Repeated pulses of volcanism drove terrestrial vegetation and climate changes during the Late Triassic Carnian Pluvial Episode in North China

Abstract

The Late Triassic Carnian Pluvial Episode (CPE; ∼234–232 Ma) witnessed profound changes in terrestrial ecosystems, vegetation, and climate, which could be related to eruptions of Wrangellia Large Igneous Province (LIP). Nonetheless, the scarcity of detailed terrestrial plant records limits understanding of whether these floral and climate changes were synchronized with Wrangellia's eruption pulses. Here, we investigated high-resolution palynological data through the CPE from the Jiyuan terrestrial Basin in North China. Our data reveal four distinct phases of terrestrial vegetation transition from xerophytes to hygrophytes, with each shift accompanied by pronounced climate transformations from relatively cool-dry to relatively warm-humid conditions. Each vegetation shift is linked temporally with volcanic activity indicators including negative organic carbon isotope excursions, Hg and Hg/TOC peaks, and near-zero Δ¹⁹⁹Hg isotope values. After the first, third and fourth eruptions, vegetation recovery showed resilience with floral reassembly broadly similar to pre-eruption floras. In contrast, the impact of the second eruption was apparently larger and triggered more dramatic changes including a surge in terrestrial plant diversity and hygrophytic species, with vegetation recovery having a distinct and more modern floral composition (e.g., Dipteridaceae, Matoniaceae, Pinaceae, and Podocarpaceae) that persisted after the CPE. Our findings offer new insights into the links between LIP volcanism and terrestrial vegetation and climate changes during the CPE, and demonstrates differential floral and climatic responses to different scales of major CO₂-driven global warming events in deep time in otherwise similar environmental contexts.