LAKE    SUPERIOR   REGION.  305 
phenomena,  if  not  explained  as  above,  may  be  regarded  as  due  to  the 
intrusion  of  disturbing  masses  or  dikes,  as  suggested  by  Whittlesey 
and  Norwood,  or  the  sandstone  may  be  supposed  to  belong  to  the 
upper  division  of  the  Keweenaw  series  let  down  by  a  great  fault. 
The  first  of  these  suppositions  is  forbidden  by  the  bedded  structure  of 
the  rocks,  and  the  second  is  shown  by  the  general  structural  features 
of  Lake  Superior  to  be  a  physical  impossibility. 
The  amygdaloidal  and  porphyritic  rocks,  and  the  granite,  granitic 
porphyry,  and  felsite  of  the  Duluth  gabbros  and  the  Minnesota  coast, 
are  found  in  every  case  to  be  original  eruptive  rocks  having  all  the 
evidences  in  their  structure  of  this  origin  and  none  whatever  of  being 
metamorphosed  shales  and  sandstones  resulting  from  the  red  sand- 
stones of  Fond  du  Lac,  as  supposed  by  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  Keweenawan  traps  at 
Bete  Grise  Bay,  along  Hungarian  River,  and  in  Douglass  Houghton 
ravine,  are  described  and  sections  are  given  showing  the  sandstone  to 
rest  unconformable  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  Ke- 
weenawan 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  KewTeenawTan 
sandstone,  is  a  pure  supposition.  Farther  west,  on  and  near  Ontona- 
gon River,  as  at  Bete  Grise  Bay,  near  the  contact,  the  sandstone  dips 
away  from  the  northward-dipping  Keweenawan  diabases  at  a  rather 
high  angle,  which  rapidly  flattens  as  distance  from  the  contact  in- 
creases. Finally,  along  the  north  face  of  the  South  range  eastward 
from  Lake  Agogebic,  the  sandstone  is  not  infrequently  met  in  a  flat- 
lying  position,  and  at  one  place  lies  directly  across  the  course  of  the 
Keweenawan  belt. 
As  to  the  age  of  the  Eastern  sandstone,  it  is  regarded  as  demon- 
strated that  it  is  older  than  the  Trenton ;  hence  its  Triassic  age  is  not 
discussed.  The  Western  sandstone  is  regarded  as  the  equivalent  of 
the  Eastern  sandstone,  although  they  are  not  found  connected,  nor. 
is  the  Western  sandstone  at  any  point  connected  with  the  Mississippi 
55721— Bull.  300— 09 20 
