Drivers of benthic extinction during the early Toarcian (Early Jurassic) at the northern Gondwana paleomargin: Implications for paleoceanographic conditions

摘要: Abstract During the early Toarcian multiple environmental perturbations led to genesis of Oceanic Anoxic Event (T-OAE), expressed by widespread occurrence black shales that were formed under oxygen-deficient conditions. Factors promoting organic matter preservation also drove benthic extinction due low aqueous O2 levels and habitats poisoned H2S. However, development barren intervals in oxygenated shelf areas, lacking shales, indicates even these areas communities experienced a crisis. To understand changes determine factors driving we applied paleontological geochemical techniques matter-lean Ratnek El Kahla section (Saharan Atlas, Algeria). Early Jurassic study site was located at northern Gondwana paleomargin, belonging southern West Tethys Shelf. The interval coincides with climax T-OAE correlates major carbon cycle perturbation, negative isotope excursion. Compared background values, sediments are enriched redox-sensitive metals. In combination enhanced intact bacterial lipids increased rates sulfurization, data attest decline pore water H2S concentration. It is thus reasonable propose that, similar suffered from prolonged Absence activity less intensive sediment reworking sulfurization favored preservation. Productivity proxies δ15N indicate moderate primary productivity rates. Lowered did not result excessive aerobic breakdown. Seafloor anoxia rather promoted rising seawater temperatures sluggish ocean circulation during transition icehouse into greenhouse climate. These conditions may have been pre-requirement for T-OAE.