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Redox heterogeneity of subsurface waters in the Mesoproterozoic ocean

Sperling, E.A.; Rooney, A.D.; Hays, L.; Sergeeva, V.N.; Vorob’eva, N.G.; Sergeeva, N.D.; Pearson, A.; Selby, D.; Johnston, D.T.; Knoll, A.H.

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Authors

E.A. Sperling

A.D. Rooney

L. Hays

V.N. Sergeeva

N.G. Vorob’eva

N.D. Sergeeva

A. Pearson

D. Selby

D.T. Johnston

A.H. Knoll



Abstract

A substantial body of evidence suggests that subsurface water masses in mid-Proterozoic marine basins were commonly anoxic, either euxinic (sulfidic) or ferruginous (free ferrous iron). To further document redox variations during this interval, a multiproxy geochemical and paleobiological investigation was conducted on the approximately 1000-m-thick Mesoproterozoic (Lower Riphean) Arlan Member of the Kaltasy Formation, central Russia. Iron speciation geochemistry, supported by organic geochemistry, redox-sensitive trace element abundances, and pyrite sulfur isotope values, indicates that basinal calcareous shales of the Arlan Member were deposited beneath an oxygenated water column, and consistent with this interpretation, eukaryotic microfossils are abundant in basinal facies. The Rhenium–Osmium (Re–Os) systematics of the Arlan shales yield depositional ages of 1414 ± 40 and 1427 ± 43 Ma for two horizons near the base of the succession, consistent with previously proposed correlations. The presence of free oxygen in a basinal environment adds an important end member to Proterozoic redox heterogeneity, requiring an explanation in light of previous data from time-equivalent basins. Very low total organic carbon contents in the Arlan Member are perhaps the key—oxic deep waters are more likely (under any level of atmospheric O2) in oligotrophic systems with low export production. Documentation of a full range of redox heterogeneity in subsurface waters and the existence of local redox controls indicate that no single stratigraphic section or basin can adequately capture both the mean redox profile of Proterozoic oceans and its variance at any given point in time.

Citation

Sperling, E., Rooney, A., Hays, L., Sergeeva, V., Vorob’eva, N., Sergeeva, N., …Knoll, A. (2014). Redox heterogeneity of subsurface waters in the Mesoproterozoic ocean. Geobiology, 12(5), 373-386. https://doi.org/10.1111/gbi.12091

Journal Article Type Article
Acceptance Date Apr 23, 2014
Online Publication Date May 29, 2014
Publication Date Sep 1, 2014
Deposit Date Jul 1, 2014
Publicly Available Date Jan 12, 2015
Journal Geobiology
Print ISSN 1472-4677
Electronic ISSN 1472-4669
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 12
Issue 5
Pages 373-386
DOI https://doi.org/10.1111/gbi.12091

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Copyright Statement
This is the accepted version of the following article: Sperling, E. A., Rooney, A. D., Hays, L., Sergeev, V. N., Vorob'eva, N. G., Sergeeva, N. D., Selby, D., Johnston, D. T. and Knoll, A. H. (2014), Redox heterogeneity of subsurface waters in the Mesoproterozoic ocean. Geobiology, 12 (5): 373–386, which has been published in final form at http://dx.doi.org/10.1111/gbi.12091. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.







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