Mineral magnetic investigation of the Talede loess-palaeosol sequence since the last interglacial in the Yili Basin in the Asian interior

Abstract

The loess-palaeosol deposit in the Asian interior is sensitive to the evolution of the Westerlies, thus providing a good opportunity to investigate regional palaeoenvironmental evolution and its relationship with global climatic changes. Multiparameter mineral magnetic investigations have been conducted on the Talede section in the Yili Basin, Asian interior. Our study finds that: (1) loess samples have higher concentration magnetic minerals than palaeosols, though the magnetic mineral composition is similar (ferrimagnetic magnetite, antiferromagnetic hematite and lepidocrocite). (2) Large pseudo-single domain (PSD) and multidomain (MD)-like grains dominate both in loess and palaeosols. However, magnetic mineral grains in loess are much coarser than those in the palaeosols. (3) Palaeosols contain approx 30 per cent more amount of hematite than the loess samples. The frequency-dependent susceptibility of both loess and palaeosols is very low, indicating the small amount of super-paramagnetic grains. And the higher χ fd per cent values of palaeosols also reveal that palaeosols have more amounts of ultrafine magnetic grains than loess. The magnetic variations in part (1) and (2) can be well explained by the wind vigour model, but the observed enrichment of hematite and ultrafine magnetic grains in palaeosols also reveals the first onset of pedogenic enhancement. Therefore, the Talede section could be seen as an end-member of the classic Chinese Loess Plateau (CLP) magnetic enhancement model. © 2012 The Authors Geophysical Journal International © 2012 RAS.