蒙古戈壁天山断裂带晚新生代构造变形与构造地貌研究

跨越中蒙边境线的戈壁天山断裂带是一条大型左旋走滑断裂带,东西展布约700 km。通过解译分析Landsat ETM卫星遥感影像和SRTM数字高程模型(DEM)数据,对戈壁天山断裂带晚新生代构造活动及其地貌特征进行了研究。结果表明,沿戈壁天山断裂带发育了一系列断层陡坎、系统的水系错位、挤压脊等典型的走滑构造地貌类型。遥感影像解译结果还显示3处系统水系错位,均受戈壁天山断裂左旋走滑运动的影响,表现出系统的左旋水平位错。结合历史地震数据、先存的基底构造和断层系统,本区地震活动性呈现出不可预测性和复杂性。此外,发育在断裂带上的3个大型挤压脊构造中:Karlik Tagh和Gurvan Sayhan就位于走滑断裂的终端,其走滑分量减弱并逐渐转为以逆冲分量为主的构造特征。Nemegt Uul位于2条不连续的走滑断裂的汇合和叠置部位。走滑断层均穿过了挤压脊构造,同时伴随有逆冲作用分量,造成了挤压脊沿走向和垂直走向上的构造地貌生长,显示了是陆内造山带演化的重要过程。

戈壁地区煤田地震资料处理的特点分析

戈壁地貌主要分布在我国的西北地区,由于其特殊的地貌特征和表层岩性特征,使得地震原始资料具有静校正问题突出、信噪比偏低以及地震波场复杂等特点。以内蒙古自治区额济纳旗路井南地区地震资料处理为例,在分析原始资料有效反射波和各种干扰波特点的基础上,围绕如何提高成果剖面的精度和信噪比这个问题,探讨了资料处理的难点和重点,总结了适合戈壁地区地震资料处理的关键的方法技术。

大口径长输管道地貌恢复的施工管理

大口径长输管道工程施工过程中,地貌恢复是施工管理的一项重要工作。本文根据农田段熟土层薄,戈壁滩植被少、环境脆弱等特点,借鉴西气东输二线平顶山-泰安支干线新郑-平顶山段农田地貌恢复的施工经验,阐述了新疆维吾尔自治区地貌恢复过程中采取的有效措施,总结出一些地貌恢复施工的管理经验。

The recent evolution of dune landforms and its environmental indications in the mid-latitude desert area(Hexi Corridor)

The history of dune landform changes and dust activity at mid-latitudes is a good archive for exploring environmental changes and related landscape response.In this study,the dynamic changes,material sources,dust activity history and the influencing factors of typical sand dunes in the Hexi Corridor were comprehensively analyzed from the aspects of aeolian geomorphology,grain-size sedimentology,geochemistry and climatology.The results show that in the past half century,the typical crescent-shaped dunes and chains of crescent-shaped dunes in the study area have moved or swayed greatly,with an average speed ranging from 0.8 m/a(Dunhuang)to 6.2 m/a(Minqin).The dynamic changes of sand dunes are mainly affected by annual precipitation,annual average wind speed and annual gale days,which indicates that climate is the primary influencing factor of dune landform changes.The three-stage grain-size curve model of dune sands is obviously different from that of gobi sediments(two-stage),revealing the“immaturity”of the latter in sedimentology,while the former has experienced efficiently aeolian differentiation and non-local origin.The comprehensive evidences of paleogeography,sedimentology and geochemistry reveal that the source materials of sand dunes are mainly alluvial/proluvial and palaeo-fluvial sediments,including clastic sediments in the denudation/erosion zones of the north and south piedmonts.Indicators such as the proportion of surface fine particles,the coverage of surface salt crusts,and the content of erodible sandy materials indicate that the western gobi areas are not the main source areas of wind-blown dust in the central and eastern parts of the Hexi Corridor.The spatial distribution of the movement direction of sand dunes is similar to that of the regional dominant wind direction,which indicates that the difference in the dynamic evolution of dune landforms between the east and west of the Hexi Corridor should be controlled by the regional-scale wind system,that is,controlled by the dynamic mechanism rather than the difference in material sources.The warming and humidification of the Hexi climate is a synchronous response to the global warming and the strengthening of the Asian Summer Monsoon.It is also the main reason for the reduction of dust storms in the study area,which means that a potential inverse desertification process exists in the Hexi Corridor during the same period and it is also controlled by climate change.However,the process of desertification in the oasis areas during the period is caused by groundwater fluctuation affected by human activities.

中纬度荒漠区河西走廊沙丘地貌的演化特征及其环境指示

北半球中纬度地区的沙丘地貌变化和粉尘活动历史是探索全球环境变化与景观响应问题的良好档案。本文从风沙地貌学、粒度沉积学、地球化学和气候学等方面综合分析了中纬度典型荒漠区河西走廊的典型沙丘动态变化、物质来源、粉尘活动历史及其影响因素等。结果表明,20世纪60年代以来研究区典型新月形沙丘和新月形沙丘链等发生了较大的移动或摆动,平均移动速度介于0.8~6.2 m/a之间。沙丘的动态变化主要受年降水量、年平均风速和年大风日数的影响,表明气候是沙丘地貌变化的首要影响因素。沙丘沙(三段式)与戈壁沉积物的两段式粒度曲线模式明显不同,揭示了后者在沉积学上的"不成熟性"而前者经历了高效的风成分异作用且非局地起源。古地理、沉积学和地球化学综合证据揭示沙丘沙的母源物质主要是冲洪积物和古河流沉积物等,包括南北山麓剥蚀带的碎屑沉积等。地表细颗粒物质的比例、表层盐结皮的覆盖率和可蚀性砂质物质含量等指标指示了西部戈壁区不是中东部风尘的主要来源区。沙丘移动方向与区域性主导风向在空间分布上具有相似性,表明河西走廊东、西部间之间在沙丘地貌动态演化上的差异应受控于区域尺度的环流风系,即受控于动力机制而不是物质来源上的差异。区域气候的暖湿化是对全球增温和亚洲夏季风增强的同步响应,也是研究区沙尘暴减少的主要原因,同期河西走廊潜在的逆沙漠化过程亦受控于气候变化;但绿洲区沙漠化过程还是起因于人类活动影响的地下水波动。