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Age of the Acraman impact ejecta layer in the adelaide superbasin and Implications on clay-mineral provenance from the Rb–Sr systematics of middle Ediacaran shales

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dc.contributor.authorCollins, A.S.
dc.contributor.authorBlades, M.L.
dc.contributor.authorSubarkah, D.
dc.contributor.authorCooke, H.
dc.contributor.authorEdwards, L.
dc.contributor.authorForbister, C.
dc.contributor.authorJolly, J.
dc.contributor.authorLloyd, J.C.
dc.contributor.authorGilbert, S.E.
dc.contributor.authorLöhr, S.
dc.contributor.authorFarkaš, J.
dc.contributor.authorGostin, V.
dc.date.issued2026
dc.description.abstractThe Acraman bolide hit the Gawler Craton of South Australia in the middle Ediacaran. Debris from this impact punctuates the Ediacaran sequences of the Adelaide Superbasin and the eastern Officer Basin. Here we date an argillaceous Acraman impactite layer sampled from Arkaba Creek, in the Bunyeroo Formation of the Adelaide Superbasin at 585 ± 15 Ma (MSWD = 1.8, 2 σ error) using the in-situ Rb–Sr ICP-MS/MS technique that we interpret to date the impact event. The analyses have a radiogenic 87 Sr/ 86 Sr initial ratio of 0.7210 ± 0.0028 and elevated light rare earth element values. Shales from both above and below the impact horizon yielded ages significantly pre-dating deposition and are interpreted to reflect detrital input into the Bunyeroo Formation, which is consistent with previous petrographic studies. Intriguingly, all 10 shales analysed yielded Rb–Sr ages within error of each other, with a Tonian weighted mean age of 778 ± 17 Ma (MSWD = 0.83). This is interpreted to reflect a very similar clay mineral age provenance for these shales despite being found in samples over 600 km apart. A similar mix of detrital mineral ages cannot be discounted. However, considering the spatial distribution, an alternative interpretation that the age similarity reflects Tonian pedogenic clay formation on the Gawler Craton, is thought more likely.
dc.description.statementofresponsibilityAlan S. Collins, Morgan L. Blades, Darwinaji Subarkah, Holly Cooke, Leslie Edwards, Chelsea Forbister, Jake Jolly, Jarred C. Lloyd, Sarah E. Gilbert, Stefan Lohr, Juraj Farkas, Victor Gostin
dc.identifier.citationPrecambrian Research, 2026; 435:108015-1-108015-8
dc.identifier.doi10.1016/j.precamres.2026.108015
dc.identifier.issn0301-9268
dc.identifier.issn1872-7433
dc.identifier.orcidCollins, A.S. [0000-0002-3408-5474]
dc.identifier.orcidSubarkah, D. [0000-0002-9028-4232]
dc.identifier.orcidCooke, H. [0009-0008-8364-4157]
dc.identifier.orcidJolly, J. [0009-0002-6611-8469]
dc.identifier.orcidLloyd, J.C. [0000-0002-4429-873X]
dc.identifier.orcidGilbert, S.E. [0000-0003-3259-7983]
dc.identifier.orcidLöhr, S. [0000-0002-1242-552X]
dc.identifier.orcidGostin, V. [0000-0001-5928-7403]
dc.identifier.urihttps://hdl.handle.net/2440/148846
dc.language.isoen
dc.publisherElsevier
dc.relation.granthttp://purl.org/au-research/grants/arc/LP200200822
dc.relation.granthttp://purl.org/au-research/grants/arc/FL240100114
dc.rights© 2026 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
dc.source.urihttps://doi.org/10.1016/j.precamres.2026.108015
dc.subjectAcraman impact; Ediacaran; South Australia; LA-ICP MS/MS, Rb/Sr; Adelaide Superbasin
dc.titleAge of the Acraman impact ejecta layer in the adelaide superbasin and Implications on clay-mineral provenance from the Rb–Sr systematics of middle Ediacaran shales
dc.typeJournal article
pubs.publication-statusPublished

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