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