THE KAZANIAN OF THE VOLGA-URALS REGION

By the early Late Permian, the Urals mountain system had completely replaced the remains of an ocean. This resulted in an inversion of the Platform relief and the formation of an Upper Permian sedimentary basin. During the period of maximum development (Kazanian), the basin was filled with sea water to become a complex system: marine in the west and typically molassic-continental in the east. The molassic area widened during the elevation of the Urals causing regression of the sea. The processes of denudation in turn narrowed the continental molassic zone causing a transgression so that the sea was fully replaced by late Kazanian times. The axis of the sedimentary basin gradually moved to the west where sedimentation continued up to late Early Triassic time.

The development of normal marine conditions in this area took place at its maximal rate during Early Kazanian time when the sedimentation was accompanied by the reiterative development of the formation of bryozoan-crinoid bioherms along the eastern margin of the sea. Kazanian deposits in the Vyatka River area contain a diverse marine fauna including bryozoans, brachiopods, ostracodes, foraminifers, ammonoids, and conodonts. Limestone above a bioherm in the Nemda River basin contains the ammonites Sverdrupites ex gr. S. harkeri, Popanoceras ex gr. P. subtumarense, Altudoceras sp., Medlicottia sp. and Neuddenites sp. Particularly noteworthy is the location in one place of two endemic forms from the Arctic province, Neuddenites sp. and Sverdrupites ex gr. S. harkeri. The eastern sections of the Kazanian are characterised by the presence of the conodonts Kamagnathus khalimbadzhae, K. volgensis and Stepanovites meyeni Kozur. A species similar to Kamagnathus khalimbadzhae has been found in the Phosphoria Formation (Roadian/Wordian) of Utah. The cyclic alternation of marine and continental conditions permits a broader description of the Kazanian by using the marine and continental flora and fauna.