Lawson.] 



Post-Pliocene Diastropliism. 



'57 



new one is being cut, the choking was doubtless due to accumula- 

 tion of delta material during the Pliocene depression, and the facts 

 are in harmony with our notions of a post-Pliocene uplift, although 

 we cannot from the information given make deductions as to its 

 measure. 



The Santa Clara Valley of the Sonth. — This valley extends from 

 Soledad Pass in the mountains overlooking the Mohave Desert, 

 with a trend a little south of west, to the coast below San Buena- 

 ventura, where it opens funnel-like upon the Santa Barbara Chan- 

 nel. The valley affords a pass for the railway to the coast. From 

 the railway junction at Nevvhall, according to information given to 

 the writer by a friend, who, as a traveler, is familiar with the country, 

 the slopes of the valley are terraced up to elevations of probably 

 not less than 150 feet above the railway. The railway track at 

 Nevvhall has an elevation of 1,265 feet,* from which it appears that 

 the terraces have an altitude of 1,415 feet above sea. The informa- 

 tion is defective, inasmuch as the nature of the terraces has not 

 been critically determined; but, taken with other more definite infor- 

 mation set forth in this paper, there is little doubt but that they are 

 significant of uplift of the coast. 



CONCLUSIONS. 



The facts adduced in the present paper establish a recent uplift 

 of the continental margin, from the Golden Gate to San Diego, of 

 from 800 to 1,500 feet. The geographical extent of the uplift is not 

 measured by the range of the observations here recorded. There 

 is evidence that the uplift extends far to the south and far to the 

 north of the strip of coast subjected to inspection. The uplift is 

 clearly epeirogenic in its character.! 



This event is comparable to the well-known post-Pliocene diastro- 

 phism of the Sierra Nevada. Accepting Whitney's determination of 



*Gannett, Bull. U. S. G. S., No. 76. 



fThis statement does not imply that all parts of the coast were elevated at 

 precisely the same time, but simply that the effect, up to date, of the elevatory 

 process is an uplift of continental extent. The process may have been fitful, 

 active now in one locality, now in another ; the movement may have operated 

 as a slow wave, or it may have had a single focus of direct uplift ; it may yet 

 be active. 



