Sr/Ca,Mg/Ca:珊瑚岛鸟粪沉积的物源指示计  

USING Sr/Ca AND Mg/Ca RATIOS AS SOURCE INDICATORS OF ORNITHOGENIC LACUSTRINE SEDIMENTS ON CORAL ISLAND

作　　者：赵三平[1] 孙立广[1] 刘晓东[1] 谢周清[1] 罗泓灏[1] 刘克新[2] 吴小红[3] 丁杏芳[2] 付东坡[2] 

机构地区：[1]中国科学院中国科学技术大学壳幔物质与环境重点实验室 [2]北京大学物理学院重离子物理研究所,北京100871 [3]北京大学考古文博学院,北京100871

出　　处：《第四纪研究》2007年第1期149-156,共8页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40231002)资助

摘　　要：文章尝试用Sr/Ca,Mg/Ca比值作物源指示计,区分了珊瑚岛屿受到海鸟粪影响的湖泊沉积物中鸟粪、珊瑚砂、植物这几种主要的环境介质对沉积物的相对贡献,据此恢复1800年来西沙群岛东岛海鸟数量变化和植被演化的历史。结果表明,东岛海鸟数量的变化历史可划分为潜伏期、增长期、稳定期和衰退期4个阶段,历史时期东岛海鸟生态系统的建立和发展与岛屿植被的演变有着密切的联系。研究获得的方法和初步结论为进一步开展西沙岛屿海鸟数量变化、植被演化的广泛对比并探讨与气候变化、人类活动的相互联系提供了基础。Sr/Ca and Mg/Ca ratios in tropical corals are commonly applied to reconstruct sea surface temperature （SST）, in this study, however, they have been used as indicators of sedimentary material source in the lacustrine sediments influenced by seabird droppings on coral island. Using 11cm diameter PVC tube, a lacustrine sediment core with a length of 126cm was collected from a fresh water lake ＂Cattle Pond＂ on Dongdao Island （16°39′- 16°41′N,112°43′ - 112°45′E） South China Sea. Lithology and chronology analyses indicated that the sediment core was well preserved without human activity disturbance and the calibrated ^14C-age as a function of depth is described by the equation： Depth （cm） =0. 0717 ^14C-age （cal. aB. P. ） （r =0.99, n =5）. Linear extrapolation of the equation gives an age of 1750cal. aB. P. for the bottom sediments. Down-core variation profiles of grain-size textures, loss in ignition at 950℃ （LOI950℃ ） and 550℃ （LOI550℃ ）, total organic carbon （TOC）, Total nitrogen （TN）, as well as some geochemical element concentrations such as Sr, Ca, Mg were analyzed. Furthermore, Sr, Ca and Mg concentrations in the sediment media around the Cattle Pond （e. g. coral sand, plant, cattle excrement and seabird dropping） were also examined. The results showed that the ratios of Sr/Ca and Mg/Ca in the plant, coral sand and seabird dropping on Dongdao Island are quite different from each other, thus these three major sediment-medium involved in the lacustrine sediments could be distinguished by Sr/Ca, Mg/Ca ratios. Using three end-member mixing model, we have calculated relative contribution of seabird dropping, coral sand and plant remains to the ornithogenic lake sediments. The change of seabird dropping input can be used to measure the relative size of historical seabird population. Based on above calculation, we have reconstructed the historical change of seabird populations on the Dongdao Island over the past 1800 years; the results are in good accordan

关 键 词：西沙群岛东岛 Sr/Ca MG/CA 海鸟数量 植被演化 

分 类 号：P959.7[天文地球—自然地理学]