Hyperpycnal Subaqueous Fans in an Active Margin Basin, Northern Santa Barbara Channel, California

Steel, Elisabeth; Simms, Alexander; and Warrick, Jonathan
[email protected]

The small mountainous rivers of southern California are known to form hyperpycnal plumes during El Nino Southern Oscillation (ENSO) related flooding events. Despite this understanding, no hyperpycnal deposits have yet been recognized in offshore southern California. A recent bathymetric survey conducted by the USGS found multiple fan-like features offshore of several coastal rivers draining into the Santa Barbara Channel. These features are thought to represent alternating hyperpycnal flow deposits and stream bed-load material. We present preliminary results of a high-resolution seismic survey conducted over one of these fans located near Refugio Beach. Internal reflectors define three seismic packages within the fans and isopach maps of these packages will be presented. Seismic profiles are used to determine the internal architecture of the fans and future work will provide insight into the characteristics and recurrence intervals of hyperpycnal flows in an active margin basin.

AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013