vanhisb]  THE    CORDILLERAS.  331 
complex,  consisting  of  most  intricately  mingled  and  folded  granites, 
gneisses,  micaceous  and  hornblendic  schists,  etc.,  precisely  as  in  the 
previous  sections  concerned  with  the  Rocky  mountain  system.  This 
complex  occurs  at  many  points,  constitutes  the  axes  of  many  ranges, 
and  its  structure  is  of  so  intricate  a  character  that  no  attempt  has  been 
made  to  estimate  its  thickness  or  to  work  out  its  structure,  although  in 
general  the  laminated  rocks  have  been  referred  to  as  metamorphic. 
The  granite  in  this  complex  plays  the  same  part  with  reference  to  the 
crystalline  schists  as  in  the  other  areas  referred  to.  Besides  this  an- 
cient granite,  which  existed  before  the  next  newer  series  of  rocks  was 
formed,  there  is  apparently  in  certain  areas  granites  of  later  age,  and 
these  are  more  plentiful  as  the  western  part  of  Arizona  is  reached. 
In  eastern  New  Mexico  and  western  Arizona,  so  far  as  the  descrip- 
tions guide  us,  there  is  no  certainty  that  any  clastic  rocks  exist  older 
than  the  fossiliferous  series.  In  the  central  part  of  Arizona,  however, 
in  the  Colorado  canyon  district,  is  the  most  complete  section  of  rocks 
older  than  the  Cambrian  and  newer  than  the  fundamental  complex  in 
any  known  part  of  the  world,  with  the  exception  of  the  lake  Superior 
region. 
The  Tonto  sandstone  of  the  Grand  canyon  region,  called  by  Powell 
and  Gilbert  Silurian  in  accordance  with  the  nomenclature  of  the  time, 
by  present  classification  is  to  be  placed  as  Upper  Cambrian.  The  great 
unconformity  which  separates  this  sandstone  from  the  earlier  series 
makes  it  very  probable  that  the  latter  are  pre-Cambrian.  These  inferior 
series  in  descending  order  are  the  Chuar,  Grand  canyon,  Vishnu  series 
(together  the  equivalents  of  Powell's  Grand  canyon  group),  and  the 
basal  complex.  The  upper  series  consists  of  shales  and  limestones. 
Below  this,  with  an  erosion  interval,  is  the  second,  consisting  of  sand- 
stones, with  interbedded  and  cutting  basic  eruptives.  Inferior  to  this 
series,  and  separated  by  a  great  unconformity,  is  a  set  of  thinly  bedded 
and  nearly  vertical  quartzites  of  undetermined  thickness,  broken  by 
intrusive  masses  of  granite.  These  three  are  clearly  clastic  series.  The 
basal  complex  as  described  by  Powell  and  Gilbert  consists  of  thor- 
oughly crystalline  hornblendic  and  micaceous  schists,  gneisses,  and 
granites,  like  the  fundamental  complex  of  the  remainder  of  New  Mexico 
and  Arizona.  Between  this  basal  complex  and  the  Vishnu  series,  as 
shown  by  Powell,  is  a  vast  unconformity.  We  have  then  in  this  region 
passing  from  the  base  upward,  a  fundamental  complex ;  great  uncon- 
formity ;  quartzite  series  of  unknown  thickness  (Vishnu)  5  great  uncon- 
formity 5  Grand  canyon  series  5  minor  unconformity ;  Chuar  series  5  great 
unconformity;  Cambrian. 
The  fundamental  complex  of  Arizona  has  all  the  characteristics  of 
the  fundamental  complex  of  lake  Superior.  The  next  overlying  series 
is  a  quartzitic  one,  and  quartzite  is  one  of  the  most  abundant  and  char- 
acteristic formations  of  the  Upper  Huronian  of  the  Northwest.  The 
next  great  succession  is  the  Grand  canyon  and  Chuar  series,  which  in 
