132 PECKHAM — THE GENESIS OF BITUMENS. [April 1, 



filled with bitumen. As far as I have investigated it, the bitumen 

 is uniform in kind and quality. It has saturated beds of sand, 

 strata of sandstone and limestone, some of which are hard and 

 crystalline, others magnesian and almost as soft as chalk, some of 

 them without fossils and some almost all fossils, and all of them 

 conformable with the Upper Silurian and Lower Carboniferous rocks 

 that enclose them. In one locality a sort of bituminous breccia 

 occurs, of immense extent, consisting of fragments of limestone 

 and quartzite cemented together with bitumen. In another an im- 

 mense horizontal bed of sand, completely saturated with bitumen, is 

 overlaid with thirty or forty feet of conglomerate that has been 

 more or less penetrated with it. 



Almost all the beds north of the river are in very sharp folds, 

 that bring the strata to the surface nearly vertical, in eroded anti- 

 clinals that extend across the country in parallel lines, often many 

 miles in length. What is of especial interest in this connection is 

 the occurrence in the vertical limestones and sandstones of imper- 

 fectly saturated strata. The bedding varies from the thickness of 

 paper to a few inches. The rock mass was usually most easily 

 penetrated along the lines of the thinnest beds. Fractures which 

 cross all these beds, including both the thin and thick ones, show 

 the bitumen completely filling the thin beds and only partially pene- 

 trating the seams and the mass of the thicker cryptocrystalline 

 strata. Nothing could more beautifully and clearly demonstrate the 

 fact that the bitumen was not indigenous to these rocks, but had 

 penetrated them while previously and as at present in their nearly 

 vertical position. 



19. Continuing our journey across the continent, bitumen is fre- 

 quently encountered in positions contiguous to normal or local 

 metamorphism, until we descend into the great valley of California, 

 west of the Sierra Nevadas. Here the development of bitumen has 

 proceeded on a scale of vast magnitude. On the western slope of 

 the Sierras the region around Roseville, in Placer county, and the 

 vicinity of the city of Stockton, are well known to be rich in 

 natural gas.^ There are localities on these slopes that have also 

 furnished limited supplies of petroleum, but, as before stated, the 

 bitumen deposits of California are principally found in the Coast 

 Ranges, including the ocean area lying between the Santa Barbara 



^ \V. L. Watts, T/ie Gas and Petroleum Forviatiojis of the Central Valley 

 of California, 1894. 



