新疆焉耆盆地开都河不同河型段砂砾质沉积特征与差异分析

Depositional characteristics and variations of different channel deposits in the Kaidu River of Yanqi Basin,Xinjiang

新疆焉耆盆地开都河自察汗乌苏水电站流入博斯腾湖的河口之间,发育单一物源供给下的山间河段、辫状河段、曲流河段、顺直河段以及三角洲平原顺直型分流河道段等多种类型河道沉积。通过探坑挖掘与观察、砂砾质沉积物结构的测量、碎屑组分与重矿物分析以及数据统计分析等方法,分析开都河不同类型河段的砾石质沉积特征与搬运距离关系、砾质与砂质组合特征、砂质碎屑组分与沉积构造特征及变化等,认为沉积地形与坡度、沉积物组成以及气候条件等因素控制了不同河段类型的变化与沉积特征的差异。同时,建立了不同河型段砾石径变化与沉积搬运距离的定量关系。在此基础上,统计了在干旱气候与充沛物源供给条件下,开都河不同河型沉积中的有利储集体分布范围及其比例关系数据,可为陆相湖盆河流沉积相图的编制提供重要的参考依据。

The Kaidu River is a typical perennial internal river with abundant sediment located in the Yanqi Basin under arid climate condition.The catchment of the river is the Tianshan Mountain and the river drains into the Bostan Lake.A complete range of different channel deposits are recognized from source to sink of the associated depositional system,including straight,meandering,braided and anastomosingchannel patterns.Depositional facies,depositional processes and heavy mineral distributions were documented and analyzed statistically in relation with transport distance.The result shows that channel patterns and sedimentary facies are controlled by climate,composition of sediments,geography and slope.The grain size of sediments shows strong decreasing trend over transport distance.These results promoted the development of a facies models for the Kaidu River and the Bostan Lake.Since the proposed model incorporates quantitative analysis of the sediments and facies,it＇s promising to provide a modern analog for the interpretation of its ancient counterparts.