What is the major control on barium isotopes within the sediment and pore-water fraction in surface sediments?

Barium (Ba) isotopes are a novel tracer with the potential to provide information on past marine biological productivity (Bridgestock et al., 2018; Bridgestock et al., 2019). A major benefit of barium isotopes over marine barite accumulation is that they should be insensitive to preservation and dilution effects (Carter et al., 2020). The basis of this application is that Ba in marine sediment is assumed to inherit its isotopic signature from the upper water column (Bridgestock et al., 2018). However, the fidelity of this assumption is currently poorly constrained, and requires validation through obtaining Ba isotope data for modern sediments spanning gradients in biological productivity and early diagenetic conditions. IODP EXP 391 provides a unique opportunity to collect core-top sediments and pore-waters ideally suited to addressing this knowledge gap. To this end, the proposed research aims to measure [Ba] and Ba isotope values from seawater, core-top sediments and pore-waters from all sites of the IODP EXP 391 cruise. This data will be used to test the integrity of top sediments inheriting their isotopic signature from the overlying waters across a range of shallow sediment redox environments and a large gradient in marine biological productivity. This study will fill key knowledge gaps on sedimentary barium accumulation and barium isotopes in modern marine setting thus helping improve the use of marine barite as a palaeo-productivity proxy.