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A Tournaisian (earliest Carboniferous) conglomerate-preserved non-marine faunal assemblage and its environmental and sedimentological context.

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posted on 19.08.2019, 09:15 by JA Clack, CE Bennett, SJ Davies, AC Scott, JE Sherwin, TR Smithson
A conglomerate bed from the Tournaisian Ballagan Formation of Scotland preserves a rich array of vertebrate and other nonmarine fossils providing an insight into the wider ecosystem and paleoenvironment that existed during this pivotal stage of Earth history. It challenges hypotheses of a long-lasting post-extinction trough following the end-Devonian extinction event. The fauna recovered includes a wide size range of tetrapods, rhizodonts, and dipnoans, from tiny juveniles or small-bodied taxa up to large adults, and more than one taxon of each group is likely. Some fauna, such as actinopterygians and chondrichthyans, are rare as macrofauna but are better represented in the microfossil assemblage. The fauna provides evidence of the largest Carboniferous lungfish ever found. The specimens are preserved in a localized, poorly-sorted conglomerate which was deposited in the deepest part of a river channel, the youngest of a group of channels. In addition to the fossils (micro- and macro-), the conglomerate includes locally-derived clasts of paleosols and other distinctive elements of the surrounding floodplains. Charcoal fragments represent small woody axes and possible larger trunk tissue from arborescent pteridosperms. Preservation of the fossils indicates some aerial exposure prior to transport, with abrasion from rolling. The findings presented here contrast with other published trends in vertebrate size that are used to interpret a reduction in maximum sizes during the Tournaisian. The richness of the fauna runs counter to the assumption of a depauperate nonmarine fauna following the end-Devonian Hangenberg event, and charcoal content highlights the occurrence of fire, with the requisite levels of atmospheric oxygen during that stage.

Funding

This work was supported by the Natural Environment Research Council UK, Consortium grants: NE/J022713/1 (Cambridge), NE/J020729/1 (Leicester), and a Leverhulme Trust Emeritus Fellowship to J. A. Clack EM-2016-038.

History

Citation

PeerJ, 2019, 6:e5972

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/School of Geography, Geology and the Environment

Version

VoR (Version of Record)

Published in

PeerJ

Publisher

PeerJ

issn

2167-8359

Acceptance date

19/10/2018

Copyright date

2019

Available date

19/08/2019

Publisher version

https://peerj.com/articles/5972/

Notes

The following information was supplied regarding data availability: Dryad: DOI 10.5061/dryad.2mg27sh

Language

en