Temporal Patterns of Deposition at the Termination of an Active Submarine Channel-Levee System: Hueneme Fan (4 Ka - Present), Santa Monica Basin, California Borderland

The amount of sediment moving through Hueneme submarine canyon and channel today is only slightly less than it was at last glacial maximum (18-25 ka). Distinct depositional landforms that reflect the activity of the modern Hueneme submarine channel system are present in two locations: (1) constructional levees adjacent to the channel in the upper fan and (2) lobate deposits at the termination of the channel in the middle fan. A comprehensive understanding of the dynamics and evolution of a channel-levee system should include analysis of flows that bypassed. Lobate deposits at the channel mouth are the product of this bypass. Characterization of the distribution and rate of sedimentation from 4 ka to the present documents the relationships between these sites of deposition. A tight grid (1-2 km spacing) of 2D seismic reflection profiles (< 1 m vertical resolution) tied to a radiocarbon-dated ODP core in the basin plain provides an exceptional stratigraphic framework. Mapping of the upper 30 m (100 ft) of the modern Hueneme submarine fan reveals a history of shifting lobe complexes through time. Movement of depocenters between mapped intervals is dominantly lateral, reflecting compensation and incremental construction of the fan. A composite map of sediment distribution indicates the dominance of the Hueneme canyon-channel system regarding sediment delivery and renewed construction of the middle fan area during the transition from a transgressive to highstand state.