146 OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
the lower Puente shale or to a portion of the Yaqueros formation, 
but the larger part is doubtless contemporaneous with the Puente 
sandstone of the Puente hills district. The best exposures of the 
Puente sandstone in the region about Los Angeles are in the Elysian 
Park hills, which are developed on the southern limb of a great 
anticline. (See PL XXI, B.) The formation as here developed con¬ 
sists of at least 2,000 feet of heavy-bedded, coarse-gray to rusty- 
arkose sandstone, interbedded at irregular intervals with dark-col¬ 
ored earthy and siliceous shale. The sandstone beds vary in thick¬ 
ness from 1 to 12 feet. Some are uniformly hard throughout, while 
others are concretionary, the concretions usually being elliptical in 
shape and in some cases coarser grained than the surrounding rock. 
As a rule, however, the sandstone is soft and falls an easy prey to 
weathering agents, being much less resistant than the interbedded 
shale. This differential weathering is well exemplified in certain 
ridges in Elysian Park, which cut transversely across alternate layers 
of the steeply dipping sandstone and shale, the latter forming promi¬ 
nent knobs at its outcrops along the top of the ridge. Jointing is 
well developed in the sandstone in certain localities, notably at the 
south end of Elysian Park, where hardening along the cracks of 
three different systems forms a kind of block structure. This is 
common in similar sandstones at many places throughout the Coast 
Range. In the region west of Edgemont and also along the hanks 
of the Santa Monica Mountains west of Sherman the basal beds of 
the Puente consist of conglomerate and sandstone, with appreciable 
amounts of interbedded gray to drab shale. The pebbles and cob¬ 
bles in the conglomerate consist of granite rocks, diorite porphyry, 
quartzite, etc., some attaining a diameter of 3 feet. In the region of 
the basalt intrusions and flows about Caliuenga Pass the sandstone 
appears to have been slightly baked, and is harder, more jointed, and 
darker colored than in the Elysian Park hills. It may also represent 
a somewhat lower horizon than the Elysian Park rock. 
FOSSILS. 
The Puente sandstone has yielded fossils in several localities in 
this region. In a street cut in Pasadena on the west side of Ray¬ 
mond Hill, about 2 miles northeast of the corner of the area shown 
in the accompanying map (PI. XVIII) was found the following fauna: 
Puente fossils from Raymond Hill , Pasadena , Cal. 
Area cf. montereyana Osmont. 
Chione n. sp.? (small, with prominent concentric frills). 
Leda cf. taphria Dali (PI. XXXVIII, fig. 5). 
Panopea generosa Gould. 
Phacoides cf. acutilineatus Conrad. 
Thracia n. sp. 
