Publication details
Evolution of a sedimentary infill of a palaeovalley at a distal passive margin of the peripheral foreland basin
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| Year of publication | 2018 |
| Type | Conference abstract |
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| Description | The paleovalleys along the basal unconformity in the foreland plate feeding the distal part of the foreland basin provide unique information about the flexureally induced sea-level changes, about the role of external factors (climate, tectonics, sediment supply and palaeogeomorphology) and constitute basic data for the stratigraphic organisation of sedimentary basins. An enormous diversity of valley sizes, shapes, settings, infills, and potential for hydrocarbon reservoirs predispose them as a „popular“ targets of study. The presented study focuses on an entrenched valley near the town Odry at the north-western/distal margin of the Carpathian Foreland basin (Moravia, Czech Republic). Two recently drilled boreholes 2212_B and 2212_W provide together an almost completely cored sedimentary profile of the Neogene infill of the Odra palaeovalley, which is more than 280 m thick. The sedimentary succession consists of five facies associations. The facies associations were interpreted (from bottom to top i.e. from the oldest to the youngest) as: FA 1 - colluvial deposits to deposits of alluvial fan, FA2 - deposits of alluvial fan, FA 3 - fan delta deposits, FA 4 - shallow water delta to nearshore deposits and FA 5 - open marine deposits. This fining-up and deepening-up Neogene succession reveals: formation of the new flexural shape of the basin; the Lower/Middle Miocene sea-level fall; deep erosion connected with uplift and tilting of the forebulge and reactivation of the NE-SW trending basement faults; alluvial deposition mostly driven by tectonic and morphology; forebulge flexural retreat; Middle-Miocene sea-level rise; back-stepping of valley infill; marine invasion during the Lower Badenian with shift of the coastline further landward of the palleovalley. Tectonics related to contemporary thrusting processes in the Western Carpathians is supposed to be the principal ruling factor of studied deposition at the expense of eustatic sea-level changes. The provenance studies proved that the paleovalley-fill conglomerates were mostly locally derived from pre Neogene-basement (i.e. Lower Carboniferous clastic “Culmian facies” of the Moravian-Silesian Palaeozoic). However, they also showed that the deposits of the earlier Carpathian Foredeep Basin sedimentary stage covered the area under study and were eroded and resedimented. Paleovalley formation and infill provide unique information about development of palaeodrainage network at the distal margin of the Carpathian Foredeep basin during Middle Miocene, about local forebulge kinematic behaviour and basin evolution. |