LAKE    SUPERIOR   REGION.  145 
Wadsworth,56  in  1891,  modifies  somewhat  the  account  of  the  Azoic 
system  given  by  him  in  1890.53  A  portion  of  the  jaspilites  and 
associated  iron  ores  are  still  held  to  be  eruptive,  but  it  is  suggested 
that  the  present  relations  of  even  these  supposed  nonfragmental 
jaspilites  of  Ishpeming  and  Negaunee  may  be  due  to  sedimentary 
and  chemical  action  and  the  squeezing  together  of  the  jaspilite  and 
schist.  The  jaspilite  and  ore,  with  the  associated  quartzites,  occurring 
at  Cascade,  Republic,  Humboldt,  and  a  part  of  those  at  Ishpeming 
and  Negaunee,  as  well  as  those  of  the  overlying  quartzites  and  schists, 
are  sedimentary.  In  the  Marquette  district  there  are  three  distinct 
geological  formations  or  ages,  in  ascending  order  as  follows:  First, 
the  hornblende  schist  and  granite  of  Cascade  or  Palmer  and  the 
nonfragmental  jaspilite  and  ore  of  Ishpeming  and  Negaunee — the 
Cascade  formation.  Second,  the  fragmental  jaspilite  and  ore,  with 
their  associated  quartzites  and  schists,  of  Cascade,  Republic,  Hum- 
boldt, Ishpeming,  Negaunee,  and  elsewhere — the  Republic  formation. 
Third,  the  overlying  conglomerates,  quartzites,  and  schists  of  Cas- 
cade, Republic,  Holyoke,  and  elsewhere — the  Holyoke  formation. 
Above  the  detrital  Republic  formation  at  the  Cascade  range  is 
another  detrital  formation  which  contains  waterworn  debris  derived 
from  the  underlying  deposits  of  jaspilite  and  ore,  and  is  therefore 
uncomformably  above  it.  At  present  it  is  not  possible  to  determine 
positively  whether  there  are  really  three  formations  as  given,  or  from 
four  to  six  different  ones,  or  whether  the  three  may  be  reduced  to  two. 
Wadsworth,57  in  1891,  finds  that  the  Lower  Silurian,  containing 
Trenton  fossils  near  L'Anse,  overlies  the  sandstone  conformably,  both 
having  a  synclinal  structure;  which  tends  to  confirm  the  commonly 
received  view  of  the  Potsdam  age  of  the  Eastern  sandstone. 
Wadsworth,58  in  1891,  gives  observations  upon  the  south  trap 
range  and  adjacent  sandstones.  Various  places  are  mentioned,  in- 
cluding Silver  Mountain,  which  are  composed  of  lava  flows.  These 
traps  sometimes  have  a  dip  not  higher  than  9°  to  20°.  In  sees.  11,  13, 
and  14,  T.  46  N.,  R.  31  W.,  sandstone  is  found  overlying  the  lava 
flows.  The  Eastern  sandstone  on  Traverse  Island,  in  Keweenaw  Bay, 
is  said  to  have  an  inclination  of  5°  to  14°,  while  in  the  vicinity  of 
Torch  Lake  it  has  a  dip  of  5°  to  23°.  It  is  concluded  that  the  above 
observations  go  to  show  that  the  lava  flows  of  the  south  trap  range 
east  of  Lake  Gogebic  do  not  dip  at  a  high  angle,  as  lias  been  generally 
asserted,  and  further  that  the  Eastern  sandstone  is  not  horizontal, 
as  has  been  generally  stated,  but  that  the  two  dip  at  a  low  angle, 
generally  5°  to  20°.  These  observations  also  indicate  that  the  Eastern 
sandstone  and  the  lava  flows  of  the  south  trap  range  are  one  forma- 
tion, and  are  as  conformable  as  eruptions  of  lava  can  be  with  a  con- 
temporaneous sedimentary  deposit. 
55721— Bull.  360—09 10 
