LOESSFEST'09 | Aug. 31st – Sept. 3rd, 2009 |Novi Sad-Serbia
Geochemistry of Three Last Interglacial S1 Paleosols and its Climatic Implications in the Chinese Loess Plateau
Wang, H.1,2, Feng, Zd.1,3, Liu, L.2
1Key Laboratory of West China’s Environmental system, Ministry of Education, Lanzhou University, Lanzhou 730000, China
2Key Laboratory of Environmental Change and Natural Disaster, Ministry of Education, Beijing Normal University, Beijing 100875, China
3Department of Geology, Baylor University, Waco, TX 76798-7354, USA
Three last interglacial paleosols across the Chinese Loess Plateau was investigated for geochemistry. The Al-Ti-Zr ternary diagrams showed that the Al- Ti-Zr ratios are very close to the average composition of the Upper Continental Crust(UCC) and to the composition of the Post-Archean Australian shale (PAAS), indicating 1) the source material was homogeneous or underwent thorough mixing, or 2) back mixing in the depositing area, or both . The approximately identical La/Th ratios (~2.8) indicated that the source material for the Chinese Loess Plateau must have undergone multiple upper crustal recycling processes during last interglacial. In combination with datasets from other authors, we inferred that the source material for western part and eastern part of the Chinese Loess Plateau is homogenous. In addition, several previously suggested East Asian Monsoon proxies were subjected to examination with our high-resolution data. We found that the previously suggested winter monsoon strength index, e.g., Zr/ Rb, is obviously at least dominated by sorting processes and chemical weathering, suggesting that premise for this proxy is problematic. The previously used summer monsoon proxy, Rb/Sr, failed to express stronger pedogenesis in southeastern margin of Loess Plateau (Lantian) compared to S1 of Tianshui section. We emphasized that geochemical proxies should be adopted cautiously.