Biostratigraphy of Upper Jurassic of the Valy clay pit (Samarskaya Luka) by ammonites, ostracods and dinocysts

The results of integrate biostratigraphic study Upper Jurassic deposits the clay pit near village Valy (Syzran district, Samara region) are presented. For first time a bed-by-bed description was made and subdivision section into zones, subzones biohorizons by ammonites established. Bauhini Kitchini zones (Bayi subzone) established in Lower Kimeridgian, while Kimmeridgian is represented Autissiodorensis zone only. In Volgian Sokolovi Pseudoscythica were recognized, Middle Panderi zone. age regionally developed unconformity at base Trazovo Formation has been clarified. As sections located to south from studied section, this zone, overlying different Oxfordian lower Kimmeridgian. for Central Russia marlstone band (bayi biohorizon) solitary corals conditionally attributed genus Trochocyathus found. Along with other warm-water taxa (belemnites Hibolithes, rare Taramelliceras) found same bed, suggesting deposition bed during short-time warming event. 6 units (zone beds fauna) recognized ostracods, along 2 dinocyst-based (assemblage zone) which compared stratigraphic subdivisions these groups, previously proposed Kimeridgian stages Russian Platform. paleo-ecological analysis allowed assume, that sediments have accumulated conditions warm shallow eutrophic basin depth 50 m, gradual increase eutrophy through time. At some levels, short-term episodes severe shallowing or freshening recorded ostracods.