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 km 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.