184 
GEOLOGY. 
but several very thick beds of conglomerate and breccia of porphyry, and other volcanic rocks, 
overlie them. A section will he found on page 56. 
The sedimentary formations of the high valley of Lake Elizabeth, being on the north slope 
of the Bernardino Sierra, are also within the Basin, and are separated from the upraised 
strata just described by a long but low ridge of granite. The strata in the valley are horizontal, 
and composed of coarse, gray sandstone. They form a line of hills, with rounded, soil- 
covered surfaces, so that the strata are not well exposed to view. 
A range of sedimentary hills is found throughout the chain of high valleys extending par¬ 
allel with the Bernardino Sierra on the north, and at times they form the only ridge of separa¬ 
tion between the valleys and the slope of the Basin. Thus, in passing from Lake Elizabeth 
towards Williamson’s Pass, hills composed of horizontal strata are either found in the valley or 
upon the left, nearly to the Pass, when they become low and gradually disappear under the 
slope. Beyond this, however, and opposite the entrance to the Pass, there is a wide area of 
rounded hills, which, in all probability, are a continuation of the same deposits. The strata at 
all these different points do not present the same lithological characters. Those near Lake 
Elizabeth are more firm and compact, and contain beds of hard sandstone. Those nearer to 
the Pass are more argillaceous, and less firmly consolidated. At one point, beds of white, red, 
and greenish clays were observed; the white beiug the debris of white feldspathic granite. 
Gypsum was also seen in thin sheets. These formations have considerable resemblance in their 
external aspect to the lower hills of the Miocene deposits of Ocoya creek. 
Although the topography, and several slight exposures of the strata, indicate their horizontal 
position, one or more outcrops were highly inclined, a dip of seventy-five degrees being observed 
at the eastern point of the low range separating the Basin slope from the mountains. This 
may be a local disturbance, or an older series of strata. Near the lower ridges of the moun¬ 
tains, at the Pass, there are hills and outcrops of hard strata of sandstone and a thick bed of 
breccia of volcanic rocks, porphyries, and the like, the fragments being from eight to twelve 
inches in diameter, and closely packed together. These strata incline northeasterly at an angle 
of twenty degrees, and dip away from a dyke, or ridge, of igneous rocks. They appear to 
underlie the less firmly consolidated, and probably horizontal, strata lower down the slope. No 
break or want of conformity was observed. 
Further east, along the base of the mountains, outcrops of other strata are seen in the banks 
of Cottonwood Creek. They do not resemble, lithologically, either of the outcrops which have 
been described. They consist of the fragments and fine debris of granitic rocks, and have a 
red or pinkish color, due to the presence of a large portion of pink feldspar. A somewhat 
similar rock was seen in the Canada de las Uvas, and occurs again in the Cajon Pass. At the 
last mentioned place the strata are greatly developed, and form high hills, conspicuous for their 
peculiar forms, due to the action of the weather. They are inclined at an angle of forty-five 
degrees both in the Pass and along the banks of Cottonwood Creek ; and the similarity of their 
lithological characters is such as to lead to the conclusion that they had a synchronous origin. 
Both localities are free from indications of fossils ; and the coarse materials indicate the rapid 
formation of the beds under the action of swift currents. 
Other sedimentary deposits were observed along the Mojave River, at the point where the 
road first crosses the stream, and beyond, towards the end of the valley, in the Soda Lake. 
These deposits are soft, marly clays, or clay and sand, of light colors, but sometimes bluish and 
red. They rise in high banks along the lower parts of the river, and are worn by the weather 
