Biostratigraphy and paleoenvironment of the Sarmatian (s. l.) deposits from the eastern part of the Moldavian Platform (Comarna borehole) based on foraminifera

Abstract

Due to the change of the Paratethys’ marine regime with normal salinity to the brackish regime, the Moldavian Platform deposits of this time period are characterized by euryhaline microfaunal forms. Foraminifera species Lobatula lobatula (W. et J.) (Cibicides lobatulus W. et J.), Cycloforina karreri ovata (Serova) (Quinqueloculina karreri ovata Serova), Cycloforina fluviata (Vengl.) (Q. fluviata Vengl.) mark the beginning of the Sarmatian period in the Moldavian Platform; the presence of other genera, like Nonion, Elphidium, Articulina indicate that part of the Upper Badenian specific microfauna adapted to lower salinity water of the Paratethys. Having a small size, the Cibicides genus, marks the sudden change in the environmental conditions and the installation of the brackish regime. The predominance of benthic foraminifera forms indicates a normal oxygen content at the substrate surface, and the abundance of foraminifera species with calcareous tests indicates that the sedimentation of the Lower Sarmatian deposits was made in warm sea conditions.