中文摘要：

选择位于西风区的乌伦古湖为研究对象,利用AMS14C测年手段,建立了乌伦古湖沉积岩芯全新世以来的时间序列。对湖泊沉积物中的介形类组合特征及其壳体氧碳同位素的综合分析表明,全新世以来乌伦古湖地区气候环境演变经历了3个阶段：9985～5250cal.aB.P.为剖面最湿润阶段,气候经历了温干-冷湿-暖湿的转变,湖水水位和湖面相应地经历了由浅变深、由小变大的变化,出现了高湖面特征;5250～1255cal.aB.P.为剖面最干燥阶段,气候由早期暖干向中后期暖湿转变,湖泊水位先下降后回升;1255cal.aB.P.以来先低温后升温,气候干燥,降水较少,湖水位降低。乌伦古湖介形虫记录的气候环境演化不但与孢粉资料记录相吻合,而且与周边区域环境变化记录一致,很好地响应了区域环境和全球气候突变事件,在百年尺度上主要遵循西风带模式,表现为冷湿暖干组合特征。

英文摘要：

Compared to that of the East Asia Monsoon area, the study of the Westerly area is sparse and has controversy on the pattern of temperature and precipitation. Ostracode assemblage and stable isotopes of the shell are sensitive proxies to indicate changes of paleoclimate. A 225-cm sediment core from the Ulungur Lake, Xinjiang, China, which lies in the westerly area, had been obtained using piston on the above-water platform in July, 2004 for ostracode analysis to reconstruct paleoclimatic and environmental change. The core chronology was constructed from six AMS radiocarbon dates on the bulk organic matter for 9985 calendar years which is in good relation to the depth. The depositing rate was 0.13 -0.91mm/a, with the average of 0.22mm/a. Five ostracode taxa including Limnocythere inopinata, Candona, Darwinula, Cyclocypris, and Ilyocypris were identified in the core sediment, with Limnocythere inopinata the dominant. The distribution characters of ostracode assemblages and abundance, body length, and shell stable isotopes are distinct： The 9985 -5250cal. aB. P. （222- 160cm）layer has the maximum number of species, the minimum abundance and body length, and more negative δ^18O and δ^13Cearb; the 5250 - 1255cal. aB. P. （160 -50cm）layer has the minimum abundance and number of species, the maximum body length, and more positive δ^18O and δ^13Ccarb ; while the 1255cal. aB. P. （50cm）layer has all characters the medium. Different species of ostracode has different temperature and salinity living conditions and thus can be used as indicator to paleoclimate change. δ^18O has been used as an indicator to effective moisture （ratio of precipitation/ evaporation）. High δ^13O indicates high evaporation and low precipitation while low δ^18O indicates the contrary ones. The curve of δ^13C changed in-phase with that of δ^18O would indicate that they were controlled by the same factors. Body length is commonly considered as an indicator of salinity, an indirect proxy to effective moisture. Based on