NEOTECTONIC CONTROL ON HOLOCENE RIVER DYNAMIC CHANGES IN THE KÖRÖS BASIN (E-PANNONIAN BASIN, HUNGARY): FROM UPLIFT TO SUBSIDENCE

The latest phase of the multi-storey development of the Neogene Pannonian Basin in Central Europe comprises a still active compressional basin inversion (5 to 0 Ma). This resulted in significant uplift of most of the marginal parts and local subsidence of some depressions. Neotectonic field and literature data showed, that in addition to climate changes, tectonic activity had an important control on avulsion and changes in river dynamics of the recent fluvial systems. The study area is situated in the eastern part of the Pannonian Basin, and represents a key-setting of a transitional zone from uplift to subsidence. The recent rivers display a transverse pattern, draining the Apuseni Mountains in Romania, and transport sediment to the west to the Körös Basin which is an actively subsiding depression. The present study focuses on changes in river course pattern of the transverse river system based on the analyses of airborne photographs. The reconstruction of the most important morphological features (channels, levees, terraces, marshes) showed, that the area can be subdivided into three E-W striking zones: (1) on the north large, well developed meanders are found, (2) the central part is characterised by a dense pattern of small-scale former meanders, (3) on the south, a braided pattern can be seen. A detailed analysis of seismic profiles, supported by digital elevation models, geological cross-sections, and neotectonic field data showed, that NE-SW to E-W striking faults, connected with basement highs correspond to the above described zones, characterised by different morphological patterns. A preliminary conclusion is that tectonics was an important allogenic control on the development of river dynamics that manifested in the form of alternating meandering and braided patterns.