Abstract

Volcanism from large igneous provinces is often inferred to have had a significant global environmental impact, but demonstrating synchronicity between the volcanism and sedimentary records of environmental change is not straightforward. Several studies use sediment Pb isotopes to fingerprint the timing of input of volcanic Pb from a particular large igneous province. Published data on Ocean Drilling Program Site 1149B sediments in the Pacific Ocean, associated with the Valanginian δ13C excursion that has been linked to the Paraná-Etendeka volcanism in central South America and Namibia, require input of radiogenic Pb. The Pb isotope analyses of Paraná-Etendeka lavas show that this radiogenic Pb is uniquely associated with the large-volume silicic eruptions rather than the effusive basaltic lavas. This strengthens the case for a temporal link between the Paraná-Etendeka volcanism and the Valanginian δ13C excursion. Although basaltic magmatism dominates the province (>95%), there is no evidence for Pb associated with volatile metal degassing from such eruptions in the Site 1149B sediments on the other side of the globe, suggesting that eruption columns produced by the basaltic eruptions did not reach the stratosphere. Instead, the widespread global dispersal of Pb is apparently linked to the ability of large-volume (>1000 km3) silicic eruptions to loft aerosols into the upper stratosphere.

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