Reconstructing the history of fluid flow at cold seep sites from Ba/Ca ratios in vesicomyid clam shells

Hydrogen sulfide discharge at cold seep sites is recorded as enrichment in the barium to calcium (Ba/Ca) ratio in shells of vesicomyid clams collected live from cold seeps in Monterey Canyon and the Cascadia margin. A direct relationship between increased Ba fluxes from cold seeps and Ba incorporati on into shells was established for the Caseadia margin site. For the Monter ey canyon site, a 2-yr episode of high fluid flow centered on 1992 was infe rred from coherent changes in the Ba/Ca profiles of three Calyptogena kilme ri shells. Comparison with precipitation and delta O-18 data indicates that this high-flow period may have been driven by an increase in rainfall afte r the 1988-1990 California drought. High-resolution records preserved in cl am shells are shown to be useful in elucidating characteristics, history, a nd possible mechanisms driving fluid discharge at continental margin seeps, thus establishing their potential use as paleotracers of fluid Seepage eve nts.