Refining the use of vanadium and uranium as paleoredox proxies by examining sediments from the Baltic Sea

The Baltic Sea is largely anoxic and sulfidic at depth but periodically oxygenated by the inflow of oxic seawater from the North Sea. This present an ideal natural laboratory to develop the application of the uranium (U) and vanadium (V) ‘paleoredox proxies’, which rely on interpreting the abundance and isotopic composition of these redox-sensitive metals. Although these are key tools for redox reconstructions in ancient oceans, basic uncertainties remain regarding the application of paleoredox proxies such as the oxidation state and coordination environment of these metals. This will be addressed in this proposal by determiningy the distribution and speciation of U and V in anaerobically preserved Baltic Sea sediments using HERFD-XANES, EXAFS and XRF mapping techniques at the Rossendorf Beamline (ROBL-II). The combination of these data with elemental abundances and isotope compositions will offer unprecendeted insights into the application of the U and V paleoredox proxies.