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根据青藏高原东北部甘肃南部郎木寺泥炭总有机碳含量的时间序列,重建了该区7.3~4.0kaB.P.(中全新世)期间气候演变的历史,其中较为显著的变冷事件分别集中在6.8cal.kaB.P.,5.0cal.kaB.P.和4.3cal.kaB.P.。同时分析了3个不同深度的泥炭脂类分子化合物。结果表明,正构烷烃和直链烷基-2-酮都由长链组分所构成,具有明显的奇碳优势和很高的碳优势指数值(CPI>5)表明,这些长链组分来自草本高等植物。样品中还检出脂肪酸甲酯系列,也以长链组分为主,可能是沉积早期生物地球化学作用的产物。异构烯烃的存在及菲系列化合物低的甲基菲指数(MPI)和镜质体反射率(Rc)值,说明样品受成岩作用的影响很小而且几乎没有遭受现代的污染,即泥炭保存完好,各个指标可以真实反映泥炭的组成、性质及其形成时的环境条件。根据总有机碳含量的时间序列和不同阶段样品中的脂类分子化石的组合特征,探讨了各阶段气候和植被的演化特征。
According to the time series of the total organic carbon content of the pelag in Langmusi Monastery in the northeastern Gansu Province of the Qinghai-Tibet Plateau, the history of the climate evolution during the 7.3 ~ 4.0kaB.P. (Mid-Holocene) period was reconstructed. The more significant chilling events were concentrated in the 6.8cal.kaB.P., 5.0cal.kaB.P. and 4.3cal.kaB.P. At the same time, three peat lipid compounds with different depths were analyzed. The results showed that both n-alkanes and linear alkyl-2-ketones were composed of long-chain components with obvious odd carbon and high carbon index (CPI> 5), indicating that these long-chain components From herb higher plants. Samples also detected fatty acid methyl ester series, also long-chain components, may be the product of early biogeochemical geochemical deposition. The presence of iso-olefins and the low MPI and Rc values of the phenanthrene series compounds indicate that the sample has little effect from diagenesis and has little to no modern pollution, ie, peat remains intact , Each indicator can truly reflect the peat’s composition, nature and the environmental conditions when it is formed. According to the time series of total organic carbon content and the combination characteristics of lipid molecular fossils in different stages of samples, the evolution characteristics of climate and vegetation in each stage were discussed.