Open AccessMagnetic properties of loess deposits on the northeastern Qinghai‐Tibetan Plateau: palaeoclimatic implications for the Late Pleistocene
Author(s) -
Wang Xiaoyong,
Lu Huayu,
Xu Huifang,
Deng Chenglong,
Chen Tianhu,
Wang Xianyan
Publication year - 2006
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2006.03007.x
Subject(s) - paleosol , maghemite , geology , loess , pedogenesis , magnetic susceptibility , magnetic mineralogy , magnetite , rock magnetism , interglacial , geochemistry , plateau (mathematics) , pleistocene , mineralogy , paleontology , soil water , soil science , remanence , chemistry , magnetic field , magnetization , physics , mathematics , quantum mechanics , crystallography , mathematical analysis
SUMMARY The loess–palaeosol deposit on the northeastern Qinghai‐Tibetan Plateau is sensitive to environmental changes, thus providing a good opportunity to investigate regional palaeoenvironmental evolution and its relationship with global climatic changes. Detailed rock magnetic investigations and grain‐size determination were carried out on a 35‐m‐thick loess–palaeosol sequence at Dongchuan, the northeastern Qinghai‐Tibetan Plateau. The principal ferrimagnetic minerals in both the loess and palaeosol units are large pseudo‐single domain magnetite/maghemite. Palaeosol units are generally enriched in ultrafine‐grained magnetite/maghemite of pedogenic origin. Variations of low‐field magnetic susceptibility and frequency‐dependent susceptibility in the loess and palaeosols can mainly be attributed to changes in the concentration of these minerals. Higher values of frequency‐dependent susceptibility occur in the palaeosol horizons except for the weakly developed palaeosol, suggesting that higher concentrations of ultrafine magnetite/maghemite particles occur in palaeosol units due to in situ pedogenesis. The frequency‐dependent susceptibility of the loess units is very low and uniform, indicating absence of the super‐paramagnetic grains and negligible pedogenically induced enhancement of magnetic susceptibility. Generally, magnetic susceptibility combined with the frequency‐dependent susceptibility of the loess–palaeosol sequences reflect the glacial‐interglacial changes, thus can be employed as a proxy measure of palaeoclimate in this region. However, the low‐field magnetic susceptibility record does not consistently correlate to the variations in stratigraphy of the Dongchuan loess–palaeosol sequence. It is thus suggested that multiparameter rock magnetic investigations combined with non‐magnetic measurements, such as grain‐size analysis, represent a more powerful approach for palaeoclimatic research into the complex loess–palaeosol record in the Qinghai‐Tibetan Plateau.