Sedimentary molybdenum and uranium: Improving proxies for deoxygenation in coastal depositional environments

• DOI: 10.1016/j.chemgeo.2022.121203
• Publication Date: 2022-11-07T16:41:20Z
• Authors: K. Mareike Paul; Niels A.G.M. van ...; Caroline P. Slomp; Sami A. Jokinen; Joonas J. Virtasalo; Helena L. Filipsson; Tom Jilbert
• Keywords: Deoxygenation; Continental Margin

Sedimentary molybdenum (Mo) and uranium (U) enrichments are widely used to reconstruct changes in bottom water oxygen conditions aquatic environments. Until now, most studies using Mo U have focused on restricted suboxic-euxinic basins continental margin minimum zones (OMZs), leaving mildly reducing oxic (but eutrophic) coastal depositional environments vastly understudied. Currently, it is unknown: (1) what extent enrichment factors (Mo- U-EFs) can accurately sites experiencing mild deoxygenation, (2) degree secondary (depositional environmental) impact Mo- U-EFs. Here we investigate 18 with varying redox conditions, which define by means of five "redox bins", ranging from persistently euxinic, a variety Our results demonstrate that U-EF-based proxies sedimentary contents be differentiate concentration among range modern This underpinned the contrasting EFs along gradient, shows substantial difference Mo-EFs between bins 3–5 (ir/regularly suboxic – ir/regularly dysoxic oxic) U-EFs 1–2 (persistently euxinic euxinic). Surprisingly, observe comparatively low proxy potential for deoxygenation (redox 3–5). Further, found bias Mo-and such an do not reliably reflect conditions. We limited sequestration sulfidic (i.e., "basin reservoir effect", equilibrium FeMoS4), Fe/Mn-(oxy)(hydr)oxide "shuttling", oxidative dissolution, sulfate methane transition zone sediment, sedimentation rate, local Al background