Marine Strontium Isotope Evolution at the Triassic-Jurassic Transition Links Transient Changes in Continental Weathering to Volcanism of the Central Atlantic Magmatic Province

The end-Triassic extinction (ETE) is one of the most severe biotic crises in the Phanerozoic. This event was synchronous with volcanism of the Central Atlantic Magmatic Province (CAMP), the ultimate cause of the extinction and related environmental perturbations. However, the continental weathering response to CAMP-induced warming remains poorly constrained. Strontium isotope stratigraphy is a powerful correlation tool that can also provide insights into the changes in weathering regime, but the scarcity of 87Sr/86Sr data across the Triassic-Jurassic boundary (TJB) hindered the use of this method. Here we present new high-resolution 87Sr/86Sr data from bulk carbonates at Csovar, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in 87Sr/86Sr ratio from the late Rhaetian to the ETE, terminated by a 300 kyr interval of a flat trend and followed by a transient increase in the early Hettangian that levels off. We suggest that the first in the series of perturbations is linked to the influx of non-radiogenic Sr from the weathering of freshly erupted CAMP basalts, leading to a delay in the radiogenic continental weathering response. The subsequent rise in 87Sr/86Sr after the TJB is explained by intensified continental crustal weathering from elevated CO2 levels and reduced mantle-derived Sr flux. Using Sr flux modeling, we also find support for such multiphase, prolonged continental weathering scenarios. Aggregating the new data set with published records employing an astrochronological age model results in a highly resolved Sr isotope reference curve for an 8.5 Myr interval around the TJB. The end-Triassic mass extinction similar to 201 million years ago was one of the most severe crises in the history of life, triggered by massive volcanism in areas around the present-day Central Atlantic Ocean. Although volcanism is expected to produce greenhouse warming through carbon-dioxide outgassing that leads to increased weathering in the continents, finding direct proof for such a scenario is challenging. We report new measurements of the ratios of strontium isotopes from marine limestones and reconstruct the weathering history at the Triassic-Jurassic transition. In the ocean, unradiogenic 86Sr isotopes are sourced from submarine volcanism or weathering of fresh volcanic rocks from Earth's mantle, whereas radiogenic 87Sr isotopes are delivered by rivers from weathering of rocks in Earth's continental crust. We find that a steady long-term decreasing trend in strontium isotope ratio was disturbed by a series of short-term changes at the end of the Triassic. Supported by modeling, we suggest that these changes reflect the eruption of basalts of the Central Atlantic Magmatic Province and the effect of volcanism in intensifying the continental weathering. Knowing more detail about one component in a cascade of environmental changes ultimately helps our understanding of a critical event in the history of the Earth and its biosphere. High-resolution 87Sr/86Sr data spanning 2.5 Myr across the end-Triassic extinction reveals multiphase perturbation of the marine Sr system Aggregation with other Sr data documents long-term and short-term changes over 8.5 Myr during the Triassic-Jurassic transition Modeling supports the role of Central Atlantic Magmatic Province volcanism in a stepped weathering scenario of fresh basalt and continental crust