Formation of microbial organic carbonates during the Middle Oxfordian (North East Amu Darya Basin, Uzbekistan): palaeoenvironmental significance and implications for Jurassic anoxic events

International audience; The Late Jurassic was a period of major global carbon cycle perturbations with episodes of anoxia leading to regional accumulation of organic matter in sediments worldwide. The Tubegatan section (SW Gissar Mountains, Uzbekistan) located in the Northern Tethys, shows atypical organic-rich limestone and marl deposits (up to 6% of total organic carbon) marked by pronounced excursions of δ13Ccarb (amplitude of ca. 12‰) and δ13Corg (amplitude of ca. 4‰) recorded during the Middle Oxfordian (Transversarium Zone). A transdisciplinary approach including sedimentology, palynofacies study, mineralogy, organic and inorganic geochemistry was carried out to elucidate the origin o…