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Pioneer organisms after F-F mass extinction in Dushan region,Guizhou Province,and their significance in establishing new ecosystem

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Science China Earth Sciences 2006年第5期49卷 449-460页

作者： WANG Yue1, 2, WANG Xunlian1 & SHI Xiaoying1 1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China 2. School of Resources and Environment, Guizhou University, Guiyang 550003, China School of Earth Sciences and Resources China University of Geosciences Beijing China School of Resources and Environment Guizhou University Guiyang China

After mass extinctions, most areas became “ecologically barren areas” lacking or even without ecosystem over an extensive region. Studying the pioneer organisms and the reconstruction process of a new ecosystem in the “ecologically barren area” is very important for revealing the evo- lution after bio-mass extinctions. In the Dushan region, Guizhou Province, China, the trace fossils appeared and flourished evidently earlier than body fossils after Frasnian-Famennian (F-F) mass extinction. The pioneer organisms and pathfinders in the “ecologically barren areas” are the trace-makers that are deposit-feeders with relatively simple structure and conformation on or near the deposit surface. The trace-makers have undergone an evolutionary process that their trace structures changed from simple to complex, and their living and moving areas and spaces enlarged from linear to planar and then to three-dimension spaces. Those characters show that the ability of the trace-makers to deposits and their efficiency of looking for food have been enhanced gradually and that those trace-makers constructed gradually a base for the new ecosystem. This process is similar to that of the trace fossils near the Precambrian-Cambrian boundary. In the Dushan area, only the recovery intervals have been identified for the Famennian body fossils, with no eminent radiation interval recognizable due to the Devonian-Carboniferous (C-D) mass ex- tinction. However, both the recovery and radiation intervals may be clearly recognized in the Famen- nian trace fossils based on their conformation and diversity. The evolution and diversification of the trace fossils in the “ecologically barren area” is considered to have played a role of necessary foun- dation for the recovery of body fossils in the ecological chain. With the gradual disappearance of the unfavourable environment factors resulting in the F-F mass extinction, a new ecosystem was reconstructed in the “ecologically barren area” through a three-

关键词： pioneer organisms, reconstruction of ecosystem, trace fossils, F-F mass extinction, Later Devonian, Dushan region, Guizhou Province, China.

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Carbon isotopic studies of individual lipids in organisms from the Nansha sea area, China

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Science China Earth Sciences 2004年第7期47卷 593-598页

作者： DUAN Yi1,2, SONG Jinming3 & ZHANG Hui1 1. Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou 730000, China 2. School of Geology, Lanzhou University, Lanzhou 730000, China 3. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China

Carbon isotopes of individual lipids in typical organisms from the Nansha sea area were measured by the GC-IRMS analytical technique. d 13C values of saturated fatty acids in different organisms examined are from -25.6 to -29.7 with the average values ranging from -26.4 to -28.2 and the variance range of 1.8 between different organisms is also observed. Unsaturated fatty acids have heavy carbon isotopic compositions and the mean differences of 2.9—6.8 compared to the same carbon number saturated fatty acids. d 13C values of n-alkanes range from -27.5 to -29.7 and their mean values, ranging from -28.6 to -28.9, are very close in different organisms. The mean difference in d 13C between the satu-rated fatty acids and n-alkanes is only 1.5, indicating that they have similar biosynthetic path-ways. The carbon isotopic variations between the different carbon-number lipids are mostly within 2.0, reflecting that they experienced a biosynthetic process of the carbon chain elon-gation. At the same time, the carbon isotopic genetic relationships between the biological and sedimentary lipids are established by comparative studies of carbon isotopic compositions of individual lipids in organisms and sediments from the Nansha sea area, which provides scientific basis for carbon isotopic applied research of individual lipids.

关键词： marine organisms, individual lipids, carbon isotopic compositions, genetic relationships.

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