U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia
Published online: 15 January 2024 The Llangynog Inlier of south Wales contains an assemblage of Ediacaran macrofossils from a shallow-marine environment, including discoidal morphs of Aspidella and rare examples of Hiemalora, Palaeopascichnus and Yelovichnus. These are taxa found at other sites in t...
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ftunivadelaidedl:oai:digital.library.adelaide.edu.au:2440/140580 2024-05-12T08:07:14+00:00 U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia Clarke, A. Kirkland, C. Menon, L. Condon, D. Cope, J. Bevins, R. Glorie, S. 2024 https://hdl.handle.net/2440/140580 https://doi.org/10.1144/jgs2023-081 en eng Geological Society http://purl.org/au-research/grants/arc/DP200101881 http://purl.org/au-research/grants/arc/FT210100906 Journal of the Geological Society, 2024; 181(1):jgs2023-081.-1-jgs2023-081-12 0016-7649 2041-479X https://hdl.handle.net/2440/140580 doi:10.1144/jgs2023-081 Glorie, S. [0000-0002-3107-9028] © 2024 The Author(s). Published by The Geological Society of London. All rights reserved. http://dx.doi.org/10.1144/jgs2023-081 Journal article 2024 ftunivadelaidedl https://doi.org/10.1144/jgs2023-081 2024-04-17T14:31:05Z Published online: 15 January 2024 The Llangynog Inlier of south Wales contains an assemblage of Ediacaran macrofossils from a shallow-marine environment, including discoidal morphs of Aspidella and rare examples of Hiemalora, Palaeopascichnus and Yelovichnus. These are taxa found at other sites in the Avalonian microcontinent (e.g. Charnwood Forest and eastern Newfoundland) and in the younger White Sea Ediacaran assemblages. As the Charnwood fossils reflect a deep-water environment, and no macrofossils have been found in the Ediacaran rocks of the Long Mynd, the fossils of the Llangynog Inlier represent a unique glimpse of shallow-marine life in southern Britain (East Avalonia). However, the lack of absolute age constraints has hampered direct comparison with other assemblages. Here, we report in situ zircon and rutile U–Pb dates from a rhyolitic ash-flow layer of the Coed Cochion Volcaniclastic Member, Llangynog Inlier, which constrains the age of the fossiliferous strata. A weighted mean single grain zircon isotope dilution thermal ionization mass spectrometry U–Pb age of 564.09 ± 0.70 Ma is interpreted as the rhyolite's crystallization age. This age is consistent with in situ laser ablation inductively coupled plasma mass spectrometry zircon and rutile U–Pb dating. The Llangynog age temporally correlates these fossils to dated horizons within East Avalonia at the Beacon Hill Formation, Charnwood (565.22 ± 0.89 Ma) and the Stretton Shale Formation, Long Mynd (566.6 ± 2.9 Ma). Correlations to West Avalonia include the time-equivalent Fermeuse Formation, St John's Group, eastern Newfoundland (564.13 ± 0.65 Ma). The data presented here establish the biota of the Llangynog Inlier as a lateral equivalent to the similarly shallow-marine, tidally influenced ecosystem of the upper Fermeuse Formation. Intra-terrane depositional environmental variability also affects what is preserved in Avalonian fossil sites. Further, time-constrained geochemical data reinforce the Llangynog Inlier's classification within the Wrekin ... Article in Journal/Newspaper Newfoundland White Sea The University of Adelaide: Digital Library Beacon Hill ENVELOPE(-66.376,-66.376,-68.071,-68.071) White Sea Journal of the Geological Society 181 1 |
institution |
Open Polar |
collection |
The University of Adelaide: Digital Library |
op_collection_id |
ftunivadelaidedl |
language |
English |
description |
Published online: 15 January 2024 The Llangynog Inlier of south Wales contains an assemblage of Ediacaran macrofossils from a shallow-marine environment, including discoidal morphs of Aspidella and rare examples of Hiemalora, Palaeopascichnus and Yelovichnus. These are taxa found at other sites in the Avalonian microcontinent (e.g. Charnwood Forest and eastern Newfoundland) and in the younger White Sea Ediacaran assemblages. As the Charnwood fossils reflect a deep-water environment, and no macrofossils have been found in the Ediacaran rocks of the Long Mynd, the fossils of the Llangynog Inlier represent a unique glimpse of shallow-marine life in southern Britain (East Avalonia). However, the lack of absolute age constraints has hampered direct comparison with other assemblages. Here, we report in situ zircon and rutile U–Pb dates from a rhyolitic ash-flow layer of the Coed Cochion Volcaniclastic Member, Llangynog Inlier, which constrains the age of the fossiliferous strata. A weighted mean single grain zircon isotope dilution thermal ionization mass spectrometry U–Pb age of 564.09 ± 0.70 Ma is interpreted as the rhyolite's crystallization age. This age is consistent with in situ laser ablation inductively coupled plasma mass spectrometry zircon and rutile U–Pb dating. The Llangynog age temporally correlates these fossils to dated horizons within East Avalonia at the Beacon Hill Formation, Charnwood (565.22 ± 0.89 Ma) and the Stretton Shale Formation, Long Mynd (566.6 ± 2.9 Ma). Correlations to West Avalonia include the time-equivalent Fermeuse Formation, St John's Group, eastern Newfoundland (564.13 ± 0.65 Ma). The data presented here establish the biota of the Llangynog Inlier as a lateral equivalent to the similarly shallow-marine, tidally influenced ecosystem of the upper Fermeuse Formation. Intra-terrane depositional environmental variability also affects what is preserved in Avalonian fossil sites. Further, time-constrained geochemical data reinforce the Llangynog Inlier's classification within the Wrekin ... |
format |
Article in Journal/Newspaper |
author |
Clarke, A. Kirkland, C. Menon, L. Condon, D. Cope, J. Bevins, R. Glorie, S. |
spellingShingle |
Clarke, A. Kirkland, C. Menon, L. Condon, D. Cope, J. Bevins, R. Glorie, S. U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia |
author_facet |
Clarke, A. Kirkland, C. Menon, L. Condon, D. Cope, J. Bevins, R. Glorie, S. |
author_sort |
Clarke, A. |
title |
U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia |
title_short |
U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia |
title_full |
U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia |
title_fullStr |
U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia |
title_full_unstemmed |
U-Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow-marine fossil assemblage from East Avalonia |
title_sort |
u-pb zircon-rutile dating of the llangynog inlier, wales: constraints on an ediacaran shallow-marine fossil assemblage from east avalonia |
publisher |
Geological Society |
publishDate |
2024 |
url |
https://hdl.handle.net/2440/140580 https://doi.org/10.1144/jgs2023-081 |
long_lat |
ENVELOPE(-66.376,-66.376,-68.071,-68.071) |
geographic |
Beacon Hill White Sea |
geographic_facet |
Beacon Hill White Sea |
genre |
Newfoundland White Sea |
genre_facet |
Newfoundland White Sea |
op_source |
http://dx.doi.org/10.1144/jgs2023-081 |
op_relation |
http://purl.org/au-research/grants/arc/DP200101881 http://purl.org/au-research/grants/arc/FT210100906 Journal of the Geological Society, 2024; 181(1):jgs2023-081.-1-jgs2023-081-12 0016-7649 2041-479X https://hdl.handle.net/2440/140580 doi:10.1144/jgs2023-081 Glorie, S. [0000-0002-3107-9028] |
op_rights |
© 2024 The Author(s). Published by The Geological Society of London. All rights reserved. |
op_doi |
https://doi.org/10.1144/jgs2023-081 |
container_title |
Journal of the Geological Society |
container_volume |
181 |
container_issue |
1 |
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1798849830465830912 |