Reconstructing sediment age profiles from historical bathymetry changes in San Pablo Bay, California

Sediment age profiles reconstructed from a sequence of historical bathymetry changes are used to investigate the subsurface distribution of historical sediments in a subembayment of the San Francisco Estuary. Profiles are created in a grid-based GIs modeling program that stratifies historical deposition into temporal horizons. The model's reconstructions are supported by comparisons to profiles of Cs-137 and excess Pb-210 at 12 core sites. The predicted depth of the 1951 sediment horizon is positively correlated to the depth of the first occurrence of Cs-137 at sites that have been depositional between recent surveys. Reconstructions at sites that have been erosional since the 1951 survey are supported by a lack of detectable Cs-137 and excess Pb-210 below the upper 6-16 cm of the core. A new data set of predicted near-surface sediment ages was created to illustrate an application of this approach. Results demonstrate other potential applications such as guiding the spatial positioning of future core sites for contaminant measurements. (C) 2007 Elsevier Ltd. All rights reserved.