A quasi-continuous long-term (5 Ma) Mid-European mountain permafrost record based on fluvial magnetic susceptibility and its contribution to the explanation of Plio–Pleistocene glaciations

Abstract

The low field magnetic susceptibility (χ_LF) measured in the 1116-m-long Dévaványa core (Pannonian Basin) is a quasi-continuous record of the Plio–Pleistocene Mid-European mountain permafrost development. The continuity of fluvial conditions is confirmed by seismic data, and the detrital origin of magnetite is indicated by frequency-dependent susceptibility measurements, scanning electron microscope, and hysteresis investigations. The χ_LF record is correlated to the δ¹⁸O curve (LR04) supported by palaeomagnetic data. The colour of samples documents precession and obliquity cycles in local facies variations, but the χ_LF indicates the dominance of 100-ka eccentricity cycles in the linked mountainous permafrost events. Comparison with orbital solutions revealed that the long-term development of permafrost occurs as a result of amplitude modulation of the 100-ka eccentricity cycles. Increases in amplitude of the 100-ka cycles inhibits permafrost development due to shortened winters. Thus, if extremes are present, the permafrost regions are limited or disappear, but if the 100-ka eccentricity cycles are attenuated, permanent frost can extend into the temperate zone. This amplitude modulation may also be responsible for the early glaciations during the Pliocene, for the intensification of Northern Hemisphere glaciation, foreshadows cooling in the forthcoming 405-ka term, and allows the change from 41-ka cycles to 100-ka ones in the Mid-Pleistocene Transition to be explained. The 41-ka cycles are the result of obliquity-controlled changes close to the polar cycles, while 100-ka cycles occur when the amplitude attenuation of the 100-ka eccentricity cycles enables extended glaciations that suppress the regular 41-ka cycles. Higher mountains in the catchments enable higher resolution of permafrost records documenting even smaller glaciations. However, the similarities in the overall trends in χ_LF records of catchment areas with 1500-m difference in their altitude is a potential counter-argument when considering the role of tectonic elevations in the expansions of mountainous permafrost.