• 责任者：Zhang Pu (State Key Laboratory of Loess and Quaternary Geology ; Institute of Earth Environment ; Chinese Academy of Sciences ; Xi’an 710075 ; China) ; Liu Weiguo
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(1)
• 关键词：碳酸盐岩 ; carbonate rocks ; 黄土 ; loess ; 碳同位素 ; carbon isotopes ; 鄂尔多斯盆地 ; Ordos Basin
• 页码：p.179-186
• 图表：illus., 57 refs.
• 分类号：1400
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

Previous morphological and carbon isotope studies have indicated the pure biogenicity of rhizolith that is applied in high-resolution modeling of climates of different continents. Therefore, the loess-paleosol sequences of Xifeng（35°47＇N, 107°36＇E） and Luochuan（35°47＇N, 109°26＇E） located in the middle of a loess plateau were chosen, at a profile depth of 11.0m and 9.3m,respectively. Both of the two sections contain L1 and SO loess-paleosol sequences. A total 205 samples in 10cm interval （111 samples for the Xifeng section, and 94 samples for the Luochuan section）were collected for magnetic susceptibility （MS）. In Xifeng and Luochuan sections, the high MS values occur in SO paleosol and LlSS1 weakly developed paleosol,varing from 60×10-a m3/kg to 160×10-8 m3/kg. The low MS values occur in LILL1 and L1LL2 loess,varing from 30×10-a m3/kg to 60×10-8 m3/kg. And the TOC content show similar variation with MS values in both sections. A total 87 Rhizoliths samples（65 samples for the Xifeng section in 20cm interval, and 22 samples for the Luochuan section in 40cm interval）were collected by wet sieving the loess samples through 80mesh screen using a sharp needle under a binocular microscope. The collected rhizoliths were subjected to carbon isotope analysis to compare the magnetic susceptibilities, stable isotopic compositions,and TOC content of the loess-paleosol sequences. The following variations were noted in the Xifeng profile： δ13CcR from -8.6‰ to -3.7‰; δ13CTOC from -23.68‰ to - 19.47‰; and δ13CTIC from -8. 65‰ to -4. 95‰. By contrast, the Luochuan profile showed the following variations： δ13CCR from -8.30‰ to -3.58‰; δ13CTOC from -23. 28‰ to -18. 72‰; and δ13CTic from -8. 50‰ to -3. 78‰. The δ13CcR values did not correspond completely to MS, TOC and δ13CToc variations in the Xifeng and Luochuan profiles since the last glaciation, indicating a contrasting trend in SO and a similar trend in L1. However, they showed similar variation trends and amplitudes to δ13CTIC in the glacial-interglacial interval. These results indicate that theδ13CcR values are similar to the δ13CTIC values. This phenomenon may be caused by complicated processes such as leaching and movement of carbonate, the interference of vegetation, and the influence of the primary carbonate, particularly in undetermined leaching depth. Therefore, a careful reconstruction of the paleovegetation （ C4/C3 ） using only the δ13CCR value was performed.