Morphostratigraphy of river terraces in the Eger valley (Czechia) focused on the Smrčiny Mountains, the Chebská pánev Basin and the Sokolovská pánev Basin

The Eger (Ohře) River terraces originated in varied morphotectonic and climate-morphogenetic conditions that existed during the late Cenozoic evolution of the western part of the Bohemian Massif. In the area between the Smrčiny Mountains and the Sokolovská pánev Basin, these levels of the Eger River terrace system were identified (Table 1): the Pliocene terrace level B, the Cheb terrace (I), the Hradiště terrace (II), the Chvoječná terrace (III), Jindřichov terrace (IV), Nebanice terrace (V), Chocovice terrace (VI), Chotíkov Terrace (VII) and the recent flood plain (N). It was determined to be a morphostratigraphical system of 7 river accumulation terraces of Quaternary age. Older levels of fluvial sediments, occupying a still higher morphological position in the area between the Smrčiny Mountains and the Sokolovská pánev Basin, have been classified to the Pliocene. A comparison of terrace flights in the longitudinal profile of the Eger River between the Smrčiny Mountains and the Doupovské hory Mountains indicated that the Cheb terrace (I) in the Smrčiny Mountains is tectonically uplifted around 10 m in comparison with its level in the Chebská pánev Basin. In the Chlumský práh Horst area, the oldest Pleistocene terraces, which originated during the Tiglian stage, were uplifted by approximately 15 m. The Chebská pánev Basin originated at the intersection of the Eger rift and the Cheb-Domažlice fault zone and its river network is incised ca 40 m into the planation surfaces of the sedimentary basin. Both volcanic processes and frequent seismic activity in the region are associated with the Late Cenozoic tectonic movements. According to the current stratigraphical scheme of the Quaternary, the Eger terrace system was formed mostly by the Pleistocene (Table 2) during the Tiglian to the Weichselian stages.