Enhanced Denudation of the Emeishan Large Igneous Province and Precipitation Forcing in the Late Permian.

Hydroclimate is an important factor controlling landscape evolution. But establishing the impact of hydroclimate is complicated by the influences of other processes and is especially hard to prove for those in deep time from geological record. During the late Permian, voluminous basaltic sediments were derived from the erosion of the Emeishan large igneous province in western South China. They provide a unique record critical in understanding the responses of tropical basaltic erosion to hydroclimate change without impacts of orogenic uplift, lithologic variation, vegetational difference and glacial‐interglacial change. Sampled successions define a negative carbon isotope excursion capable of making regional and global stratigraphic correlations in the middle Wuchiapingian interval corresponding to the final phase of the late Paleozoic ice age. This interval is associated with a petrofacies shift and a decreasing source weathering intensity, a downward shift of erosion loci, and a reduced coastal water paleosalinity. Applying present‐day temperature dependence pattern of basaltic weathering and using land surface temperatures approximated from nearby paleo‐seawaters, denudation rates were calculated for the Emeishan basaltic province and shows an increase from ∼71 to ∼107 m/Ma. This erosional acceleration is temporally correlated with a decrease in paleosalinity and likely linked to enhanced freshwater discharge in the middle Wuchiapingian. Scaling and landscape erosion modeling suggest ∼80%–130% increase in catchment precipitation could have driven this acceleration in denudation. Our work provides a positive test for the hydroclimate forcing on landscape erosion in deep time and underlines the mechanistic linkage of sediments with erosion and climate change. Plain Language Summary: Sedimentary records provide a unique way to track source weathering and erosion in the deep geological past. During the late Permian to early Triassic voluminous basaltic sediments were eroded from the Emeishan large igneous province, which was emplaced at ca. 260 Ma in southwestern China, into the adjacent basins. These late Permian sedimentary records are studied to understand the denudation of this tropical basalt province in the final period of the late Paleozoic ice age (LPIA). Our data reveal a negative organic carbon isotope excursion, decreasing weathering intensity and deepening erosional loci in the Emeishan basaltic province, and a reduced salinity due to greater rainfall in the middle Wuchiapingian interval. Denudation rate was estimated for the Emeishan province and a correlation of high denudation rates with lowered paleosalinity was documented in the Wuchiapingian. The accelerated denudation in the Emeishan basaltic province was ascribed to ∼80%–130% increase in catchment precipitation during the final phase of the late Paleozoic ice age. This work highlights the importance of sedimentary records to understand the deep time landscape evolution. Key Points: A negative carbon isotope excursion enables middle Wuchiapingian stratigraphic correlations from South China to GondwanaA decrease in weathering intensity and a deepening of erosional exhumation are indicated for the Emeishan basaltic provinceDenudation was accelerated due to ∼80%–130% increase in precipitation during the late Permian in SW China [ABSTRACT FROM AUTHOR]