Abstract The Ediacaran Shuram Excursion recorded globally in shallow marine carbonates represents a pivotal carbon cycle perturbation coinciding with key tectonic and evolutionary events. While its driving mechanism(s) are debated, our integrated study supports that a marked increase in congruent continental weathering associated with widespread mountain building and high p CO 2 was responsible for this biogeochemical event. Here, we utilize lithium isotope data from two disparately-located carbonate sections in Siberia and South China to assess the intensity and nature of the global continental weathering flux during the Shuram Excursion. Our results indicate nearly crustal δ 7 Li values in Shuram carbonates (~3–5‰), in stark contrast to modern marine carbonate δ 7 Li values (>20‰). This observation suggests that the Shuram Excursion was characterized by intense congruent continental weathering that delivered river water to the global ocean with extremely low δ 7 Li composition, as well as muted fractionation of lithium isotopes associated with marine clay formation. Enhanced congruent continental weathering would have increased the fluxes of nutrients, dissolved ions, and oxidants to the oceans, facilitating primary productivity, potential oceanic oxygenation, and an increase in the oceanic carbonate saturation state that promoted the rapid deposition of carbonates, and possibly set the stage for carbonate biomineralization by metazoans.
Gan et al. (Tue,) studied this question.
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