Obliquity-driven mountain permafrost-related fluvial magnetic susceptibility cycles in the Quaternary mid-latitude long-term (2.5 Ma) fluvial Maros Fan in the Pannonian Basin

• Main Authors: Püspöki, Z, Gibbard, PL, Kiss, LF, McIntosh, RW, Thamó-Bozsó, E, Krassay, Z, Szappanos, B, Maigut, V, Kovács, P, Karácsony, D, Stercel, F, Visnovitz, F, Demény, K, Bereczki, L, Szőcs, T, Rotár-Szalkai, Á, Fancsik, T
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: 37 Earth Sciences; 3709 Physical Geography and Environmental Geoscience; 3705 Geology; 3706 Geophysics; permafrost
• Online Access: https://www.repository.cam.ac.uk/handle/1810/349226; https://doi.org/10.17863/CAM.96486

Magnetic susceptibility (SUS) of the Quaternary long-term mid-latitude Maros fluvial fan (Pannonian Basin) was recorded to understand the stratigraphic features of source proximal fluvial depositional settings. Three fully cored 500 m deep boreholes were sampled with 0.5 m intervals; low field and frequency dependent magnetic susceptibility were measured, and complementary hysteresis and SEM-EDAX investigations were performed on selected samples. Logged SUS data were also used to log correlations established by a comparison of wireline log and laboratory measurements. The time-series analyses of the SUS records reveal the apparent occurrence of the ~41 ka frequency together with the customary ~100 ka cycles. Towards the source-distal sections the intensity of the ~41 ka cycles decreases, while that of the ~100 ka cycles remains strong. Stratigraphic and spectral similarities were observed between fluvial fan and loess SUS records however, based on complementary magnetic data, the magnetic phase of the Maros Fan sections is related to the detrital magnetite that originates from the catchment during early postglacial permafrost degradations. The amplification of the ~41 ka cycles revealed can be attributed to the very high SUS values in source proximal settings and to the special stratigraphic feature of the distributive fluvial settings. This comprises the increased avulsion frequency on the fluvial fans in ‘glacial recession periods’, in concert with the ‘early postglacial’ occurrence of the permafrost-related magnetite originated from the catchment. As a local phenomenon, this is significant since it records the obliquity-driven variations of permafrost development in a catchment. However, fluvial and alluvial fans are widespread depositional landforms within the Eurasian Mountains and were possibly the same during the Quaternary deglaciations. Thus, obliquity-driven SUS variations of source-proximal fan deposits attached or adjacent to regions of loess deposition should also be considered when scanning for ...