Paleogene–Neogene tectonic evolution of the lignite-rich Szamotuły Graben

The Szamotuly Graben covers the southernmost part of Permo-Mesozoic Poznan–Szamotuly Fault Zone. Along this regional discontinuity there are several salt structures, including diapir, over which an extensional graben formed in Paleogene and Neogene. is located north Poznan central-western Poland, NW–SE-trending, ~20 km long, 3–5.5 wide, up to 160 m deep. It filled with Lower Oligocene Neogene sediments, relatively thick lignite seams. Data from boreholes allow assignment graben-fill sediments appropriate lithostratigraphic units. Furthermore, analysis of changes thickness these units provides evidence for periods accelerated subsidence or uplift relative its flanks. As a result, two distinct stages tectonic subsidence one inversion the Paleogene–Neogene evolution have been distinguished. Thus, significant subsidence occurred Early middle Early–earliest Mid-Miocene, while slight inversion took place Mid-Miocene.