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Evidence for Late Devonian (Kellwasser) anoxic events in the Great Basin, western United States

Bond, D.P.G. and Wignall, P.B. (2005) Evidence for Late Devonian (Kellwasser) anoxic events in the Great Basin, western United States. In: Over, J., Morrow, J. and Wignall, P.B., (eds.) Development in Palaeontology and Stratigraphy. Understanding Late Devonian and Permian-Triassic Biotic and Climatic Events, 20 (Chapte). Elsevier , pp. 225-261. ISBN 0444521275

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The Frasnian-Famennian (Late Devonian) mass extinction has often been related to the development of the Kellwasser anoxic events in Europe and North Africa but the synchronous development of the anoxia has not been reported from the Great Basin of the western United States. An integrated sedimentological, palaeoecological, and pyrite petrographic study has been undertaken on a range of F-F boundary sections from Nevada and Utah spanning a spectrum of carbonate and clastic depositional environments from distal basin, base-of-slope, mid-slope, and intrashelf basin settings. These reveal a range of facies from oxic strata, fully bioturbated and lacking any pyrite, to euxinic strata characterised by fine lamination and pyrite framboid populations of small size and narrow size range. Oxygen-restricted deposition is seen in all sections at various times, but the only interval characterised by basin-wide euxinicity occurs at the end of the Frasnian Stage late in the linguiformis Zone. This is the peak of the F-F mass extinction and it is also contemporaneous with the Upper Kellwasser Horizon of Europe. The study therefore reinforces the claim that the mass extinction coincides with the global development of marine anoxia. Shallow-water sections were not studied but slope and base-of-slope sections record many sediment-gravity flows that transported an allochthonous fauna into deeper water settings. This shallow-water fauna temporarily disappears late in the linguiformis Zone perhaps indicating the development of oxygen-restriction in shallow-water settings. Intriguingly the condensed, deepest water sections from the Woodruff basin record somewhat higher oxygenation levels than the contemporaneous slope sections. The most oxygen-restricted conditions may therefore have occurred in a mid-water oxygen-minimum zone that expanded its vertical range both upwards and downwards and became sulfidic late in the linguiformis Zone.

Item Type: Book Section
Copyright, Publisher and Additional Information: Reprinted with permission from Elsevier. This is an author produced version of a book chapter published in Development in Palaeontology and Stratigraphy.
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds)
Depositing User: Repository Officer
Date Deposited: 21 Aug 2006
Last Modified: 27 Jul 2016 21:53
Published Version: http://www.elsevier.com/
Status: Published
Publisher: Elsevier
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/221

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