Continental weathering and recovery from ocean nutrient stress during the Early Triassic Biotic Crisis

Following the latest Permian extinction similar to 252 million years ago, normal marine and terrestrial ecosystems did not recover for another 5-9 million years. The driver(s) for the Early Triassic biotic crisis, marked by high atmospheric CO2 concentration, extreme ocean warming, and marine anoxia, remains unclear. Here we constrain the timing of authigenic K-bearing mineral formation extracted from supergene weathering profiles of NW-Pangea by Argon geochronology, to demonstrate that an accelerated hydrological cycle causing intense chemical alteration of the continents occurred between similar to 254 and 248 Ma, and continued throughout the Triassic period. We show that enhanced ocean nutrient supply from this intense continental weathering did not trigger increased ocean productivity during the Early Triassic biotic crisis, due to strong thermal ocean stratification off NW Pangea. Nitrogen isotope constraints suggest, instead, that full recovery from ocean nutrient stress, despite some brief amelioration similar to 1.5 million years after the latest Permian extinction, did not commence until climate cooling revitalized the global upwelling systems and ocean mixing similar to 10 million years after the mass extinction. Following the latest Permian extinction, nutrient availability from enhanced continental weathering enabled biological recovery in the ocean, according to K-Ar dating of clay minerals and nitrogen isotope analyses from high northern latitudes.

Automated summary

This study reveals that intense continental chemical alteration occurred during the Early Triassic period due to an accelerated hydrological cycle. Although the enhanced ocean nutrient supply did not trigger increased ocean productivity, the recovery from ocean nutrient stress began around 10 million years after the mass extinction, when global upwelling systems and ocean mixing were revitalized.