64 



BULLETIN 61, U. S. DEPAKTMENT OF AGKICULTURE. 



The shore lines in the bottom of the basin, which appear with great distinctness, indi- 

 cate the slow recession and evaporation of the waters. Sufficient time is indicated 

 for the development of a structure similar to that shown in sketch b. Wind erosion, 

 no doubt, played an important part in the closure of the saline beds. The soft char- 

 acter of the Lahontan sediments and the fact that the prevailing winds are from the 

 west would indicate favorable conditions for seolian action. The east end of the 

 Carson Desert, and particularly that portion along the flanks of the Sweetwater Range, 

 is conspicuous for the large sand dunes which have resulted from the wind action of 

 the present. 



The general features involved in the search for the buried salines of the Carson Sink 

 may well be considered. A study of the probable structural relations attending the 

 formation and closure of a saline deposit such as might have taken place in the Carson 

 Sink has shown that the most favorable area is removed from the delta area, either old 

 or new. In the particular case of the Carson Desert a line might be drawn at the present 

 mouth of the Carson and extending southeast and northwest. Southwest of this line 

 is the delta area. Northeast is the area considered as most favorable for the search of 

 a saline deposit. The area between the line established above and the lowest con- 

 tour — 3,900 feet — inclosing the present lake is about 350 square miles. The main 

 deposit of Searles Lake occupies an area having a ratio of 1 to 404, as compared with 

 the area of the whole present basin including the salt deposit. The drainage area of 

 the Carson and Humboldt Rivers is 27,575 square miles. Using the above ratio would 

 give a probable area of saline deposit of 68 square miles. The extent of a saline deposit 

 would be determined by its thickness. Consequently the above area might be larger 

 or smaller. Again, the deposit might be divided, which is not at all unlikely in the 

 present case. The prospecting problem would be to locate by boring an area greater 

 or less than 68 square miles in an area of 350 square miles. 



The nature of the saline bed, if it were discovered, might be similar to that in Searles, 

 or the salines might be distributed in a relatively thick bed of aeolian sediments. 

 Respecting the probability of potassium little can be said. Gale's discovery in 

 Columbus Marsh opens up possibilities which in my judgment would warrant explora- 

 tion in this area. 



The only other instance of exploration for buried salines is in Railroad Valley, Nev., 

 where a 1 , 200-foot bore was siink, but without results. Tlje valley is unlike the Carson 

 Sink in that no large stream discharges into it, and there is no lake of consequence. 

 The results of the bore have been discussed. 



SALINES IN PRESENT LAKES. 



The composition of the waters of the more important lakes of the basin region are 

 given in Table XV (Appendix). The three most important lakes from the standpoint 

 of concentration and amount of salines are Great Salt, Owens, and Mono Lakes. The 

 computed quantities of the more important salines in these lakes are given in the 

 table which follows: 



Quantities of salts in Great Salt, Owens, and Mono LaTces. 



Lake. 



NaCl. 



NajSO^. 



KCl. 



NajCO,. 



NajBiO;. 



Great Salt i 



Tons. 



400,000,000 



20,000,000 



86,099,600 



Tons. 

 30,000,000 

 22,000,000 

 47,586,400 



Tons. 



Tom. 



Tons. 



Owens 2 



2,140,000 

 10,538,000 



22,000,000 

 92, 101, 100 





Mono 2 



945,100 





1 Monograph 1, U. S. Geol. Survey, p. 253. 



2 8th Annual Report. Quaternary History of Mono Valley, Cal., pp. 295-296. Potassium sulphate has 

 been recalculated to potassium chloride in the case of Owens Lake. 



Salt is separated from the brines of Great Salt Lake and at Owens Lake sodium 

 carbonate and bicarbonate have been separated by solar evaporation and crystalliza- 

 tion for a number of years. At Large Soaa Lake, Nev., soda was also separated. Out- 

 side of this, there has been no other commercial utilization of the waters of the basin 

 lakes. Only two other lakes in the basin approach the three mentioned above in 

 degree of salinity — South and Middle Alkali Lakes, Oreg. (PI. V, fig. 1.) The 

 saline content of the remaining lakes is of little present importance. No important 

 concentration of potassium salts has taken place in the present lakes, excepting incon- 

 sequential cases which have been mentioned before. Later investigations have not 

 supported the earlier estimates of notable concentrations of potash salts in Abert Lake 

 and the Surprise Valley. (PI. V, fig. 2, and PI. VI.) 



