A comparison of multiple proxies for export production in the equatorial Pacific

Abstract

Several commonly used paleoproductivity proxies were compared to evaluate the validity of assumptions and limitations associated with each proxy. Export production fluxes (Cexport) over glacial‐interglacial timescales were calculated from previously developed, proxy‐specific algorithms at TTN013‐pc72 and TTN013‐pc114, both located in the equatorial Pacific. Comparison of data from the same core intervals yields conflicting results despite calibrations based on the same core top samples. The periodicity of marine barite, excess Ba, and excess Al‐based Cexport records is similar. The relative magnitude of Cexport when calculated using excess Ba and algorithms based on sediment trap data is significantly different than records based on core top calibrations, particularly during glacial intervals. At both sites, bulk sedimentary Al/Ti and Ba/Ti ratios covary; however, these ratios do not correspond with the downcore records of their respective excess concentrations (and their accumulation rates), or with contemporaneous records based on marine barite, excess Ba, and excess Al accumulation. Although downcore records based on sediment mass accumulation rates may be compromised by sediment focusing, this process cannot explain all the differences observed among the various data sets presented here. This implies that some or all of these proxies do not exclusively respond to changes in export production. The contradictions among these data highlight the importance of addressing inconsistencies among paleoproxies and re‐examining assumptions imbedded in proxy fundamentals, prior to applying paleoproductivity proxies and interpreting paleoceanographic records.