Climatically driven sedimentary cycles in the Late Miocene sediments of the Pannonian Basin, Hungary

Abstract By detailed cycle analysis of marginal, mostly delta plain facies successions of Pannonian sediments the frequency of water-level changes of the Late Miocene Pannonian Lake, Hungary, can be identified. Cycle analysis is presented with the object of defining the orbital record preserved in the strata. We use the bed thickness as input data for our cycle analysis. Statistical analysis revealed a slow, upward increase of both the frequency and thickness of sand beds in the boreholes resulting from infilling of the lake by a basinward migration of the marginal facies. Cycles of different order were detected in the sediments. The higher-order cycles are very close to or are equivalent with the Milankovitch climatic cycles: ∼19 ka caused by precession, ∼50 ka caused by obliquity, and ∼400 ka is the longer period of eccentricity. The longer, >1 m.y., cycle is very poorly developed here. It is probably the analogue of the 3rd-order, global climatic cycle. Cycle analysis suggests, that one of the main controlling factors of the water-level changes of the Pannonian Lake was high-frequency climatic oscillations. The long-term climatic changes only had a faint impact on the sediments. The record of the 3rd-order water-level changes is very subtle. Our results show that the water-level changes followed the rhythm of that of the eustatic changes, but being asynchronous to them, i.e., at high sea-level stage the Pannonian lake-level was low, and vice versa.