Vegetation Response and Floral Turnover During the Carnian Pluvial Episode: Insights from High-Resolution Macrofossil and Palynological Data in South China 13

The Carnian Pluvial Episode (CPE; ~237–232 Ma) represents a pivotal interval of global climatic perturbation and biotic restructuring. This study investigates plant macrofossil assemblages from the Jiuligang Formation in the Jingmen-Dangyang Basin, South China. Our results reveal an abrupt transition from xerophytic vegetation to a high-biomass, diverse hygrophilous flora at the base of Layer 5. This “biological pulse”, dominated by Marattiaceae (e.g., Danaeopsis) and Dipteridaceae, signifies the establishment of dense subtropical-tropical rainforests in response to intensified hydrological cycling. The CPE onset likely occurred within the lower Jiuligang Formation, evidenced by the sudden proliferation of hygrophilous taxa. Notably, peak floral diversity in Layer 8 reflects the complex, multi-pulse nature of the CPE, consistent with global oscillations. Biogeographically, the Jiuligang flora serves as a critical “bridge” between the Northern (Danaeopsis-Bernoullia) and Southern (Dictyophyllum-Clathropteris) realms, representing a transitional ecosystem and communal habitat for disparate Late Triassic lineages between the Yangtze Platform and North China Block. On a macro-evolutionary scale, the Carnian in South China represents a “Great Biotic Reset”. A sharp spike in the origination rate (Rori) facilitated a fundamental restructuring from depauperate Middle Triassic recovery phases to the taxonomic zenith of the “Southern Flora” in the Norian–Rhaetian. This study underscores the CPE as the primary driver of Late Triassic terrestrial biodiversity and provides a high-fidelity benchmark for global land-sea biotic correlations.