Constraints on the late Ediacaran sulfur cycle from carbonate associated sulfate

Tostevin, Rosalie and He, Tianchen and Turchyn, Alexandra V. and Wood, Rachel A. and Penny, Amelia M. and Bowyer, Fred and Antler, Gilad and Shields, Graham A. (2017) Constraints on the late Ediacaran sulfur cycle from carbonate associated sulfate. Precambrian Research, 290. pp. 113-125. ISSN 03019268 DOI 10.1016/j.precamres.2017.01.004

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Official URL: http://doi.org/10.1016/j.precamres.2017.01.004

Abstract

We report new sulfur isotope compositions (δ34S) in carbonate associated sulfate (CAS) and pyrite from the lower Nama Group, Namibia (∼550 to <547 Ma), and use these data to interrogate terminal Ediacaran sulfur cycle dynamics. Our extraction method utilizes an improved pre-leaching procedure that reduces the likelihood of contamination from matrix-bound sulfur. Data generated with the improved extraction method show CAS δ34S as much as 12‰ higher (34S-enriched) than previously reported which suggests a reevaluation of the phenomenon of ‘superheavy’ pyrite. The average δ34S of seawater sulfate increases from 30 to 38‰ in the lower Nama Group, and we correlate this rise in δ34S among contemporaneous marine basins. Global seawater sulfate δ34S >35‰ is highly unusual in Earth history, and in the terminal Ediacaran is best explained by a high pyrite burial flux. Pyrite in the Nama Group is close in isotopic composition to coeval sulfate, but the sulfur isotope fractionation between sulfate and pyrite varies widely among different studied basins, suggesting highly heterogeneous redox and depositional conditions.

Item Type: Article
Uncontrolled Keywords: 2016AREP; IA71;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Precambrian Research
Volume: 290
Page Range: pp. 113-125
Identification Number: 10.1016/j.precamres.2017.01.004
Depositing User: Sarah Humbert
Date Deposited: 04 Aug 2017 13:31
Last Modified: 04 Aug 2017 13:31
URI: http://eprints.esc.cam.ac.uk/id/eprint/4005

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