324  PRE-CAMBKIAN    GEOLOGY   OF   NORTH   AMERICA. 
The  lowest  sedimentary  series  of  the  Lake  Superior  region  is  the 
Lower  Huronian.  These  sediments  were  included  in  the  areas  mapped 
as  Huronian  by  Logan  in  1863,  and,  although  not  actually  found  in 
place  by  him,  were  recognized  from  their  fragments,  and  to  him 
should  be  given  the  credit.  As  so  used  the  term  Lower  Huronian  is 
nearly  equivalent  to  the  term  Archean  as  used  by  Van  Hise,  and  the 
term  Upper  Huronian  is  equivalent  to  Van  Hise's  Lower  Huronian. 
Accordingly  the  Animikie  or  the  Upper  Huronian  of  Van  Hise  is 
younger  than  the  Original  Huronian  series.  That  the  Animikie  is 
later  than  the  true  Upper  LIuronian  or  Original  Huronian  may  be 
shown  in  the  following  ways : 
1.  Stratigraphically  it  is  the  third  series  of  sediments  upward  from 
the  bottom  of  the  geological  column  in  the  Lake  Superior  region ;  the 
Upper  Huronian  is  the  second. 
2.  Lithologically  the  two  series  are  quite  different,  and  so  presum- 
ably are  of  different  age.  There  is  very  little  conglomerate  at  the  base 
of  the  Animikie ;  in  the  Huronian  the  quartzites,  slate  conglomerates, 
and  jasper  conglomerates  are  of  great  thickness.  The  Oolitic  jaspers 
found  in  the  Animikie  are  quite  absent  from  the  Huronian.  The 
shales,  so  important  in  the  Animikie,  are  almost  unknown  in  the  Hu- 
ronian. The  laccolithic  sills  of  the  Animikie  are  lacking  in  the  Orig- 
inal Huronian. 
3.  Structurally  the  two  series  are  usually  said  to  be  alike  in  that 
both  lie  flat  and  undisturbed.  While  this  is  quite  true  of  the  Ani- 
mikie, it  is  only  partially  true  of  the  Huronian  north  of  Georgian 
Ba}^,  and  is  untrue  of  the  Upper  Huronian  about  Batchawana  and 
Michipicoten.  Coleman  a  and  Murray  b  have  described  cases  of  verti- 
cal dip  within  the  so-called  Original  Huronian,  and  others  have  been 
observed  by  Willmott.  These  seem  to  occur  around  the  outer  portion 
of  the  Huronian  basin,  and  more  gentle  dips  prevail  in  the  central 
part.  Evidently  the  Huronian  has  been  subjected  to  forces  which  the 
later  Animikie  has  escaped. 
4.  Assuming  that  the  large  areas  of  eruptive  granite  gneisses  in 
the  Lake  Superior  region  are  of  the  same  age,  we  find  that  the  Upper 
Huronian  has  in  many  cases  been  pierced  by  them,  but  that  the  Ani- 
mikie always  overlies  them. 
Van  Hise,  Bell,  Adams,  Miller,  and  Lane,88  in  1904,  made  a  six 
weeks'  reconnaissance  trip  through  the  Lake  Superior-Lake  Huron 
region.  These  men  were  selected  by  the  Canadian  and  the  LTnited 
States  geological  surveys  to  attempt  to  reach  some  agreement  in  mat- 
ters of  nomenclature  and  correlation  in  the  boundary  area  of  the  Lake 
"  Rept.   Bureau   of  Mines,   Ontario,   1901,   p.    189. 
6  Geol.  Survey  of  Canada,  1858,  p.  95. 
