Utwory mioceńskie w strefie uskokowej środkowej Odry, między Lubinem a Bytomiem Odrzańskim (bez warstw poznańskich)
Abstract
Lithostratigraphy and depositional setting of the Miocene deposits between the vicinities of Lubin and Bytom Odrzański in the middle-Odra dislocation zone, Sudetic Foreland
Abstract
The Miocene succession under consideration (excluding the Poznań Beds), itself averaging more than 250 m in thickness, is part of the sedimentary basinfill of an extensive Tertiary basin of the Central European Lowland. The sedimentary succession is, therefore, characterized by considerable lithostratigraphic and genetic similarities to the Miocene sequences of the remaining parts of Polish Lowland and of the nearby region of Lusatia (East Germany). Lithostratigraphical and sedimentological investigations enabled the writer to distinguish five lithological units within the Miocene succession in the study area. These are reviewed below according to their ascending stratigraphic order.
The Rawicz Beds (Lower Miocene) consist of light coloured, kaoline-rich clayey deposits containing numerous detrital grains of weathered feldspar. These sediments are inferred to have originated through fluvial deposition in an alluvial-fan environment. Temporal development of local swamps and vegetation cover within abandoned alluvial-fan segments resulted in the origin of lenticular brown-coal seams; these latter are referred to as the Rawicz Group of Coal-Seams (II). The overlying Ścinawa Beds and Pawłowlce Beds (Middle Miocene) consist of clayey-sandy and sandy deposits, respectively. They are interpreted as the result of sediment deposition in a lacustrine-swamp environment, with subordinate role of in-channel fluvial deposition. The Ścinawa Beds contain numerous brown-coal seams, the total thickness of which exceeds 30m; these coal layers form what is termed the Ścinawa Group of Coal-Seams (II). The overlying Pawłowice Beds, in turn, contain only thin lenticular coal layers, which are jointly referred to as the Lubin Group of Coal-Seams (IIA). The Pawłowice Beds appear also to contain trances of marine ingressions. At this point it is noteworthy that at the Middle/Late Miocene transition there took place an episode of intense regional erosion, which locally stripped away the whole unit of the Pawłowice Beds.
The overlying Adamów Beds and Central-Polish Beds (Upper Miocene) display a virtually transitional mutual contact in their vertical profile. The former unit is sandy and lacks coal (except for occasional plant remains), while the latter is clayey and contains coal seams (total coal thickness attains 13 m); these coal seams are referred to as the Central-Polish Group of Coal-Seams (I). The sediments of the Adamów unit are thought to have been laid down in a lacustrine environment, while the Central-Polish Beds did probably originate in a lacustrine-swamp environment. This last-named unit, in turn, is overlain by the Poznań Beds (Upper Miocene-Pliocene), at the top of which there are present some more-or-less isolated sheets of the Gozdnica Beds (Pliocene); as already stated above, these latter two lithostratigraphic units are not considered in the present study.
In total, the coal-content index of the Miocene succesion averages 8.1%. The brown-coal seams and lenses are of autochthonous origin. The coal belongs to the energetistic variety of moderate caloricity.