Barium and its Importance as an Indicator of (Paleo)Productivity

Barium (Ba) is a trace element which occurs predominantly as barite mineral (BaSO4) in the marine environment. Previous work suggests that barite concentrations are related to the organic carbon flux and marine biological debris in the water column suggesting a direct or indirect involvement in the marine biological cycling. In addition, barite has a high preservation rate (similar to 30%) in sediments and it is less affected by early diagenesis than other proxies for productivity such as carbonates (similar to 10%) and organic carbon (similar to 1%), for example. Therefore, Ba is considered an excellent proxy for ocean (paleo) productivity. However, correlating barite to productivity involves some caveats. Specifically, the post-depositional formation of barite in oxic sediments can lead to Ba release into porewaters under anoxic conditions, which can form barite again under oxic conditions. This diagenetic formation is not correlated to export production as the seawater authigenic barite formed with decaying organic matter in the water column. Therefore, the main goal of this work is to briefly review the marine Ba cycle and highlight its importance for (paleo) productivity research.