Unlocking the barite paleoproductivity proxy: A new high-throughput method for quantifying barite in marine sediments

Abstract

The accumulation rate of barite (BaSO4) in marine sediments is a powerful tracer of paleo export productivity due to the refractory nature of barite in sediments and its ability to record ecosystem-wide productivity. It has been used to reconstruct past export productivity and to infer the effects of ocean circulation and nutrient supply on ocean ecosystems. However, the difficulty in generating large datasets of reliable barite accumulation rates has limited the use of this proxy. Here we present a new method for quantifying barite in marine sediments that promises a dramatic increase in sample throughput while also improving recovery of barite in a wide variety of marine sediments. This method relies on selective dissolution of barite using a chelating ligand that avoids liberating Ba from silicate phases, and it can therefore work reliably on small (~250 mg) sediment aliquots. Rigorous evaluation of the method reveals that it quantitatively extracts barite and is largely unaffected by other Ba sources. Due to the relatively simple analytical requirements of this barite extraction method and the small sample amount needed, it can also be used to rapidly generate paleoproductivity records both during and after coring expeditions. Altogether, this new technique should expand the study of the marine biologic system in the past by dramatically increasing analytical efficiency and widening the range of questions that are accessible using barite accumulation rate as a paleoproductivity proxy.