16 



THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 











discussing the phenomena of the more recent formations of the Sierra Ne- 

 vada. For further information in regard to the topics of this section the 

 reader may consult Geology of California, Vol. I., a considerable portion of 

 which is devoted to the Coast Ranges. The material exists for a much more 

 elaborate account of the geology of these ranges than has as yet been pub- 

 lished, and it is the wish and expectation of the writer that this work shall 

 be performed. Meanwhile the brief synopsis which here follows will be of 

 service to those who have occasion to use the present volume. 



The most striking fact in regard to the Coast Ranges is, that this very 

 extensive group of mountain chains is of comparatively very recent geo- 

 logical age. It is made up of Cretaceous and Tertiary strata, with no rocks 

 older than these showing themselves in any portion of the complicated series 

 of elevations which are properly included under the above designation. 

 There are some areas within the Coast Ranges occupied by volcanic rocks, 

 and others where granite and granitoid masses make their appearance on 

 the surface. But by far the larger portion of these ranges consist exclu- 







sively of sedimentary beds, which have been bent, folded, and crushed, so as 

 to form numerous subordinate ranges, as already indicated in the preceding 

 section. 



The Coast Ranges resemble the Appalachians in having no central axis or 

 dominant range to which the others are subordinated. Neither is there in 

 the Californian mountains any core of igneous rock, to the elevation of 

 which the folding or disturbance of the sedimentary beds might be attrib- 

 uted. There are circumscribed areas where such rocks make their appear* 

 ance; but it is evident that these cannot be considered as having played 

 any prominent part in the structural development of the system of moun- 

 tains in which they occur. The folds of the Pacific Coast Ranges differ also 

 from those of the Appalachians in being much less regular and symmetrical 

 in their form than are those of the system of mountains which runs parallel 

 with the Atlantic side of the Continent. On the western edge of the country 

 the work of mountain-building seems to have been much more rapidly ac- 

 complished than it was on the eastern. In the first place, the formations 

 themselves are far more irregular in development and thickness than are 

 those of the Appalachian system ; they differ from the latter, moreover, in 

 being more or less irregularly broken through by both granitic and volcanic 

 outbursts. But the rocks of the Coast Mountains are especially distinguished 

 by the fact, that the movements to which they have been subjected, and 









