| OCR Text |
Show 176 The deposits of the Quaternary are formed by sandstone, conglomerate, clays, and gravel- beds, with occasional saline masses, and till not only the valleys, but also occur at considerable altitudes in the uplifted niouutain- rauges. To the saline efflorescences less attention was hitherto paid than they deserve. Their occurrence appears to indicate that since the recession of the ocean not enough rain has fallen to dissolve them and carry them off. It is true, in several instances, they are of so recent an origin that our conclusions must naturally be much restricted, but, in other caBes again, they are of a considerable age. Their origin may be due either to the drying up of salt- lakes left in natural basins after the rising of the country above the sea, or to the desiccation of fresh- water lakes, containing generally, although a very small, amount of mineral salts in solution, or they are the residue of mineral springs. As the chemical composition of ihese saline masses may give in many places a clew as to the origin, a number of specimens were analyzed. In the following three cases, the composition is that of table- salt of average quality: Constituents. * Sodium chloride Sodium sulphate Calcium sulphate Mftjfne « rinm chloride , , • A. 95.51 2.44 1.01 0.60 99.56 B. 94.02 4.35 1.24 Trace. 99.61 C. 95.49 2.78 0.27 Trace. 98.54 * In every analyais mentioned here, the substance was freed of its moisture in order to facilitate the comparison of the results. A. Salt of Panamint Valley, deposit 1 to 2 feet deep, covering a number of square miles. B. Salt covering the plains of Columbus,. Nevada. C. Salt of Death Valley, deposit 1 to 3 inches deep and covering many square miles. Analogous deposits exist in Salinas Valley. ( For information and specimens regarding A and C, I am indebted to Lieut. R. Biruie, jr., of your survey.) Other specimens have a very different composition, as the following table shows; the amount of sulphate of soda is increased and forms in one case ( C) the whole soluble portion. Also, carbonate of soda forms a constituent pointing to another source than sea- water. Constituents. TnnnlnhlA ( A& nri Rijd clfty) . , . . , Sodium chloride ". Sodium sulphate Sodium carbonate A. 42.32 38.02 10.61 7.51 98.66 B. 48.68 28.08 8.73 15.06 100.55 C. 44.30 Trace. 54.08 None. 9a 38 D. 51.57 29.00 19.51 Trace. 100.08 A. From the saline flats of the Mohave, thickness 1 to 3 inches; area, about half a square mile. B. From Point of Rocks, forming isolated saline spots. C. From shore of Kent Lake. ) n i i * ^ i T k A ¥ i • •. * A XT n D. From Tehachapi Pass. ( Collected by D. A. Joy, geologist of party No. 2. Another deposit of small extent, however, derived from a spring near Stone's Ferry, gave the following result: Insoluble ( clay) 4 57.40 Sodium sulphate 32.30 Magnesium sulphate 6.32 Calcium sulphate 3.51 99.53 An alkaline deposit near Benton, ( Mono County.) gave the following result: Insoluble ( sand) 3.70 > Sodium carbonate ^ 70.31 Sodium sulphate 11.25 Sodium chloride 13.76 |
