Latest Triassic marine Sr isotopic variations, possible causes and implications

Large igneous provinces have been suggested to trigger global environmental perturbations and, in turn, major biotic crises. The high resolution of marine biostratigraphy is here applied to constrain the detailed timing of the Central Atlantic Magmatic Province onset. Analyses of biogenic apatite from stratigraph- ically well-constrained Tethyan realm conodont samples indi- cate two significant shifts of the oceanic 87Sr ⁄ 86Sr composition during the latest Triassic: a rapid drop of 87Sr⁄86Sr during the lower Rhaetian, followed by an increase during the upper Rhaetian. These shifts are positively correlated with synchro- nous variations of oceanic 187Os ⁄ 188Os and they may be attributed to a rapid emplacement and erosion of the Central Atlantic Magmatic Province, followed by a rapid increase in continental weathering. These interpretations require a short duration for the Rhaetian stage (<2 Ma) and are consistent with volcanogenic triggering of end-Triassic climatic perturbations and biotic crisis starting from the Norian–Rhaetian and culmi- nating at the Triassic–Jurassic boundary.