ORIGIN AND TAXONOMY OF THE NEOPLEISTOCENE-HOLOCENE PONTO-CASPIAN BENTHIC FORAMINIFERA

Abstract

This paper outlines the origin and taxonomy of the Neopleistocene—Holocene Ponto-Caspian benthic foraminifera for their future use in stratigraphy, geological history, and paleogeographic reconstructions, including water exchange between the neighboring basins. It is shown that the Caspian foraminiferal fauna is shallow, highly endemic (92%), and contains many (61%) agglutinated species and subspecies. The Pontic foraminiferal fauna is characterized not only by insignificant endemism (0.6%) at the species and subspecies level, but also by a large number (83%) of Mediterranean and Atlantic (mainly boreal) forms. All Pontic (Azov-Black Sea) foraminifera are shallow, most probably due to the shallowness of the Bosphorus or any other strait that connected the Pontic and Mediterranean basins to each other. The particular group of the Ammoniidae- Elphidiidae creates a unique image of the Ponto-Caspian foraminiferal assemblages and indicates a tendency of forming foraminiferal fauna from a limited number of shelf genera of the southern genesis Ammonia, Elphidium, and Porosononion typical for the southern closed and semi-closed seas. The low number of high rank taxa (orders) is a result of the low salinity of the Ponto-Caspian and its restricted connection to the open ocean. The main concept of the origin and taxonomic peculiarities of the Ponto-Caspian benthic foraminifera is as follows. The foraminiferal fauna of the Caspian Sea originated largely from the Tethys and Eastern Paratethys. They evolved in a basin that was isolated from the World Ocean for a long time. The foraminiferal fauna of the Black Sea has a Mediterranean-Atlantic-Caspian origin. It is younger when compared to the Caspian fauna, and is characterized by much smaller evolutionary transformations, but much higher taxonomic diversity. The foraminiferal fauna of the Ponto-Caspian is formed by representatives of a limited number of euryfacies orders (Ammodiscida, Astrorhizida, Ataxophragmiida, Buliminida, Lagenida, Miliolida, Rotaliida) characteristic of the internal and marginal seas and their specific hydrological regime.