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, Guido, Roberts, Nick M. W., Arslan, Arzu, Jensen, Sören, Ebbestad, Jan Ove R., Högström, Anette E. S., Hoyberget, Magne, Agic, Heda, Palacios, Teodoro, Taylor, Wendy L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Uppsala universitet, Evolutionsmuseet 2020
• Subjects: U-Pb calcite geochronology; calcite spherulites; cone-in-cone calcite; Ediacaran; Caledonides; Norway; Geology; Geologi; Other Earth and Related Environmental Sciences; Annan geovetenskap och miljövetenskap; Arctic; Finnmark
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-421537; 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 post-depositional processes that operated during burial and metamorphic overprinting.