220 



GUIDEBOOK OF THE WESTEEN UNITED STATES. 



The dark Cretaceous shales near the railroad station at Vallejo 

 Junction are soon succeeded by brown shales and massive sandstones 

 belonging higher in the Cretaceous system. The contact between 

 the Chico and the Martinez (Eocene) beds is in a fault zone cut by 

 the railroad tunnel a short distance west of Vallejo Junction. Just be- 

 yond the tunnel the contact between the Martinez and the Monterey 

 (Miocene) is clearly shown in a high cliff to the left, opposite the 

 Selby Smelting Works, where the buff-colored Monterey sandstones 

 and shales rest with marked unconformity upon the black Eocene 

 shales. Near the contact the Eocene shale is filled with innumerable 

 fossil shells of boring Miocene mollusks- The Monterey beds are 

 extraordinarily well exposed in the chffs to the left, and immediately 

 beyond the contact, where they consist of fine buff shales with shaly 

 sandstones and thin bands of yellow limestone. 



After leaving these chff exposures the train passes Tormey station, 

 crosses a little swamp, and approaches a tunnel cut into vertical 

 cliffs of massive gray sandstone; this is the type locality of the 

 San Pablo formation (upper Miocene), The refining plant of the 

 Union Oil Co., at the cast end of this tumiel, is located on the upper 

 part of the San Pablo beds. Vertical beds of massive tuff imme- 

 diately west of the oil refuiery represent the lower part of the Pinole 

 tuff. Beyond these beds the train crosses another swamp and enters 

 a cut in which white volcanic ash beds of the Pinole tuff dip at 

 a relatively low angle to the northeast. This change in dip shows 

 that these beds are on the southwest side of the San Pablo Bay 

 syncline, the axis of which passes through the swamp area. Resting 

 upon the tilted ash deposits in this part of the section are horizontal 

 beds of Pk^istocene shale* 



name 



Rodeo. 



Elevation 12 feet, 

 Omiiha 1 .757 mile 



formerly 

 train en 



point. Beyond 

 i. Near the sta- 



massive 



the Pinole tuff. Beyond this point the San Pablo 

 Oliocene) appears, with low dips to the northeast. 

 In the sea cUffs on San Pablo Bay a few yards from the rail- 

 road are excellent exposures of the Miocene capped by Pleistocene 

 shale. At Hercules, where there are large powder works, the rail- 



same 



smelt 



tyncline. Beyond Hercules the railroad passes over Monterey shale 



feuna of the Pinole tuff is represented by 

 moUusean species. Leaves and remains 

 of vertebrates are also present. The 

 Pleistocene shale contains abundant 



with 



mal bones representing the e 

 horse, camel, bison, ground slol 

 lope, lion, wolf, and other forma. 



