vanhise.]  LAKE    SUPERIOR    REGION.  83 
Owen,"  in  L852,  discusses  fclie  age  of  the  red  sandstones  of  lake 
Superior.  The  test  of  lithological  character,  if  alone  applied,  is  in  favor 
of  the  view  that  they  are  of  the  same  age  as  the  red  sandstones  of  New 
Jersey  and  Nova  Scotia.  On  the  St.  ('mix  river,  in  Wisconsin,  the 
white  and  buff  quartzqse  sandstones  belonging  to  the  lowest  Protozoic 
formation  are  succeeded  by  red  sandstones  similar  to  those  of  lake  Su- 
perior, and,  like  them,  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  upthrusl  of 
igneous  rocks,  which  sometimes  break  through  the  lossiliferous 
strata,  entangling  and  partially  indurating  the  fragments  without  alter- 
ing or  tilting  the  adjacent  beds,  that  tilted  red  sandstones  dipping 
to  the  south  really  may  never  rest  conformably  under  the  white  and 
buff  sandstones,  but  merely  abut  against  them  and  not  in  fact  overlie 
them  at  all;  but  the  natural  and  reasonable  inference  is  that  the  white 
bud  buff  sandstones  do  actually  rest  conformably  upon  the  red  sand- 
stones in  question. 
Norwood,79  in  1852,  gives  a  great  number  of  details  as  to  the  geology 
of  middle  and  western  Minnesota  and  the  country  adjacent  to  the 
southwest  shore  of  lake  Superior,  illustrating  the  relations  of  the  shales, 
trap  rocks,  granites,  etc.,  and  showing  the  manner  of  intrusion  of  the 
eruptives  and  the  complicated  folding  to  which  the  strata  have  been 
subjected.  At  the  St.  Louis  and  Black  rivers  the  sandstone  rests 
unconformably  upon  the  underlying  argillaceous  and  siliceous  slates. 
Whittlesey,7"  in  1852,  gives  geological  descriptions  of  part  of  Wis- 
consin south  of  lake  Superior.  Passing  from  the  lake  southerly  four 
great  classes  of  rocks  are  seen  in  eacli  section:  (1)  Sedimentary,  includ- 
ing red  sandstone,  black  slate,  conglomerate.  (2)  Trappose  rocks,  or 
those  of  volcanic  origin,  including  amygdaloid,  greenstone,  augitic, 
hornblendic,  and  feldspathic  rocks,  embracing  syenites  and  granites  oi 
the  same  age.  (3)  Metamorphosed  rocks,  including  hornblende  slnies, 
iron  slates,  black  slates,  talcose  slates,  slaty  quartz.  (4)  Granitic,  includ- 
ing syenite  and  granite.  The  granites  and  syenites  of  the  interior  are 
the  most  ancient  rocks  of  the  district.  After  the  protrusion  of  these 
granitic  masses  many  changes  have  occurred.  The  sandstone  deposits 
of  lake  Superior  must  have  been  subsequent  to  the  granites  of  the 
Wisconsin,  Chippewa,  and  Montreal  rivers;  since  that  period  has 
been  one  of  long  and  intense  igneous  action  in  which  the  trap,  horn- 
blendic, and  greenstone  masses  have  been  ejected,  and  also  with  them 
protrusions  of  recent  granites  and  syenite.  The  metamorphic  slates 
have  been  elevated  during  these  convulsions,  and  the  sedimentary 
cocks  thrust  away  to  the  northward  and  tilted  up  at  high  angles.  The 
old  granites  and  syenites  have  been  rent  with  fluid  matter,  such  as 
quartz  and  hornblende.  The  northern  part  of  (he  Pentfkee  range 
shows  evidence  of  four  formations  of  trappose  rocks,  which  fill  ;i  geolog- 
ical epoch  of  no  great  duration  between  the  area  of  the  red  sandstone 
