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

钡（Ba）同位素是一种新的示踪剂，具有提供关于过去海洋生物生产力的信息的潜力（Bridgestock等人，2018; Bridgestock等人，2019年）。钡同位素相对于海洋重晶石积累的一个主要优点是它们对保存和稀释效应不敏感（Carter等人，2020年）。这种应用的基础是假定海洋沉积物中的Ba从上层水柱继承其同位素特征（Bridgestock等人，2018年）。然而，这一假设的保真度目前受到很大的限制，需要通过获得Ba同位素数据的现代沉积物跨越梯度的生物生产力和早期成岩条件进行验证。IODP EXP 391提供了一个独特的机会来收集岩心顶部沉积物和孔隙水，非常适合解决这一知识空白。为此，拟议的研究旨在测量国际海洋学勘探计划EXP 391号考察所有地点的海水、岩心顶部沉积物和孔隙水的[Ba]和Ba同位素值。这些数据将被用来测试表层沉积物的完整性，这些沉积物的同位素特征是从一系列浅沉积物氧化还原环境和海洋生物生产力的大梯度的上覆沃茨继承的。这项研究将填补现代海洋背景下沉积钡积累和钡同位素的关键知识空白，从而有助于提高海洋重晶石作为古生产力代用指标的使用。

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.