TOPOGRAPHIC FEATUEES OF THE DESERT BASINS. 59 



necessarily mean that they lack scientific interest. For instance, the 

 small saline ponds of Alkali Lake are known to contain about 4 per 

 cent of potash (KgO) in their total dissolved sohds, and the Teels 

 Marsh carries a number of the minerals which are associated with 

 potash brines at Searles. It is quite possible that some of these 

 smaller basins may prove to contain potash accumulations of rela- 

 tively high grade, but the amount of the material is Ukely to be too 

 small to warrant commercial exploitation. 



It is possible to eUminate two additional basins on special grounds. 

 First, Bonneville, in spite of its great size, can be safely dropped from 

 the Hst of possibiUties. This is true on two grounds — previous over- 

 flow and the areal geology of the basin. The overflow in itself might 

 not be sufficient, for there has been a considerable period since the 

 overflow ceased and time has probably been available for extensive 

 potash accumulation. But the Bonneville Basin is set almost en- 

 tirely in sedementary rocks, which can not reasonably be expected to 

 yield any important quantity of potash to the drainage. Further- 

 more, nearly all of the saline material accumulated within the basin 

 is probably now in the Great Salt Lake, and the salts contained in 

 this lake carry less than 2 per cent of potash (K3O). 



The last basin to be ehminated is the Otero, in central New Mexico. 

 This was possibly once subject to overflow and is set almost entirely 

 in nonpotash rocks, but its efimination is not based upon these facts 

 so much as upon a detailed examination made of the basin specifically 

 from the present point of view, and which resulted in a strongly 

 negative conclusion.^ 



The basms which remain may be divided into three divisions: 

 (1) Those in which the known topographic and geologic conditions 

 are fully favorable, (2) those in which some conditions are favorable 

 and some adverse, and (3) those concerning which there is sufficient 

 uncertainty to render classification doubtful and decision as to promise 

 impossible. The basins of these three divisions are given in Tables 

 II and III and IV, respectively. Of those in Table III the topo- 

 graphic features are favorable in all cases but one — Owens. In this 

 case the previous overflow into Searles introduces an unfavorable 

 factor which has, however, been partially overcome by the length of 

 time elapsed since this overflow ceased. At the present time the salts 

 of Owens Lake contain approximately 2.25 per cent of potash (KjO). 

 With the other basins of Table III the unfavorable factor is in all 

 cases a lack of potash-bearing rocks in the drainage basin, the Che- 

 waucan Basin being set almosi; entirely in basalts and the others in 

 Paleozoic sediments. 



Of the uncertain basins of Table IV, the Salton is doubtful, because 

 of the difficulty of interpreting the influence of the Colorado River 



I Free, Circ. No. 61, Bureau of Soils, U. S. Dept. of Agr. (1912). 



