如何从现有的地貌形态定量提取构造活动信息是构造地貌研究的重要内容.乌鲁木齐河是天山北麓发育的主要河流之一,构造上可分为天山主脉、后峡断陷、南山隆起和山前坳陷等4个构造分区.本文运用河流坡降指标SL和Hack剖面以及标准化坡降指标SI/K等地貌计量指标,结合地层岩性等信息,探讨了乌鲁木齐河流域4个构造分区的新构造活动特征.结果显示,乌鲁木齐河流域干流全河段Hack剖面形态上凸,同时均衡坡降指标值(K)较高(K=531),表明其目前构造仍较为活跃;天山主脉和南山隆起分区干流河段Hack剖面曲线形态表现为上凸,显示分区内部处于相对强烈的构造隆升状态;后峡分区除局部因规模较大的支流汇人导致干流河段SL/K异常偏高外,其整体Hack剖面曲线形态趋于下凹,表明其内部构造活动性较弱;在南山隆起和山前坳陷过渡带,受准噶尔南缘断裂带的影响,干流河段的Hack剖面曲线形态表现为“上凸下直”,表明这部分河段目前尚处在向新均衡剖面调整的阶段;乌鲁木齐河流域干流河段SL/K在多处出现了异常高值,研究表明这和构造活动、岩性改变、支流汇入有关.%How to extract tectonic activity information from the existing geomorphic form is an important part of geomorphic research.The river slope index SL can indicate the local slope of the longitudinal profile of the river,and is often used to discuss the problem of tectonic activity (fault) or lithology difference.The Hack profile can reflect the changes in the longitudinal profile of the river and is often used to indicate the structural movement of larger time scales.In this paper,we choose the stream length-gradient SL index,Hack profile and gradient index (SL/K)with the method of ArcGIS statistical analysis technology to interpolate the basin K value and meanSL/K value.Combining the spatial distribution characteristics of the K value and the meanSL/K value with the lithology,we discusses four partitions tectonic division of neotectonic activity and landform evolution stage of the (U)rümqi River.The Jrümqi River is one of the main rivers in the northern Tian Shan foreland,which flows through the Tianshan uplift zone,Houxia graben,Nanshan uplift zone and piedmont depression successively.The strata are distributed in succession from old to new.The Tianshan uplift zone is mainly Paleozoic.The Houxia graben is mainly dominated by Mesozoic strata.The Nanshan uplift zone is composed mainly of Carboniferous tuff and tuffaceous siltstone.The piedmont depression is mainly composed of Quaternary alluvial and gravel.The digital elevation model(DEM)data used in this paper are derived from the ASTER GDEM elevation data with an initial resolution of 30 m × 30 m.Based on the analysis of SL and Hack profiles of river slopes in the mainstream of the ~rümqi River Basin and its four major structural strata,this paper draws the following conclusions:(1) The whole Hack profile of the (U)rümqi River basin is on convex form and the balancing grade index K value is high(K=531),which shows that current structure in this basin is still active.(2) Analysis of 4 partitions in the (U)rümqi River basin about SL and Hack profile reveal that the Tianshan uplift zone and partition of nanshan Hack profile present convex curve;Houxia graben after integral to Hack profile curve tends to sink;in the Nanshan uplift zone and piedmont depression junction,Hack profile is convex shape with the downstream into a linear form.Additionally,the four partitions balancing grade index K value are 149,653,1388 and 653,respectively.These show that Tianshan uplift zone and partition of Nanshan interior is currently in a state of intense tectonic uplift;Houxia graben is in the weak current tectonic activity;Nanshan uplift zone and piedmont depression are due to the southern margin of Junggar fault dislocation effects,which might be in a new equilibrium profile adjustment stage.(3) There are 9 abnormally high values of the SL/K in the mainstream reach of the (U)rümqi River Basin.These values from the upstream to the downstream are about:2.1 (2400m),6.0 (2275 m),6.2 (2100m),4.8(2070 m),6.0 (2010 m),48.0 (1900 m),11.0 (1700 m),10.0 (1575 m) and 10.8 (1550 m),respectively.These anomaly values correspond to the position of the Hack profile curve,which indicates that there is a good topography correspondence between the SL/K and the Hack profile in the (U)rümqi River Basin.The causes of abnormal high values of SL/K in the mainstream slope of the (U)rümqi River Basin are due to tectonic activity,lithological change,tributary import,etc.The high value of SL/K at 2100 m above sea level is affected by tectonic activity,lithological change and tributary import.The high value of SL/K at an altitude of 1550 m is mainly affected by the fault structure and tributary import.The high value of SL/K anomaly at 1900 m is mainly affected by lithological differences and fracture structures.Among them,the high value of SL/K at the altitude of 2400 m,2275 m,2010 m,1575 m and 1700 m is mainly affected by the tributary import.
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