Magnetic susceptibility as a possible correlation tool in Quaternary alluvial stratigraphy

Abstract

Correlation of the fluvial magnetic susceptibility (MS) record of borehole Devavanya‐1 in the Körös Basin (eastern Hungary) with Chinese aeolian MS records (Jingbian, Lingtai) and the marine δ18O record from the Equatorial Pacific (V28‐239) is established here based on cross‐correlations and singular spectral analysis. A basin‐scale well‐to‐well correlation based on magnetic susceptibility records was also performed involving unpublished cores. To refine the age model, a Monte Carlo simulation was conducted using the Chinese Jingbian section as a tuning target. Spectral analysis of the tuned record revealed c. 400, c. 100 and c. 41 ka cycles over the 2.5 million years of the Quaternary fluvial succession. To ensure a complementary palaeoclimate proxy, the full width at half maximum of smectites was measured as a facies‐independent indicator of weathering intensity. This investigation was carried out on a subset of samples involved in MS measurements representing a c. 400 ka time interval across the top of the Olduvai subchron. A phase‐shift between MS and weathering intensity recorded in the clay mineralogy indicates different response times of the considered proxies. The fluvial MS record is determined by the climatic control on delivery and preservation of magnetic minerals, mainly of magnetite. Under cold‐and‐dry climate these minerals were released owing to frost shattering in the adjacent hinterlands and were transported to alluvial plains in the early postglacial periods thanks to the increasing discharge of rivers. With further warming the weathering‐sensitive magnetic minerals soon disappeared from the soils of the catchment area and thus from the fluvial load. As a result, in fluvial successions early postglacial warmings are expressed by the occurrences of MS maxima (magnetic episodes), while the palaeotemperature maximum and the subsequent cooling remain concealed within the tract of low MS values. The early postglacial magnetic episodes may serve as ideal stratigraphical markers in regional and global correlations.

High‐resolution stratigraphy of Quaternary fluvial deposits in the Makó Trough and the Danube‐Tisza Interfluve, Hungary, based on magnetic susceptibility data

“…The two sets of extreme MS maxima (MP10 and 10a) representing the ~2500 and ~2700 ka MS episodes, respectively (Püspöki et al . 2016), indicate that the Pliocene–Pleistocene transition is continuous not only in the Körös Basin, but also in the Makó Trough.…”

“…(2003), reinterpreted by Püspöki et al . (2016, 2020). [Colour figure can be viewed at www.boreas.dk]…”

“…Püspöki et al . 2016, 2020). Between STS surfaces magnetically identified sedimentary cycles (magnetic susceptibility cycles) were defined.…”

“…The possible climatic control on the fluvial early postglacial magnetic susceptibility episodes was discussed already (Püspöki et al . 2016). The role of the geological formations in the related catchment area was investigated based on the comparison of the Körös and Jászság Basins (Püspöki et al .…”

“…Thus, at first, to confirm that the formerly established global correlation of the reference fluvial MS record (Dévaványa in Püspöki et al . 2016) is reliable, the re‐evaluated versions of the magnetostratigraphical records of the Dévaványa and Vésztő sections (Cooke et al . 1979) are presented in correlation with the Geomagnetic Instability Time Scale (GITS) (Singer 2014; Cohen & Gibbard 2019).…”