Thallium isotope evidence for a permanent increase in marine organic carbon export in the early Eocene

摘要: article The first high resolution thallium (Tl) isotope records in two ferromanganese crusts (Fe-Mn crusts), CD29 and D11 from the Pacific Ocean are presented. record pronounced but systematic changes 205 Tl/ 203 Tl that unlikely to reflect diagenetic overprinting or fractionation between seawater Fe-Mn crusts. It appears more likely track composition of over time. present-day oceanic residence time is estimated be about 20,000 yr, such isotopic should ocean-wide events. New published Os data used construct age models for these consistent with each other significantly different previous models. Application reveals changed systematically ~55 Ma ~45 Ma. Using a simple box model it shown present day depends almost exclusively on ratio principal output fluxes marine Tl. These rate removal via scavenging by authigenic oxyhydroxide precipitation uptake during low temperature alteration crust. highly latter has greatly. Therefore, assuming budget also not Cenozoic,