Upper Ediacaran carbonates on the Digermulen Peninsula, Finnmark, Arctic Norway: insights into syn- to post-depositional processes at the edge of Baltica

The Digermulen Peninsula in eastern Finnmark has attracted renewed research interest in recent years due to discoveries of new Ediacara-type fossils, marking the rise of macroscopic life on Earth. The entire upper Ediacaran and Cambrian sedimentary succession was considered to be siliciclastic. However, carbonates were discovered within the 2nd cycle of the Manndrapselva Member of the Stáhpogieddi Formation of the Vestertana Group (Meinhold et al., 2019, Precambrian Research, 328, 99-110). These carbonates occur as calcareous siliciclastic beds, lenses, and concretions, some with calcite spherulites and cone-in-cone calcite, in a mudrock to fine-grained sandstone succession approximately 40 m below the Ediacaran–Cambrian boundary. The calcite spherulites were probably formed at the sediment–water interface or a few centimetres below, either in a coastal littoral environment or in situ in the sublittoral zone under high alkaline conditions. In situ calcite U−Pb isotope data from an upper Ediacaran carbonate concretion provide timing constraints for depositional, diagenetic, and potentially metamorphic processes, overlapping and confirming previous estimates based on relative bracketing of events (Meinhold et al., 2020, Geological Magazine, 157, 1367-1372). The cone-in-cone calcite formed during burial diagenesis and clearly before low-grade metamorphism and cleavage formation, the latter being caused by the Scandian Orogeny.