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University of California. 



[Vol. i. 



numerous pieces of white quartz, and of vitreous quartz, fragments 

 of quartzite, and one piece of a dense light-colored rock, probably 

 a rhyolite. All of these are perfectly water worn. In structure the 

 beach presents the confused accumulation characteristic of beaches. 

 There are no stratification or structural planes of any kind apparent. 

 The beach appears to rest directly upon the surface of the granite 

 which is revealed in the lower slopes of the ridge. The altitude of 

 this beach, 800 feet, was determined by a large aneroid barometer 

 checked half an hour later on a known elevation on the Coast Sur- 

 vey chart, and an hour later at sea level, both checks being in agree- 

 ment. 



Ancient Delta of tlie San Jose. — Of a somewhat different order are 

 the evidences of coastal oscillation afforded by the ancient delta of 

 the San Jose Creek. The location, altitude, and extent of the lower 

 portion of this delta are represented on the map with a very fair 

 degree of precision. As there indicated, the delta occupies a tri- 

 angular area on the north side of the present canon of the San Jose, 

 and mantles a sloping surface of the Santa Lucia granite and the 

 shale of the Monterey series. The highest point of the delta is 620 

 feet, and the delta formation spreads out fan-like down the antece- 

 dent slope to within less than 100 feet above tide. The delta is com- 

 posed very largely of incoherent stream detritus, the pebbles being 

 chiefly granite, quartz, white rhyolite, and some few pebbles of the 

 white shale of the Monterey series. The upper portion of the delta 

 is coarse and shows little or no assortment of the detritus; the lower 

 portion, which spreads downward over the slope of the hill, is less 

 coarse and more sandy in character, and shows bedding, with a steep 

 seaward dip. These beds are also partially consolidated into light 

 gray to yellowish sandstones. 



The delta as mapped is not the product of any single stage in 

 the varying relations of sea and land, but has had a somewhat com- 

 plex history, all the details of which have not been unraveled. The 

 upper portion of the delta has been dissected by the San Jose Creek 

 and by a small tributary creek which comes in on the north side 

 just east of the limits of the area mapped. This dissection, together 

 with the degradation of the delta by ordinary subaerial erosion, 

 reveals some facts of interest. The most striking of these facts is 



