SEDIMENTARY FORMATIONS. 41 
little unconformity of dip, however, indicating that the period of 
erosion between Cretaceous and Tertiary was not characterized by 
folding. 
In general the Pinto sandstone dips steeply away from the, lac- 
coliths, but south of The Three Peaks, at the Desert Mound, and 
west of Iron Mountain the dip is gentle. East of Iron Mountain 
the dip is steeply toward the laccolith; to the southeast it gradually 
becomes vertical ; and south of Iron Mountain it is steeply away from 
the laccolith. East of Upper Point, south of Joel Springs Canyon, 
and elsewhere the beds are nearly horizontal. 
It is hard to determine the thickness of the Pinto formation because 
of the abundance of faults. The greatest thickness exposed in 
cliffs is about 500 feet, but thicknesses across the formation southeast 
of Iron Mountain, calculated from the dip and width of exposure, 
are as high as 3,500 feet. The average thickness is considerably 
over 1,000 feet. 
TERTIARY SYSTEM (EOCENE). 
CLARON LIMESTONE. 
DISTRIBUTION. 
The Claron formation surrounds the laccoliths outside of the Pinto 
sandstone. In the northeast quarter it occupies an area just inside 
of the north boundary of the area shown on the map. It is much 
faulted, giving an irregular contact between it and the Pinto sand- 
stone to the south. 
East of Granite Mountains the Claron limestone occupies an area 
which, on account of faulting, is broad at the north and narrow at 
the south and west. Narrow strips of the formation follow the north- 
western base of the Swett Hills. 
Southwest of the Antelope Range the Claron limestone comes out 
from underneath the lavas and extends eastward to where it is cov- 
ered by the Pleistocene lake deposits and southward to where it has 
been eroded away from the underlying Pinto sandstone. In Chloride 
Canyon, southwest of the Antelope Range, and northwest of Iron 
Mountain it appears again, owing to the erosion of the overlying lavas. 
The largest area of Claron limestone in the district borders the 
eastern and southern sides of Iron Mountain, then goes outside of the 
area, but reappears west of Iron Mountain, on the border of the area 
shown on the map. Both by its distribution and by its structure it 
brings out well the laccolithic shape of the andesite mass. 
On the northeast side of the Harmony Mountains little areas of 
Claron limestone are brought up by faulting. It appears also west 
of the Stoddard Mountain intrusive. 
