SPECTER RANGE AND SKELETON HILLS. 
assume red, yellow, and gray colors of varying tints, rendering the 
mountain structure legible at great distances. Near the middle of the 
section, as exposed, are a few layers of black chert, while a bed of 
quartzose sandstone, 20 to 30 feet thick, occupies a similar position 
in the more northerly hills east of Fortymile Canyon. This rode, 
locally a quartzite, is white or pinkish white and fine grained. 
The formation appears to be between 5,000 and 6,000 feet {hide. 
It was deposited in a sea of medium or shallow depth, in ay hi eh 
depression - of the sea bottom kept pace with deposition and into 
which little detrital material was introduced. A few poorly pre- 
served fossils were collected north of the Skeleton Hills. Mr. E. O. 
Ulrich reports that these consist of trilobite fragments and a valve 
of a brachiopod, probably referable to the genus Billingsella. He 
believes that they are of Cambrian age. The limestone is without 
much doubt the Prospect Mountain (Cambrian) limestone of Eureka, 
Nev., a although the upper portions may belong more property with the 
Pogonip limestone. 
IGNEOUS ROCKS. 
In no other equal area surveyed during this reconnaissance do 
igneous rocks cover so little territory. The writer saw no indications 
Fig. 15. — Northwest-southeast section through Specter Range. 
of granite or other intrusions, an observation verified by statements 
of several prospectors who have examined the hills in considerable 
detail. A single small butte of vesicular basalt similar to that of 
the mesa south of Cane Spring protrudes from the desert gravels 
northeast of Point of Rocks. This butte is probably an erosional 
remnant of a flow which extended from this mesa southward. 
STRUCTURE. 
The Cambrian rocks are folded in a complex manner. Two sets 
of folds are present in almost equal development, the axes of one 
striking northeast, those of the other striking east and west. Zones 
of brecciation and normal faults occur at a number of places, but 
few of the faults show a displacement of more than 30 feet. The 
fault 2 miles north of west of Point of Rocks is normal and has a 
displacement of 100 feet. It trends N. 30° E. and the western side 
is downthrown. A sag in the hills coincides with the fault, the 
downthrown side being slightly higher than the upthrown. Fig. 1~> 
is a section passing through the hills from northwest to -out lie; 
a Hague, Arnold, Mod. U. S. Geol. Survey, vol. 20, 1892, pp. 2 
