Observations of sediment flux to the Eel continental slope, northern California

Sediment flux on the northern California slope off the Eel River was observed using time-series sediment traps between September 1995 and January 1997. A mooring that held three sediment traps (at 60, 220 and 435 m) and three current meters/transmissometers was placed in 450 m water depth. Thirty-three sampling periods of 10-16 days in length covered 394 days. All samples were analyzed for total mass, calcium carbonate, combustible matter and biogenic silica, and from these, lithogenic fluxes were determined. Total sediment-trap fluxes ranged from 0.1 to 24.2 g m(-2) d(-1), and annually averaged 1.1, 4.5 and 11.8 g m(-2) d(-1) at the top, middle and bottom traps, respectively. Lithogenic fluxes were 53, 70 and 83% at the top, middle and bottom traps. The middle trap experienced the greatest absolute variability as a result of intermediate-nepheloid-layer activity; 6 of the 33 intervals accounted for mon than 50% of the flux. River, wind, wave, current, transmissometer and satellite data reveal that the magnitude of sediment flux was controlled by a variable mix of shelf sediment resuspension, river discharge, and margin circulation. (C) 1999 Elsevier Science B.V. All rights reserved.