56  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull. 86. 
with  the  trap,  constitute  the  copper-bearing  series.  The  affinities  of 
the  Sault  Ste.  Marie  red  sandstone  appear  to  bring  it  into  the  position 
of  the  Chazy  rather  than  the  Potsdam  formation,  and,  if  this  were  es- 
tablished, the  copper-bearing  portion  of  the  lake  Superior  rocks  might 
reasonably  be  considered  to  belong  to  the  Calciferous  and  the  Potsdam 
formations. 
Macfarlane,  12  in  1866,  gives  observations  on  the  Laurentian,  Hu- 
ronian,  and  Upper  Copper-bearing  rocks  of  lake  Superior.  The  Lauren- 
tian series  on  lake  Superior  seems  to  differ  somewhat  from  other  parts 
of  Canada.  The  rocks  are  all  highly  crystalline,  seldom  thoroughly 
gneissoid,  and  all  are  unaccompanied  by  crystalline  limestone,  which  is 
such  a  marked  feature  in  some  Laurentian  districts.  The  gneiss  strata 
are  much  contorted  and  are  intersected  with  granite  in  almost  equal 
quantity  with  the  gneiss  itself  j  and  although  this  latter  occurs  in  irreg- 
ular veins,  at  the  point  of  junction  it  is  as  firmly  cemented  with  the 
gneiss  as  any  two  pieces  of  one  and  the  same  rock  could  well  be.  On 
the  Goulais  bay  fragments  of  hornblende  rock  or  schist  up  to  3  feet  in 
diameter  are  inclosed  in  a  coarse  grained  syenitic  granite.  In  this  series 
the  oldest  rock  is  the  most  basic  in  constitution,  and  this  is  the  case 
without  regard  to  mineralogical  composition  or  structure  of  the  rocks 
associated  together.  The  indistinctness  of  parallelism  in  the  rocks  ren- 
ders it  a  matter  of  extreme  difficulty  to  form  any  clear  ideas  as  to  their 
succession,  even  if  such  should  exist.  Besides  the  above  rocks  there 
are  considerable  areas  of  granite,  syenite,  dolerite,  diorite,  and  mela- 
phyre  found  in  the  Laurentian. 
The  rocks  of  the  Huronian  system  consist  in  large  part  of  diabase, 
amygdaloid,  diabase-schist,  greenstone,  breccias,  and  slaty  greenstones. 
Interstratified  with  these  are  slate,  slate  conglomerate  and  quartzite. 
The  bowlders  and  pebbles  of  the  conglomerate  of  Dore  river  are  for  the 
most  part  granite;  they  are  elongated  and  flattened,  the  pebbles  some- 
times being  scarcely  distinguishable  from  the  slate.  Granitic  veins  or 
masses,  like  the  Laurentian,  are  found  in  the  schistose  greenstones, 
which  are  regarded  as  belonging  to  the  Huronian.  As  to  the  succes- 
sion of  the  strata,  the  author  is  as  much  at  a  loss  among  the  irregular 
schistose  Huronian  greenstones  as  among  the  gneissoid  granites  of  the 
Laurentian. 
The  Mamainse  section  of  Upper  Copper -bearing  rocks  consists  of 
interbedded  basic  lava  flows,  often  amygdaloidal,  sandstones,  and  con- 
glomerates, the  total  thickness  being  more  than  16,000  feet.  The  total 
thickness  of  the  series  at  Mamainse  and  Michipicoten  is  believed  to  be 
at  least  20,000  feet.  As  to  the  relations  of  the  horizontal  Sault  sand- 
stone to  the  upper  copper  bearing  series,  a  place  was  found  on  the  south 
of  point  aux  Mines  where  the  Mamainse  series  adjoins  the  Laurentian 
rocks.  The  lowest  member  of  the  former  is  unconformably  overlain  by 
thin  bedded  bluish  and  yellowish  gray  sandstone,  striking  N.  50°  E., 
and  dipping  18°  JfW.    The  lowest  layer  is  a  conglomerate  with  granitic 
