Temporal constraints on the Paleoproterozoic Lomagundi-Jatuli carbon isotopic event

The Paleoproterozoic Lomagundi-Jatuli positive [[delta].sup.13]C 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 [sup.207]Pb/[sup.206]Pb dates at 2058 [+ or -] 2 Ma ([+ or -]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 [sup.13]C-rich carbonate accumulation. Keywords: Fennoscandia, Paleoproterozoic, dolostone, carbon, isotopes, age.