Interfacial assemblages of foraminifera in the Carpathian Flysch

Abstract

O międzyrytmowych zespołach otwornicowych we fliszu karpackim Aggregates of small, benthonic Foraminifera occur at the interfaces between thin, fine-grained sandstone and shale layers of successive beds in sequences of Eocene flysch belonging to the Magura Series, Polish Western Carpathians. These interfacial assemblages are frequently seen as intermittent layers of thickness equal to the diameter of a single test. For descriptive purposes, four different types of interfacial assemblage were named after the most commonly occurring genera. Varying degrees of lateral displacement of foraminiferal tests by the currents which deposited fine sand above the interfaces may be deduced. In many cases, however, lateral displacement of tests was at a minimum and the interfacial assemblages are residua, formed when bottom muds were selectively eroded by sand-bearing currents. The burrowing activities of larger invertebrates were effective in the disruption of interfacial assemblages and in the mechanical fragmentation of tests.