New Insights Into the Genesis of the “Poznań Clays” – Upper Neogene of Poland

The present study focuses on the upper Neogene deposits, called the “Poznań Clays”, that cover more than 75,000 km² of Poland. They are situated between the first mid- Polish lignite seam and the glaciogenic deposits of the Pleistocene age. Lithostratigraphically, the “Poznań Clays” belong to the uppermost portion of the lignite-bearing Grey Clays Member and the whole Wielkopolska Member (Poznań Formation). The examined fine-grained sediments include mud-rich floodplain deposits with palaeosol remnants and large sandy-muddy or muddy palaeochannel bodies. Therefore, taking into account facies analysis, cross-sectional geometry, and the planform of the palaeochannels, it can be stated that the “Poznań Clays” formed in the environment of a late Neogene anastomosing river.