Magnetic enhancement paths in loess sediments from Tajikistan, China and Hungary

Saturation magnetization and saturation remanence of 139 loess and paleosol samples from Tajikistan, China and Hungary increase linearly with low field susceptibility in all sections investigated. Thus magnetic enhancement is caused by increasing quantities of ferrimagnetic minerals. The observed variations of high field susceptibility chi(h) are attributed to variations in the amount of clay minerals as chi(h) is linearly correlated with the < 2 mu m grain size mineral fraction. The magnetic enhancement process is compared with a theoretical mixing model based on two magnetic mineral assemblages with different but invariable coercivities. The two-component model provides a good approximation to the data from Hungary and the magnetically enhanced paleosol samples in Tajikistan and China. Discrepancies between model calculation and data arise in the behaviour of the loess samples in Tajikistan. Here a three-component model improves the agreement between data and mixing calculation. The magnetic enhancement in the loess in Tajikistan (and China) is different from the one in the paleosols and;the link between paleoclimate and susceptibility is not as strightforward as in the Hungarian loess-paleosol sequence.