Homotryblium-dominated Eocene dinoflagellate cyst assemblages from Middle Miocene (Badenian) glauconitic sands at Lipowiec (Roztocze, SE Poland)

Abstract

A section over 20 m thick of the basal Middle Miocene succession exposed at Lipowiec (Roztocze, SE Poland) was studied for palynology. Thirteen samples were collected from quartz and glauconitic-quartz sands and thin clay layers. Sand samples were barren but clay samples yielded dinoflagellate cysts. Their assemblages consist of reworked Paleogene specimens dominated by the Homotryblium floripes complex (H. floripes and morphologically similar H. plectilum and H. vallum). The presence of reworked Paleogene specimens indicates intense erosion of marine Paleogene strata during initial stages of the Middle Miocene transgression at Roztocze. Analysis of stratigraphical ranges of reworked dinoflagellate cysts and comparison with their occurrences in known epicontinental Paleogene sites of SE Poland suggest an Upper Eocene age of the washed-out strata. The taxonomic composition of the assemblages described suggests that the Upper Eocene deposits accumulated in a near-shore, lagoonal embayment characterized presumably by oligotrophic waters of slightly increased salinity. A high proportion of the Homotryblium floripes complex is also characteristic of reworked assemblages found in younger Miocene strata of neighbouring exposures in Roztocze, which indicates widespread Eocene lagoonal environments in this part of Roztocze. Coeval Eocene strata from the eastern part of Roztocze and from the Carpathian Foredeep show different taxonomic compositions suggesting varied sedimentary settings during Eocene transgression in this region. These differences reflect variable amounts of freshwater influence resulting in a range of environments that ranged from oligotrophic to brackish.