Describing post-GOE oxygen availability with trace metal paleoredox proxies

Abstract

Methods of describing local oxygen availability using coupled Mo isotopes and redox sensitive trace metal enrichments are applied to the Hotazel Iron Formation of the Transvaal Supergroup. These trace metal paleoredox proxies are used to track the presence of Mn-oxides in the ancient depositional environment, and an indication that Mn-oxides were present in the ancient environment implies local oxygenation. The Hotazel Formation was deposited in the wake of the GOE, and this sample set is utilized with the motivation of developing and calibrating a proxy for local oxygen availability. Indeed, the results suggest an oxygenated depositional environment, and therefore the findings of the work support the application of coupled Mo isotopes and trace metal enrichments to describe ancient oxygen availability. Moreover, since similar methods of oxygen detection have previously been applied to sediments deposited at 2.95 Ga, the results presented herein provide further support for locally oxygenated seawater and the advent of oxygenic photosynthesis by 2.95 Ga.