The Triassic Carbon Cycle Rebuild

This study presents a high-resolution, comprehensive synthesis of the Triassic carbon isotope (δ13C) record, providing critical insights into the interplay between large-scale volcanism, carbon cycle sensitivity, and ecosystem restructuring. Our compilation consists of 4744 data points from 35 sites and reveals a fundamental bifurcation in the Triassic Earth system. The initial ~25 million years were characterized by extreme δ13C volatility, initiated by the Siberian Traps Large Igneous Province (LIP) and sustained through the Wrangellia eruptions. This interval is marked by high-amplitude negative δ13C excursions—reaching magnitudes of 8–10‰—which signify massive injections of δ13C enriched carbon into the exogenic reservoir. These perturbations were followed by significant positive rebounds, reflecting accelerated organic carbon burial during transient phases of ecosystem recovery and nutrient-driven productivity. In contrast, the terminal ~25 million years of the Triassic (Norian–Rhaetian) witnessed a profound decline in isotopic variability, with δ13C fluctuations narrowing to a mere ~2‰. This transition represents a shift toward long-term carbon-cycle homeostasis. We argue that this stabilization was not merely a result of waning volcanic activity, but was fundamentally driven by the establishment of resilient, modern-style ecosystems. The increased complexity and buffering capacity of these newly dominant biotic communities effectively dampened environmental shocks, marking the emergence of a more stable biogeochemical state that persisted until the end-Triassic extinction.