332  PRE-CAMBRIAN   ROCKS    OF    NORTH    AMERICA.  [bull.  80. 
i 
their  unmetaruorphosed  condition,  and  in  the  character  of  the  sedi- 
ments are  almost  identical  with  the  great  thickness  of  sediments  of  the 
Keweenawan.  Also  the  eruptives,  which  are  interbedded  with  the  Grand 
canyon  series  and  cut  it,  are  practically  identical  with  the  basic  eruptives 
of  the  Keweenawan.  These  interbedded  and  cutting  greenstones 
are  characteristic  of  the  lower,  but  are  not  found  in  the  higher  series, 
a  still  further  analogy  with  the  Keweenawan,  for  the  lower  Kewee- 
nawan contains  eruptives  and  the  upper  Keweenawan  is  wholly  detrital. 
The  Grand  canyon  succession  is  then  remarkably  like  that  in  the  lake 
Superior  region,  and  the  respective  series  are  lithologically  alike. 
It  is  exceedingly  unsafe  to  correlate  a  single  series  with  another  se- 
ries in  a  different  geological  basin  upon  lithological  grounds;  but  when 
two  great  series  of  rocks  are  found,  each  of  which  has  respectively  similar 
lithological  characteristics  in  two  regions,  and  they  are  both  separate*! 
by  a  physical  break,  and  both  sets  of  series  are  in  exactly  similar  posi- 
tions with  reference  to  the  overlying  Cambrian  and  to  the  basement 
complex,  the  likeness  suggests  that  they  stand  respectively  as  the  time 
equivalents  of  each  other.  Between  the  two  regions  is  the  difference 
that  in  the  Grand  canyon  area,  a  possible  equivalent  of  the  Lower  Hu- 
ronian  of  the  lake  Superior  is  not  known.  The  correlation  suggested 
can  be  considered  no  more  than  a  conjecture  since  the  parallelism  in 
the  two  regions  may  be  no  more  than  a  remarkable  coincidence.  It  is 
remarked  by  Walcott  that  in  the  pre-Tonto  series  are  a  few  obscure 
fossils,  and  that  this  locality  is  perhaps  one  of  the  best  in  the  world  in 
which  to  search  for  a  pre-Gambrian  fauna.  Since  in  the  lake  Superior 
region  the  beginning  of  a  pre-Cambrian  fauna  is  also  known,  it  may 
not  be  too  much  to  hope  that  within  a  few  years  we  shall  have  the 
assistance  of  fauna  of  sufficient  fullness  in  these  distant  regions  upon 
which  the  correlation  above  suggested  may  be  tested. 
SECTION  VIII.     CALIFORNIA,  WASHINGTON  AND  BRITISH  COLUMBIA. 
LITERATURE  OF  CALIFORNIA,  WITH  ADJACENT  PARTS  OF  NEVADA  AND  ARIZONA. 
Dana,73  in  1849,  describes  various  crystalline  rocks  in  the  Umpqua 
and  Shasty  ranges.  These  include  granite,  syenite,  porphyry,  talcose 
rocks,  serpentine.  The  hornblendic  and  talcose  rocks  are  rarely  schist- 
ose. Associated  with  the  former  rocks  are  conglomerates  and  sand- 
stones. 
Tyson,74  in  1850,  describes  sections  in  the  Sierra  Nevada  and  the 
Coast  range.  The  rocks  are,  first,  metamorphic,  consisting  of  those  of 
sedimentary  origin,  such  as  slate,  but  subsequently  altered  by  the 
effects  of  heat,  and  second,  of  hypogene  rocks,  which  include  granite, 
trap  rocks,  and  others.  At  the  summit  of  the  Sierra,  granite  is 
the  prevailing  rock,  and  upon  its  flanks  slates.  The  cleavage  of 
the  slates  have  a  uniform  course,  about  north  of  west.  These  lines  of 
cleavage  are  usually  taken  for  those  of  stratification,  but  it  is  fre- 
