Faunal condensation and mixing in the•uppermost Maastrichtian/Danian Greensand (Middle Vistula Valley, Central Poland)

Abstract

The Greensand exposed at Nasiłów and Bochtnica near Kazimierz-on-Vistula (Middle Vistula Valley, Central PoIand) contains diverse uppermost Maastrichtian and Danian fossils. One may here distinguish the phosphatized Maastrichtian, unphosphatized Maastrichtian and the Danian assemblages. Their occurrence in the Greensand is a result of condensation and mixing processes, among which the most important were: the formation of the residual lag composed of fossils and concentrations, and the vertical displacement of sediment·and fossils by infaunal organisms. The recognition of the complex history of fossil assemblages in connection with sedimentologicaI data permits to place the Cretaceous/Tertiary boundary within the Greensand just below the residual lag.