PUENTE HILLS: PUENTE FORMATION. 105 
north to south: In the axis, shale that is believed to be the lower divi¬ 
sion of the Puente; at the southern edge of the crest, sandstone that is 
identified as Puente, 200 or 300 feet in all; and on the southern face of 
the ridge, other shale, also of the Monterey type, bearing the fossil Pec- 
ten pedroanus , and succeeded across a fault plane by the next younger 
(Fernando) formation. The uppermost two beds have a northerly 
dip; the inclination of the Puente sandstone is exceedingly steep, with 
a dip here north and there south, and a consequent uncertainty as to 
which of these directions is the normal. The shale in the heart of the 
hills is crushed and crumpled. Were it not for this extensive crum¬ 
pling and the attendant faulting the sequence given above might be 
regarded as normal; yet an alternative is possible, namely, that the 
suspected uppermost shale, with its northerly dip, occupying the 
southern face of the ridge adjacent to the fault line, may be instead 
the lower member and pass beneath the highly inclined Puente sand¬ 
stone at the crest of the ridge, the two together being faulted down 
against the lower shale farther north, or that it may, by a sharp rever¬ 
sal of its dip, again return to the surface in a compressed and broken 
synclinal fold. 
CORRELATION OF THE PUENTE FORMATION WITH THE 
MONTEREY. 
The resemblance of both lower and upper divisions of shale, if such 
there be, to the Monterey, as it is known in other parts of the 
Coast Range, may warrant their correlation, the Puente sandstone to 
be regarded as an intercalated member. Yet, before finally accepting 
this view, it is well to recall the marked lithologic similarity of portions 
of the lower division of the Puente formation to certain strata in the 
Santa Clara Valley and elsewhere in the Coast Range that have been 
determined by their fossils to be lower Miocene and possibly Oligo- 
cene—lower than the Monterey. From geologic conditions to the 
south of the Puente Hills in the Santa Ana Range, however, the 
writer is inclined to consider the entire succession of beds described 
above as the local equivalent of the Monterey. The only fossil thus 
far obtained from the Puente shales is Pecten pedroanus Trask (see PI. 
XXXVI, figs. 5 and 6), a form which is found both in the Miocene and 
lower Pliocene. A nearly related form, Pecten peck h ami Gabb (PI. 
XXXI, fig. 3), is a characteristic species of the Monterey (middle Mio¬ 
cene). 
