SOUTHERN PACIFIC LINES 285 
The Los Angeles region is underlain by a thick succession of 
Tertiary and Cretaceous strata, some of them deeply buried and 
others presenting prominent outcrops, especially in the hills and 
mountains. They are flexed, tilted, and faulted and vary considerably 
in character from place to place. The eastern part of the Santa 
Monica Mountains, projecting into the northern part of the city, 
contains an extensive uptilted succession of the rocks that underlie 
the region. At the base are old slates and schists (Triassic?) cut by 
granites and granodiorites, similar to those in some other ranges of 
southern California. They are overlain by a thick body of conglom- 
erate, sandstone, and shale of Upper Cretaceous and Tertiary age. 
Formations in Santa Monica Mountains 
[H. W. Hoots] 
Formation ea in 
Shale, with beds of sandstone and ash non paa ae: PRE ee Pia! 4,500 | Upper Miocene. 
Unconformity (folding, faulting, and basalt in : : 
eee bag hance ry shale, ceo flows, sare other Voleanic rocks 4,500-7,500 | Middle Miocene, 
(Topanga f on). Basal 1,000 feet of conglomerate east of 
Cahu uenga peer may be Vaq : 
Light-gray and red ccrmiiaaele. (Vaqueros? and Sespe? formations) -/3, 500-4, 000 i oct ag and 
Unconformity. 
sae ty nd sandstone; some fossiliferous sandstone (Martinez forma- 250+] Lower Eocene. 
Conetcmerate, sandstone, and dark shale, fossiliferous (Chico forma- 8, 000+) Upper Cretaceous. 
In the hilly region southeast of the Santa Monica Mountains, and 
mainly in the east-central part of Los Angeles, younger formations 
are also present, notably sandstones, conglomerates, and clays of 
Pliocene age, which overlie the Miocene beds. These are in turn 
overlain unconformably by the terrace and alluvial deposits of the 
Los Angeles Plain, above referred to. 
The east end of the Santa Monica Mountains is an open anticline, 
the axis of which is in a broad central area of Santa Monica slate 
(Triassic?) and plunges westward from the main granite mass just 
north of Hollywood. Although the general structure is anticlinal, 
the original folding is much complicated by faults, flexures, and 
igneous intrusions. Post-Modelo flexing resulted in widespread anti- 
clinal uplift. In the Martinez formation, and possibly also in the 
Chico formation, are prominent reefs of limestone 50 to 60 feet thick, 
the largest one being 500 feet long. (Hoots.) The Santa Monica 
Mountains extend to the Pacific Ocean at Santa Monica. (See 
pl. 48, A.) 
In the ceniral part of Los Angeles are many exposures of Miocene 
beds, including shale filled with diatom remains. On Hill and First 
