Cr isotopic insights into ca. 1.9 Ga oxidative weathering of the continents using the Beaverlodge Lake paleosol, Northwest Territories, Canada

• DOI: 10.1111/gbi.12342
• Publication Date: 2019-04-22T06:22:16Z
• Authors: Jonathan Toma; Chris Holmden; Paul Shakotko; Yuanming Pan; Luke Ootes
• Keywords: Paleosol; Genetic algorithm

Abstract The ca . 1.9 Ga Beaverlodge Lake paleosol was studied using redox‐sensitive Cr isotopes in order to determine the isotopic response paleoweathering of a rhyodacite parent rock 500 million years after Great Oxidation Event. Redox reactions occurring modern weathering environments produce Cr(VI) that is enriched heavy compared igneous inventory. species are soluble and easily leached from soils into streams rivers, thus, leaving particle‐reactive isotopically light Cr(III) build up soils. two other published profiles similar age, Flin Flon Schreiber Beach paleosols, not as soils, indicating rivers were at time. Considering global average δ 53 value for oxidative flux oceans today just 0.27 ± 0.30‰ (1σ) based on steady‐state analysis ocean cycle, would have likely been shifted lower values, possibly than inventory (–0.12 0.10‰, 2σ). Mn oxides main oxidant but there no evidence they formed paleosols. may by direct oxidation molecular oxygen or H 2 O , neither pathway efficient producing Cr(VI). picture emerges this studies isotope variation paleosols atmospheric concentrations high enough oxidize iron, too low Mn, resulting inventories Earth surface environments.