板块构造单元划分方法探讨——以青藏高原为例     

高延林 《青海国土经略》1993,(1)

作者认为板块构造单元划分应遵循4个基本原则,即系统原则、时空原则、层次原则,综合原则。在此基础上,提出岩石圈板块、地壳板段、构造沉积环境、板片构造(薄皮构造)四级划分方案。青藏高原岩石圈厚度120—170km,地壳厚度大密度低,上地幔厚度小密度大,莫霍面呈一“盆地”状。上地壳厚15—30km;壳内低速层厚5—10km,呈南浅北深产出;下地壳平均厚25km,藏北、青南有明显分层,藏南与固体上地幔成突变,缺少壳幔层。壳幔混合层,埋深50—65km,厚度13—21km。固体上地幔,平均厚度50—70km。本文将青藏高原划分为5个板块(一级单元),7个板段(二级单元),30个构造沉积环境(三级单元),着重对主要板块构造单元包容的主要板段特征进行了分析与研究,对秦祁昆板块构造域的范围与演化特征给予了分析。  相似文献   

西安地区软黄土工程地质特征和分布规律雏议     

段真富  徐洪安  张玲 《地球科学与环境学报》1992,(1)

本文介绍了西安地区软黄土的物理力学性质,指出了以软黄土作地基土时所需要注意的主要工程地质问题,还介绍了如何识别软黄土的方法及软黄土在西安地区的分布规律。这对西安地区的工程地质勘察和对软黄土的研究具有一定的参考意义。  相似文献   

Formation of asymmetrical loess gullies in the northeastern loess plateau of China     

Si-Ming Chen  Li-Yang Xiong  Jia-Zhen Duan  Guo-An Tang 《地球表面变化过程与地形》2021,46(4):758-774

Loess gullies are the most active and changeable landform unit on the Loess Plateau of China. Under the influence of inhomogeneous internal and external forces, various gully morphologies have been identified as specific forms of asymmetrical loess gullies in the northeastern Loess Plateau. Thus, the formation mechanisms of asymmetrical gullies should be examined to better understand the gully evolution processes in this area. In this study, a typical asymmetrical gully area and its geological background in the northeastern Loess Plateau are investigated. Then, the asymmetrical gullies are extracted and ordered under different watershed hierarchies using 5 m horizontal resolution digital elevation models. The asymmetrical gullies are characterized using the gully deviation index and gully asymmetrical coefficient to quantitatively and qualitatively describe the gully formation from the perspective of gully morphology. Subsequently, environmental factors, such as the bedrock, climate, vegetation and interactions with neighbouring watersheds, are combined to achieve an in-depth understanding of the mechanisms of asymmetrical gully formation. The results show that most watersheds shift to the right side of the watershed geometric centre line, thereby forming a specific asymmetrical gully morphology. The phenomenon in which the asymmetrical degree characteristics decrease with the increase in drainage area suggests evident morphological differences on both sides of the main channel on a small scale, and relatively weak morphological differences on both sides of the main channel on a large scale. The degree of loess gully asymmetry appears higher in the area where only the windward slope is covered by loess than in areas where all slopes are covered by loess. The interaction between adjacent watersheds also influences the formation of asymmetrical gullies. These results support the understanding of asymmetrical gully formation in relation to the underlying bedrock structure and gully reorganization, thereby contributing to the development of process-based gully evolution models.  相似文献   

Snow cornice dynamics as a control on plateau edge erosion in central Svalbard     

Markus Eckerstorfer  Hanne H. Christiansen  Stephan Vogel  Lena Rubensdotter 《地球表面变化过程与地形》2013,38(5):466-476

Snow cornices grow extensively on leeward edges of plateau mountains in central Svalbard. A dominant wind direction, a snowdrift source area and a sharp slope transition largely control the formation of snow cornices in a barren peri‐glacial landscape. Seasonal snow cornice dynamics control bedrock weathering and erosion in sedimentary bedrock on the Gruvefjellet plateau edge in the valley Longyeardalen. Air, snow and ground temperature sensors, as well as automatic time‐lapse cameras on a leeward facing plateau edge were used to study seasonal cornice dynamics. These techniques allowed for monitoring of cornice accretion, deformation and collapse/melting in great detail. The active layer of the top plateau edge is characterized by high moisture content due to rain before freeze‐up in autumn and cornice meltdown during spring thaw. Thus frost weathering there can be very efficient in this otherwise cold and dry environment. Within the first autumn snowstorms, a vertical fully developed cornice was in place (190 cm thick). The backwall surface beneath the thickest part of the cornice remained in the ice segregation ‘frost cracking window’ for almost nine months. Highly weathered rock material from the plateau edge is thus incorporated into the cornice during cornice accretion. Brittle snow deformation leads to the opening of cornice tension cracks between the cornice mass and the snowpack on the plateau. These cracks are a prerequisite for cornice collapses, and often trigger cornice fall avalanches on the slope beneath. In these open cornice tension cracks, weathered rock debris, plucked from the plateau edge, can be visible, demonstrating the erosional property of the cornices. The cornice will either collapse or melt, resulting in suspended sediment transport downslope by cornice fall avalanche or release as rock fall respectively. Therefore, cornices both promote and trigger high weathering rates on Gruvefjellet, and thus control presently the development of the rockwall free faces and the talus cones. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

青藏高原东缘新构造与活动构造研究新进展及展望   总被引：1，自引：1，他引：0  

刘凤山  吴中海  张岳桥  杨振宇  王书兵  张虎  仝亚博  李海龙 《地质通报》2014,33(4):403-418

新构造运动与活动构造对人类的出现、演化、生存和发展都产生着深刻影响。近年来在青藏高原东缘部署开展的活动断裂调查与活动构造体系研究、川滇地块旋扭变形的古地磁学研究、西秦岭地区新构造与活动构造研究、滇西盆谷区的新构造幕划分、腾冲火山活动特征及其新构造背景调查等都取得了一系列重要进展与成果。这些成果对于深入认识和理解青藏高原东部地区现今地壳变形特征及其动力学机制和探索活动构造体系控震作用都具有重要意义,并可为该区的重大工程规划建设与国土规划利用的科学决策和城镇化发展等提供重要的地质依据。  相似文献   

The Deep Geophysical Structure of the Middle Section of the Longmen Mountains Tectonic Belt and its Relation to the Wenchuan Earthquake   总被引：1，自引：0，他引：1  

YU Nian  WANG Xuben  HU Xiangyun  CAI Xuelin  KAN Aike  ZHAO Ning 《《地质学报》英文版》2014,88(2):483-497

Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes. By using magnetotelluric sounding profiles of the Luqu–Zhongjiang and Anxian–Suining; seismic sounding profiles of the Sichuan Maowen–Chongqing Gongtan, the Qinghai Huashi Gorge–Sichuan Jianyang, and the Batang–Zizhong; and magnetogravimetric data of the Longmen Mountains region, the deep geophysical structure of the Songpan–Ganzi block, the western Sichuan foreland basin, and the Longmen Mountains tectonic belt and their relation was discussed. The eastward extrusion of the Qinghai–Tibet Plateau thrusts the Songpan–Ganzi block upon the Yangtze block, which obstructs the eastward movement of the Qinghai–Tibet Plateau. The Maoxian–Wenchuan, Beichuan–Yingxiu, and Anxian–Guanxian faults of the Longmen Mountains fault belt dip to northwest with different dip angles and gradually converge in the deeper parts. Geophysical structure suggests that an intracrustal low-velocity, low-resistivity, and high-conductivity layer is common between the middle and upper crust west of the Longmen Mountains tectonic belt but not in the upper Yangtze block. The Sichuan Basin has a thick low-resistance sedimentary layer on a stable high-resistance basement; moreover, there are secondary paleohighs and depression structures at the lower part of the western Sichuan foreland basin with characteristic of high magnetic anomalies, whereas the Songpan–Ganzi block has a high resisitivity cover of upper crust and continues to a low-resistance layer. Considering the Longmen Mountains tectonic belt as the boundary, there are Bouguer gravity anomalies of "one belt between two zones." Thus, we infer that there is a corresponding relation between the inferred crystalline basement of the Songpan block and the underlying basin basement of the Longmen Mountains fault belt. Furthermore, there may be an extensive ancient Yangtze block, which is west of the Ruoergai block. In addition, the crust–mantle ductile shear zone under the Longmen Mountains tectonic belt is the main fault, whereas the Beichuan–Yingxiu and Anxian–Guanxian faults at the surface are earthquake faults. The Wenchuan Ms 8.0 earthquake might be attributed to the collision of the Yangtze block and the Qinghai–Tibet Plateau. The eastward obduction of the eastern edge of the Qinghai–Tibet Plateau and eastward subduction of its deeper part under the influence of the collision of the Indian, Pacific, and Philippine Plates with the Eurasia Plate might have caused the Longmen Mountains tectonic belt to cut the Moho and extend to the middle and upper crust; thus, creating high stress concentration and rapid energy release zone.  相似文献   

Prospects of Carboniferous Shale Gas Exploitation in the Eastern Qaidam Basin   总被引：2，自引：0，他引：2  

LI Yingjie  SUN Yanling  ZHAO Yan  CHANG Chun  YU Qingchun  MA Yinsheng 《《地质学报》英文版》2014,88(2):620-634

Shale gas is a resource of emerging importance in the energy field. Many countries in the world have been making big financial investments in this area. Carboniferous shale in the eastern Qaidam Basin shows good exploration prospects, but limited research and exploration work for shale oil and gas resources has been undertaken. Geochemical analyses were performed on shale derived from the Upper Carboniferous Hurleg Formation in the eastern Qaidam Basin, Qinghai Province, and secondary electron imaging capability of a Field Emission scanning electron microscope(FE-SEM) was used to characterize the microstructure of the shale. The reservoir and exploitation potential of the studied shale was assessed by comparison with research results obtained from the Barnett Formation shale in Fort Worth Basin, North America and the Basin shale of Sichuan province. The results indicate that the eastern Qaidam Basin Carboniferous shale is high-quality source rock. There are four major microstructural types in the study area: matrix intergranular pores, dissolution pores, intergranular pores, and micro-fractures. The size of the micropores varies from 6–633 nm, the majority of which is between 39–200 nm, with a relatively small number of micro-scale pores ranging from 0.13–1 μm. The pore characteristics of the studied shales are similar to the North American and Sichuanese shales, indicating that they have good reservoir potential. No micropores are present in the organic matter, which is induced by its composition; instead we found an important lamellar structure in the organic matter. These micropores and microfractures are abundant, and are connected to natural visible cracks that form the network pore system, which controls the storage and migration of shale gas. This connectivity is favorable for shale gas exploitation, providing great scientific potential and practical value.  相似文献   

Discovery and Significance of Malan Loess on the Piedmont Plain in Pinggu District,Beijing     

LU Lu  ZHAO Yuanyi  WANG Xiaoliang  ZHAO Xitao  YANG Zhenjing  WANG Chengmin  BI Zhiwei  LU Wenhui 《《地质学报》英文版》2014,88(5):1565-1578

The platforms on both sides of the Malangou River （a lateral ditch of the Qingshui River that is a tributary of the Yongding River） where Malan Village in Zhaitang Town of Mentougou District of Beijing is located are the place of China＇s typical section of the Quaternary Malan loess. During the investigation in the eastern suburbs of Beijing City, the authors not only clarified 5 grades of terraces on the Pinggu piedmont plain, but also found a clayey silt section mixed with a small amount of alluvial-diluvial gravel layers at a height of 15-25 m above the river level near a Fishpond in Xinli Village of Nandule Town. Results of the study of grain size of the section document that the loess mostly is silty soil （0.05--0.005 mm）, and that the grain size probability cumulative curves of the section are dominated by single-peak, coarse-grained segment I and coarse-grained segment II types, reflecting that its depositional environment is similar to eolian phase. Identification results of heavy minerals from the section show that their contents account for 0.01%-0.11%, averaging 0.04%. There are 24 kinds of heavy minerals, most of which are stable heavy minerals, and the clay minerals mostly are illite, which is consistent with the Malan loess on the Loess Plateau. The chemical composition data reflect that the source area of the loess is relatively arid. The six grade classification of sporopollen in the section further shows the subdivision of the history of alternating warm and humid phases in this geological period. The thermoluminescence dating results range from 21.0 ka to 59.2 ka, convincingly demonstrating that the section indeed consists of Malan loess. The above studies provide a new basis for overall understanding of the distribution of the Malan loess at the northeast margin of the North China Plain and its environment change in the Late Pleistocene.  相似文献   

西秦岭中—新生代红层的构造层划分及其构造意义   总被引：2，自引：0，他引：2  

郭进京  韩文峰  赵海涛  张帆宇  梁收运 《地质论评》2014,60(6):1231-1244

西秦岭及其邻区中—新生代红层地层包括白垩系、古近系和新近系。这些红层地层的沉积组合、构造变形、空间分布及相互关系等是西秦岭中—新生代陆内地质过程的客观记录,对其系统研究是重建西秦岭及其邻区中—新生代构造演化过程之基础。依据这些红层地层之间的角度不整合、沉积序列与沉积环境、空间分布型式和构造线方向及构造样式,西秦岭及邻区中—新生代红层地层可分为早白垩世、晚白垩世、古近纪—新近纪三个构造层。三个构造层对应于西秦岭中—新生代陆内构造演化的三个不同阶段,即早白垩世北东向盆—山构造、晚白垩世区域左旋走滑拉分构造和渐新世—上新世区域伸展泛盆地阶段。结合印支期多块体拼贴形成的中国大陆中—新生代陆内构造格局与岩石圈动力学过程分析,认为西秦岭早白垩世北东向盆山构造格局是中生代以来西太平洋板块向西俯冲导致的东亚区域性伸展构造的组成部分;晚白垩世走滑拉分盆地则是白垩纪拉萨地块与羌塘—昌都地块汇聚碰撞背景下中国西北大陆区域性左旋走滑作用的结果;而渐新世—上新世的泛盆地阶段则指示了印度板块与欧亚板块碰撞的远程构造—地貌响应之前经历了漫长区域伸展均衡坳陷和侵蚀夷平期,这说明上新世,西秦岭尚未成为现今青藏高原的组成部分,也就是说新生代以来印度板块与欧亚板块碰撞汇聚的构造响应起始于上新世末期。  相似文献   

基于U Pb定年和单颗粒锆石粒径分析示踪 中国黄土高原黄土和红粘土物源   总被引：3，自引：0，他引：3  

李云  宋友桂  聂军胜  孙博亚 《地质论评》2014,60(2):380-388

中国黄土高原的风成沉积蕴含着丰富的大陆古气候和大气环流变化信息,但关于黄土和红粘土物源是否有变化目前仍存在着争论。近些年,锆石的LA-ICP-MS定年被广泛用于追踪沉积物来源,本文把碎屑锆石的UPb定年运用到红粘土中,并结合前人的数据和碎屑锆石粒径分析对黄土和红粘土物源进行了重新的讨论,认为黄土高原黄土碎屑锆石主要来源于黄土高原北部戈壁沙漠和附近的沙漠,极少量锆石来源于青藏高原北部,而不是主要来源于青藏高原北部和柴达木盆地,红粘土的锆石物源受近缘的基岩影响较大,朝那6.2~3.6Ma红粘土锆石碎屑部分来源于附近的六盘山。而且在0.12 Ma、0.86 Ma、1.25 Ma之间,黄土碎屑锆石物源较稳定,存在少量变化,在2.6 Ma和3.6 Ma前后,黄土、红粘土碎屑锆石物源存在明显变化,这可能和全球变冷导致近地面冬季风增强有关。  相似文献