Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

168 PATA Days 2024 The study area is defined by a catchment of the Malše River, the ridges of the Novohradské hory Mountains occupy the largest part of the study area. The Novohradské hory Mts. and their foothills are composed mainly of metamorphic rocks of the Moldanubian Unit and granites of the Moldanubian Batholith (Variscan age). An elongated depression – Kaplice Furrow -, lies in the western part of the study area. This area is bounded by tectonic faults and it generally has a gentler relief than the surrounding highlands. The north-eastern part of the area is occupied by the flat terrain of the Třeboň Basin. It is also tectonically bordered, particularly on its western and southwestern edge, where it is adjacent to the Novohradské hory Mountains. The Třeboň Basin is filled with Cretaceous and Tertiary clastic sediments of lacustrine and fluvial origin (see Fig. 2) There are also local deposits of Neogene and Pleistocene lacustrine and fluvial sediments in the foothills of Novohradské hory Mts., mainly in the area of the Kaplice Furrow (Přibyl, 1999). They are probably remnants of shallow lakes and meandering water streams (probably predecessors of current streams), dated to the younger Pliocene (Tschegg et al., 2013). The interesting phenomenon in this area are the occurrences of fluvial deposits, so called Koroseky sands and gravels (KSG), which contain the Central European tektites from Ries impact crater, locally known as moldavites. Moldavites themselves are of Miocene age (Trnka et al., 2002; Di Vicenzo et al., 2009) however, the KSG containing reworked moldavites are considered younger, Pliocene (Ševčík et al., 2007) These moldavites were used as an important marker for correlating the morphostratigraphical position of occurrences of fluvial deposits (Balatka et al., 2015). The late reactivation of Palaeozoic fault systems (e.g., Donau (NW-SE) and Blanice-Rodl (NNE-SSW; Brandmayr et al., 1995) has been described by various authors (e.g. Kopecký 1970; Popotnig et al., 2013). They supposed the most intensive reactivation to have been at the end of Pliocene. This study suggests – in accordance with Tyráček et al., (2004), Cloething et al. (2006), and Štěpančíková et al. (2019) - that the tectonic activity was present even until the late Quaternary. This study is based on the previous research of the authors (Flašar et al., 2022; Flašar et al., 2023) and newly combined the results. The main goal of this study is a) to test the influence of local tectonic movements on changes in terrain morphology and river geometry, b) to find the indications of recent/Quaternary/Neogene movement on local faults, c) to analyse the influence of proposed tectonic activity (mostly uplift) on the evolution of the fluvial systems and drainage d) to date, at least approximately, the main changes in drainage geometry, which was previously assumed to had happened in Miocene/Pliocene; and e) to test the suitability of the combination of used methods. M E T H O D S Tectonic analysis The goal of the analysis was to interpret a number of linear indications, which could represent faults and other tectonic structures, such as the main fracture zones or shear zones. Data were obtained from several independent sources: a) geological and tectonic maps of the study area, b) airborne geophysical data (gravimetric, radiometric, magnetic survey) and c) morphotectonic analysismade fromthe digital elevation model. Brittle tectonic structures were measured at 119 rock outcrops through the majority of the study area and in total 400 structures were measured. The dip direction and dip were obtained; however, the direction of the tectonic structure was the most important value for the subsequent comparison with the results from the remote sensing methods. Geomorphologic analysis Simple geomorphological methods were used to assess the evolution of the relief and stream network: