No abstract

No abstract

No abstract

Since Dymond et al. [1992] proposed the paleoproductivity algorithm based on “Bio‐Ba,” which relies on a strong correlation between Ba and organic carbon fluxes in sediment traps, this proxy has been applied in many paleoproductivity studies. Barite, the main carrier of particulate barium in the water column and the phase associated with carbon export, has also been suggested as a reliable paleoproductivity proxy in some locations. We demonstrate that Baexcess (total barium minus the fraction associated with terrigenous material) frequently overestimates Babarite (barium associated with the mineral barite), most likely due to the inclusion of barium from phases other than barite and terrigenous silicates (e.g., carbonate, organic matter, opal, Fe‐Mn oxides, and hydroxides). A comparison between overlying oceanic carbon export and carbon export derived from Baexcess shows that the Dymond et al. [1992] algorithm frequently underestimates carbon export but is still a useful carbon export indicator if all caveats are considered before the algorithm is applied. Babarite accumulation rates from a wide range of core top sediments from different oceanic settings are highly correlated to surface ocean 14C and Chlorophyll a measurements of primary production. This relationship varies by ocean basin, but with the application of the appropriate f ratio to 14C and Chlorophyll a primary production estimates, the plot of Babarite accumulation and carbon export for the equatorial Pacific, Atlantic, and Southern Ocean converges to a global relationship that can be used to reconstruct paleo carbon export.

No abstract

No abstract

No abstract

[1] In this characterization brief, report here comprehensive major and trace element analyses of over 45 sediment samples from Ocean Drilling Program Site 1149, located seaward of the Izu-Bonin trench. The combination of these core analyses with a complete set of geochemical logging data enables us to calculate the bulk composition of the sedimentary column subducting at the Izu trench with high accuracy (uncertainties 13%). Izu sediment has lower concentrations than global subducting sediment for most elements, due to $50% dilution by biogenic material ($45% opal and $10% carbonate), but is relatively enriched in Ba, Pb, and rare earth elements (REE), except Ce, due to nonterrigenous inputs. Sediments subducting into the Izu and Mariana trenches differ compositionally due to ocean island-sourced volcaniclastics in Marianas sediments, enriching them in Nb, Ta, Ti, and LREE, and continentally derived eolian material in Izu sediments, enriching them in Cs, Rb, Th, and U. These differences predict alongstrike variations in sediment input that should be manifested in the composition of volcanic output from the Honshu-Izu-Bonin-Mariana arc systems. Such variations are observed as an increase in Th/La in both sediments and arc volcanics from the Marianas in the south to Honshu in the north.