The impact of sediment provenance on barium-based productivity estimates

Biogenic barium in marine sediments has been suggested to be a reliable pro xy of export productivity from the surface ocean and algorithms have been d eveloped to link these properties. However, problems arise when the propose d algorithms are applied to predominantly terrigenous sediments. A major so urce of error is incorrect estimates of the terrigenous Ba/Al ratio in norm ative calculations of the amount of biogenic barium in the sediment. Compar ed to an often used "global average" Ba/Al ratio, much better results can b e obtained by estimating the terrigenous Ba/Al ratio from exponential regre ssion of the Ba/Al ratios of surface sediments obtained from continental sl ope transects. This method has been applied to surface sediments from the C hilean continental slope. The calculated regional terrigenous Ba/AI ratios could be verified with purely terrigenous samples from Chilean rivers. The resulting accumulation rates of biogenic barium on the Chilean continental slope reliably reproduce the regional pattern of primary productivity in th e southern Peru-Chile Current, indicating the potential of biogenic barium as a useful (paleo)productivity proxy. (C) 2000 Elsevier Science B.V. All r ights reserved.