LAKE   SUPERIOR  REGION.  299 
to  any  single  geological  event.  Its  position  in  the  main  is  doubtless 
determined  by  a  dislocation  between  the  Primitive  range  north  and 
the  sedimentary  deposit  south.  The  rocks  of  the  north  shore  of  Lake 
Superior  are  extensively  metamorphic.  The  New  Red  sandstone 
passes  into  porphyries,  quartzite,  granite,  and  gneiss,  the  metamor- 
phism  being  more  or  less  perfect,  so  that  the  stratification  is  still 
sometimes  preserved  or  passes  gradually  into  absolutely  massive  rocks. 
Owen,307  in  1851,  mentions  various  metamorphic  slates,  quartzites, 
and  other  crystalline  and  trappean  rocks  as  occurring  on  the  south 
shore  of  Lake  Superior.  On  the  north  shore,  in  Minnesota,  between 
Fond  du  Lac  and  the  British  possessions  there  is  a  repetition  in  in- 
verse order  of  the  same  formations,  forming  a  synclinal  trough  with 
the  red  sandstone  nearest  the  lake,  while  the  slates,  conglomerates, 
and  associated  traps  are  crossed  in  succession  in  proceeding  into  the 
interior,  and  these  are  followed  by  the  metamorphic  slates  and  gran- 
itic rocks. 
Owen,308  in  1852,  discusses  the  age  of  the  red  sandstones  of  Lake 
Superior.  The  test  of  lithological  character,  if  alone  applied, 
favors  the  view  that  they  are  of  the  same  age  as  the  red  sandstones  of 
New  Jersey  and  Nova  Scotia.  On  St.  Croix  River,  in  Wisconsin,  the 
white  and  buff  quartzose  sandstones  belonging  to  the  lowest  Protozoic 
formation  are  succeeded  by  red  sandstones  similar  to  those  of  Lake 
Superior  and,  like  them,  are  associated  with  coarse  red  conglomerates 
and  trap.  The  same  phenomena  are  seen  at  other  points  south  of 
Lake  Superior.  It  is,  however,  conceivable,  as  a  result  of  the  up- 
thrust  of  igneous  rocks,  which  sometimes  break  through  the  fossil- 
iferous  strata,  entangling  and  partially  indurating  the  fragments 
without  altering  or  tilting  adjacent  beds,  that  tilted  red  sandstones 
dipping  to  the  south  may  never  rest  conformably  under  the  white  and 
buff  sandstones,  but  merely  abut  against  them  and  not  overlie  them 
at  all ;  but  the  natural  and  reasonable  inference  is  that  the  white  and 
buff  sandstones  do  actually  rest  conformably  upon  the  red  sandstones 
in  question. 
Marcou,309  in  1853,  after  having  made  a  complete  tour  of  Lake 
Superior,  places  the  red  sandstone  and  traps  bearing  copper  as  the 
New  Red  sandstone,  and  correlates  it  with  the  New  Red  sandstones 
of  Nova  Scotia,  New  BrunsAvick,  Connecticut,  New  Jersey,  Mary- 
land, and  Virginia. 
Whitney,310  in  1854,  states  that  the  basin  of  Lake  Superior  is  a 
great  synclinal  trough  caused  by  a  depression  of  the  sandstone,  which 
appears  to  form  its  bed.  The  northern  and  eastern  shores  for  much 
of  their  distances  are  faced  by  perpendicular  cliffs,  while  the  south- 
ern shore  is  comparatively  low.  The  reason  for  this  difference  is 
thai  on  the  east  and  north  the  sandstone  which  originally  existed 
there  has  been  worn  away  and  the  more  enduring  granitic  and  trap- 
