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

• Published in: Geological Magazine
• Main Authors: Meinhold, G, Roberts, NMW, Arslan, A, Jensen, S, Ebbestad, JOR, Högström, AES, Høyberget, M, Agić, H, Palacios, T, Taylor, WL
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2020
• Subjects: G Geography (General); GB Physical geography; GE Environmental Sciences; Arctic; Norway; Finnmark
• Online Access: https://eprints.keele.ac.uk/id/eprint/8089/; https://eprints.keele.ac.uk/id/eprint/8089/1/Meinhold_etal_GeolMag_U-Pb%20calcite_acceptedMS.pdf; https://doi.org/10.1017/S0016756820000564

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.