CLIMATICALLY DRIVEN SEDIMENTARY CYCLES IN THE LATE MIOCENE SEDIMENTS OF THE PANNONIAN BASIN, HUNGARY

By detailed cycle analysis of marginal, mostly delta plain facies succ essions of Pannonian sediments the frequency of water-level changes of the Late Miocene Pannonian Lake, Hungary, can be identified. Cycle an alysis is presented with the object of defining the orbital record pre served in the strata. We use the bed thickness as input data for our c ycle analysis. Statistical analysis revealed a slow, upward increase o f both the frequency and thickness of sand beds in the boreholes resul ting from infilling of the lake by a basinward migration of the margin al facies. Cycles of different order were detected in the sediments. T he higher-order cycles are very close to or are equivalent with the Mi lankovitch climatic cycles: similar to 19 ka caused by precession, sim ilar to 50 ka caused by obliquity, and similar to 400 ka is the longer period of eccentricity. The longer, >1 m.y., cycle is very poorly dev eloped here. It is probably the analogue of the 3rd-order, global clim atic cycle. Cycle analysis suggests, that one of the main controlling factors of the water-level changes of the Pannonian Lake was high-freq uency climatic oscillations. The long-term climatic changes only had a faint impact on the sediments. The record of the 3rd-order water-leve l changes is very subtle. Our results show that the water-level change s followed the rhythm of that of the eustatic changes, but being async hronous to them, i.e., at high sea-level stage the Pannonian lake-leve l was low, and vice versa.