792  PRE-CAMB-RIAN    GEOLOGY    OF    NORTH   AMERICA. 
consists  of  quartzite  and  limestone,  with  a  limited  amount  of  crystal- 
line schists  and  granite.  Metamorphic  sedimentary  rocks  of  unde- 
termined age  were  seen  at  a  number  of  points  and  have  been  regarded 
provisionally  in  mapping  as  Archean,  with  which  have  been  grouped 
the  granitoid  rocks. 
Marvine,17  in  1875,  states  that  crystalline  rocks  are  found  on  the 
Salt  Lake  road  in  the  Virgin  Mountains. 
Howell,48  in  1875,  states  that  Granite  Rock  is  an  island  of  granite 
in  the  desert,  which  shows  traces  of  bedding,  with  a  high  dip  to  the 
west.  The  nucleus  of  Snake  Range  is  granite,  exposed  at  many  places, 
and  overlain  by  quartzite,  shale,  and  limestone. 
Emmons  (S.  F.)  and  Hague,35  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,  Gosiute,  Peoquob,  East  Humboldt, 
White  Pine  or  Pogonip,  Wahweah,  Cortez,  Seetoya,  Shoshone,  To- 
yabe,  Augusta,  Fish  Creek,  Havallah,  Pahute,  West  Humboldt,  Mon- 
tezuma, Pahtson,  Granite,  Pahsupp,  Sahwave,  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  interstratified  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  lithological  char- 
acter from  the  Raft,  Ombe,  Gosiute,  and  Peoquob  ranges,  and  is 
therefore  regarded  as  eruptive.  No  decisive  evidence  shows  its  age, 
but  it  is  regarded,  because  of  the  nature  of  its  occurrence,  structure, 
and  mineralogical  habit,  as  probably  Jurassic.  The  granite  of  the 
Fish  Creek  Mountains  is  structureless  and  would  seem  to  be  an  intru- 
sive body.  The  entire  mass  of  the  Pahsupp  Range  consists  of  gran- 
ites which  resemble  the  later  granite  of  the  Pahtson  Range. 
The  Cluro  Hills  of  the  Cortez  Range  are  composed  of  syenite  gran- 
ite, which  is  the  only  true  syenite  found  in  the  region. 
The  East  Humboldt,  Shoshone,  West  Humboldt,  Montezuma,  Pah- 
tson, Truckee,  Lake,  and  Pea  Vine  mountains  contain,  besides  the 
granitic  rocks,  various  crystalline  slates  and  schists  which  are  re- 
garded 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  lami- 
nated, and  similar  to  the  crystalline  schist  series  of  the  Humboldt 
Range,    The  East  Humboldt  Range,  the  main  range  of  central  Ne- 
