河西走廊东西段全新世古湖泊演化对比研究

我国干旱区内陆河流域分布有数量众多的古湖泊，其沉积记录已被广泛应用于第四纪地质、地貌研究。为了解亚洲夏季风水汽输送北部边界在全新世期间的气候、环境、地质和地貌演化情况，本文选择了位于河西走廊东段的石羊河流域和西段的疏勒河流域作为研究区，对其空间地形、沉积物的年代、沉积相、堆积及侵蚀速率、粒径指标、地球化学指标和孢粉指标等特征进行了分析。空间分析显示石羊河流域尾闾猪野泽具有湖盆地形，该地区湖泊形成逻辑斯蒂回归模型公式为：P（1）=1/[1+e^{-（1356.0930759+0.00004759D-1359.3707216R+1.32323064S）}]。剖面分析显示这一地区早、中全新世时期气候湿润，具备成湖条件；晚全新世气候逐渐干旱，湖泊逐渐缩小并最终干涸。疏勒河流域古冥泽地区具有狭长湖盆地形，该地区湖泊形成逻辑斯蒂回归模型公式为：P（1）=1/[1+e^{-（1266.439446+0.006063DE+0.00000752D-1275.58117R+1.0918188S）}]。剖面分析显示这一地区早、中全新世时期气候湿润，具备成湖条件；晚全新世气候则逐渐干旱，河道湖消失，河流改道。此外，根据两个流域沉积物的演化信息，可以推测，亚洲夏季风在早、中全新世到达了河西走廊西段，而在晚全新世时期退缩至河西走廊东段，疏勒河流域所在的西段则主要受西风带的影响。

THE COMPARATIVE STUDY OF PALEOLAKES EVOLUTION BETWEEN THE EASTERN AND WESTERN PARTS OF THE HEXI CORRIDOR IN HOLOCENE

Quaternary paleolakes are widely distributed in arid China, and the sedimentary records of these lakes can be used as research materials. The Hexi Corridor is located in the arid region of China; besides, the Shiyang River drainage basin(36°29'~39°17'N, 101°41'~104°16'E) is in the eastern part of the Hexi Corridor, and the Shule River drainage basin(42°48'10″~38°23'48″N, 93°21'27″~99°1'20″) is in the western part. In order to understand the climatic, environmental, geological and geomorphologic evolution around the north boundary of summer monsoon water vapor transport zone, we analyzed spatial features of the Shiyang River and the Shule River drainage basins including DEM, slope, aspect, earth surface roughness and section. Furthermore, we also analyzed ages, sedimentary facies, deposition and erosion rates, grain sizes, geochemical proxies and pollen proxies of these two drainage basins. According to the spatial analysis, Zhuye Lake area of the Shiyang River drainage basin is a basin-shaped region, and the logistic regression model of this area is P(1)=1/[1+e-(1356.0930759+0.00004759D-1359.3707216R+1.32323064S)]. The height from the bottom to top of the basin is around 180m. The distance from modern river, slope and earth surface roughness can affect the probability of lake existence in this region. Based on the sedimentary records, climate of the Shiyang River drainage basin is humid during the Early and Middle Holocene and is relatively arid in the Late Holocene. Therefore, the stable terminal lake have existed during the Early and Middle Holocene and have disappeared later. On the other hand, Gumingze of the Shule River drainage basin is a narrow basin-shaped region, and the logistic regression model of this area is P(1)=1/[1+e-(1266.439446+0.006063DE+0.00000752D-1275.58117R+1.0918188S)]. The height from the bottom to top of the basin is around 200m. The DEM, distance from modern river, slope and earth surface roughness can affect the probability of lake existence in this region. In the Shiyang River drainage basin, sediments with pollen and geochemical materials are deposited in the middle and lower reaches during Early Holocene, so the river power is relatively strong and the climate is humid; however, the sediments from middle reaches are eroded in the Late Holocene, and the climate is relatively dry. Therefore, a temporary lake have existed for a short time and disappeared in the Late Holocene due to arid climate. The sedimentary records of the Shule River are similar with those of the Shiyang River, but the aridification appears later than the Shiyang River drainage basin. Based on the results above, we can know that the summer monsoon have reached western part of the Hexi Corridor in Early and Middle Holocene, but retreated back to the eastern part in the Late Holocene when the western part is affected by the westerly winds.