TEMPORAL CONSTRAINTS ON THE PALEOPROTEROZOIC LOMAGUNDI-JATULI CARBON ISOTOPIC EVENT

Abstract

The Paleoproterozoic Lomagundi-Jatuli positive δ13C excursion in sedimentary carbonates represents an event whose magnitude and duration is unique in Earth history, although precise absolute chronology of this event remains poorly constrained. In northeastern Fennoscandia, an ˜1300-m-thick sedimentary-volcanic succession of the Pechenga Greenstone Belt records decline of this isotopic excursion. Zircons from sedimentary rocks that occur within the decline have yielded 207Pb/206Pb dates at 2058 ± 2 Ma (±6 Ma including U decay constant uncertainties) and provide the first maximum age constraint on the termination of the Lomagundi-Jatuli event. Combined with existing constraints, these data indicate an ˜140 m.y. interval characterized by 13C-rich carbonate accumulation.