A Phosphorus Control on Oceanic Anoxic Events under Greenhouse Climates?

This project will examine controls on the development, spatial extent and duration of anoxia in the Cretaceous greenhouse ocean. Specifically, high resolution, multi-proxy records from shelf and deeper margin/basin sites, covering two contrasting greenhouse scenarios of differing intensity, will be studied to test orbital effects on:

1) Redox state: A state-of-the-art multiproxy approach will be used to distinguish between key water column redox states linked to potential perturbations of the Fe and S cycles.
2) Response of the P cycle: P speciation will be utilized in order to understand the ocean biogeochemical response to changes in weathering and ocean redox.

These records will unravel feedbacks between redox and P cycling on the shelf and in the deep basins, leading to a step-change in our understanding of some of the most dramatic perturbations to the Earth system of the last 120 million years. This, in turn, will inform on generic processes that likely operated during other episodes of ocean anoxia under past, and potentially future, greenhouse conditions.