798  PRE-CAMBRIAN    GEOLOGY    OF    NORTH   AMERICA. 
The  foregoing  ranges  are  referred  to  the  Archean  simply  on 
petrological  evidence.  This  mode  of  correlation  is  dangerous,  but  a 
general  study  of  the  whole  region  has  strengthened  the  belief  that  in 
the  Paleozoic  series  as  a  whole  there  are  none  of  those  results  of 
extreme  metamorphism  which  in  the  Appalachian  system  are  de- 
scribed by  some  geologists  as  closely  approximating  to  Archean 
forms. 
Besides  mentioning  localities  given  by  Hague  in  which  Cambrian 
is  found,  it  is  said  that  an  excellent  exposure  of  Cambrian  schists  and 
quartzites  is  found  underlying  the  Pogonip  limestone  in  the  range  of 
hills  including  the  Eureka  mining  district  and  connecting  the 
Diamond  and  Pirion  ranges. 
Hague,56  in  1883,  describes  the  Eureka  district  as  a  mountain  block 
standing  between  the  Piiion  and  Diamond  ranges.  At  the  base  of  the 
series  is  the  Prospect  Mountain  quartzite,  1,500  feet  thick,  over  which 
is  a  shale  100  feet  in  thickness  bearing  the  Olenellus  fauna.  One 
small  area  of  granite  is  found.  The  Prospect  Mountain  quartzite  lies 
in  contact  with  it  and  dips  away  from  it  in  irregular  broken  masses. 
Walcott,20  in  1886,  describes  the  Eureka  series  of  Nevada  as  mid- 
dle Cambrian  and  finds  at  the  top  of  the  Prospect  Mountain  quartzite 
the  Olenellus  fauna.  In  the  adjacent  Highland  Range  a  more 
abundant  fauna  is  found  in  the  lower  1,500  feet  of  quartzite. 
Walcott,21  in  1889,  places  the  lower  quartzite  of  the  Eureka  and 
Highland  sections  as  basal  Cambrian. 
Spurr,57  in  1903,  describes  and  maps  the  geology  of  Nevada  south 
of  the  fortieth  parallel  and  adjacent  portions  of  California.  He  men- 
tions the  occurrence  of  pre-Cambrian  rocks  in  the  Colorado  Canyon 
and  in  the  Colorado,  Egan,  Eldorado,  Humboldt,  Kern,  Sierra 
Nevada,  Snake,  and  Virgin  ranges. 
Ball,58  in  1907,  reports  on  a  geologic  reconnaissance  in  south- 
western Nevada  and  eastern  California.  The  presence  of  pre- 
Cambrian  rocks  was  not  definitely  determined.  The  Prospect  Moun- 
tain quartzite  (lower  Cambrian)  of  the  Specter  Range  contains  peb- 
bles of  quartzite,  jasperoid,  and  vein  or  pegmatitic  quartz  derived 
from  pre-Cambrian  formations.  The  mica  schist  of  the  Bullfrog 
Hills  is  pre-Ordovician,  and  although  considered  of  Cambrian  age, 
it  may  be  pre-Cambrian.  The  schist  at  Trappmans  Camp  and  the 
series  in  the  south  end  of  Amargosa  and  Panamint  ranges  are  also 
probably  Cambrian,  although  possibly  pre-Cambrian. 
Weeks,59  in  1907,  discusses  the  pre-Cambrian  geology  of  the  Snake 
Range  of  eastern  Nevada.  It  is  in  general  an  east- west  anticline,  the 
structure  being  nearly  at  right  angles  to  its  trend.  The  southern 
side  of  the  fold  is  quite  symmetrical,  but  the  northern  is  broken  by 
many  faults  having  the  same  general  trend  as  the  anticline. 
