--> Sequence Stratigraphy of Submarine-Ramp Deposits: Miocene Puente Formation, Los Angeles Basin, by Kevin T. Lyons and Robert K. Suchecki; #91024 (1989)

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Sequence Stratigraphy of Submarine-Ramp Deposits: Miocene Puente Formation, Los Angeles Basin

Kevin T. Lyons, Robert K. Suchecki

Outcrop and subsurface studies of deep-sea clastic sediments of the Miocene Puente Formation in the eastern Los Angeles basin (Puente Hills and northern Santa Ana Mountains) indicate that these sediments were deposited in a submarine-ramp setting rather than in a traditional canyon-fed submarine fan system. The principal depositional components of this dominantly base-of-slope and ramp system are ramp-fan channels and lobes, and slope and slope-apron channel/interchannel deposits. The lateral distribution of channelized conglomeratic facies within slope-channel and proximal-ramp deposits indicates a line source of sediment to the slope and deeper basin.

Patterns of stratigraphic sequence development and system tract geometries of the Puente Formation differ from passive-margin examples due to the complex interplay of eustatic sea level change and tectonics in the Los Angeles basin. However, eustatic sea level changes appear to exert first-order control on sequence development in this basin that subsided at an apparent uniform rate during the late Miocene. Intervals of dominantly coarse-grained sediment correlate approximately with times of sea level lowstand from published curves. Likewise, dominantly fine-grained intervals correlate approximately with times of sea level highstand. Coarse sand and conglomerate reached the base of the slope and built up a near ramp profile as fan-delta lobes prograded across the relatively narrow shel edge during times of relative sea level lowstand. During relative sea level highstands, mostly finer grained sediment was transported across the shelf and ramp profile and was deposited on the base of the ramp and basin floor. These stratigraphic components form large clinoformal wedges with complex internal architecture. Depositional facies associations and distributions of sediment of the Puente Formation are described as a result of sequence stratigraphic evolution in a ramp-fan setting.

AAPG Search and Discovery Article #91024©1989 AAPG Pacific Section, May 10-12, 1989, Palm Springs, California.