资源环境科技发展态势分析平台

At an ocean margin site 37 degrees S offshore Chile, we use the meteoric cosmogenic Be-10/Be-9 ratio to trace changes in terrestrial particulate composition due to exchange with seawater. We analyzed the marine authigenic phase in surface sediments along a coast-perpendicular transect and compared to samples from their riverine source. We find evidence for growth of authigenic rims through coprecipitation, not via reversible adsorption, that incorporate an open ocean Be-10/Be-9 signature from a deep water source only 30km from the coast, overprinting terrestrial Be-10/Be-9 signatures. Together with increasing Be-10/Be-9 ratios, particulate-bound Fe concentrations increase, which we attribute to release of Fe-rich pore waters during boundary exchange in the sediment. The implications for the use of Be-10/Be-9 in sedimentary records for paleodenudation flux reconstructions are the following: in coast-proximal sites the authigenic record will likely preserve local riverine ratios unaffected by exchange with seawater, whereas sites beneath well-mixed seawater will preserve global flux signatures.