| The Eurasian loess has a wide distribution and a large thickness, which contains a wealth of environmental information. The loess in the sea of Azov region of Russia and the Pamir region of China is a transitional zone of loess deposits in Europe and China, they have its unique features of regional environment, the study of the Loess record paleoenvironmental information is useful to us further understand the different climate system responses to global change. In recent decades, the magnetic susceptibility of loess has been widely used as an indicator of environmental change, but there are differences in the current susceptibility to climate change and need for a wider range of comparative study. The typical Beglitsa loess profile in the north shore of the sea of Azov in southern Russia, and the the Tucker(AYTK) loess profile in the Pamir region, which are controlled by mid-latitude westerlies, were selected in this study as the research object, with the help of various indicators on magnetic properties conducting a series of environmental magnetism research, and combining the chromaticity, granularity, carbonate(CaCO3%), total organic carbon(TOC%) with X-ray diffraction(XRD) and other proxies, we expect to explore the magnetism mechanism of loess sediment and its influencing factors in these two areas, and to discuss the ancient climate change since MIS5. By conducting these works, we can have a better understanding on process of environmental evolution in the Azov region of Russia and Pamir region of China since MIS5, and provide the reference for predicting climate trends in the future. At the same time,compared with the typical loess profile in the chinese loess plateau, we also analyzes the spatial heterogeneity and provides the possibility of comparison betwwen regional and global climate, and try to rebuild the ancient rainfall of Azov region in the southern Russia since MIS5. The main conclusions of this study include the following aspects:1. The magnetic characteristics of loess sediments in the Azov of Russia and Pamir region of China are mainly controlled by ferrous magnetic mineral, and magnetite mainly consist of ferrous magnetic mineral, meanwhile, existing the incomplete antiferromagnetic minerals. Magnetic mineral grains mainly are pseudo single domain(PSD)- multiple domain(MD); The super paramagnetic(SP) magnetic minerals in the Azov region of Russia formed by soil have a certain contribution to the magnetic susceptibility, whlie the super paramagnetic(SP) magnetic minerals in Pamir region of China formed by soil play a limited role in susceptibility contributions. Compared with the typical loess in Chinese loess plateau, average values of magnetic susceptibility show the following characteristics: Beglitsa < AYTK < Jingyuan < Luochuan, space changes show west < east < central. The reason of differences may be the content of magnetic mineral and the change of particle size, different material source area and climate condition difference. Overall, the stronger magnetic samples have the great contribution ferrous magnetic mineral make.2. The color of Beglitsa loess samples in the Azov region of Russia is darker on the whole, L* value is lower, a* value is smaller. However, the color of Pamir region of China is brighter on the whole, L* value is higher, a* value is smaller. Compared with the Jingyuan section of Chinese loess plateau, chromaticity normalized distributions of Beglitsa loess profile and AYTK loess profile, which are dominated by westerlies, are relatively similar. While the Jingyuan section shows different performance whose domination is moonsoon.3. In the Azov region of Russia and Pamir region of China, the loess mainly are coarse silts(10~50 um). Sand(>50 um) contents of Beglitsa loess profile in the Azov region of Russia are low, but sand contents of AYTK loess profile in the Pamir region of China are high, reaching 15.68%; The frequency distribution of particle size in these two loess profiles are in unimodal. Compared with the typical profiles of Chinese loess plateau, we found that the sand(> 50 um) content in LuoChuan section is the lowest, but clay(< 5 um) content has the highest levels, soil pedogenesis is strongest. Normalization distribution of particle size shows the distribution characteristics of AYTK and Jingyuan loess is similar, there exist certain differences with the Azov region of Russia. The loess magnetic susceptibility(χ), Saturation isothermal remanent magnetization(SIRM), soft remanent magnetization(SOFT) and coarse silt(10~50 um) levels were positively correlated in the Azov region of Russia and Pamir region of China, showing that loess magnetic minerals mainly gathered in coarse silt(10~50 um).4. The eluviation or migration of loess CaCO3 in the Azov region of Russia is conducive to magnetic mineral enrichment, and having an impact on magnetic characteristics to varying extent. The loess CaCO3 contents are higher and more stable in Pamir region of China; High CaCO3 content may play a dilution effect in loess magnetic mineral content, making the loess magnetism relatively less. The TOC contents of Beglitsa loess samples show that magnetic susceptibility enhancement is associated with "biological magnetic effect", but the TOC contents in Pamir region have no effect on magnetic susceptibility. According to the degree of mineral weathering, mineral weathering of the Beglitsa loess samples is relatively strong. The chemical weathering intensity of loess in Pamir region is not high, maybe it is in a early stage of chemical weathering.5. The pedogenesis of the Azov region of Russia is stronger, magnetic susceptibility and pedogenesis are positively correlated, and there exist the similar climate change process between the Azov region of China and the Chinese loess plateau region, That is: it is hot and humid in the formation of paleosoil, dry and cold in the formation of loess. The χ, SIRM and SOFT magnetism parameters can better reflect the environmental process. Relationship between magnetic susceptibility and pedogenic process is complex in Pamir region of China, the climate is relatively dry since MIS5, loess-paleosol layer is not obvious. Only the combination of mineral weathering analysis and magnetism parameters, such as HIRM, SIRM/χ, can we clearly indicate the strength of weathering pedogenesis in Pamir region and the ancient environmental information that contains. Furthermore, the climate change of our study area was compared with other geological record, the results showed that there were similar with the scale of glacial-interglacial cycle, but there were some regional differently characteristic; Process of climate evolution in the Azov region of Russia was consist with other areas in eastern Europe.Stage MIS5 c is the warmest and wettest since MIS5, and the pedogenesis is also the strongest in the Azov region of Russia, it has obviously different with other areas in Chinese loess plateau. We rebuilt ancient rainfall of the Azov region of Russia since MIS5 using χfd/HIRM, the rainfall of last interglacial S1 in Azov region of Russia was within the scope of 254.3~676.6±70 mm, the rainfall of S1SS2(MIS5c) was basically identical with present amount. |
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