Evolution of volcanic activity and its impact on continental weathering, paleoproductivity, and runoff during the early Aptian in southern Tibet (eastern Tethys): Implications for regional to global environmental perturbations

The Oceanic Anoxic Event 1a (OAE1a), or the Selli Event, occurred in the early Aptian (~120 Ma) and represents an episode of global carbon-cycle perturbation caused by substantial greenhouse gas emissions, leading to profound environmental and climatic changes. However, our understanding of the impact of OAE1a in the eastern Tethys region, particularly regarding regional volcanic activities in southern Tibet and their influence on environmental changes, remains limited. Here we presented high-resolution inorganic and organic geochemical data from marine sediments of the lower Aptian Gucuo Formation in southern Tibet (eastern Tethys). This study aims to reveal the impact of volcanic activity and related regional to global environmental perturbations, such as continental weathering, detrital input, and bioproductivity. Our results suggested that the lower Aptian sediments in southern Tibet were influenced by regional volcanic activity linked to the disintegration of eastern Gondwana. Continental weathering showed a declining trend preceding the OAE1a, followed by a significant increase at the onset of OAE1a associated with regional volcanic activities in southern Tibet. Additionally, changes in weathering intensity at the Gucuo area coincided with contemporaneous weathering signals observed in the western Tethyan and Boreal realms, indicating a supra-regional intensification of continental weathering at this time. Increased fluvial detrital input revealed heightened continental runoff at the onset of OAE1a, driven by elevated continental weathering. The role of marine primary productivity during the early Aptian was governed by regional volcanism, global climate, and hydrological cycling. Prior to OAE1a, nutrient-rich inputs from regional volcanic sources and volcanism-induced climate variation controlled bioproductivity evolution. High biological paleoproductivity at the onset of OAE1a was associated with increased nutrient input under enhanced continental weathering and riverine runoff linked to warm and humid climates. This study contributes to our understanding of organic carbon distribution in the eastern Tethys region and its correlation with TOC patterns observed in the western Tethys realm.