Deconstructing the Lomagundi-Jatuli Carbon Isotope Excursion

Abstract

The early to mid-Paleoproterozoic Lomagundi-Jatuli Excursion (LJE) is ostensibly the largest magnitude (approximately +5 to +30‰), 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 ∼9,400 δ13Ccarb 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 13C-enrichment. ▪ The Lomagundi-Jatuli Excursion (LJE) continues to challenge current understandings of the carbon cycle. ▪ Understanding this excursion is critical for reconstructing biogeochemical cycles and atmospheric oxygenation through Earth history. ▪ Some evidence indicates local rather than global changes in δ13CDIC and raises the possibility of asynchronous, local excursions. ▪ Resolving whether the LJE was globally synchronous or asynchronous is essential for discriminating between different models.