中文摘要：

对甘肃敦煌伊塘湖沉积物进行了野外钻探采样,采用光释光测年技术确定了沉积物的年代,测定了总有机碳含量（TOC）、碳氮比（TOC/TN）和有机质稳定碳同位素组成（δ13Corg）等环境代用指标.结果表明,23ka至今,湖区沉积物δ13Corg在-27.84‰～-22.86‰之间变化,可与TOC对比.干旱气候条件下湖泊沉积物的δ^13Corg变化主要受到沉水植物和挺水植物含量变化的控制,生长于较深水的沉水植物δ13Corg值偏正,而生长于较浅水的挺水植物δ13Corg值偏负;另外,部分时期有外源陆生植物产生的有机质输入,影响沉积物的碳同位素值.总体上,干旱区湖相沉积物δ13Crg值可指示湖水面的变化、间接指示气候干湿变化.δ13Corg变化的时间序列显示出明显的冰期-间冰期变化,从末次盛冰期到全新世暖期可将伊塘湖的环境演化分为4个阶段：23～ 13ka是一个气候不稳定时期,整体呈冷干并且湖面水位偏低,但后期有转暖的趋势;13～9ka为冰期向全新世暖期的过渡阶段;9～5ka整体湖面水位偏高、气候暖湿,含有短时间的干事件;5ka至今有变干的趋势.23ka以来,伊塘湖区的湖泊环境演化受全球大气环流与水汽输送路径控制.

英文摘要：

Yitang Lake is located in southeastern Dunhuang region of Northwestern China, with extremely arid climate; its formation and evolution was associated with migration of the Danghe River during Quaternary. In autumn of 2011, we drilled a 292.8-m core （40°18＇N, 94°58＇E） from this lake to reconstruct the past climatic and environmental changes. This paper investigates samples from the upper 21.5-m cores. The depositional sequence can be divided into three stages： the brown yellow and blue-yellow clay layer from 0.30m to 9.36m, the black clay and peats from 9.36m to 13.52m, and the alternations of brown-yellow clay and blue-yellow sand from 13.52m to 21.50m. We measured TOC （total organic matter content） and stable carbon isotopic composition （δ^13Corg） at 10cm intervals and TOC/TN （carbon-nitrogen ratio） at 20cm intervals; four samples were selected for optically stimulated luminescence dating, which provide an age control for this depositional sequence. A new independent time scale is obtained by linearly interpolating ages of the dating levels, and extrapolating ages to the surface sediments. The results show that these sediments were deposited in the past 23ka, the δ^13Cots. varied between - 27.84‰ and -22. 86‰, and it can be compared with the TOC changes. The stable carbon isotopic composition of organic matter of these lake sediments is determined mainly by the ratio of submerged plants and emergent plants, that is, the δ^13Cog from submerged plant is more positive, while the δ^13Corg. of emergent plant is more negative. As a result, the δ^13Cots indicates content of the submerged plants and emergent plants in a lake, and, the contents of submerged plants and emergent plants were determined by the lake water depth, respectively. On the basis of this interpretation and the δ^13Cog. changes, the paleoenvironment variation of the Yitang lake is divided into four phases over the past 23ka： the lake level was lower and the climate was dry and cold during 23 - 13ka; between 13 - 9k