10 BORAX OF DEATH VALLEY AND MOHAVE DESERT, [bull. 200. 
point it extends in a nearly straight line up Cajon and Lone Pine 
can} T ons, and finally it reaches the edge of Mohave Desert in the 
vicinity of Rock Creek. 
So far as could be determined from the debris brought down the 
canyons, the high mountains south of the fault are composed of dark- 
green hornblende-schist, and the low ridges north of the fault are 
made up of coarse gray granite, with occasional outcrops of white 
marble and other highly metamorphosed sedimentary rocks. 
North of the granite hills lies an obscurety marked valle} r , separat- 
ing the granite range from immense accumulations of gravel which 
lie upon the southern edge of Mohave Desert. The origin of this 
valley is not well understood, but it seems possible that a fault has 
occurred along this line, and that the mountain on the south has 
dropped away from the gravel that formerly rested upon its flanks. 
At the intersection of Lone Pine and Cajon canyons the granite 
range is replaced by low hills of sandstone and conglomerate. This 
formation occupies a rudely triangular area on the west side of the 
creek, and at the extremities of the outcrop the beds extend across 
the stream and are visible for a short distance in the eastern wall of 
the canyon. 
The beds are made up of granitic debris in which feldspar fragments 
are so abundant as to give the rocks a decidedly pinkish tinge. 
Coarse, well-rounded gravel is abundant, and waterworn bowlders 12 
inches in diameter are of common occurrence at certain horizons. 
Some of the beds are sufficiently indurated to stand up in prominent 
cliffs, but most of them disintegrate readily into coarse sand and 
gravel. The rocks are considerably disturbed, being thrown into 
anticlines and sj^nclines with dips of from 10° to 30°. 
The age of this formation is not definitely known. Fossil shells are 
reported as occurring in beds associated with a coal seam near the 
base of the series, but the writer was unable to find the locality, and 
search in another portion of the series was not rewarded by fossils of 
any kind. Marine Eocene fossils have been found in similar rocks on 
Rock Creek, and the fossiliferous beds, according to report, are 
associated with coal/' Similar fossils are reported from other locali- 
ties in the southwestern end of Mohave Desert. It seems probable, 
therefore, that these various outcrops, which hold similar positions 
relative to the old granitic land mass and are composed of the same 
kind of material, were deposited at the same time and in the same 
body of water. 
The data at hand are not sufficient to enable one to determine 
whether the crustal movements which tilted these beds into their pres- 
ent position, and which presumably occurred soon after their deposi- 
tion, were common to the entire Mohave Desert region or were limited 
«.T. E. Spurr, unpublished manuscript. 
