Bulletin - United States Geological Survey, Ausgabe 208


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Seite 194 - The mountains were eroded, producing minor irregular forms. The climate being slightly moister than now, a shallow lake a few hundred feet deep was formed in the bottom of Death Valley. This soon became charged with salt, borax, etc., derived chiefly from the leaching of the earlier lake beds, now become mountains. At this period the late Pleistocene shore gravels were formed. 10. The climate becoming drier, the lake evaporated, leaving a salt desert. Since that time there has been only a slight...
Seite 24 - Op. cit., p. 240. e. cit. uppermost of the lithologic divisions of the Devonian in the Eureka district. It. consists of 2,000 feet of black argillaceous shales, more or less arenaceous, with intercalations of red And reddish-brown friable sandstone, changing rapidly with the locality. The beds contain plant impressions. The formation is underlain by the Devonian Nevada limestone and overlain by the Carboniferous Diamond Peak quartzitp.
Seite 215 - Lake, there is a series of beds of clays, sandstone, volcanic tuffs and interbedded lava flows. These are probably 1000 feet or more in thickness and extend over a considerable area between the El Paso range and the Sierra Nevadas. On the north and northeast they pass beneath Salt Wells valley and the wash from the Sierra Nevadas. They are finely exposed in Red Rock Canon and about Black Mountain, the highest peak of the district. . . . The beds are tilted northward at an angle of 15°-20°.
Seite 220 - ... of the range. On the flanks of the range, about Fish Springs, are flows of basalt, described by Mr. WA Goodyear." Mr. II. W. Fairbanks* suggest.s that these may be of the same age as the basalts of the Coso Range. According lo Air.
Seite 101 - Emmons has described in the following terms" : The lowest exposures show strata of a greenish, somewhat cherty quartzite. Above these, forming the summit of the ridge, is a breccia-like conglomerate, made up of greenish and purple cherty fragments, with a red cement, overlaid by a thickness of about 1 .000 feet of quartzite and conglomerate, weathering with a peculiar yellowish-brown earthy surface.
Seite 168 - Total 2,395 The fossils here show that the rocks of the section are Upper Carboniferous. At Olcott Peak the fossils, according to Mr. Gilbert, are Lower Carboniferous. oU. S. Geog. Surv. W One Hundredth Mer., Vol. IlI, p. 166. 6 Ibid., p 82. At Mountain Spring, a point about (i miles west of Oottonwood .Spring, Mr. Gilbert
Seite 68 - The ores are distinctly connected with the fault lissures and have formed largely in their vicinity. Mr. Hague" describes the occurrence of the silver deposits of Treasure Hill as (1) in fissures, striking east and west; ('2) in deposits between the limestone and shale; (3) in beds or chambers in the limestone and parallel to the stratification of the rock; and (4) in the regular seams or joints across the rock bedding, most frequently with a northsouth trend. The minerals found in the mining district...
Seite 129 - Price 5 cents. 17. On the Development of Crystallization in the Igneous Rocks of Washoe, Nevada, with Notes on the Geology of the District, by Arnold Hague and Joseph P.
Seite 130 - J According to Dr. Becker, the succession of igneous rocks in this district is, beginning with the oldest: Granite, metamorphics, granular diorites, porphyritic diorites, quartz-porphyry, porphyritic diabase, later diabase (black dike), earlier hornblende-andesite, augite-andesite, later hornblende-andesite, basalt. The succession, according to Hague and Iddings, is as follows: 1. Pyroxene-hornblende-andesite (in its coarser inner portions becoming pyroxene-hornblende-diorite-porphyry and pyroxene-hornblende-dio...

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