MODERN SEDIMENTARY ARCHIVES TO FINGERPRINT THALLIUM AND VANADIUM ISOTOPES TO BETTER CONSTRAIN THE LOW OXYGEN ISOTOPE SIGNATURES (Invited Presentation)

Ocean deoxygenation can severely impact the chemical cycling of many elements (e.g. carbon, manganese (Mn), and nutrient elements). As recent modern biological studies have shown the range of impacts and many (mass)extinction events have been tied to expansive variations in the redox landscape. However, there is a heterogenous biogeochemical response to marine redox conditions which is likely tied to the quantitative extent of various parts of the marine redox ladder. With the addition of several new geochemical tools, including vanadium (V) and thallium (Tl), it might be possible to better parse out local and/or global redox conditions when a combination of redox proxies are applied simultaneously.

The most recent isotope mass balances for V and Tl suggest that the modern marine isotopic signature is dominantly controlled by the fractionation of either ferro- and/or manganese (Fe-Mn) oxide burial flux. Importantly, the precipitation and burial of Fe-Mn oxides are directly tied to the local redox conditions in the water column and diagenetic sedimentary environments. Therefore, both Tl and V have the potential to explore local and global redox variability which both elements have been linked to biological implications. A compressed redox ladder in which oxide reduction occurs near sulfide production has the potential to record the isotopically fractionated elements, thus providing a false positive signature for oxic conditions. However, such archives have not been explored especially using downcore profiles. A detailed modern study to better constrain the isotopic fingerprints in a range of local bottom water oxygen conditions and progressively reducing downcore profiles are needed to better understand these two elemental systems.