Foraminiferal Response to Oceanic Anoxic Events: Tethyan Case Studies

Oceanic Anoxic Events (OAEs) represent intervals of widespread marine oxygen depletion that profoundly altered global biogeochemical cycles and marine ecosystems during the Mesozoic. Foraminifera, as sensitive and rapidly evolving marine microfossils, provide a high-resolution record of ecological stress, extinction patterns, and recovery dynamics associated with these events. foraminiferal responses to major OAEs within the Tethyan realm, integrating sedimentological, geochemical, and micropaleontological datasets from key carbonate and pelagic successions. Case studies from the western and eastern Tethys, including sections in Italy, Tunisia, Oman, and South China, reveal consistent ecological restructuring during OAE intervals. Benthic foraminiferal assemblages show marked reductions in diversity, test size diminution, and increased dominance of opportunistic and low-oxygen tolerant taxa. Planktic foraminifera exhibit shifts toward smaller, thin-walled morphotypes, reflecting surface-water stratification and nutrient imbalance. These biotic patterns closely coincide with positive carbon isotope (δ¹³C) excursions, enhanced organic carbon burial, and trace metal enrichments indicative of dysoxic to euxinic conditions.