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U-Pb dating of calcite in ancient carbonates for age estimates of syn- to post-depositional processes: a case study from the upper Ediacaran strata of Finnmark, Arctic Norway

U-Pb dating of calcite in ancient carbonates for age estimates of syn- to post-depositional processes: a case study from the upper Ediacaran strata of Finnmark, Arctic Norway Thumbnail


Abstract

Results of in situ U-Pb dating of calcite spherulites, cone-in-cone (CIC) calcite and calcite fibres from a calcareous concretion of the upper Ediacaran of Finnmark, Arctic Norway, are reported. Calcite spherulites from the innermost layers of the concretion yielded a lower intercept age of 563 ± 70 Ma, which although imprecise, is within uncertainty of the age of sedimentation based on fossil assemblages. Non-deformed CIC calcite from the bottom part of the concretion yielded an age of 475 ± 25 Ma, which is interpreted as the age of CIC calcite formation during a period of fluid overpressure induced during burial of the sediments. Deformed CIC calcite from the top part of the concretion yielded an age of 418 ± 23 Ma, which overlaps with a known Caledonian tectono-metamorphic event, and indicates a potential post-depositional overprint at this time. Calcite fibres that grew in small fissures along spherulite rims, which are interpreted as a recrystallization feature during deformation and formation of a cleavage, gave an imprecise age of 486 ± 161 Ma. Our results show that U-Pb dating of calcite can provide age constraints for ancient carbonates and syn- to postdepositional processes that operated during burial and metamorphic overprinting.

Citation

(2020). U-Pb dating of calcite in ancient carbonates for age estimates of syn- to post-depositional processes: a case study from the upper Ediacaran strata of Finnmark, Arctic Norway. Geological Magazine, 1367-1372. https://doi.org/10.1017/S0016756820000564

Acceptance Date May 11, 2020
Publication Date Jul 11, 2020
Journal Geological Magazine
Print ISSN 0016-7568
Publisher Cambridge University Press
Pages 1367-1372
DOI https://doi.org/10.1017/S0016756820000564
Keywords U–Pb calcite geochronology; calcite spherulites; cone-in-cone calcite; Ediacaran; Caledonides; Norway
Publisher URL https://doi.org/10.1017/S0016756820000564

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