GEOLOGIC RELATIONS. 223 



are found around San l^ernardino mountain, as well as at several places 

 in clay -slate near the summit of the range,* in the central and northern 

 part of Los Angeles county. Very scattered and isolated deposits occur 

 in Ventura, Santa Barbara, San lAiis Obispo, Monterey and Santa Cruz 

 counties, in ^lonterey paying veins have been found near the coast at 

 TjOs Burros, sandstone being mentioned as the country-rock. A short 

 distance north of Santa Cruz a few gold-(piartz veins are said to occur in 

 unaltered sedimentary formations. In Kern county there is a line of 

 paying veins with a northeasterly strike, extending from Kernville to 

 Tehachipi })ass. Granitic rocks predominate, but contain a number of 

 smaller schist areas, with which the gold de})osits api)ear to be associ- 

 ated. The locality is of interest on account of the number of hot springs 

 occurring near the veins. Tulare county contains but few quartz-veins, 

 but placer diggings are found along several of the rivers. 



In Fresno county, again, several streaks and smaller areas of schists 

 and slates occur in the main granitic mass ; again, the quartz-veins, 

 which here attain greater importance, are closely associated with the 

 former, though not exclusively occurring in them. Continuing north- 

 ward for about fifteen miles to Mariposa, these belts of schists and slates 

 suddenly widen, and at the same time begin to contain numerous and 

 rich quartz veins. Between this region and the lava fields of the north 

 lie the most productive gold-mining regions of California. 



The western slope of the Sierra Nevada is from here northward occu- 

 pied by a gradually widening belt of rocks, to which the name "meta- 

 morphic series " is usually given. It attains its maximum width in 

 Butte and Plumas counties and continues across northwestern California 

 and southwestern Oregon to tlie Pacific ocean. The eastern part and 

 the summit of the Sierra Nevada are still occupied by the continuation 

 of the southern granitic area, bordering upon the " metamorphic series," 

 with an irregular and jagged contact-line, along whicli evidence of tlie 

 later origin and intrusive cliaracter of the granite may be frequently 

 observed. This contact-line is indicated on the ma}). The " metamor- 

 j)liic series," sometimes also referred to collectively as the " auriferous 

 slates," is a very complex mass of rocks. It consists largely of more or 

 less altered and highly compressed sediments, of an age ranging from 

 early Paleozoic to late .Jurassic, and bearing evidence of having Ijeen 

 subjected t«) several mountain-building distur])ances. Associated with 

 these sediments are igneous masses— augite-porpliyrito, diabase, seri)en- 

 tine, etcetera — also ranging in age from Paleozoic to late Mesozoic, though 

 the greater mass of them ap[)ear to date from late .Jurassic or early Cre- 

 taceous time. To a considerable extent these ignecjus rocks liave been 



* Acton mining Uiutrict. 



