Paleoclimatic Significance of Oxygen Isotope Composition of Carbonates from a Sediment Core at Bosten Lake, Xinjiang, China

• 责任者：Zhang Jiawu (Key Laboratory of Western China’s Environmental Systems ; Ministry of Education ; Research School of Arid Environment and Climate Change ; Lanzhou University ; Lanzhou730000 ; China) ; Wang Junlan
• 刊名：Quaternary Sciences
• 出版年：2010
• 卷期：30(6)
• 关键词：湖泊沉积物 ; lake sediments ; 氧—18 ; O-18 ; 新疆 ; Xinjiang
• 页码：p.1078-1087
• 图表：5 illus., 28 refs.
• 分类号：0803
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

The authors analyzed the oxygen isotope composition of authigenic carbonates,　fine-grained calcite and ostracode shells from a sediment core BST04H recovered from the deep part of Bosten Lake,　Xinjiang,　China in this paper.　Based on detailed analyses of isotopic compositions of the regional rainfall and hydrological settings of the lake region, climatic implications of the oxygen isotope composition of authigenic carbonates deposited in Bosten Lake was investigated. The data suggest that the oxygen isotope composition of carbonates in the lake sediments reflects changes in both the regional precipitation/evaporation ratio and the long-term isotopic composition of the input water controlled by the proportion of winter precipitations to the annual precipitation. The oxygen isotope composition has become heavier from the early Holocene before ca.8100cal.aB.P.to the Late Holocene after ca.1300cal.aB.P.Such a pattern was interrupted by shifts towards very negative δ¹⁸O occurring 4500～3500 cal.aB.P. and 1300～500 cal.aB.P.although the climate was relatively dry during both intervals as indicated by fine grain sizes and high carbonate contents of the same sediment core.　The negative δ¹⁸O values might be related to the input of snowmelt and/or groundwater into the lake,　implying decreases in the summer precipitation.　However some short periods characterized by the input of increased summer precipitation can also be seen as demonstrated by the oxygen isotope composition.　The authors therefore suggest that attention should be paid to the paleoclimatic implication of oxygen isotope composition of lacustrine sediments in the arid regions where the local hydrology may be variable.