The geology of the deepest Cenozoic lignite-rich grabens in Poland with particular reference to their lithostratigraphy: a comparative study

Abstract

The thickest lignite seams in Poland are located in tectonic depressions such as the Kleszczów, Złoczew, and Lubstów grabens, as well as the Zittau (Żytawa) Basin. Their depth ranges from 220 m to 550 m, while the maximum lignite thickness ranges from approximately 90 m to over 250 m. The areas selected for this study include two Miocene lignite seams that have been exploited or prepared for mining, i.e. the third Ścinawa lignite seam (ŚLS-3) and the second Lusatian lignite seam (LLS-2). Currently, more than 95% of the Polish lignite production comes from the exploitation of these seams. Both lignite seams are accompanied by siliciclastic sediments that are lithologically very diverse. The lignite-rich grabens examined in this study form isolated structures and their individual geology is complex. Hence, apart from the Lubstów Graben, local lithostratigraphy is applied for each case, an approach that makes it difficult to compare the lithological units and their stratigraphic position with the Paleogene and Neogene lithostratigraphy used for the Polish Lowlands area. Therefore, it seems appropriate to present an outline of the geology of the Polish regions bearing most of the lignite seams, including a brief overview of their lithological and palaeotectonic characteristics. However, it is first necessary to clarify and compare the lithostratigraphy of the Cenozoic sediments that fill the studied grabens.