Volcanism as trigger of Sinemurian/Pliensbachian environmental changes? Evidence from Lower Jurassic marine (Western Tethys, Italy) and continental (Sichuan Basin, China) successions

The Sinemurian–Pliensbachian transition in the Early Jurassic is characterized by a negative perturbation of the global carbon cycle named “Sinemurian–Pliensbachian Boundary Event” (SPBE, ~192.5 Ma). The SPBE is associated with sedimentological evidence of environmental and climate changes such as increased runoff, modifications in marine shallow water carbonate production, enhanced preservation of organic matter, dysoxic conditions in the oceans end possible hyperthermal intervals. The SPBE has been mainly reported in the marine realm, while other sedimentary settings around the world has been less investigated, and its causes are still unclear. This study reports records of mercury abundance and other geochemical data (TOC, δ13Corg, ∆199Hg, ∆202Hg) from two stratigraphic sections from the continental succession of the Sichuan Basin (Eastern Tethys) and the deep marine Lombardian Basin (Western Tethys). δ13Corg Results allow refining global scale correlations with other marine records and highlight that the SPBE time is characterized by Hg enrichments both in continental and marine realms. The relative low correlation of Hg content with TOC data and the clay minerals abundances, points to a volcanogenic source of the mercury. This is further confirmed by ∆199Hg, ∆202Hg data. The fact that mercury enrichments are seen both in the continental and the marine deep-water sedimentary record, strengthen the global significance of the environmental changes occurred at the SPBE and point to enhanced volcanism as their primary driver, calling for further investigations to identify where such volcanic activity was taking place.