中文摘要：

通过对内蒙古西部额济纳古湖小狐山剖面沉积物中总有机碳（TOC）、总氮（TN）和碳酸盐（CaCO3）含量的测定，分析了沉积物中有机碳来源和无机碳酸盐成因，结果表明在额济纳古湖相沉积物中TOC与TN含量呈同步变化规律，TOC／TN（9．91～10．16）较稳定，其有机质为湖泊自生藻类和外源维管束植物共同提供。沉积物中有机质含量受温度、降雨量变化控制，当气候暖湿时，沉积物中有机碳含量高，气候冷干则有机碳含量低，因此，有机碳含量是所研究剖面气候温湿与干旱（冷）的有效环境指标。湖泊自生碳酸盐含量则由湖区有效湿度和生物量的共同控制，其稳定碳同位素指示有效湿度的大小。粒度，特别是小于2μm组分含量与水动力和搬运介质相关，其组分含量大于5％时为湖相沉积且随其含量增加指示水深加大。根据沉积物中有机碳、碳酸盐、无机碳同位素和粒度，并结合剖面岩相特征，探讨了研究区该时段（按剖面深度划分）气候变化和湖泊演化历史：？～38．15^14CkaB．P．（1039～949cm）湖区气候为冷于环境特征，风沙盛行；38．15～31．73^14CkaB．P．（949～780cm）气候环境逐步改善，降水量增加，湖泊开始发育并到达湖泊高水位阶段；31．73～22．79^14CkaB．P．（780～482cm）湖泊水位有所下降，气候有明显的波动，但仍维持在较高的水位上，湖区环境仍为暖湿气候；22．79～17．37^14CkaB．P．（482～304cm）气候开始变冷变干，湖区有效适度持续减小，湖泊退缩；17．37～14．00^14CkaB．P．（304～178cm）湖泊退出研究点，区域有效湿度小，风沙盛行，存在短暂气候事件，造成暂时性流水；14～4^14CkaB．P．（178～0cm）湖泊开始再度扩张、水位上升，湖水变淡，到该阶段的后期气候又一次发生转变，湖区再度成为干旱环境，有效湿度减小，湖泊开始萎?

英文摘要：

Base on the analysis of organic element, carbonate contents and the stable carbon and oxygen isotopes of the Xiaohushan section in Ejina Basin, western Inner Mongolia, China,the source of organic matters in the sediment and the formation mechanisms of the inorganic carbonate were discussed. To the Xiaohushan section in Ejina Basin,it was found that when the TOC content is higher than 0. 15% and that of TN is higher than 0. 015%, the sediments are lacustrine deposits, otherwise are eolian （sandy）accumulations. The results show that the organic matters in the sediments was mainly composed of algae and vascular plants formed during the paleolake evolution, and the TOC/TN ratio ranges from 9.91 - 10.16. When the TOC,/TN ratios are stable,both TOC and TN content variations are closely related with temperature and precipitation changes. Therefore,the TOC in the studied section is an effective proxy of the climate. The content of authigenic carbonate was controlled by the water temperature and biomass and the stable carbon isotope of the authigenic carbonate was a proxy of the effective humidity in the study area. It could be deduced that the climate recorded in the section was mainly fluctuated between warm-humid and cold-dry. According to the TOC,CaCO3 contents, 13C and grain size variations of the sediments, and the lithofacies of the studied section,the climate change and paleolake evolution history of the studied section can be divided into six stages： Before 31.73^14CkaB. P. （〉949cm）, it was a cold and dry. Between 38. 15^14CkaB. P. and 31.73 ^14C kaB. P. （949 -780cm） , the climate in the study area was warmer and wetter, and the lake level was high. From 31.73 ^14C kaB. P. to 22.79^14C kaB. P. （780 -482cm） ,the climate was still warm and wet and the paleolake level was high, but with strong fluctuations and decreases of the lake level. The climate was deteriorated and the water level decreased obviously between 22.79 ^14CkaB. P. and 17. ：37^14C kaB. P. （482 - 304cm）. From 17.37^14C kaB.