300  PRE-CAMBRIAN   ROCKS    OF    NORTH   AMERICA.  [bull.  86. 
Emmons,  (S.  F.),  and  Hague,6  in  1877,  describe  the  mountain  ranges 
of  the  Nevada  plateau  and  the  Nevada  basin. 
Granites  constitute  the  entire  cores,  or  a  large  part  of  the  cores,  in 
the  following  ranges:  Ibenpah,  Wachoe,  Antelope,  Schell  creek,  Egan, 
Franklin  buttes,  Ombe,  Gosi-ute,  Peoquob,  East  Humboldt,  White  Pine 
or  Pogonip,  Wah-weah,  Gortez,  Seetoya,  Shoshone,  Toyabe,  Augusta, 
Fish  creek,  Havallah,  Pah-ute,  West  Humboldt,  Montezuma,  Pah-tson, 
Granite,  Pah-supp,  Sah-wave,  Truckee,  and  Lake. 
In  the  hills  between  Antelope  and  Schell  creek  mountains,  in  the 
Goose  creek  hills,  and  in  Franklin  buttes,  granite-porphyry  is  also  found. 
In  the  Franklin  buttes  there  is  a  gradation  from  syenitic  granite, 
through  granite-porphyry,  into  genuine  felsite-porphyry.  The  hills 
between  the  Antelope  and  Schell  creek  ranges  contain  cores  of  granite, 
east  of  which  are  inter  stratified  beds  of  dolomite,  marble,  and  dikes  of 
granitic  porphyry.  These  are  considered  to  represent  the  development 
of  an  Archean  body. 
The  granite  of  the  Wachoe  range  is  different  in  its  lithological  char- 
acter from  the  Eaft,  Ombe,  Gosi  ute,  and  Peoquob  ranges,  and  is  there- 
fore regarded  as  eruptive.  No  decisive  evidence  shows  its  age,  but  it 
is  regarded,  because  of  the  nature  of  its  occurrence,  structure,  and  min- 
eralogical  habit,  as  probably  Jurassic.  The  granite  of  the  Fish  creek 
mountains  is  structureless  and  would  'seem  to  be  an  intrusive  body. 
The  entire  mass  of  the  Pah-supp  range  consists  of  granites  which  resem- 
ble the  later  granite  of  the  Pah-tson  range. 
The  Cluro  hills  of  the  Gortez  range  are  composed  of  syenite- granite, 
which  is  the  only  true  syenite  found  in  the  region. 
The  Peoquob,  East  Humboldt,  Shoshone,  West  Humboldt,  Monte- 
zuma, Pah-tson,  Truckee,  Lake,  and  Pea  Vine  mountains  contain, 
besides  the  granitic  rocks,  various  crystalline  slates  and  schists  which 
are  regarded  as  Archean.  On  Spruce  mountain  of  the  Peoquob  range 
are  mica-schists  and  mica-slates  which  probably  belong  to  the  older 
series,  but  the  relations  are  obscure.  They  are  distinctly  bedded,  finely 
laminated,  and  similar  to  the  crystalline  schist  series  of  the  Humboldt 
range.  The  East  Humboldt  range,  the  main  range  of  central  Nevada, 
is  a  mass  of  Archean  rocks?  which  acts  as  the  axis  of  an  anticlinal  fold 
and  upon  which  rest  unconformably  the  Devonian  and  Carboniferous 
strata.  The  southern  part  of  the  range  is  composed  of  granite  in  two 
large  areas,  which  possesses,  at  White  Cloud  peak,  the  characteristics 
of  an  eruptive  granite,  there  being  no  distinct  lines  of  bedding,  although 
divisional  planes  are  noticeable.  The  northern  granite  mass  is  uncon- 
formably overlain  by  a  series  of  quartzites,  hornblende-schists,  andj 
gneisses  which  contains  beds  of  dolomitic  limestone  from  1  to  6  feet 
in  thickness,  separated  by  micaceous  quartzites  and  mica- schists.  This 
series,  estimated  in  the  northern  part  of  the  range  to  be  from  5,500  to 
6,000  feet  in  thickness,  is  best  seen  on  Clover  canyon  and  Boulder 
creek.    There  is  every  gradation  between  the  coarse  gneissoid  phases 
