Tectonic control on changes in sediment supply: Quaternary alluvial systems, Körös sub-basin, SE Hungary

Abstract

AbstractThe Pannonian Basin of Hungary is Europe’s largest inter-mountain basin, where an evolution in drainage development patterns during the Quaternary was caused by changes in sediment flux to the basin, the dynamics of basin morphology development and the uplift history of the Apuseni Mountains source area, all directly or indirectly related to the tectonic systems operating in the region. Micro-mineralogical data of detrital heavy minerals from modern rivers and two key boreholes covering a time span from the present back to 2.6 Ma have been grouped by statistical analysis into two main clusters and some sub-clusters. The samples within the same cluster have a similar composition, and originated from the same source area. Based on the similar palaeogeographical setting of the potential source areas during the Quaternary, it has been possible to extrapolate the present transport directions of the rivers with a well-known catchment area geology and the heavy mineral composition to Pleistocene borehole data. The changes in transport directions were clearly sharp and related to significant changes in the uplift history of the Apuseni Mountains catchment area. During the Pliocene and Early Pleistocene the compressional stress field operating in the East Carpathians region resulted in the thrust-driven uplift of the Apuseni Mountains and the formation of a syn-sedimentary trap at the western margin of the source area, which captured the sediments of short, transverse rivers. During this period the drainage of the study area was characterized by axial drainage parallel to this trap, and sediments were transported from the northeast, also shown by micro-mineralogical data of detrital heavy minerals. At about 1.95 Ma this trap stopped being active due to the release of the compressional stress field and the isostatic uplift of the Apuseni Mountains, together with the adjoining basin area. This resulted in the filling of the thrust-bounded trap, and the development of transverse drainage, which was shown by characteristic SE transport directions, based on micro-mineralogical data in the study area, and also by an increase of sediment flux. The axial capturing shifted further to the west, developing a configuration approaching to the present river course pattern. By analogy with the Himalayan foreland and retro-arc basins of the Cordilleran-Andean ranges, it was demonstrated that tectonic activity exerts a strong control on the drainage pattern through its influence on variations in sediment supply.