Barium cycling in the North Pacific: Implications for the utility of Ba asa paleoproductivity and paleoalkalinity proxy

Benthic incubation chambers have been deployed in a variety of geochemical environments that provide a comprehensive geochemical framework from which to address issues related to Ba geochemistry and the use of Ba as a paleopr oxy. First order budgets for barium show that in the equatorial Pacific, pr esent rates of Ba rain and benthic remobilization are nearly in balance, in dicating that the rate of net accumulation is negligible and is clearly muc h less than the average for the Holocene; thus any paleoproxy algorithms bu ilt on the assumption of steady state an: questionable. In contrast, budget s for sediments in the southern California Borderland indicate much higher burial efficiencies, in the range of 50-80%. The Ba:alkalinity (Alk) flux r atio is found to be remarkably constant throughout the environments studied and is indistinguishable from the deep water ratio used for paleoceanograp hic reconstructions. However, the Ba:organic carbon remobilization ratio is not constant. Combined, these results do not indicate a simple, first-orde r direct link between Ba and alkalinity remobilization via organic carbon o xidation; however, the similarities in the Ba and alkalinity source functio ns conspire to maintain the Ba:Alk ratio near the global water column avera ge. This latter observation provides promise for the use of the Ba:Ca ratio in benthic foraminifera as a paleocirculation tracer.