anhise.]  LAKE    SUPERIOR    REGION.  137 
md  in  structure  with  the  similar  rocks  of  Keweenaw  point  and  have 
>een  shown  to  be  in  actual  continuity  with  them.  At  Snake  and  Ket- 
le  rivers  the  diabase  and  diabase-ainygdaloids  with  interbedded  por- 
)hyry  conglomerates  are  in  all  respects  like  those  of  Keweenaw  point, 
md  here,  as  shown  by  Chamberlin  and  McKinlay,  the  horizontal  Oam- 
)rian  sandstone  overlies  these  beds  unconformably.  Sweet's  examina- 
ion  of  the  Kettle  and  St.  Croix  rivers  shows  that  here  are  cupriferous 
ocks  which  are  identical  with  those  of  Keweenaw  point,  npon  which 
:he  red  sandstone  of  lake  Superior  west  of  the  Montreal  reposes  uncon- 
brmably,  at  Black  river,  Copper  creek,  Aminicon  river,  and  Middle 
iver.  The  disturbances  of  the  overlying  sandstone  described  by  Sweet 
tre  due  in  part  to  the  irregularities  of  an  unconformable  contact  and  to 
he  pressure  of  the  deep-seated  Keweenaw  rocks  against  the  more 
ihallow  sandstone,  but  also  in  large  measure  to  a  faulting  that  has 
iaken  place  along  the  contact  line.  The  phenomena  if  not  explained  as 
ibove  may  be  regarded  as  due  to  the  intrusion  of  disturbing  masses  or 
likes,  as  suggested  by  Whittlesey  and  Norwood,  or  the  sandstone  may 
>e  supposed  to  belong  to  the  upper  division  of  the  Keweenaw  series  let 
iown  by  a  great  fault.  The  first  of  these  suppositions  is  forbidden  by 
;he  bedded  structure  of  the  rocks,  and  the  second  is  shown  by  the  gen- 
ral  structural  features  of  lake  Superior  to  be  a  physical  impossibility. 
The  amygdaloidal  and  porphyritic  rocks,  and  the  granite,  granitic 
)orphyry,  and  felsite  of  the  Duluth  gabbros  and  the  Minnesota  coast 
ire  found  in  every  case  to  be  original  eruptive  rocks  having  all  the 
evidences  in  their  structure  of  this  origin  and  none  whatever  of  being 
netamorphosed  shales  and  sandstones  resulting  from  the  red  sand- 
stones of  Fond  du  Lac,  as  supposed  by  Prof.  N".  H.  Winchell. 
It  is  concluded  that  the  Eastern  sandstone  along  the  south  face  of 
Keweenaw  range  is  both  a  fault  cliff  and  a  shore  cliff  against  which  the 
newer  sandstone  was  laid  down,  but  not  until  after  a  large  erosion,  and 
that  faulting  again  took  place  during  or  after  the  deposition  of  the 
Sandstone;  that  this  original  faulting  is  demanded  along  this  line  by 
the  relations  of  the  Keweenaw  and  South  ranges,  without  which  the 
Keweenaw  rocks  would  have  an  enormous  thickness. 
;  The  relations  of  the  Eastern  sandstone  and  Keweenaw  an  traps  are 
described  at  Bete  Grise  bay,  along  the  Hungarian  river  and  Douglass 
Houghton  ravine,  and  sections  given  showing  the  sandstone  to  rest 
unconformably  upon  the  eruptives.  At  the  Torch  lake  quarry  the 
Eastern  sandstone  is  found  horizontally  disposed  in  heavy  layers,  con- 
taining no  fragments  of  porphyry  such  as  are  distinctive  of  the  Kewee- 
nawau  sandstones.  No  evidence  of  a  northwesterly  dip  described  by 
Wadsworth  was  here  found.  The  sandstone  adjacent  to  the  trap  is  of 
the  ordinary  quartzose  character.  It  is  remarked  that  Wads  worth's 
statement  that  the  feldspathic  constituents  have  been  leached  from  it, 
thus  accounting  for  its  differences  from  the  Keweenawan  sandstone,  is 
a  pure  supposition.    Farther  west  on  and  near  the  Ontonagon  river,  as 
