294 Adventures in Scenery 



tributed largely. It seems to be apparent that these organisms 

 were the ultimate source of the oil. It appears that the source 

 of the oil is different in the different fields, depending upon 

 the amount of diatomaceous and foraminiferal material in the 

 formations. From the relationship between the diatom-bearing 

 formations on the two sides of the Coast Ranges it seems to be 

 apparent that these organisms were the ultimate sources of oil, 

 as claimed by the geologists Arnold, Anderson, and Johnson. 

 If this is granted it will stand out as one region in which, and 

 one case in which, it has been possible to make a positive deter- 

 mination regarding the origin of oil, and to these geologists will 

 be the distinction of being the first to do more than theorize 

 concerning it (M. R. Campbell, see appendix) . 



In California diatoms have existed in the geologic past in 

 such numbers that "diatomaceous shales" have been formed 

 over wide areas. Diatoms formed the deep sea ooze of the 

 ancient sea bottoms. The ooze became compressed into shale. 

 Sometimes these shales, consolidated diatomaceous ooze, have 

 been upheaved, bent, and folded, and now are seen in rock out- 

 croppings, as in the Berkeley Hills, Mount Diablo, and many 

 places, but oil is not always associated with diatomaceous ooze 

 (shale). It may never have been there, and it may have mi- 

 grated drained away. 



Oil-bearing Formations Largely Porous 

 Sandstones and Conglomerates 



A large proportion of the oil-bearing sedimentary forma- 

 tions of California are highly porous sandstones and con- 

 glomerates, which make exceptionally good reservoirs for pe- 

 troleum. The presence in California formations of many 

 angular unconformities afford opportunities for the accumula- 

 tion of oil and asphalt, or for the migration of these substances 

 from one formation to another. "Large accumulations in anti- 

 clines may be accounted for primarily by the cavities offered 

 by the strata along upward folds, and secondarily by the pres- 



