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) compromised the use of this method. Here we present new high-resolution 87Sr/86Sr data from bulk carbonates in Csővár, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in 87Sr/86Sr the from the late Rhaetian to the ETE, terminated by a 300 kyr interval of no 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 scenario. Aggregating the new dataset 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.

Tritium (³H) has become synonymous with modern groundwater and is used in a myriad of applications, ranging from sustainability investigations to contaminant transport and groundwater vulnerability. This study uses measured ³H groundwater activities from 722 samples locations across South Africa to construct a ³H groundwater distribution surface. Environmental co-variables are tested using geostatistical analysis to constrain external controls on ³H variability, namely: [1] depth to the water table, [2] distance from the ocean and [3] summer vs winter rainfall proportion. The inclusion of co-variables in the ‘fit’ of residual variograms improved prediction variance significantly, yet does not mitigate issues with sample density. The distribution of ³H in groundwater surface agrees well to expected controls, with proximal (<100km) coastal regions, winter rainfall zones and deeper groundwater tables predicted to have lower ³H activities. Conversely, inland localities with shallower water tables and/or summer rainfall are predicted to have elevated ³H activities. High groundwater ³H anomalies could potentially be attributed to uranium-bearing deposits, as geogenic production of ³H amplifies the activity contributed through recharge. Some ³H high and low anomalies cannot be explained by known phenomena and may simply be regions of variable recharge and/or longer isolated groundwater flow paths. Regions of active recharge are more vulnerable to climate change as well as modern pollution. Less actively recharged groundwater may be more resilient to climate change, yet represents a potentially non-renewable resource for abstraction. The application of ³H distributions in the assessment of hydrological resilience is pertinent to effective groundwater management studies.