Oceanic Anoxic Event 2 (OAE2; ca. 94 Ma) represents one of the most profound perturbations to the global carbon cycle during the Cretaceous greenhouse climate and has been widely linked to large igneous province (LIP) volcanism. However, the temporal evolution of volcanic activity during OAE2 and its environmental consequences remain poorly constrained. Here, we present high-resolution records of sedimentary mercury (Hg) concentrations and Hg isotopes (Δ¹⁹⁹Hg) from the Gongzha section in southern Tibet. Three prominent Hg enrichment events are identified during OAE2, including one major pulse during the early stage C3 and two successive peaks near the C3–C4 transition. Elevated Hg/TOC ratios coupled with positive Δ¹⁹⁹Hg values indicate enhanced input of volcanogenic Hg delivered primarily through atmospheric transport and deposition. Correlation with Hg records from the Eastbourne section indicates that these events reflect globally significant volcanic pulses.
Integration of published paleoenvironmental proxy records suggests that the three volcanic pulses exerted contrasting environmental effects during OAE2. The initial pulse coincided with intensified weathering, enhanced nutrient supply, and expanding marine anoxia, suggesting a key role in triggering OAE2. In contrast, the subsequent pulses were considerably weaker and produced more limited environmental perturbations, although they may have intermittently enhanced nutrient delivery and marine productivity. Under persistently anoxic conditions, phosphorus recycling–driven feedbacks likely became increasingly important in sustaining elevated productivity and widespread marine anoxia during the later stages of OAE2. This study provides new constraints on the pacing of volcanism during OAE2 and highlights the role of pulsed volcanic forcing in driving earth system instability under extreme greenhouse conditions.
Keywords: OAE2; Southern Tibet; Volcanism; Mercury isotopes; Large igneous provinces