414 abstracts: geology 



GEOLOGY. — A geologic reconnaissance of the Inyo Range and the 

 eastern slope of the southern Sierra Nevada, California. Adolph 

 Knopf. With a section on the stratigraphy of the Inyo Range. 

 Edwin Kirk. U. S. Geol. Survey Prof. Paper no. Pp. 130, 

 pis. 23, figs. 8. 1918. 



The region described in this report comprises Owens Valley, in eastern 

 California, and the portions of the Inyo Range and the Sierra Nevada 

 between which it lies. The sedimentary rocks of the Inyo Mountains 

 are more than 36,000 feet thick and range in age from pre-Cambrian 

 to Triassic. The Silurian is the only Paleozoic system not represented. 

 The Lower Cambrian of this area is not only notable for its great thick- 

 ness (10,200 feet), but it contains the oldest Cambrian deposits known 

 on the continent. 



Early in Cretaceous time great masses of granitic rocks were intruded, 

 both in the Inyo Range and the Sierra Nevada. The escarpment of 

 the Sierra is composed dominantly of such rocks. Quartz monzonite 

 predominates, and is represented by two varieties — a normally granular 

 quartz monzonite and a porphyritic variety holding large orthoclase 

 crystals, which makes up the summit region of the range. Younger 

 than these is a coarse white alaskite (an orthoclase — albite granite), 

 which occurs in large masses in this part of the Sierra. Notable fea- 

 tures of the geology of the region are the great alluvial cones that ex- 

 tend out from the flanks of both ranges into Owens Valley; the two 

 epochs of glaciation recognizable in the moraines in the canyons of 

 the east slope of the Sierra; and the group of basaltic cinder cones on 

 the alluvial slope between Big Pine and Independence, some of which 

 stand on fault lines marked by fresh alluvial scarps. 



The region is rich in mineral resources — silver, lead, zinc, tungsten, 

 gold, and marble— and the waters of Owens Lake yield soda and other 

 chemicals. The mines at Cerro Gordo in the Inyo Range have pro- 

 duced more silver-lead ore than any other mine in California. In 1913 

 large bodies of tungsten ore were discovered in the Tungsten Hills 

 west of Bishop. The ore consists of scheelite associated with garnet, 

 epidote, quartz, and calcite, and is of contact-metamorphic origin. 

 The ore bodies are important additions to the number of recognized 

 contact-metamorphic scheelite deposits, a class of deposits that pre- 

 viously had hardly been suspected as a possible source of tungsten. 



A. K. 



