Sediment geochemistry of the Thetis hypersaline anoxic basin (eastern Mediterranean Sea)

•Permanent anoxia in Thetis basin generates specific cycling of trace elements.•Microbial sulphate reduction in brines and sediments drives trace metal cycles.•Thetis sediments do not offer reliable analogues to past anoxic basins.

The Thetis basin is a deep hypersaline anoxic basin in the western part of the Mediterranean Ridge (eastern Mediterranean Sea). It is characterised by highly sulphidic NaCl-saturated brine with one of the highest values of salinity reported from similar basins (S ~ 348‰). The strong pycnocline at the seawater–brine interface induces permanent anoxic bottom conditions driving depositional processes and distribution patterns of redox-sensitive metals in the sediments. This work presents a high-resolution dataset of sedimentological, mineralogical and geochemical features and planktonic foraminifera distribution, derived from the exploration of a 52 cm long box-core sampled in the Thetis sediments. Basing on direct comparisons with available data from other hypersaline records and ancient anoxic organic-rich deep-sea records (sapropels and black shales), we aim to explore the potential of these anoxic basins as natural laboratories to better understand the mechanisms driving geochemical patterns in recent/ancient anoxic sediments.