Campbell.] GEOLOGY 4LONG ROUTE TRAVERSED. 17 
From the character of the Tertiary sediments it seems probable that 
they were largely derived from the Paleozoic rocks composing the 
escarpment, consequently the movement that produced the scarp ante- 
dated the lake, and it is altogether possible that the valley in which the 
waters accumulated was formed by this movement. There are also 
some indications that recent movements have occurred along the same 
line; in fact, the general tilting of the Tertiary rocks to the northeast 
may be due to a recent depression on the south side of this fault line, 
or to the tilting down toward the northeast of the block of strata that 
originally formed the floor of the lake. The southern edge of these 
deposits has not been examined. It is reported, on what seems to be 
good authority, that the lake beds extend south from the forks of 
Furnace Creek for a distance of only S or 10 miles; it therefore seems 
highly probable that the territory occupied by these beds is narrow, 
and that originally it was the southeastern extension of Mesquite 
Valley. 
As previously stated, the mountains and valleys of the Death Valley 
region appear originally to have trended northwest and southeast, and 
at a later date crustal movements operated in a north-south direction, 
dropping or tilting large blocks of strata and forming a new set of 
features at an angle of about 00° from the original lines. 
The range of mountains on the east side of Death and Mesquite 
valleys is separated into two parts by the low gap formed on the lake 
beds. The mass lying north of these sediments is known as Grape- 
vine Mountain, and that to the south, including the lake beds, is called 
Funeral Mountain. 
The lake sediments of this region are similar to those previously 
described. They are composed of clay, sand, and gravel, with many 
beds of volcanic tuff and intrusive lava sheets toward the base of the 
series. Coarse gravel abounds near the contact between these beds and 
the Paleozoic rocks of Grapevine Mountain, showing that at the time 
of deposition this was a shore or boundary wall of the valley in which 
the lake was located. The strike of the beds is parallel with the north- 
eastern margin, and the dip is 20° to 45° toward the northeast. The 
beds maintain this attitude on both sides of the range, and they do not 
dip under the valleys on either side, as they have been supposed to do. 
Interbedded with the rocks of this series is a bed of colemanite 
(borate of lime), which, though probably not continuous, shows in out- 
crop in a number of places across the mountain, a distance of at least 
25 miles. This constitutes the largest deposit known in this country, 
and presumably the largest in the world. The bed has been opened 
low in the foothills on the east side of the mountain -4 or 5 mile- south 
of the Ash Meadows road. At this point the bed is visible for several 
hundred yards, and in the prospect pits it has a thickness of from 
4 to 10 feet. It is said to exceed these figures, but no thicker sections 
Bull. 200—02 2 
