Chromium isotope behaviour in oxygen minimum zones
The Cr isotopic composition (δ53Cr) of authigenic marine sediments is increasingly being used to determine past changes in the Cr isotopic composition of seawater. These records of ancient seawater δ53Cr are thought to provide important information as to past levels of oceanic and atmospheric oxygenation, and may provide new understanding of the evolution of life and past climatological events. However, the terrestrial and oceanic processes which contribute to the δ53Cr of marine deposits are not well characterised. In this talk I will discuss the factors which affect δ53Cr behaviour within low oxygen seawater environments based on results from my PhD. I will demonstrate that seawater δ53Cr is impacted by oxygen levels of 0μmol/L in the Black Sea, but is more sensitive to hydrological mixing and continental shelf processes within the Atlantic oxygen minimum zone. Finally I will discuss how these findings should direct future interpretations of the δ53Cr paleoredox proxy.