OxyQuant is a research project funded by the European Commission’s Marie Skłodowska-Curie Global Postdoctoral Fellowship scheme. Started in March 2023 it will last three years - the first two years at the Institute of Earth Sciences at the University of Lausanne, Switzerland) and the last year at GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany).
Within the OxyQuant project I aim to develop a geochemical toolkit with which we can gain quantitative information about ocean water oxygen concentrations from the composition of marine sediments. With such a toolkit, if we applied it to older, deeper buried marine sediments, we would be able to reconstruct ocean oxygenation in the past. My aim is to use this toolkit to investigate deep ocean oxygenation, carbon storage, and circulation during the peak of the last ice age, circa 21 thousand years ago.
I am sampling sediment cores from diverse biogeochemical settings within their upper sections. Ideally, these sections are as young as possible, but should definitely be of Holocene age. Furthermore, the redox front (the sediment depth where pore water oxygen is consumed) lies within the sampling interval, so that samples above and below the redox front can be used to study the geochemical systems of interest.
(A) Oxygen is replenished at the sea surface, distributed via ocean currents, and depleted by organisms consuming organic matter. (B) Metabolic activity of microbes consumes oxygen in the sediment pore waters within the upper layers, typically within the first centimetres, or up to one meter sediment depth. (C) The strategy is to sample sediment cores across the redox front, but within the Holocene layer, so that proxy data can be compared to modern oceanographic conditions. Therefore, sites with a shallow redox layer or a thick Holocene layer are necessary.
(A) Bottom water oxygen (BWO) is distributed unequally in the deep oceans. Fresh oxygen is mainly supplied by deep water formation in the North Atlantic and around Antarctica, connecting the deep ocean with the ocean surface. Similarly, the flux of organic matter (total organic carbon, TOC) onto the seafloor is widely variable. (B) For OxyQuant I am going to use sediment cores from a variety of locations with very different combinations of local BWO concentrations and TOC fluxes. For each of these cores, the general sedimentology and geochemistry is going to be determined, and then a series of parameters is going to be analysed and their suitability as proxies for local BWO assessed. Grey and dark grey shadings indicate hypoxic and suboxic conditions, respectively. Potential sites are shown as symbols. Existing qualitative (dashed) and quantitative (solid) proxies are indicated by their calibration ranges at the bottom of panel B.