Abstract
The magnetic susceptibility of loess from the Ily Basin, northwestern China shows maximum values in S0 paleosols but minimum values in other paleosols, the mechanism of which has been well debated. In this work, systematic magnetic measurements were made on a representative section from Neleke county. The results show that the loess horizons (L1, L2 and L3) have multi-domain magnetite grains of aeolian origin, S0 is characterized by production of pedogenetic ultrafine-grained ferrimagnetic minerals, and the other paleosols (S1, S2, and S3) are characterized by the formation of nonferrimagnetic minerals associated with waterlogging. The correlation between the low concentration of ferrimagnets, high paramagnetic content, high magnetic coercivity remanence, fine ferrimagnetic grain size and intensified pedogenesis suggest two competing processes of pedogenetic enhancement and pedogenetic depletion in the lower paleosols. Pedogenetic depletion dominates and is responsible for the low susceptibility. Changes in magnetic grain size distribution occur during pedogenetic depletion. The susceptibility variations are of multiple origins in the loess of the Ily Basin. Pedogenetic enhancement, pedogenetic depletion, and allochthonous input of magnetic minerals should all be taken into account to explain the variations of magnetic parameters.
Highlights
The magnetic susceptibility of loess from the Ily Basin, northwestern China shows maximum values in S0 paleosols but minimum values in other paleosols, the mechanism of which has been well debated
The results show that the loess horizons (L1, L2 and L3) have multi-domain magnetite grains of aeolian origin, S0 is characterized by production of pedogenetic ultrafine-grained ferrimagnetic minerals, and the other paleosols (S1, S2, and S3) are characterized by the formation of nonferrimagnetic minerals associated with waterlogging
The low fd and Anhysteretic remanent magnetizations (ARMs) values indicate that pedogenesis of S1, S2 and S3 does not produce a high content of ultrafine SP and SSD ferrimagnetic minerals [37,38,39,40,41]
Summary
The magnetic susceptibility of loess from the Ily Basin, northwestern China shows maximum values in S0 paleosols but minimum values in other paleosols, the mechanism of which has been well debated. The susceptibility variations are of multiple origins in the loess of the Ily Basin. The pedogenetic enhancement model suggests that ultrafine ferrimagnetic minerals were formed during the pedogenesis process This accounts for the high susceptibility in paleosols and low susceptibility in loess, and can be used to explain loess deposits on the Chinese Loess Plateau [3,4,5,6,7,8]. The wind vigor model displays low susceptibility in paleosols and high susceptibility in loess It argues that for loess from Alaska and Siberia, allochthonous input plays an important role in magnetic concentration and intensified wind vigor is responsible for increases in susceptibility [9,10,11,12,13,14,15]. Except for in the west, the Ily Basin is surrounded by high mountains, the average altitudes of which are >3500 m. With increasing altitude and improving climate conditions towards the east, the desert steppe changes into mountain steppe and the sierozems change into kastarozems (1100–1500 m) and chernozems (1500–1800 m)
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