No. 1. 

 RETORT UPON THE (JEOLOGY OE THE ROUTE 



BY J. S. NEWBERRY, M. D . 



GEOLOGIST OF THE EXPEDITION. 



CHAPTER I. 



GEOLOGY OF THE VICINITY OF SAN FRANCISCO. 



General features given by parallel axes of elevation. — Bay of san francisco occupying a synclinal trough. — General 

 trend of ranges northwest and southeast. — coast mountains give outline and direction to the coast.- — local 

 geology. — san francisco range. — golden gate cut through it. — centre, trap and serpentine. — physical characters of 

 the serpentine. — chemical analysis. — serpentine, sandstones, and shales. — fltness of the sandstone for architectural 

 purposes. — it contains few fossils. — scutella interlineata. — jasper — drifting sand. — alluvial deposits. — geology of 

 san pablo bay. — sandstones and shales of the san francisco group. — sandstones fossiliferous. — pecten bed. — other 

 fossil shells. — tcfas and marls forming series of great thickness. — upper members very modern, and of volcanic 

 origin. — Beds of recent oyster shells. — Changes of level. — Probable communication formerly existing between san 



PABLO BAY AND THE OCEAN. — STRAITS OF CARQUINES .• — SANDSTONES AND SHALES. — LaMIN/E OF GYPSUM. — BENICIA. — SANDSTONES 



equivalents of those of san francisco. — rldge of jasper northwest of benicia. — warm sulphur spring. — soil — geology 

 of mount diablo. — gold. — suisun bay. — calcareous tufa. — trap hills. — san francisco sandstone forming hills near 

 Vacaville. 



GENERAL FEATURES. 



The configuration of the country in the vicinity of San Francisco has been given by two prin- 

 cipal, and nearly parallel lines of upheaval, one passing between the city and the Pacific, 

 forming the barrier through which the Golden Gate has been cut, the other that of the Contra 

 Costa mountains. These, with several subordinate axes, which exert a local influence on its 

 structure, properly belong to the compound chain of the coast mountains, have the same geo- 

 logical structure, and are doubtless of the same age. They are composed of serpentine or trap 

 at centre, flanked by heavy beds of shales and sandstones of the tertiary period. 



The general trend of these ranges is northwest and southeast, and they belong to the same 

 system of elevation with that which has given the general outline and direction of the coast 

 from Cape St. Lucas to Cape Mendocino. The islands which are scattered along the coast of 

 California within the limits specified apparently lie in the lines of some of the axes of this 

 system. 



The Bay of San Francisco and the valley south of it occupy the synclinal trough which lies 



between the two axes I have mentioned. This depression, geologically considered, forms but a 



single area, which should be viewed as a whole, and which may properly be termed the valley 



of San Francisco bay. Of this area the valley of San Juan forms the southern, San Francisco 



2 Y 



