Pedogenic carbonate isotope record of vegetational evolution since late Miocene in Loess Plateau  

作　　者：Shiling Yang Zhongli Ding Zhaoyan Gu Jimin Sun Shangfa Xiong 

机构地区：[1]Chinese Acad Sci, Inst Geol, Beijing 100029, Peoples R China

出　　处：《Chinese Science Bulletin》1999年第11期1034-1038,共5页

摘　　要：lsotopic analyses for paleovegetational evolution have been carried out on samples of the pedogenic carbonate nodules in the Red Clay-Loess sequence at Lingtai （35°N）, the Loess Plateau. Stable carbon isotopic composition indicates that （ ⅰ ） C₄ plants might be present at least by7.0 Ma; （ ⅱ ） C₄ plants expanded gradually between ～4.0 and ～3.2 Ma, and their biomass fraction was up to 50%; and （ ⅲ ） the biomass of C₄ vegetation since ～2.0 Ma seems to have been decreased to the level （about 20%） before 4.0 Ma. C₄ plant expansion at Lingtai cannot be fully understood with the 'global C₄ expansion' model because it occurred much later up to 3.0 Ma than in Pakistan, which indicates that some changes in the regional climatic system may also contribute to C₃/C₄ shift except changes in atmospheric CO₂ concentrations and temperature. The latitudinal zone for C₃/C₄ transition seems to move southwards slightly in East Asia, compared with the case in North America where 37°N is the idealIsotopic analyses for paleovegetational evolution have been carried out on samples of the pedogenic carbonate nodules in the Red Clay-Loess sequence at Lingtai (35°N), the Loess Plateau. Stable carbon isotopic composition indicates that (i) C4 plants might be present at least by 7.0 Ma; (ii) C4 plants expanded gradually between ～4.0 and ～3.2 Ma, and their biomass fraction was up to 50%; and (iii) the biomass of C4 vegetation since ～ 2.0 Ma seems to have been decreased to the level (about 20%) before 4.0 Ma. C4 plant expansion at Lingtai cannot be fully understood with the “global C4, expansion” model because it occurred much later up to 3.0 Ma than in Pakistan, which indicates that some changes in the regional climatic system may also contribute to C3/C4 shift except changes in atmospheric CO2, concentrations and temperature. The latitudinal zone for C3,/C4 transition seems to move southwards slightly in East Asia, compared with the case in North America where 37°N is the ideal boundary for the C4, expansion.

关 键 词：pedogenic CARBONATE PALAEOVEGETATION shift atmospheric CO2 concentrations. 

分 类 号：P534.621[天文地球—古生物学与地层学]