First insights into the Devonian–Carboniferous boundary conodonts from the depression deposits of the Kama-Kinel Trough System, East European Platform (Volga-Ural petroleum province, Sarailinskaya Depression)

Conodonts from the Devonian–Carboniferous boundary deposits in two wells within the Sarailinskaya Depression of the Kama-Kinel Trough System were studied. The expansa conodont zone (Upper Famennian) was recognized, as well as the duplicata and quadruplicata conodont zones (Lower Tournaisian). Platform conodonts were absent in the intervals between the well-defined Famennian and Tournaisian deposits in both wells. These stratigraphic intervals span the praesulcata (uppermost Famennian) and sulcata (lowermost Tournaisian) conodont zones and are likely to be associated with the global Hangenberg Extinction Event. The conodont changes across the Devonian–Carboniferous boundary indicated a restructuring of the conodont assemblages between the Famennian and Tournaisian, with the dominant Devonian genera ( Palmatolepis , Branmehla , and Bispathodus ) replaced by the genus Siphonodella in the early Carboniferous. Data on the conodont distribution were presented, along with SEM images of index species.