Abstract: Loess-paleosol sequences in the Chinese Loess Plateau reflect glacial/interglacial environmental changes,and have been regarded as the most detailed and continuous terrestrial records of past environmental change in the Quaternary. These records have been correlated to the changes in past climate found in the marine and ice core oxygen isotope curves. Similar to the loess in the Chinese Loess Plateau,the loess deposits in the Pamir of Central Asia arid area also play an important role in understanding the climate and environmental changes. As a substitute indicator for climate,magnetic susceptibility has been widely used for paleoclimatic and paleoenvironmental studies. However,there exist ambiguities and complexity when accurately interpreting this mineral magnetic proxy. To figure out the enhancement mechanisms behind magnetic susceptibility appears to be of vital significance. Based on the above analysis,combined with grain size,chroma,calcium carbonate and organic matter proxies,this paper analyzed the magnetic susceptibility features and discussed the differences in the enhancement mechanism of magnetic susceptibility in the Pamir loess dominated by the westerlies. Results show that the average value of magnetic susceptibility,27.72×10^-8 m³·kg^-1,was lower in the Pamir loess than that in typical loess on the loess plateau,and the frequency dependence(x_fd%) of which the average value was 0.27% also showed low value as it intended to estimate the relative contribution of fine viscous grains at the border between superparamagnetic and signal domain to the total ferromagnetic assemblage,suggesting that the study area had a weak pedogenic environment. Coarse silt(4~63 μm) was the dominant component of the section,accounting for 67.71%~85.48%,and magnetic susceptibility was positively correlated with coarse particles,however negatively with fine particles whose content were about 5.78%~19.92%. Meanwhile,magnetic susceptibility and L^* showed a positive correlation,for a^*,it showed a negative correlation;this is due to the fact that the dominant matter is different. Analysis of correlation between calcium carbonate,organic matter and magnetic susceptibility manifested that these two indexes made trivial contributions to magnetic susceptibility. From what has been discussed above,we can see that magnetic susceptibility features are complicated in this area due to the influence of various factors,such as sedimentary environment and climate,and the enhancement mechanism of magnetic susceptibility in the Pamir loess has spatial discrepancy. Conducting the relevance analysis between magnetic susceptibility and other climatic proxies is just a fundamental research;as to the influential proportion to magnetic susceptibility,much research work will still be needed in the future,such as the determination of the magnetic mineral content and so on.

Key words: magnetic susceptibility, grain size, chroma, Pamir enhancement mechanism