Lithium Isotope Evidence for Enhanced Continental Weathering at ~1.4 Ga

The Mesoproterozoic (ca. 1.6‒1.0 Ga) is primarily characterized by pervasive tectonic stasis under greenhouse climate. However, the coeval weathering regime still remains elusive. Here, we conduct comprehensive investigations (including detrital δ7Li values, elemental compositions, and clay mineral assemblage) on the 1.4-billion-year-old iron formation (IF) hosted shales from the Xiamaling Formation to reconstruct coeval detailed continental chemical weathering history. Our results show a ‒3.5‰ δ7Li excursion, in comparable to Paleocene–Eocene Thermal Maximum (PETM), and notably high chemical index of alteration (CIAcorr) values (> 80) during the deposition of iron formation. This intensification of continental chemical weathering was probably triggered by increased exposure of easily weatherable rocks in the tropics. Furthermore, the enhanced nutrients availability, resulting from enhanced continental weathering, could have boosted marine primary productivity, thereby facilitating increased organic carbon burial and atmospheric oxygenation.