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

Alexander G. Liu (Corresponding Author), Sean McMahon, Jack J. Matthews, John W. Still, Alexander T. Brasier

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Microbially mediated early diagenetic pyrite formation in the immediate vicinity of organic material has been the favored 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. Scanning electron microscope (SEM), cathodoluminescence microscopy (CL), 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.
Original languageEnglish
Pages (from-to)215-218
Number of pages4
JournalGeology
Volume47
Issue number3
Early online date18 Jan 2019
DOIs
Publication statusPublished - 2019

Fingerprint

Ediacaran
coating
pyrite
silica
sandstone
fossil
cathodoluminescence
silicification
bedding plane
iron oxide
hematite
clay mineral
microscopy
cement
electron
organism

Keywords

  • arenite
  • clastic rocks
  • Australia
  • Australasia
  • Metazoa
  • sedimentary rocks
  • South Australia

Cite this

Petrological evidence supports the death mask model for the preservation of Ediacaran soft-bodied organisms in South Australia. / Liu, Alexander G. (Corresponding Author); McMahon, Sean; Matthews, Jack J.; Still, John W.; Brasier, Alexander T.

In: Geology, Vol. 47, No. 3, 2019, p. 215-218.

Research output: Contribution to journalArticle

Liu, Alexander G. ; McMahon, Sean ; Matthews, Jack J. ; Still, John W. ; Brasier, Alexander T. / Petrological evidence supports the death mask model for the preservation of Ediacaran soft-bodied organisms in South Australia. In: Geology. 2019 ; Vol. 47, No. 3. pp. 215-218.
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abstract = "Microbially mediated early diagenetic pyrite formation in the immediate vicinity of organic material has been the favored 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. Scanning electron microscope (SEM), cathodoluminescence microscopy (CL), 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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note = "Specimens were collected by AGL with permission and assistance from J. Gehling in 2015. 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, and thanks M. Hall and A. McDonald for help with thin section polishing and Raman spectroscopy respectively. JJM recognises support from Mitacs, and all authors are grateful to N.J. Butterfield for constructive discussions during manuscript preparation. We thank R. Gaines, S. Darroch and J. Gehling for constructive reviews of this manuscript.",
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