Knowledge Resource Center for Ecological Environment in Arid Area
| 雅丹地貌形成发育过程研究——以敦煌雅丹国家地质公园区为例 | |
| 其他题名 | Formation and Evolution Process of Yardang Landforms:A Case Study in Dunhuang Yardang National Geo-park |
| 牛清河 | |
| 出版年 | 2011 |
| 学位类型 | 博士 |
| 导师 | 屈建军 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 雅丹地貌具有独特的形态特征和神秘的成因，在很早就受到地质地理学者的重视。它通常被认为是风蚀地貌的一种，与风积地貌相比，研究进展缓慢，甚至处于驻足不前的状态。近年来随着干旱区旅游在雅丹地貌区的开展，已受到广大旅游爱好者的青睐和相关管理部门的关注。然而，迄今对雅丹地貌的定义、分布分类、形成条件、发育过程及其形成年代和环境等方面尚有不同认识或科研盲点。显然，研究这些问题，不仅有助于揭示雅丹地貌与沙漠、戈壁的内在联系，丰富风沙地貌学的研究内容，而且对促进干旱区旅游开发与品位提升，以及搞好雅丹地质公园的保护等具有重要的理论和实践意义。\n作者选择在中国敦煌首建的雅丹国家地质公园作为研究区域，通过3年多来对研究区及其周边地区野外地质、地貌和水文调查，建立风沙观测场，搜集区域气象和遥感影像资料，野外风沙观测和风洞实验，利用3S技术、室内风洞实验技术和光释光测年技术等方法，获取了大量原始数据。经过比较全面深入的系统研究，取得了如下进展：\n（1）雅丹地貌的形态与分类。利用现代摄影测量和GIS技术手段，分析计算得出地质公园主体区域内共有雅丹地貌体5370个。通过对所有雅丹体的面积、周长、长、宽、高和长轴走向逐个计算、统计分析得出区域内的雅丹地貌具有形态特征参数和参数比率跨度大又相对集中，长轴走向变化明显，分布密度高的特征。研究区雅丹地貌的面积、周长、长、宽和高的平均值比为247.76:16.42:6.44:2.70:1，中值比为88.51:12.79:4.75:2.49:1，与其他区域的研究报道相比，宽高比率基本一致，而长宽和长高比率与前人研究结果均有一定程度的差别，多方向动力条件和不同发育阶段是造成这种差别的主要原因。基于形态特征参数的聚类分析方法将研究区雅丹地貌划分为特大型雅丹、大型雅丹、南北向中型雅丹、东西向中型雅丹、南北向小型雅丹和东西向小型雅丹等六类，不同类型的雅丹地貌的分布格局反映了营力条件的变化和发育阶段的不同。\n（2）地质内营力作用。晚更新世后期，研究区受构造抬升，疏勒河南迁，使河湖相地层抬升并脱水，地下水位下降，使雅丹地层高于侵蚀基准面，控制雅丹地貌生长的上限高度，在此过程中形成大量构造裂隙和节理，为外营力侵蚀提供了便利条件，同时分布在地质公园南北两侧东西走向的叠瓦状压性断裂带对雅丹分布格局起到了宏观控制作用。\n（3）地质外营力主要包括物理风化作用、流水作用、风力作用和重力作用。物理风化作用（包括温差风化、盐类风化和冻融风化）在地面形成一层疏松的风化壳，降低了沉积物胶结程度，并出现大量裂隙和裂纹，不仅加快了其他外营力作用的速度，又为风和地表水的集中下切侵蚀提供了初始通道。流水可分为地表水、地下水和雅丹体表水。其中地表水又可分为常年河流、暂时性洪流，他们在雅丹形成发育过程中的作用不尽相同。前者主要为雅丹地貌的形成提供了物质来源，后者除了上述作用外，还是雅丹地貌生消主要外营力之一。地下水一方面控制雅丹生长的上限，另一方面在其参与下，下部冻融风化、盐类风化和风沙磨蚀作用增强，上部雅丹自身重量增加，胶结程度降低，加速、加剧重力坍塌，导致雅丹地貌的衰亡。雅丹体表水对风化作用具有双重性影响，一方面侵蚀搬运已有的风化壳，加速风化作用，另一方面少量的降水在雅丹表层风化物上形成物理结皮，抑制风化作用和风力侵蚀，与此同时又在雅丹体表形成密集的沟谷系统，是雅丹地貌后期裂生的主要外营力之一。风力作用主要体现在风沙沉积物既是雅丹地貌的有机组成部分之一，并且又是伴随整个雅丹地貌生命周期的主要外营力条件之一，也是雅丹地貌流线型形态和其他细部形态的主要“塑造者”和魔鬼城的“始作俑者”。重力坍塌也伴随整个雅丹生命周期，是雅丹四周直立陡壁形成的主要营力，在雅丹地貌衰亡期表现尤甚。总体来看，风和水是雅丹地貌形成发育的最主要的外营力作用，其他外营力作用只是基础营力和伴生营力。\n（4）雅丹地貌的形成发育过程。其过程是在构造运动、地表风化、水、风和重力等内外营力共同作用下地表向准平原发展的复杂过程。根据地貌形态和动力条件不同，可将雅丹地貌的形成发育过程划分为孕育期、幼年期、青年期、壮年期和老年期五个阶段，各阶段具有不同的地貌形态特征和动力条件。地质公园区的绝大部分雅丹地貌处于鼎盛的青年期和形态最为丰富的壮年期。\n（5）通过对雅丹地貌形态、分类、形成发育条件和过程全面系统的分析，给出了雅丹地貌的科学定义及其在地貌分类系统中的位置。雅丹地貌是分布于极端干旱区和干旱区，在第三纪，特别是晚第三纪以来形成的未完全固结成岩的沉积物上（如河湖相土状沉积物），因风力和洪水等作用而形成的“槽垄”地貌组合，以流线型和长垄状为主的侵蚀地貌。按照动力分类系统将其划归到风蚀地貌，或者流水地貌都是有失偏颇的，它是干旱地区特有的风水复合侵蚀的地貌类型。\n（6）雅丹的形成年代、环境和未来发展趋势。根据现代磨蚀速率推算、相关沉积和雅丹地层顶部平坦戈壁面光释光测年等方法，确定雅丹地貌开始形成的年代约为40 ka BP。根据前人对近40 ka的区域地质构造和气候环境研究成果，雅丹地貌是在构造抬升和气候干旱的环境下形成的。在未来相当长的一段时间内，由于构造和气候环境不会有太大变化，因此雅丹地貌仍会存在，但也不排除一些突变性的地质事件(如特大地震)和气候事件(如特大洪水)，以及人类活动(如攀爬踩踏，破坏戈壁地表、人工爆破和不恰当的保护措施)加速雅丹地貌衰亡的可能。\n（7）雅丹地貌保护对策建议。雅丹保护要与科研、开发并重，使之走上相互促进的可持续发展道路，同时要加强保护管理，防止人为破坏，提高应对灾变的能力，加强环境监测。 |
| 英文摘要 | Yardang landforms, with unique morphological features and mysterious origins, had been give attention by geologist and geographers in early ages. They are always been considered as one of the aeolian erosion landforms and research process are slower than aeolian deposition landforms, even in stagnant condition. In recent years, with the tourism development at the yardang landforms regions in arid zone, yardang landforms are favored by tourists and given attention by administration. But there are different views and scientific blind spots on the yardang landforms’ definition, distribution and classification, formative conditions, evolution process, formative age and environment. Obviously, researching these problem have some important significances in theory and practice, such as revealing internal relationship among yardangs, aeolian sand desert and gobi, enriching research contents of aeolian sand desert, accelerating tourism resource development and quality improvement, promoting yardang geo-park conversation.\n In the thesis, the author choose Dunhuang Yardang National Geo-park as study area. We used field investigation on geology, landform and hydrology, Aeolian sand observation, regional meteorological data and remote sensing images collection, 3S, OSL and wind tunnel experimental technologies to get data. A thorough, in-depth and systematic research are made during past more than 3 years and make some progress as follows:\n \n \n \n\n\n(1)The morphology and classification of yardang landforms. Based on photogrammetry and GIS technologies, the author calculate and analyses that 5370 yardang landform bodies are in the geo-park. Calculating and statistical analysis for each yardang body morphology character parameters The average of area, perimeter, length, width and height ratio is 270.04:17.86:7.23:2.80:1, and the median ratio is , such as area, perimeter, length, width, height and long axis direction, the yardangs morphology character can been conclude that wide distribution range and relative concentrating on morphology character parameters and its ratio, obviously change on long axis direction and high distribution density.88.51:12.79:4.75:2.49:1 in the geo-park. Compared to former achievements, the research region’s yardang landforms are similar in width-height ratio with other region have been reported, but the length-width ratio is smaller than others obviously because of multi-directional external agent action and different evolution stages. Based on the morphological parameter of yardangs, the author uses cluster analysis method to classify the yardangs in research region, and suggest 6 yardang landform types, they are north-south directional micro-yardangs, east-west directional micro-yardangs, north-south directional meso-yardangs, east-west directional meso-yardangs, mega-yardangs and hyper-maga-yardangs. The distribution pattern of different types represents the change of external agent action and different evolution stage character.\n(2) Internal geologic process. in the Late Pleistocene, with the tectonic uplift, Shule River began to southward, the fluvio-lacustrine facies depositions were uplift and the groundwater level decline. It made the yadangs layer higher than the erosion basis and control the yadangs height limitation. Lots of structural joints formation during the process, and this provide prerequisite foundation and convenient condition. Meanwhile, the outspreaded imbricate compressive fractures that distribute at the geo-park south and north edges with east-west direction also control the yardangs distribution pattern in macro scale.\n(3) External geologic process are mainly include physical weathering, water, wind and gravity process. The physical weathering process include temperature weathering, salt weathering and freeze-thaw weathering. The physical weathering formed soft weathering crust at the surface, it decrease the cementation of the deposition and formatted many fractures and cracks, which not only accelerated other external process, and also provide initial channels for wind and water erosion. water can be divided into surface water, ground water and surface water on yardangs body. The surface water also can been divided into river stream and temporary flood flow, and they have different process on yardangs formation and evolution. The former provide materials source, and the latter is one of the main external process on yardangs growth and dying out, except for material providing. In one hand, the ground water control the yardangs height limitation, in other hand, under the participation of ground water, it will enhance for freeze-thaw weathering, salt weathering and wind erosion in the lower portion and increase the yardangs weight, decrease the cementation, accelerate the gravity collapse, and eventually result in the decline of yardangs. The yardang surface water have double influence on weathering process, in one hand, it erode and transport the crust have been formatted and accelerate the weathering process; in other hand, little precipitation can form thin physical crust at the yadangs surface, inhibit the weathering process and wind erosion. Density gully networks also been formatted by yardangs surface water and it’s one of the main external process in merisis. Wind are mainly represent as follows: aeolian sand deposit is the contents of yardang bodies，the wind process is one of the main action during the whole lifecycle of yardangs, it sculpture the teardrop and other detail morphology and the “devil city” . Gravity also process the whole yardangs lifecycle, it the main process of cliff of yardangs and represent more obviously at the decline stage. Overall, wind and water are the main process during the yardangs formation and evolution, and other process just the basis process or concomitant process. \n(4)The process of yardangs formation and evolution is a complicate pediplanation with common process of tectonic movement, weathering, water, wind and gravity. Base on morphology and dynamical conditions, the yadang evolution process can be divided into incubation stage, baby stage, youth stage, adult stage and old stage, and the character of morphology and dynamical conditions are difference in different stage. Nowadays, most of yadangs in the geo-park are in the glorious youth stage and various morphological adult stage.\n(5) Based on overall and systematically analysis on morphology, classification, formation and evolution conditions and process, the author given the scientific definition of yardang landforms and its position in the geomorphology classification system. yardang landform is one of the erosion landforms with streamlined and long ridge morphologies, and are formatted by wind and flood on un-completely consolidated deposits(such as fluvio-lacustrine facies earth deposits ) since Tertiary, especially Neogene period in hyper-arid zones and arid zones. It’s not very accurate to class the yardangs to the wind erosion or water erosion landforms, it is the peculiar erosion landforms with wind and water compound process in the arid zones. \n(6) Yardangs formation age, environment and trend of development in the future. Base on modern abrasion velocity calculation, related deposition and the surface gobi layer age-dating methods, the author conformed that the yadangs formation age is about 40 ka BP. During the past 40 ka, the regional geologic structure is uplifting, and the climate are dry, and yardangs formatted in such environment . the geologic structure and climate will not change dramatically in the future for a long time, so the yardangs will still exist in future. But the incident geological and climate event, such as destructive earthquake and catastrophic flood, and human activity such as climbing and treading, destroying gobi surface, artificial exploitation demolish and impertinent conversation will accelerate the yardangs decline. \n(7) Suggestion for yardangs conversation. The conversation should attach with scientific research and resource development, and make them on the sustainable development way. Meanwhile, strengthening management and protection, avoiding human destroy, improving capacity to disaster dealing, strengthening the environmental monitoring should also been put into practice. |
| 中文关键词 | 形态特征分类 ; 形成发育条件与过程 ; 形成环境 ; 保护对策建议 ; 敦煌雅丹国家地质公园 |
| 英文关键词 | Yardang morphological character and classification Formation and evolution condition and process Formation environment Conservation suggestion Dunhuang Yardang National Geo-park |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286945 |
| 推荐引用方式 GB/T 7714 | 牛清河. 雅丹地貌形成发育过程研究——以敦煌雅丹国家地质公园区为例[D]. 中国科学院大学,2011. |
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