云南中甸纳帕海古环境演化的有机碳同位素记录  

Palaeoenvironmental Evolution Deduced from Organic Carbon Stable Isotope Compositions of Napahai Lake Sediments, Northwestern Yunnan, China

作　　者：殷勇[1] 方念乔[2] 胡超涌[2] 聂浩刚[2] 秦尊丽[2] 

机构地区：[1]南京大学大地海洋科学系,南京210093 [2]中国地质大学,北京100083

出　　处：《湖泊科学》2001年第4期289-295,共7页Journal of Lake Sciences

基　　金：国家自然科学基金 (4 96 72 135 );国家重点基础研究发展规划项目 (G19980 40 80 0 )

摘　　要：中甸纳帕海位于云贵高原横断山脉腹地 ,其成因与碳酸岩类地层长期溶蚀有关 .在丰水期和枯水期纳帕海的水位相差很大 ,枯水期常形成浅水池沼 ,因而造成枯水期和丰水期水生植被的发育状况有很大的差异 .枯水期由于水生植物 (飘浮和挺水植物 )发育 ,造成总有机碳和氢指数的增加 ,有机碳同位素偏负 ,丰水期出现相反的演化趋势 .进一步推论表明在暖干的气候条件下纳帕海极易形成枯水位 ,在冷湿的气候下可维持相对高的水位 .古环境重建表明纳帕海在大约 32kaBP和 15kaBP出现环境的重大变迁 ,32 - 15kaBP出现高湖面 .The Napahai Lake, situated in the hinterland of the Hengduan Mountains, is a basin by the erosion of carbonate rocks. The lake levels have experienced great fluctuation between low stand and high stand stages. The lake level changes directly influences the amount and distribution of aquatic plant communities that used different sources of carbon for photosynthesis, thereby imprinting the organic sediments with a characteristic 13 C composition. Another reason influencing the 13 C composition for bulk organic sediment, in this case, is the change of reduction oxidation condition in the alternative stages. In addition with the strong dissolution of carbonate strata in humid cool conditions, the lake level fluctuations and climatic changes could be reconstructed using HI, TOC and δ 13 C. The results show that increase in total organic carbon and hydrogen index correlates in general, with decrease in δ 13 C values, which could be attributed to the flourishing of emerging and floating aquatic plants as well as a relative reduction environment in a low lake level associated with a warm dry or temperate dry climate. The decreases of TOC and HI often correlate well with δ 13 C value increasing in a high lake level stage accompanied with a cool humid climate, which might be attributed to low productivity of aquatic plants, oxidation that triggers decomposition of organic matters and strong dissolution of carbonate strata in humid cool conditions. The palaeo environmental reconstruction shows that major environmental changes took place at 32kaBP and 15kaBP respectively. The lake levels exhibited frequent fluctuations between ca.57-43kaBP, and then the lake level slightly rose from ca.43kaBP to ca.37kaBP. After then, the lake level dropped dramatically when the climate became warm and dry. From ca.32kaBP, the lake level had a distinct rise due to cool humid climate and kept high until the end of the Last Glacial Maximum. A warm dry climate returned to the areas again and the lake level rem

关 键 词：总有机碳 氢指数 有机碳同位素 云南 湖泊 古环境 中甸纳帕海 

分 类 号：P593[天文地球—地球化学]