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Petrological evidence in support of the death mask model for Ediacaran soft-bodied preservation in South Australia

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Peer-reviewed

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Article

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Authors

Liu, AG 
Matthews, Jack 
McMahon, Sean 
Still, John 
Brasier, Alexander 

Abstract

Microbially mediated early diagenetic pyrite formation in the immediate vicinity of organic material has been the favoured mechanism by which to explain widespread preservation of soft-bodied organisms in late Ediacaran sedimentary successions, but an alternative rapid silicification model has been proposed for macrofossil preservation in sandstones of the Ediacara Member in South Australia. We here provide petrological evidence from Nilpena National Heritage Site and Ediacara Conservation Park to demonstrate the presence of grain-coating iron oxides, framboidal hematite, and clay minerals along Ediacara Member sandstone bedding planes, including fossil-bearing bed soles. SEM and petrographic data reveal that framboids and grain coatings, which we interpret as oxidized pyrite, formed before the precipitation of silica cements. In conjunction with geochemical and taphonomic considerations, our data suggest that anactualistically high concentrations of silica need not be invoked to explain Ediacara Member fossil preservation: we conclude that the pyritic ‘death mask’ model remains compelling.

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Keywords

37 Earth Sciences, 3709 Physical Geography and Environmental Geoscience, 3702 Climate Change Science, 3705 Geology

Journal Title

Geology

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Journal ISSN

1943-2682
1943-2682

Volume Title

Publisher

Geological Society of America
Sponsorship
Natural Environment Research Council (NE/L011409/2)
AGL is funded by the Natural Environment Research Council [grant number NE/L011409/2]. SM acknowledges support from the European Union’s Horizon 2020 Research and Innovation Programme under Marie Skłodowska-Curie grant agreement 747877 ... JJM recognises support from Mitacs ...
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