Deconstructing the Lomagundi-Jatuli Carbon Isotope Excursion

The early to mid-Paleoproterozoic Lomagundi-Jatuli Excursion (LJE) is ostensibly the largest magnitude (approximatelyC5 toC30%), longest duration (ca. 130-250 million years) positive carbon isotope excursion measured in carbonate rocks in Earth history. The LJE has been attributed to large nutrient fluxes, an increase in the size of the biosphere, a reorganization of the global carbon cycle, and oxygenation of the atmosphere. However, significant debate remains about its genesis, synchroneity, global-versus-local extent, and role in atmospheric oxygenation. Here we review existing models and mechanisms suggested for the LJE and analyze a compilation of similar to 9,400 delta C-13(carb) and associated contextual data. These data call into question the interpretation of the LJE as a globally synchronous carbon isotope excursion and suggest that any model for the LJE must account for both the absence of a clearly defined initiation and termination of the excursion and a facies-dependent expression of C-13-enrichment.