244 H. W. TURNER GEOLOGY OP THE SILVER PEAK QUADRANGLE 



ralda formation," after the county in which they occur. There are local 

 developments of sedimentary breccias probably of subaerial origin and 

 conglomerates on a large scale. The lake beds contain the remains of 

 fresh-water mollusks and fish, which indicate that the water of the lake 

 must have been fresh or only slightly saline. In addition, there are very 

 abundant plant remains and beds of coal. Inasmuch as Professor 

 Knowlton has described the fossil plants in detail elsewhere, 19 they will 

 be only briefly referred to here. The flora is represented by ferns, the 

 fig, oak, willow, sumach, and soapberry, and includes tree trunks 6 to 8 

 feet in diameter, showing that the climate has undergone a great change 

 since Tertiary time. From a well watered region it has become an arid 

 one in which there are no running streams. 



The first published notice of these Tertiary lake beds appears to be 

 that of M. A. Knapp, describing particularly the coal deposits 20 occurring 

 in the beds at the north end of the Silver Peak range. Mr Knapp col- 

 lected some molluscan remains near the coal beds, and these were ex- 

 amined by Dr J. C. Merriam, of the University of California, who 

 considered the shells indicative of fresh water and possibly Miocene 

 in age. 



Areal distribution of the beds. — On the geological map in Spurr's 

 report the areas of the Esmeralda formation are shown as "Tertiary 

 stratified rocks." In the southern part of the quadrangle the beds are 

 visible at only a few points and are undoubtedly mostly wanting, for 

 there are older rocks at the surface nearly everywhere in the Palmetto 

 mountains and the southern part of the Silver Peak range. The lake 

 beds undoubtedly underlie the later deposits of Clayton valley, of the 

 southern part of Big Smoky valley, and of the northern part of 

 Fish Lake valley. They are also reported to have been struck in a well 

 bored at Columbus, at the west side of the valley of that name, which 

 lies just north of Silver Peak range. It is probable that they underlie 

 the Columbus marsh. They certainly extend north of the Silver Peak 

 quadrangle into Big Smoky valley. As far as present evidence goes, 

 within the limits of the Silver Peak region the basin containing lake 

 Esmeralda was bounded on the south by the Palmetto mountains at the 

 south end of Clayton valley, on the east by the Montezuma mountains, 



19 H. W. Turner : "The Esmeralda formation, a fresh-water lake deposit," with de- 

 scription of the fossil plants by P. H. Knowlton and a fossil fish by F. A. Lucas. 

 Twenty-first Annual Report of the U. S. Geological Survey, part 2, pp. 192-224. 



20 The coal fields of Esmeralda county, Nevada. Mining and Scientific Press, San 

 Francisco, vol. lxxiv, 1897, p. 133. 



It might be noted, however, that fossil fishes from this formation were collected pre- 

 viously by J. E. Clayton and W. P. Blake, but no description of these fossils appears to 

 be in print. Proceedings of California Academy of Science, vol. iii, 1866, p. 306. 



