Geology of Eastern California. — Fairbanks. 
69 
precipitous flanks. Andesite appears as flows between the 
beds, in dikes cutting them, and also capping Black moun¬ 
tain. 
Three distinct movements can be traced about Black moun¬ 
tain. The first elevated and tilted the sedimentary strata to 
the north. After a period of erosion a subsidence took place 
with the formation of a gently sloping terrace of gravels 
about the mountain and extending up to within a thousand 
feet of the summit. Following that was another elevation 
which has resulted in the cutting of the present canons in 
the tuffs and terrace gravel. 
About Borax lake, in northern San Bernardino county, 
there are many distinct beach terraces rising at least 500 feet 
above the level of ' the alkali marsh. The lake which once 
occupied this basin was many miles in extent and left depos¬ 
its of clay of considerable thickness, particularly on its 
western side. Its existence was probably coeval with the 
other Quaternary lakes of the Great basin. 
The basin occupied by Owen’s lake is separated from Salt 
Wells valley by a long narrow depression, a continuation of 
Owen’s valley toward the southwest, which is but slightly 
elevated above the lake. This must have been the outlet of 
the lake during the high water stages of Quaternary times 
unless the topography has changed greatly. This depression 
is flanked on the east by the Coso range, the western portion 
of which consists of andesite, lipa-rite, and basalt. Evenly 
stratified beds of volcanic ash lie along the western slope of 
the mountains and terminate opposite Owen’s lake where they 
reach an elevation of at least 1,500 feet above it. If these 
beds were formed under water, as seems probable, there have 
been local changes of level of great magnitude, for no deposits 
were observed about other portions of the lake. 
Panamint, Salinas, and Death valleys are much alike in 
many respects, all having been the beds of lakes during the 
Quaternary period. Panamint valley is narrower than the 
others and the alkali bottom has been obliterated through its 
central portion by the enormous amount of detritus from the 
mountains. 
The Detrital Slopes of the Desert Valleys. 
There is no more striking feature of all this desert region 
than the long gentle slopes or inclined planes which extend 
