The values δ18O obtained from belemnite rostra of Subpolar Urals show extremely high paleotemperatures (20 °C on average) for Kimmeridgian times. This result is commensurate with the data previously obtained from the same locality (18.9 °C) and from adjacent regions: Timan-Pechora (18.5 °C), South Urals and Caspian region (18.6 °C). Somewhat higher values in Subpolar Urals are probably due to the warming of water in a shallow embayment. A warm subsurface current from the west, through the straits of Polar Urals, may also contribute to this local increase in temperature. Besides, the isotope ratio could be influenced by recurrent freshening of surface water owing to fluvial runoffs, which eventually raised the paleotemperature.The evolution of paleotemperatures is in agreement with the succession of biotic events. The general drop in paleotemperatures observed from Early to Late Kimmeridgian corresponds to a decrease in the generic diversity of benthos. The maximum paleotemperatures in the Early Kimmeridgian coincide with the predominance of the thermophile family of bivalves Trigoniidae. A drastical drop in temperature in the Late Kimmeridgian was recorded above and below a bed with the least diversified benthos.Throughout the Kimmeridgian, the composition of benthic communities was steadily dominated by suspension feeders. This implies that bottom water was persistently saturated with oxygen. Low-level deposit feeders appeared in benthic communities as late as the Early Kimmeridgian and were persistent in the Late Kimmeridgian and Early Volgian. They actually were of minor importance in benthic communities. Nevertheless, the occurrence of deposit feeders is indicative of an important event in the history of the Lyapinsky embayment in Subpolar Urals (advanced transgression and general deepening of the sea). A thin interbed of organic-rich shale at the base of the Eudoxus zone is a striking illustration of the maximum transgression. Taking into account that in Eudoxus time the sea covered the maximum areas in the vicinity of the North Sea and on the territory of Great Britain (Wignall, 1994), we can interpret this short episode in sedimentation of organic-rich shale as an indication of eustatic event in northern Eurasia as a whole.
Kimmeridgian, paleontology, paleoecology, lithology, paleogeography, oxygen isotope, paleotemperatures, Subpolar Urals