Abstract

The Puente Formation is a distinct stratigraphic unit within the upper Miocene Series of the Los Angeles Basin. Lower and middle Mohnian sediments now exposed in the Whittier Hills were deposited on the distal southwest portion of the bathyal Puente fan. The Whittier area was west of the main depocenter and did not receive a significant amount of sand. However, fine-grained sand from the San Gabriel Basin to the north began to overflow into this area during middle Mohnian time.

Vertical displacement on the Whittier Fault at the beginning of upper Mohnian altered the pattern of sediment distribution in the Whittier area. Upper Mohnian and Delmontian strata record the development of the Whittier Narrows submarine canyon-channel complex during late Miocene. Thick sequences of massive sand are superseded by extensive lenses of conglomerate. Directional features and petrographic studies delineate a source area in the central San Gabriel Mountains due north of Whittier.