Tectonically controlled Quaternary intracontinental fluvial sequence development in the Nyirseg-Pannonian Basin, Hungary

摘要

The Quaternary fluvial succession of the Nyirseg (NE Hungary), a proximal sub-basin of 4000 km2 in the intracontinental Pannonian Basin, was studied based on log facies analysis. Regional mapping of sequences was established by analysis of fully cored boreholes and high scale local correlations in densely drilled areas. The age of the sequences was determined by correlating the magnetic susceptibility (MS) record of the fully cored boreholes with that of the reference Hungarian boreholes dated paleomagnetically (Devavanya-1 and Veszto-1 in Cooke et al., 1979). To give the Hungarian data global perspective they were correlated to the MS curve of the Chinese Loess (Ding et al., 2005) that are in turn correlated with the Marine Isotope Record (Lisiecki and Raymo, 2005; Gibbard and Cohen, 2008). The ages of the mapped sequence boundaries are 2.62, 2.26, 2.12, 1.22, 1.04, 0.58 and 0.34 Ma respectively and can be related to the transitions from cool to warm conditions. Regional unconformities at 2.26-2.12, 1.22 and 0.58 Ma also coincide with activity maxima of the radiometrically dated Quaternary volcanism. This high frequency of climatically controlled erosive sequence boundaries in the structurally active periods indicates that the sedimentary record of climatic erosion is better expressed in times when structural changes generate instability in the drainage network. The occurrence of packages of regional unconformities in relation to volcanic activity enables the geochronological dating of episodes in the Quaternary compression of the Carpathian-Pannonian region.The role of tectonic control on the climatically induced changes in the drainage network has been explained by a structural development model based on seismic, gravity and magnetic data. The changes in the local paleohydrology were triggered by a compression related elevation of the basement and the associated occurrence of a local transtension-related subsidence.