Quaternary fluvial succession of the Jászság Basin (Hungary) was investigated, challenging the stratigraphical potential of ‘early postglacial fluvial magnetic susceptibility episodes' recognized earlier in the Körös Basin. Low field magnetic susceptibility (MS) was measured in four boreholes from the basin centre and margins, representing channel and flood‐plain environments. Statistical distributions of MS data contain significant sets of outliers, regardless of facies conditions. The downhole distribution of these outliers produces magnetic susceptibility cycles. Supported by magnetic susceptibility cycles, high‐resolution facies correlations were performed reflecting a steady palaeohydrographical situation in the area, with a trunk river to the southeast and tributaries to the northwest. SEM‐EDX data revealed that ferromagnetic grains are responsible for the outlying MS values. The heterogeneous association of magnetite indicates a catchment area with volcanic and metamorphic rocks, while the group of small (<5 μm) magnetite octahedrons originated from nearby rhyolitic tuff formations. Magnetic grains were transported along channel belts, while small (<2 μm) magnetic particles were floated onto flood‐plains attached to clays. Climatic control is indicated by peaks at ~100 ka frequency in spectra of MS records and was also detected in palaeosol development and in flood frequency using the spectra of measured colour (~100 ka) and logged resistivity (~100 ka, ~41 ka), respectively. The climate‐dependent MS signal traceable far into the basin in both channel and flood‐plain environments can be summoned when the Quaternary fluvial succession of the Pannonian Basin is investigated, assuming some sources of magnetite in the catchment areas. According to the concept of ‘fluvial magnetic susceptibility episodes’, the early postglacial escape and spreading of the magnetite fraction control the MS signal that can support mapping of the unconformable Quaternary base and building of high‐resolution models of aquifers.
susceptibility as a proxy for long-term variations of mountain permafrost development in the Alp-Carpathian region.
High‐resolution stratigraphical architecture of a Quaternary fluvial succession in the Makó Trough and the Danube‐Tisza Interfluve (Pannonian Basin, Hungary) was investigated based on low field magnetic susceptibility (MS) measurements of seven fully cored boreholes, interpreted on the basis of the early postglacial magnetic susceptibility episodes previously described in the Körös and Jászság Basins. To confirm the reliability of the Dévaványa and Vésztő MS records (Körös Basin), the published magnetostratigraphical data were re‐investigated revealing the consequent arrangement of the MS peaks correlated with the Jingbian section and the short‐lived polarity reversals correlated with the Geomagnetic Instability Time Scale. The Quaternary climatic regime in the Körös Basin begins in the late Pliocene at 2.7 Ma. The correlation between the Körös Basin (Dévaványa) and Makó Trough (Mindszent) was confirmed by the multi‐proxy spectral investigation of the Mindszent section, revealing ~100‐ and ~41‐ka cycles in the MS, colour, logged spontaneous potential and resistivity records. Based on MS records of the seven boreholes, the base of the Quaternary can be identified irrespective of the facies, age and climatic phase of the lowermost Quaternary strata. By performing MS and log correlation of 131 boreholes, extended unconformities were detected in the Quaternary profiles in the Danube‐Tisza Interfluve (~1070±10, ~1920±10 and ~2300±10 ka) interpreted as sequence boundaries. Sedimentological and mineralogical data reveal a significant change at ~725–606 ka likely as a response to the ‘mid‐Pleistocene transition’, leading to the multiple branching of the Danube. SEM data revealed that ilmenite is also responsible for the development of the early postglacial magnetic susceptibility episodes. This increases the stratigraphical potential of fluvial successions with catchment area that contain metamorphic rocks. A gradual retreat of permafrost zone determines long‐term temporal trends of the climatically controlled fluvial magnetic susceptibility episodes, causing upward decreasing trends in the time series.
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