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Origin and Architecture of Previous HitFloodNext Hit-Derived Sand Lobes on the Continental Shelf of the Santa Barbara Channel, Southern California

Linn-Elisabeth Steel
Earth Science, University of California at Santa Barbara, Santa Barbara, CA, USA
[email protected]

Abstract

Gravity flows in the Santa Barbara Channel (SBC) of Southern California have the potential to damage pipelines leading to offshore petroleum platforms, yet their recurrence intervals and initiation mechanisms remain unknown. The recent discovery of fans on the continental shelf of the SBC poses an important question; namely, are the SBC fans deposited by sediment gravity flows capable of damaging shelf infrastructure? All fans lie directly offshore from creeks draining into the SBC and contain distinct lobes with abrupt terminations. The location and geometry of these features suggests that they were deposited by hybrid hyperpycnal-debris flows. Seismic surveys, cores, and grab samples from fans in the SBC will be studied to test two hypotheses: 1) Fans on the shelf of the SBC were deposited by hybrid sediment gravity flows, and 2) These flows could damage shelf infrastructure by remobilization of shelf sediment.

Core descriptions, grain-size analysis, and x-radiography will aid in determining the origin of the fans. Hyperpycnites are expected to be well sorted and contain sedimentary structures, while debrites are poorly sorted with abrupt boundaries. Hybrid flow events will resemble turbidites in proximal locations and debrites distally. Radiocarbon dating of organic and carbonate material will provide flow recurrence intervals. If flows are erosive, cores and seismic profiles are expected to show signs of channelization.

If these flows are active today, they pose a significant threat to nearby pipelines. Additionally, studying these Previous HitfloodTop-derived deposits will improve understanding of source-to-sink processes and depositional architecture in regions dominated by flashy, sediment-laden creeks.

AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects