Sequence Stratigraphic Architecture of Slope Fan Deposits: Miocene Puente Formation, Los Angeles Basin: ABSTRACT

Abstract

Outcrops of the Miocene Puente Formation in the eastern Los Angeles basin represent deposits of a slope and base of slope apron along the margin of a rapidly subsiding basin. In contrast to a traditional canyon-fed submarine fan, coarse-grained sediments of the Puente Formation were transported down the slope through shallow gullies fed from fan deltas prograding across the narrow shelf. Sandstone and conglomerate of the Soquel Member of the Puente accumulated in multiple lobes forming a coalescing base-of-slope apron. The principal depositional components of this system include sheet-like sands and associated shallow channels. The Sycamore Canyon Member consists of a series of overlapping, prograding wedges identifiable from aerial photo mosaics. The internal architecture of these prograding wedges is complex, consisting of stacked sand- and gravel-filled channels associated with finer grained levee and interchannel deposits. The Soquel and Sycamore Canyon members of the Puente Formation are interpreted as having been deposited during times of relative sea level lowstand, and the finer grained La Vida and Yorba members represent deposits of relative sea level highstands. Sequence and facies architecture of Puente Formation deposits correspond to reservoir quality and heterogeneity of potential reservoir units. Lowstand channel-fill deposits typically represent the best reservoirmore » facies due to their higher porosities and permeabilities and low clay contents, although slope gullies of the Soquel Member are often carbonate cemented. Interchannel and overbank facies of the Sycamore Canyon Member are clay rich resulting in lower permeabilities. Sheet sands of the Soquel Member slope-apron system have intermediate porosities, permeabilities. and clay contents.« less