Origin of mass flow sedimentary structures in hemipelagic basin deposits: Santa Barbara Basin,California Borderland

Holocene mass flow processes produce distinctive sedimentary structures in this silled, anoxic basin characterized by high sedimentation rates of fine-grained fill. Mud flow deposits possess a 0899 1444 V 3 diagnostic vertical sequence of structures on the lower slope. Basin floor turbidites possess a variety of bed set combinations of: 1) finely laminated layers, 2) graded silt and clay layers, and 3) ungraded, massive silts and clays with floating sand grains. Massive, ungraded flood-derived suspensate deposits can be distinguished from turbidites. Turbidites and suspensate deposits constitute 30% of the sampled sediment column. Varve counting of the remaining 70% provides frequencies of turbidite and flood suspensate layer deposition.