HR: 0800h
AN: B11B-0151    [Abstracts]
TI: Trace Elemental Analyses of Suspended Sediments in the San Francisco Estuary and its Tidal Marshes
AU: * Malamud-Roam, F P
EM: fmalamud@eps.berkeley.edu
AF: Geography Dept, University of California, 501 McCone Hall, Berkeley, CA 94720 United States
AU: Ingram, B L
EM: ingram@eps.berkeley.edu
AF: Earth and Planetary Sciences Dept, University of California, 307 McCone Hall, Berkeley, CA 94720 United States
AU: yang, W
EM: wenbo@berkeley.edu
AF: Earth and Planetary Sciences Dept, University of California, 307 McCone Hall, Berkeley, CA 94720 United States
AU: Collins, J
EM: Josh@sfei.org
AF: San Francisco Estuary Institute, 7770 Pardee Lane, Oakland, CA 94621 United States
AB: This research evaluates the trace elemental compositions of inorganic sediments in the San Francisco Bay estuary marshes over space and time. These sediments create and maintain the tidal marshes that surround the Sand Francisco Bay, yet a thorough analysis of the sources of these sediments remains understudied. Determining the sources of sediments is of interest because current mitigation and restoration projects around the Bay must consider whether the sediment supply will be sufficient for projects, or if opening diked wetlands to tidal flow will result in salt water intrusion further up-estuary (into the Delta). Results of trace element analyses of suspended sediments that pass through the Sacramento-San Joaquin Delta (the Delta) are compared with those of local watershed tributaries. Differences in bedrock lithology can be seen in the varying trace elemental concentrations; for example, K, Nd, Sm, Rb and Sr concentrations are significantly lower in the Sacramento river sediments than those of the San Joaquin river and can be used to differentiate further the Delta input. Results from marsh surface samples throughout the North Bay and preliminary results from 4 1-m long sediment cores collected along a transect of the Novato creek marsh (NCM) reflect local versus Delta sediment source patterns. The suspended sediment samples from the Sacramento and San Joaquin rivers and from local creeks reflect the end members of the sediment supply for local marshes. The marsh surface samples represent the most recent period (last few years or so) and reflect the extent of Delta influence into the estuary. Finally, the cores collected from the Novato creek marsh provide details on the gradient of dominant source supply (i.e., are the sediments well inland predominantly from the local watershed and how far does that influence extend downstream), as well as a history of how the sediment supply conditions have changed, comparing pre-Gold Rush and agriculture era (before about 150 years) to post.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting