POTASH SALTS AND OTHER SALINES IN THE GREAT BASIN REGION. 45 



and of varying depth and filled with brine. (PI. Ill, fig. 1.) The interior of the 

 holes is lined with salt crystals. About the edges, surface tension has drawn the 

 brine up and the margin of the hole is crusted with efHorescences of salt. Near the 

 "land" edge of the rough salt area many holes are to be seen, some more or less arched 

 over by salt crusts and dry mud, and always containing water. Areas of soft red mud 

 also occur between the rough crusts and the outer margin. These are often difiicult 

 and dangerous to cross. The formation of the rough salt crusts may often be seen 

 upon these mud areas. The explanation appears to be as follows: The surface mud 

 dries, forming cracks, and in shrinking leaves narrow channels, bottomed by soft 

 mud, between the cracks. Through these channels the brine solution slowly passes 

 up and crystallizes, forming veins of salt. As the mud cakes dry, they curl upward 

 on the edges, opening the channels wider and allowing more brine to work upward. 

 This crystallizes in part and in part is drawn by surface tension over the surface 

 already crystallized, forming thicker crusts. The brine in the soft mud below is 

 steadily supplied, and the crusts build up until they practically seal the brine over. 

 More or less evaporation must continue beneath the crusts, and as the salt crystals 

 form they must crowd the mud and crusts up, forming the characteristic windrows 

 of mud and salt on the marginal portions. The slow consolidation of the mud, as well 

 as the banking up of the ground water on the periphery against the mud mass, would 

 account for the upward movement of the brines. Rainwater would dissolve the salt 

 from the crusts thus formed , and it would collect in small puddles between the rough- 

 ened masses, where it would be evaporated to a brine. Surface tension would draw 

 this brine up upon the rough masses of salt and, evaporating there, would thicken and 

 build up the irregularities of the salt. The evaporation of a salt solution in a beaker 

 and the climbing of the salt up the sides is a familiar laboratory phenomenon. 



The smooth area of salt is built up by fresh accessions of brine coming from the 

 action of rain water upon the neighboring rough salt areas. Shallow channels (sloughs) 

 meander through the rough salt and collect part of the brine formed by the occasional 

 rains, discharging it upon the smooth salt, where it is speedily evaporated. Wind- 

 blown material collects in the thin sheets of brine and mingles with the salt crystals. 

 The general admixture of soil impurities in the rough salt is also explained in this 

 way. It is evident that the smooth salt area would eventually reach a level that 

 would permit little or no drainage to collect, and the salt bed would no longer be 

 built up. Slow consolidation of the silts and clays in the lowest depressions would 

 extend the differentiation of level over a long period. Differential consolidation 

 would be expected in an area like Death Valley. The finest clays and silts in the 

 lowest depression or sink would consolidate at a greater rate than the sand and alluvial 

 material forming the greater part of the Death Valley filling. The consolidation of 

 the clays and muds would be expected to force the solution upward and even outward. 

 The brines forced outward would be diluted by mingling with the underground 

 waters coming from the neighboring watersheds. "VVe would expect the marginal 

 water to be lower in saline content than that in the smooth salt area, and samples and 

 analyses show this to be the case. Reference is made to the results of samples Nos. 

 339, 341, and 342. The sample No. 339 was taken on the west side of the valley, due 

 west of Furnace Creek Ranch; No. 341 was taken one-fourth mile east of No. 339, and 

 No. 342 one-quarter mile east of No. 341. They show, respectively, 2.77, 15.12, and 

 34.18 grams total solids per 100 cubic centimeters. 



Campbell states that Death Valley is one of the best watered areas within the Amar- 

 gosa region and that the water is, for the most part, good. An inspection of the topo- 

 graphic sheet shows many of the water holes to be close to the edge of the central 

 playa. At Bennett's wells the water is within IJ feet of the surface. Most of the 

 wells are shallow. The explanation of this has been given under the structiiral 

 development of a playa. 



CHEMICAL DATA FOR DEATH VALLEY. 



Four sets of analyses are given in Tables XXI, XXII, XXIII, and XXIV (Appen- 

 dix). The composition of the brines in Table XXI gives perhaps the best conception 

 of the character of the salines present in Death Valley. The average percentage of 

 ions based upon the percentage of total solids in the order of their magnitude is Na, 

 36.12; K, 2.63; Mg. 0.3; Ca, 0.2; CI, 53.7; SO4, 5.62; CO3, 0.18. Sodium and chlorine 

 are the dominating ions. Carbonates are insignificant in amount. The sulphates are 

 in greater amount than in the Silver Peak brines. Potassium is in smaller amount than 

 the Silver Peak brines. The sodium-potassium ratio is 13.7; in the Silver Peak brines 

 it is 11.9. These ratios indicate parallel conditions in both places. Calcium and mag- 

 nesium are insignificant in amount. It should be noted that there is comparative 

 agreement between the results obtained upon samples taken by different persons. 



