206 University of California Publications in Geology [Vol.8 



age, and possibly much older. The rocks in the west end of the San 

 Gabriel Range are chiefly granodiorite, with gneiss and various schists. 



Rocks of the Fernando group form a border around the edge of 

 the range between the central igneous and metamorphic area and the 

 alluvium of the surrounding valleys. In Elsmere Canon, beds of the 

 Fernando group not less than 3000 feet thick were laid down upon 

 an eroded surface of the granitic rocks. The basal ten to fifteen feet 

 of Tertiary rocks consist of subangular to rounded fragments of granite 

 with abundant comminuted shells. The next 700 to 800 feet of strata 

 consist of coarse, quartzose shale made up of small angular fragments 

 and containing some volcanic ash. None of this shale seems to be 

 diatomaceous. Toward the upper part the shale becomes coarser and 

 grades into fine-grained sandstone. These beds, especially in their 

 lower part, contain hard, round concretions from six inches to three 

 feet in diameter, in which are found marine shells, mammal bones, 

 fragments of fossil wood, and teredo borings. The shales are all 

 stained a chocolate color by petroleum, and in places the bitumen is 

 abundant enough to form a cementing material. Near Elsmere Ridge 

 there are a number of small brea deposits formed by rather recent 

 oil seeps, and wells near Elsmere Canon produce a heavy oil from 

 these lower strata. 



Stratigraphically above the fine sandstones and shales is a series 

 of cross-bedded coarse sandstones alternating with conglomerates. 

 These strata are well exposed on the sides of Elsmere Ridge, in "Whitney 

 Canon, just north of Elsmere Canon, and in Placerita Canon ; and 

 they extend for an undetermined distance eastward along the northern 

 flank of the San Gabriel Range, where they attain a great thickness. 

 In Elsmere Canon the conglomerate consists of rounded to sub-angular 

 pebbles and boulders up to two feet in diameter, of granitic, and less 

 commonly of volcanic rocks. The pebbles grade down in size into a 

 coarse sand which fills the interspaces. These beds are of a light buff 

 color and are not well indurated, though they are more resistant to 

 erosion than the underlying beds, and l eather to steep slopes. The 

 lithologic character and fossils indicate that the lower sandstones and 

 shales are of marine origin, and the lithology of the conglomerates 

 indicates that they are not of marine origin. 



The lower fine sandstone and shaly beds were mapped as Vaqueros 

 by Eldridge, and were considered by him to be unconformably over- 

 lain by the conglomeratic beds. The writer believes that all these beds 

 belong properly in the Fernando group. The two lithologic divisions 



