Geochemical and palynological evidence for a two-phased end-Triassic mass extinction in the Paris Basin (Lorraine, France)

The Triassic-Jurassic transition, from the Norian to the Hettangian (corresponding to the Rhaetian), was a critical timespan marked by a series of global environmental perturbations, most notably the end-Triassic mass extinction event (201.6 Ma). Here, we present palynological, mineralogical, geochemical, and sedimentological data obtained from new core material spanning the Upper Triassic to Lower Jurassic in the northeastern Paris Basin. Together, these data give new insights into the link between terrestrial and marine extinctions, and their respective driving mechanism. The Boust core (Lorraine, France) provides a complete succession of marginal marine sedimentation. The δ¹³C_org record from Boust reveals two major C-isotope excursions that, based on the available biostratigraphy, correspond to the Negative-1 (Marshi) and Negative-2 (Spelae) negative isotope excursions. While the Marshi excursion is marked by high abundances of dinoflagellate cysts, the Spelae excursion is marked by an influx of acritarch species. The two excursions bracket an interval of strongly diminished tree pollen abundances and proliferation of fern spore taxa, marking the extinction interval associated with the ETME and forming an equivalent to the Triletes Beds in Germany. This subdivision is confirmed by sedimentological and geochemical results as well as by lithological changes, which are reflecting the development of the depositional environment during the Rhaetian.