity.  This  series  would  therefore,  in  position  and  in  litholog- 
ical  character,  be  like  the  Lower  Vermilion  and  Lower  Marquette  iron- 
bearing  series.  The  existence  of  such  a  jasper-bearing  series  was 
inferred  by  Logan  himself.  Taking  the  Original  Huronian  north  of 
lake  Huron  as  a  whole,  if  WinchelPs  general  conclusion  that  it  con- 
sists of  two  unconformable  series  be  correct,  the  analogy  between  this 
district  and  the  lake  Superior  region  is  complete.  Above  the  funda- 
mental complex  and  below  the  Keweenawan,  as  about  lake  Superior, 
are  two  discordant  scries. 
EQUIVALENTS   OF   THE    SIOUX    QUARTZITES,    ST.    LOUIS   SLATES,    ETC. 
Much  of  what  has  been  said  to  show  that  the  Upper  Huronian  series 
is  the  equivalent  of  the  Animikie,  Upper  Vermilion,  and  Upper  Mai 
quette  applies  with  equal  force  to  such  rock  series  as  the  Chippewa 
quartzites,  the  Baraboo  quartzites,  the  Sioux  quartzites  and  the  St. 
Louis  slates.  None  of  these  series  are  closely  folded,  although  often 
dynamic  movements  have  developed  slaty  cleavages.  Also  their  orig- 
inal fragmental  character  is  always  seen  under  the  microscope  at  a 
glance.  Between  these  series  and  the  Potsdam  is  a  great  unconform- 
ity. They  present  thick  beds  of  fragmental  rocks,  the  induration  of 
which  has  been  caused  by  the  same  process  which  vitrified  the  quartz- 
ites of  the  upper  Original  Huronian.  The  supposed  absence  of  ferrugi- 
nous rocks  in  these  districts  has  been  used  in  the  past  as  an  argument 
against  the  correlation  of  them  with  the  Penokee  and  Animikie  series 
below  considered,  but  this  absence  has  no  particular  weight  because 
such  beds,  as  compared  with  the  mechanical  sediments,  are  insignificant 
in  amount;  and  further,  it  is  quite  possible  that  these  formations  may 
in  the  future  be  found  in  several  or  all  of  these  districts.  This  proba- 
ability  is  rendered  greater  by  recently  developed  ferruginous  beds 
between  the  two  quartzite  ranges  of  Baraboo  and  in  the  northward 
extension  of  the  St. 'Louis  slates.  The  rocks  here  found  are  the  exact 
parallel  of  the  iron-bearing  beds  of  the  Penokee  and  other  iron-bearing 
