POTASH SALTS AND OTHER SALINES IN THE GREAT BASIN REGION. 6 
and particularly dealing with the geochemical features, has been made. In order to 
widen out the field and stimulate prospectors and others to direct their attention to 
this mineral, the Bureau of Soils, the United States Geological Survey, and the Mackay 
School of Mines established a joint laboratory for the examination of mineral and other 
naturally occurring substances suspected to contain potash. The results of the United 
States Geological Survey investigators have been presented from time to time in 
bulletins. 1 
The results of the work of the Bureau of Soils are, in part-, presented in a paper by 
E. E. Free (The Present and Past Topography of the Un drained Areas of the United 
States). 2 The purpose of the present paper is to present a review of the information 
now available on the subject of the occurrence and origin of the salines of the Great 
Basin region, as well as the chemical data which have been accumulated by the 
Bureau of Soils and the Cooperative Laboratory. Naturally a review of the geo- 
chemical features of a region of this extent will not be complete, but it is believed 
that such a review will be of value at this time and will indicate quite clearly the 
lines along which future investigation should be directed. 
For an adequate conception of the geochemistry of a region it is necessary to know 
the principal facts concerning climatology, topography, geology, the surface and under- 
ground waters, the evaporation from ground and surface waters, and the distribution 
and chemical character of the rocks. These subjects will be treated in the order 
stated. 
CLIMATOLOGY. 
The Great Basin is spoken of as an arid region, and just what is the significance of 
this term may be gathered from the tables in the Appendix. These tables have been 
compiled from Weather Bureau reports on precipitation and temperature. They are 
grouped in four divisions: Weather stations in Nevada, weather stations in western 
Utah, weather stations in the part of the basin region included in Oregon, and weather 
stations in that part of the basin region included in California. The altitude and 
mean annual rainfall of each station is given. (See Appendix, Table I.) The average 
(arithmetical mean) annual rainfall of the stations in each group is, for the Oregon 
group, 13.59 inches; for the Utah group, 12.8 inches; for the Nevada group, 10.34 
inches; and for the California group, 4.43 inches. The mean annual precipitation 
for the entire basin region is 10.31 inches. In arriving at this average the mean for 
each of the above groups and the area occupied by each group were taken into consid- 
eration. The variation of the mean annual rainfall with latitude in the basin region 
may be approximated from Table II. (See Appendix.) Latitude is less a factor in 
controlling precipitation than altitude. The basins of the Great Basin in general are 
characterized by a small rainfall. The higher mountains receive a much greater 
rainfall. An area of high aridity may be marked out, and this includes the Mojave Des- 
ert, the Amargosa Basin, the Owens, Walker, Mono, Pyramid, Carson, and Black Rock 
Desert regions. In this area the mean annual precipitation is less than 6 inches. 
An inspection of the weather reports for the basin region shows that some precipi- 
tation takes place in each month of the year. December, January, February, and 
March are the usual months of maximum precipitation; while June, July, August, 
and September are the months of minimum precipitation. There is, however, much 
irregularity in the monthly distribution of the rainfall, and the weather charts do 
not give an entirely clear conception of the situation. Rainfall may be divided into 
two classes — the normal winter precipitation and the precipitation which usually 
occurs in August and September. The latter is in the nature of torrential rains and 
cloudbursts and is conspicuous in the more arid portions of the region. The normal 
winter precipitation contributes but little run-off in the arid portions, but the August 
and September precipitations often result in heavy local run-offs which are important 
agents in the movement of detrital material from the mountains to the plains. As 
might be expected, precipitation of this nature is very irregular. Several years may 
elapse without sufficient rain to even moisten the desert watercourses. Then a 
period of heavy rains results in turning such watercourses into torrents. Stream 
flows of this nature are of short duration, but the local work of erosion and transpor- 
tation may be very great. Were it not for these rains, erosion and deposition in the 
more arid portions of the basin region would be somewhat inconspicuous and limited 
principally to the action of wind. The influence of these torrential rains extends 
over the whole arid region described above. But little study has been made of these 
i Bui. No. 523, Nitrate Deposits. Bui. No. 530-A, The Search for Potash in the United States; Potash 
Salts— Summary for 1911. Bui. No. 511, Potash Salts— Their Uses and Occurrence in the United States; 
Alunite. Bui. No. 530-R, Exploration of Salines in Silver Peak Marsh, Nevada: Press Notice No. 97, 
Feb. 10, 1913: Prospecting for Potash in Death Vallev. 
2 Circ. >,o. 61, Bureau of Soils, An Investigation of the Otero Basin, New Mexico, for Potash Salts; Circ . 
No. 62, Bureau of Soils, Report of a Reconnoissance of the Lyon Nitrate Deposit near Queen. New Mexico. 
