Sedimentary Environment Evolution and Response to Mesozoic Toarcian Oceanic Anoxic Event (T-OAE) in the Eastern Tethys

Mesozoic Oceanic Anoxic Events (OAEs) are critical geological episodes linked to global carbon cycle perturbations, climate warming, and ecosystem restructuring. However, the regional expression of OAEs in the eastern Tethys remains insufficiently constrained. This study focuses on the Early Jurassic Toarcian OAE (T-OAE)—integrating petrological, mineralogical, and geochemical analyses of two key sections to reconstruct Early Jurassic sedimentary evolution, paleoclimate-paleoenvironment dynamics, and their responses to the T-OAE. Pronounced negative carbon isotope excursions (CIEs) are recorded in both marine strata, correlatable with global T-OAE records. Intensified continental chemical weathering  and enhanced terrigenous detrital input are common responses of the eastern Tethys to T-OAE, driven by global warming. Redox proxies reveal oxic-suboxic conditions in open marine settings of the eastern Tethys during OAEs, regulated by regional factors (water depth, basin restriction, freshwater input), contrasting with the anoxic-euxinic environments in the western Tethys. Bioproductivity showed spatial heterogeneity: organic matter accumulation was controlled by redox conditions and productivity, with high accumulation in restricted lagoons versus low-moderate in open shelves.

This study reveals the regional response patterns of the eastern Tethys to Mesozoic OAEs, highlighting the spatial heterogeneity of redox and productivity dynamics, and provides new insights into the Mesozoic climate-ocean-biosphere system.