Keywords: 
• end-Triassic mass extinction /
• large igneous provinces /
• sedimentary mercury records /
• pulsed volcanism /
• spatiotemporal relationships

Abstract: [Objectives] The End-Triassic Mass Extinction (~201.5 Ma) is one of the “Big Five” mass extinction events of the Phanerozoic and is characterized by a two-pulsed extinction pattern in marine ecosystems. While widespread volcanism associated with the Central Atlantic Magmatic Province (CAMP) and subsequent massive carbon emissions are widely regarded as the principal driving mechanism, the precise spatiotemporal relationship between specific CAMP magmatic phases and the two discrete extinction pulses remains a subject of intense debate. This study aims to clarify whether these pulses were driven by immediate volcanic toxicity or delayed environmental feedbacks triggered by sustained igneous activity. [Methods] To address this, we present high-resolution sedimentary mercury (Hg) records from Dove’s Nest drilling cores, located in the Cleveland Basin (UK). Mercury is utilized here as a sensitive proxy for large-scale volcanic outgassing. To move beyond qualitative descriptions, we employed a coupled mercury?carbon emission model to quantitatively evaluate the degassing processes and the scale of CAMP activity. Furthermore, we utilized potassium/aluminum (K/Al) ratios as a robust proxy for continental weathering intensity. By integrating these geochemical datasets with previous high-resolution biostratigraphy and paleontological records, we investigated the dynamic coupling between volcanic pulses, continental weathering rates, and the staged collapses of marine biodiversity. [Results] Our analysis identifies two distinct phases of Hg enrichment within the Dove’s Nest drilling core. The first enrichment phase occurs at the base of the Cotham Member in the Rhaetian; however, its occurrence is restricted to specific local profiles, suggesting it represents a regional signal rather than a global volcanic event. In contrast, the second Hg enrichment phase spans from the top of the Cotham Member to the Langport Member. This latter phase is characterized by a significant, sustained increase in Hg concentrations that coincides precisely with the first marine extinction pulse and slightly predates the onset of the second pulse. Crucially, this second Hg anomaly is globally correlative, appearing in both marine and terrestrial sections across different paleolatitudes, which confirms its origin from large-scale CAMP activity. [Conclusions] The widespread distribution of sedimentary Hg enrichment across global marine and terrestrial profiles during the late Rhaetian provides strong evidence for massive, episodic CAMP activity. We propose a staggered casual mechanism for the ETME: the initial phase of volcanism triggered the first extinction pulse through direct, short-term mechanisms. These likely included rapid sea-surface temperature spikes and the fallout of toxic substances (e.g., Hg and SO?), leading to an immediate decline in regional and global biodiversity. Subsequently, the sustained and cumulative release of CO? drove prolonged global warming and a significant intensification of the hydrological cycle, as evidenced by elevated K/Al ratios. This intensified continental weathering accelerated the flux of terrestrial nutrients (such as phosphorus) into the oceans, fueling primary productivity and causing the expansion and intensification of marine anoxia, indirectly triggering the second extinction pulse. This study highlights the staged nature of environmental collapse and biological extinction driven by large igneous provinces in deep time, providing an important deep-time analogue for understanding the complex responses of marine ecosystems to ongoing global warming.