Benthic foraminiferal morphogroups and taphonomy of the Cieszyn beds (Tithonian-Neocomian, Polish Outer Carpathians)

Test gross morphology and taphonomy of calcareous benthic foraminifers from the Cieszyn beds were mainly controlled by depositional parameters, paleoecological conditions and paleogeographical settings. All of these control factors were influenced by a major tectonic event represented by the rifting of the Cieszyn Basin. In its earliest history it acted as a gulf adjacent to the Eastern European Platform. The Tithonian marls and marly shales known in Polish regional geology as the lower Cieszyn shales and Cieszyn limestones yielded highly diverse calcareous benthic foraminiferal assemblages which are dominated by shallow and deep infaunal morphogroups. A remarkably well-developed epifaunal component can be recognized as well. Shelf and peri-reefal foraminifera originally developed their life cycles under well-oxygenated conditions in the immediate proximity of the sea-bottom. The initiation of turbidite sedimentation lead to the removal and transportation of shelf foraminifers into deeper water environments (bathyal). Consequently, the tests of calcareous foraminifers are small, and poorly preserved, presenting dissolution traces, and abraded and corroded surfaces. The mixed and reworked microfauna were replaced by a more uniform one in the proximity of the Jurassic/Cretaceous boundary. Active omnivorous infauna survived not only the change of deposition system but also the deepening of the Cieszyn Basin during Early Cretaceous times. Periodically the supply of reworked and allochthonous calcareous benthic forms into the Cieszyn Basin took place during the Berriasian and Late Valanginian-Hauterivian times.