Tracking lateral δ13Ccarb variation in the Paleoproterozoic Pechenga Greenstone Belt, the north eastern Fennoscandian Shield

The Kuetsjärvi Sedimentary Formation (KSF) records the global Paleoproterozoic (ca. 2200–2100 Ma) positive δ13C excursion of sedimentary carbonates. This event is here called as the Lomagundi-Jatuli isotopic excursion. In this study, lateral δ13Ccarb variation in the KSF and local basinal factors amplifying global δ13Ccarb value were investigated and a secular δ13C curve for the KSF was constructed. Sedimentary carbonate samples from a new drillcore (Drillcore 5A) from the KSF were analysed for δ13C, δ18O and selected major and trace elements. The δ13C values of the samples vary from 5 to 8‰ (VPDB) and the δ18O values from −18 to −10‰ (VPDB). Most of the samples have retained their primary C isotopic composition, as they do not show correlation between the Mn/Sr ratios and the δ13C and δ18O values. The new results were compared to those previously obtained from another drillcore (Drillcore X) from the KSF (ca. 25 km along strike from Drillcore 5A). Both cores show a similar kind of generally upward decreasing trend in δ13C, excluding some negative and positive spikes in Drillcore X and samples close to a contact with a Fe-picrite dyke in Drillcore 5A. A secular δ13C curve of the KSF was constructed based on the least altered δ13C data from the cores 5A and X. The secular δ13C curve of the KSF may represent the latest part of the Lomagundi-Jatuli isotopic excursion.

► Sedimentary carbonates from the Kuetsjärvi Sedimentary Formation were investigated.
► New drillcore δ13C data was compared to published record from another core.
► In general, no lateral δ13C variation was observed.
► The combined secular δ13C curve shows a decreasing trend from 8 to 5‰.
► The secular curve may represent the final part of the Lomagundi-Jatuli excursion.