Suspended sediment transport on the continental shelf near Davenport, California J.P. Xu *, Marlene Noble, Stephen L. Eittreim United States Geological Survey, Menlo Park, CA 94025, USA Received 27 September 1999; accepted 16 July 2001 Abstract Suspended sediment transport on the shelves off Santa Cruz and Davenport, California is studied using field measurements and bottom boundary layer modeling. Strong transport events mostly occur during storms in winter ; the volume of winter sediment transport is at least one order of magnitude greater than that of summer/spring transport. Rock outcrops on the inner shelf ( 6 40 m of water) indicates an erosional environment, but an elongated mid-shelf mud deposit evidently suggests a depositional environment on the mid-shelf. The seafloor geology appears to correlate to the poleward and offshore sediment transport pattern. This study also suggests that suspended sediment moves out of Monterey Bay, roughly along the isobaths of the northern bay. This fine material, originally from river sources, and the material from the coastal cliff erosion that is subsequently introduced to the transport system through cross-shelf sediment transport, are believed to be the sources of the mid-shelf mud deposit. ß 2002 Elsevier Science B.V. All rights reserved. Keywords: Mooring; Sediment £ux; Shelf; California 1. Introduction Over the last decade or so, numerous investiga- tions aimed at studying the circulation patterns over central California shelves (Fig. 1) have been conducted (e.g. Strub et al., 1987; Noble et al., 1992; Breaker and Broenkow, 1994; Rosen- feld et al., 1994; Paduan and Rosenfeld, 1996). Satellite, radar and current meter data from these studies provided a limited picture of the circula- tion patterns from within the Monterey Bay to the Gulf of the Farallones. It is generally believed that the surface waters on the Farallones shelf, the region south of Point Reyes and north of Davenport, California, move in a single circula- tion unit. In late spring and early summer, the cold, nutrient-rich, upwelling waters that make this area productive join fresher water from San Francisco Bay and £ow generally equatorward towards Monterey Bay. However it is unknown if these waters directly enter Monterey Bay be- cause An ¬o Nuevo is a strong upwelling center that could be a dynamic barrier. The surface water inside Monterey Bay tends to £ow in a counter-clockwise gyre around the bay in the summer. Hence at the northern end, there is a convergence of westward £owing surface water from Monterey Bay and southeastward £owing 0025-3227 / 02 / $ ^ see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII:S0025-3227(01)00266-3 * Corresponding author. Fax: +1-650-329-5299. E-mail address: jpx@usgs.gov (J.P. Xu). Marine Geology 181 (2002) 171^193 www.elsevier.com/locate/margeo