344 University of California Publications in Geology [Vol. 8 



ing this valley. Further evidence of this is the occurrence of beds 

 containing identical species of fresh-water molluscs near Hawthorne, 

 lying thirty miles to the northwest in Soda Springs Valley. Beds 

 of similar aspect also occur near Sodaville, lying to the southward in 

 this valley. 



From the fact that patches of the beds, dipping toward the valley, 

 have been left lying by erosion on the range flanks, it is inferred that 

 the Esmeralda strata formerly covered large areas of the range slopes, 

 from which they have since been removed. The beds may have nearly 

 covered some of the neighboring ranges, although it is apparent from 

 a certain amount of coarse clastic material in the sections that land 

 masses occurred nearby, and as the beds at some localities abut against 

 the mountain flanks it is probable that the land-masses were approxi- 

 mately on the sites of the present ranges. 



Lithology. — Lacustral sandstones of fine, medium, and coarse tex- 

 ture constitute a large part of the total thickness of the Esmeralda 

 strata. They are for the most part evenly and thinly bedded (pis. 35 

 and 36). and the materials are usually well classified as to size and 

 fairly well rounded. Cross-bedding is, however, far from uncommon. 

 The particles consist largely of quartz and of the rocks of the sur- 

 rounding ranges. Fine ash and coarser pumice particles are frequently 

 present in considerable amounts. The sand. grains are commonly cov- 

 ered with a white coating. In some strata the coating is blue and 

 gives the rock a striking blue color identical with that seen in some 

 of the Neocene marine sandstones of the California Coast Ranges. 

 Selenite veins cutting across the bedding are quite common. Where 

 the series rests on granodiorite the basal member is often a coarse 

 arkose derived from it. Fossil wood is abundant in the sandstones 

 at many localities. About a mile southeast of Stewart Spring the 

 silicified trunk of a tree, originally not less than six feet in diameter, 

 lies exposed on the surface through the removal of its sandstone 

 matrix by erosion. 



The shales, in common with the other strictly lacustral sediments, 

 are white or very light gray in color, are evenly and thinly bedded, 

 and probably contain considerable ash (pi. 36, fig. 2) . They are almost 

 without exception calcareous, and are usually quite hard. Every 

 gradation occurs from the less calcareous shales and sandstones to 

 impure limestones. The most striking facies perhaps are the paper 

 shales, which part easily along the bedding-planes into sheets of ex- 

 treme thinness. A number of samples of shale were examined micro- 



