POTASH SALTS AND OTHER SALINES IN THE GEEAT BASIN EEGION. 67 
have not reached concentration sufficient to produce crystallization of some of the 
compounds would give little or no concentration of potassium. The absorption of 
such a solution by desert sands would give a weak and valueless brine. Doubtless 
further investigation will show many of the variations indicated above. 
Two general types in the desiccation phenomena may be distinguished, the Searles 
type, in which a large, deep lake was evaporated, and the comparatively thick body 
of saline material, restricted in area and saturated with residual brine, was formed; 
and a second type, which is best illustrated by Death Valley, in which case we have 
the building up of a mass of muds and silts with interbedded salines, by the repeated 
formation and desiccation of a shallow lake. To the latter type belong most of the 
desert, dry lakes, or playas. The line between the two types is not a sharp one. 
The possibility of deposits at depth is still not completely disproved. The geologi- 
cal evidence goes to show that several periods of desiccation occurred. Each period 
might have been characterized by deposits of the kind described above. Such evi- 
dence as we have, and it is meager, does not indicate deposits of this nature. The 
evidence goes to show that the larger Quaternary lakes existed for a long time and 
desiccation was a feature of their final stages. This would place the period of saline 
formation at the end rather than at an intermediate time, and would argue for deposits 
at shallow depths rather than otherwise. On the other hand, the geological evidence 
is not necessarily complete. The obliteration by erosion of older lake lines than the 
present ones is not improbable. Only by systematic deep boring could such a question 
be settled. As the larger Quaternary lake basins are, in almost every instance, occu- 
pied by lakes of considerable size and in some instances of considerable depth, the 
difficulties of such work are apparent. 
The question of deep deposits being uncertain, the field becomes narrowed to the 
deposits which might have resulted from the desiccation periods of the most recent 
Quaternary lakes. Only in Searles have we surface deposits of this nature. In all 
other basins, if older deposits than those at present forming exist, they must be sought 
for at depth. The size of such a deposit would depend upon the area of the drainage 
basin and the area and depth of the Quaternary lake occupying it. Desert basins 
showing no signs of former lakes might well be placed in a separate and unimportant 
class. Such basins can not be said not to have saline beds at depth, but the existence 
of such beds and their value are doubtful. Upon the criteria stated above I have 
grouped the desert basins in the following manner: 
Group I. — Basins formerly occupied by Quaternary lakes. 
A. Basins in which the Quaternary lake was over 300 feet in depth: (in 
order of magnitude on the basis of area): Square miles. 
Carson and Humboldt 27, 575 
Black Rock and Smoky Creek Deserts 10, 500 
Searles (area includes Owens) 4, 850 
Panamint 1, 950 
B. Basins in which the Quaternary lake was 300 feet or less in depth : 
Railroad Valley 6, 340 
Columbus Marsh (including Big Smoky Valley) 5, 225 
Buena Vista (part of Caron and Humboldt) 4, 000 
Dixie Valley 2, 660 
C. Basins which are now occupied by lakes: 
Bonneville Basin 54, 000 
Walker, Nev 3, 850 
Alvord, Oreg 3, 200 
Pyramid, Nev 2, 975 
Owens, Cal 2, 825 
Honey Lake, Cal 2, 660 
Surprise Valley, Cal 2, 350 
Catlow, Oreg 2, 000 
Warner, Oreg 2, 000 
Abert, Chewaucan, and Summer, Oreg 1, 500 
Madeline Plains, Cal 900 
Long Valley, Nev 775 
Mono, Cal. 770 
Silver, Oreg 500 
D . Doubtful basins : 
Diamond Valley, Nev. 
Danby and Bristol Lakes, Cal. 
Franklin and Ruby Lakes, Nev. 
