Integrated Geochemical Studies of the Shuram Excursion in Siberia and South China

Abstract

The Ediacaran Period Shuram Excursion (SE) is a globally-distributed and highly controversial phenomenon where over millions of years, sedimentary carbonates record δ13C values of -10‰ and lower. This carbon cycle anomaly may reflect disequilibrium in the world’s oceans, driven by the oxidation of a large pool of dissolved organic carbon (DOC), with the oxidants sourced from the intense weathering of the continents, forcing major changes to ocean chemistry through the ventilation of the deep ocean, evidenced by a positive shift in carbonate uranium isotope values, and invoking the onset of early animal biomineralization. This study utilizes high-resolution carbonate Li isotopes from two SE-successions, U isotopes, REE abundances and Ce anomalies which reveal the dynamic interplay between intensified continental weathering associated with tectonic reconfiguration and the subsequent environmental and ecological response that may have been amplified by the ecosystem-engineering abilities of a newly discovered sponge-grade animal.