中国大陆中轴构造带及其两侧的现今地壳垂直运动

利用中心年代分别为1964、1979及1993的3期精密水准复测资料研究中轴(构造)带及其两侧(东经90.5°至113.5°,北纬21.5°至42.0°)的现代地壳垂直运动。结果表明中轴带及其两侧近30多年的运动趋势与最近十几年运动趋势十分一致。而且与该地区的地势地貌有良好的相关性,几个垂直形变的高梯度带均分布在本区两个大盆地(四川盆地与柴达木盆地)周边。整个形变态势表现出明显的继承性运动特征。但在70年代,该区的垂直运动经历了一次明显的变化或反向。联系到同一时期中轴带南部的一系列7级以上强震的发生,提示大区域的垂直形变的趋势变化可能是强震活跃的一种指示。文中还利用得到的地壳垂直形变图研究了区内南—北、东—西向穿切几个主要构造单元的9条剖面的地壳垂直运动特征和它们的时空演化,结果进一步证明1969～1979年间,我国中西部比较强烈的地壳垂直运动与我国地震活动高潮期一致。纬向剖面的运动特征清楚地显示出东经100～105度的经向带内,整个研究区可分为地壳垂直运动速率西高东低的东、西两区;而经向剖面又可将这东、西两区分出以某些纬向高变化窄带为界的纬向区块。文中还详细讨论了这些区块所对应的构造单元的现今运动特征。     

中国东部中生代构造格局与演化

中国东部早中生代以挤压构造为主,如大别造山带的逆冲推覆构造,而晚中生代伸展构造十分显著,表现为大量发育的变质核杂岩、同构造岩浆岩、拆离断层带以及穹隆构造等,这些伸展构造使地壳深部的岩石折返至地表,从而使中下地壳结构发生了强烈的改造。拟通过对中国东部晚中生代构造发育的典型地区:北部的燕山构造带、中-东部的大别-苏鲁构造带和东部的东南沿海构造带进行系统的研究、分析、归纳和总结,恢复燕山运动启动前的构造体制,研究中国东部对多幕次燕山运动中地壳变形对板块相互作用及其深部过程的响应,阐明中国东部燕山期构造体制转折的期次、时限、动力学演变机制及其与板块运动的关系,进而探讨其对成矿作用的制约。     

沿大型走滑断裂系的隆升

伴随大型走滑断裂系的运动,可以产生出乎预料的铅直断距。由于大型走滑断裂的运动矢量只是近水平的,沿着大型走滑断裂系发生的数百公里的走滑使得微小的铅直运动分量积累成十几公里至几十公里之巨的铅直断距,足以使中-下地壳的岩石抬升出露。通常,大型走滑断裂系活动时,它的水平位移速率很大。因此,伴随它的垂直位移速率也非常可观。大型走滑断裂系复杂的几何特征和运动过程造成局部地段的隆升突出。大型走滑断裂系的运动对中国东部及邻区现今构造格局的形成和高压-超高压岩石的形成、抬升、剥露起了重要作用。     

地壳垂直运动与水平运动的伸展-挤压动力学过程

垂直运动与水平运动是地壳构造运动的两种基本表现形式。本文运用拉张伸展—挤压收缩这一辩证观点,探讨了垂直运动与水平运动形成的动力学环境、过程及成因机理,指出了垂直运动对应于地壳的伸展作用,水平运动对应于地壳的挤压作用,它们共同构成地壳构造运动的整体。     

略谈地壳的垂直运动和水平运动问题

地壳的垂直运动和水平运动是大地构造学中长期争论的一个問題。随着人类对于地质构造現象认识的扩大与深入,大地构造学中的垂直运动說和水平运动说时有兴衰和更替。十九世紀末叶,在“主火論”占优势的岁月里,人們认为地壳变动主要是由岩浆活动引起的。人們对岩浆自下而上的侵入和喷发現象的认識使地壳的垂直运动說大盛一时。后来,由于阿尔卑斯构造研究的开展,巨大冲断层和辗掩构造的发現,于是水平运动說就逐漸代替了垂直运动說。     

基于遥感与GIS的20世纪90年代中国城镇用地时空特征

文章利用20世纪90年代初期、中期和末期全国1:100000土地利用动态变化数据提取城镇用地动态变化数据,利用单元自动机和人工神经网络模型对全国城镇用地进行了区划.在此基础上,研究了90年代两个阶段中国城镇用地时空格局.研究表明:90年代前5年东部沿海地区受经济高速发展和开放政策的影响,城镇用地扩展迅速,中西部地区城镇用地扩展较慢;90年代后5年国家加大了耕地资源保护力度,在政府宏观调控政策和耕地资源保护条例的影响下,东部沿海地区城镇用地扩展大幅回落,中部地区城镇扩展也有较大幅度回落,西部地区随着经济发展加快,城镇用地扩展回落较小.     

长江口地区地面沉降的深部动力学机制分析

地表变形、活动断裂和地球物理的综合分析表明,菲律宾洋壳向欧亚大陆的俯冲导致的地幔对流是控制中国东部沿海地区晚新生代以来构造作用的主导因素,是长江口地区地面沉降的主要深部动力学机制。由于地幔对流和青藏高原挤压共同作用导致的地壳热流值的差异则是长江口地区西部隆升、东部沉降且向东沉降速率增大的直接驱动力。预测未来长江口地区的基岩沉降范围将以>10cm/a的速率向西扩大,沉降速率将呈明显加速趋势,40000a之内上海市可能被海水淹没,但板块构造演化的“渐变”特征决定其对当地未来的人类活动不会造成显著影响。根据“地壳均衡理论”,建议在长江口南西部(浙江省北东部)的丘陵山区加大重力载荷如加快城市化进程或人工造山以减小和控制上海地区的沉降。     

地壳均衡与水平运动

一般说来,地壳均衡运动是指地壳因负荷发生变化而产生的垂直运动,与地壳的水平运动无关。但是,上面这个结论是建立在地壳为一平面,而不是曲面的假定条件之下。在较小的区域内,局部地壳可以近似看成是一个平面,但就全球范围而言,地壳是一个球面。因此,大面积的地壳均衡不仅能产生地壳的垂直运动,而且能产生地壳的水平运动。     

中国大陆岩石圈等效粘滞系数的计算和讨论

大陆岩石圈的流变结构对岩石圈动力学过程有很大的影响,因此对岩石圈等效粘度的估计是大陆动力学研究中基础和重要的问题。文中对利用实验室流变实验结果估算岩石圈流变结构的计算方法中包含的多种不确定性进行了讨论,包括岩性、温度、应变速率、实验室速率数据外推到地质构造运动速率等因素对等效粘滞系数估算的影响,并以温度和应变速率的新研究成果为基础,对中国大陆地壳和上地幔等效粘滞系数做出了估计。中国中地壳等效粘滞系数一般在1021~1024Pa.s,下地壳等效粘滞系数在1021~1022Pa.s,其中青藏高原下地壳等效粘滞系数较低,约为1019~1020Pa.s;与前人研究认为青藏高原存在柔性下地壳流动的结论吻合。     

GPS观测的活动断裂滑动速率及其对现今大陆动力作用的制约

活动断裂的滑动速率是晚第四纪构造变形的定量描述 ,是制约和研究现今大陆动力过程的重要基础数据。地震地质学研究给出主要活动断裂的长期和平均运动水平 ,横跨断裂的GPS观测能够提供断裂的现今滑动速率。文中利用重大科学工程“中国地壳运动观测网络”的 10 0 0多个GPS观测站的复测数据 ,计算中国大陆主要活动断裂的现今滑动速率。发现主要活动断裂的GPS滑动速率与晚第四纪滑动速率在运动方式和运动量上是大体一致的。从GPS观测到的断层滑动速率来看 ,中国大陆的大多数活动断裂的速率都在 10mm/a之下 ,而没有类似于板块边界的大于 2 0 30mm/a的滑动速率。这种现象意味着整个中国大陆的构造变形可能是分布式的 ,而不是仅仅集中在少数几条大型活动构造带上 ,沿主要活动断裂的刚性块体滑移可能不是构造变形的主要方式。现今构造变形的分块运动图像可能只是脆性上地壳的变形方式 ,中下地壳和上地幔的运动则以连续变形为特征 ,从下部驱动脆性上地壳的变形和运动 ,使得上部地壳的变形既表现出分块特征 ,又发生块内的变形。“连续变形”理论模型能够更好地描述大陆内部的构造变形。     

Early 20th-century uplift of the northern Peninsular ranges province of southern California

Repeated leveling in the northern Peninsular Ranges province identifies an early 20thcentury episode of crustal upwarping in southern California. The episodic vertical movement is broadly bracketed between 1897 and 1934, and the main deformation is bracketed within 1906–1914 and involved regional up-to-the-northeast tilting of the Santa Ana block of as much as 4 · 10⁻⁶ rad and elevation changes exceeding 0.4 m in the Perris block and parts of the San Jacinto block, Transverse Ranges, and the Mohave block. Primary tide station records containing occasional entries since 1853 at San Pedro and San Diego show no evidence of episodic crustal movement, suggesting that the uplifted area hinged along coastal fault zones forming the west boundary of the Santa Ana block.Physiographic features and recent studies of Quaternary marine terraces by others show that this episode of regional tilting and uplift is a part of the continuing tectonic process in southern California. A crude, questionable coincidence exists between the uplift episode and a period of increased seismicity (1890–1923) in the northern Peninsular Ranges characterized by a number of moderate-size (M > 6) earthquakes on NW-trending strike-slip faults. However, releveling data are too sparse to associate the uplift development clearly with any one event.     

Coastal deformation between the Versilia and the Garigliano plains (Italy) since the last interglacial stage

The opening of the north‐central Tyrrhenian Sea is the result of the Cretaceous–Paleogene alpine collision, which triggered a series of regional uplift, subsidence and transcurrent tectonic mechanisms along the coastal Tyrrhenian sectors of peninsular Italy. These tectonic processes, in conjunction with the effects of glacio‐ and hydro‐isostasy during the Quaternary, produced substantial crustal responses that, in some cases, reached metres in extent. In the study of coastal neotectonics, geomorphological markers of the last interglacial maximum, corresponding to marine isotope stage 5.5, are generally used to quantify the magnitude of the vertical crustal displacements that have occurred since 125 kyr. Through altimetrical, palaeoenvironmental and chronological reinterpretation of the most significant works published since 1913, combined with an additional set of data reported here, a detailed reconstruction of the shoreline displacements evident along 500 km of coast between northern Tuscany and southern Latium is presented. The reconstruction was carried out by quantifying the vertical movement since the last interglacial period and by identifying the tectonic behaviour of different coastal sectors. This has been done by carefully choosing the eustatic marker, among those available at each study site, in order to minimize the margin of error associated with the measurements. Copyright © 2003 John Wiley & Sons, Ltd.     

某水准路线所经地区现代升降运动的初步探讨

本文主要是利用水准复测资料来阐述某地区的现代升降运动。文中将复、初测高程进行比较,作出了现代地壳运动幅度图,图中看出东都上升幅度小,速度梯度变化也小;西部上升幅度大,速度梯度变化也大。在整个剖面中更可以看出,在较短距离内出现大幅度的隆起,隆起中又有相对凹陷。由实际资料得出,本区现代地壳运动有继承性,并出现三种类型的上升运动:(1)平稳的上升运动;(2)掀斜的上升运动;(3)强烈隆起。     

The Mesozoic–Cenozoic structural framework of the Bay of Kiel area, western Baltic Sea

A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic, E–W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence. Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned faulting.     

祁连山北缘—河西走廊地区大地形变与地震的关系

河西走廊—祁连山北缘地区地处青藏高原北缘,受印度板块与欧亚板块中生代末—新生代早期的碰撞及持续至今的向北推挤作用的远程效应的影响,该地区是现今的地壳活动地区,其中地壳形变是最主要的表现形式。地壳形变监测显示,隆起区垂直位移速率最大可达15mm/a,沉降区最大位移速率为-15mm/a。祁连山和河西走廊的相对隆升变化与该区地震具有密切的关系,河西走廊相对下降、祁连山相对隆升的后期是地震多发时期,河西走廊相对隆升、祁连山相对下降的后期是地震少发时期,这与该区处于挤压体制下的区域构造背景密切相关。GPS水平位移监测显示,河西走廊—祁连山北缘地区全区都一致向东位移,且位移速率非常大,大者大于10mm/a;位移速率具有南部大于北部、东部大于西部的特点,水平位移速率变化与现代活动断裂具有非常密切的关系,并以主要断裂构造为区带的边界;水平位移速率矢量与2002年玉门地震的震源机制解所显示的沿地震破裂面发生的滑动方向非常一致。     

Development of regional uplift and uplift-related strata in Gunsan Basin,Yellow Sea: implications for Cenozoic crustal extension

ABSTRACT

The Mesozoic–Cenozoic Gunsan Basin is the northeastern part of the Northern South Yellow Sea Basin between eastern China and the Korean Peninsula. On the basis of seismic interpretation, this study presents and interprets geologic features of regionally uplifted structures, the Haema Arch, located in the central western part of the basin. The Haema Arch is defined as dome-shaped uplift complexes, 95 km long and 60 km wide. It is characterized by prominent basement uplifts along its margin and plunging syncline inside the arch. The marginal large-scale uplifts are bounded by outward-dipping faults. The uplift-related strata are identified on the hanging wall block of the bounding faults and within the Haema Arch, which can be divided into pre-, syn-, and post-uplift units. The pre-uplift unit rests on the acoustic basement and shows an upturned stratal pattern near the marginal large-scale uplift. The syn-uplift unit locally occurs on the hanging wall block of the bounding faults along the northern and southern margins. The uplift of the Haema Arch and its coeval fault-controlled subsidence possibly occurred during the late Oligocene. The post-uplift unit initially formed on remnant topographic lows during the early Miocene and subsequently covered the overall area of the Haema Arch and the Gunsan Basin. The late Oligocene uplifting of the Haema Arch can be interpreted as an isostatic response to tectonic unloading by the arch-bounding faults that possibly extend to detachment faults. We suggest that the Gunsan Basin underwent crustal thinning and extensional deformation during the late Oligocene, which accounts for the coeval uplifting and fault-controlled subsidence in the study area.     

Hierarchy of tectonic control on stratigraphic signatures: Base-level changes during the Early Permian in the Paraná Basin,southernmost Brazil

The Lower Permian sedimentary succession of the Paraná Basin in southernmost Brazil has an overall transgressive sedimentation regime, recorded by a clear retrogradation of the facies belt. However, important depositional strike-orientated variations and regional inversions occur in the sedimentation regime along the paleo-shoreline (i.e., along-strike) of the basin. At the regional scale, a huge source area was uplifted by the end of the Artinskian in the north and caused regression; the southern part of the study area increasingly was transgressed by the epicontinental sea (= regional inversion). This important tectonic overprint on the stratigraphic signature of the basin’s infill has a tectonic origin. The variable sedimentation regime along the paleo-shoreline is controlled by the structural framework of the basement, which is formed by several crustal blocks with different responses to tectonic strain induced by terrain accretion on the occidental margin of Gondwana during the Permian. Stratigraphic data indicate that during the Early Permian, there were at least two differential subsidence and uplift events, one by the end of the Sakmarian–Artinskian and another during the Late Artinskian–Kungurian.     

塔里木盆地库车坳陷西秋古隆起的形成及其演化

重力异常资料显示,库车坳陷南缘西秋构造带深层发育有基底隆起。本文通过地震资料解释确认了西秋构造带深层占隆起的结构,分析了占隆起的形成和演化过程。西秋构造带南侧边缘存在一条区域性基底断裂,断裂北侧新生界下伏中生界、古生界明显减薄或地层缺失,总体上表现为断背斜形态的古隆起构造。结合区域构造演化分析认为,泥盆纪~石炭纪(D-C)塔里木克拉通边缘隆升、二叠纪-三叠纪(P-T)受南天山负荷影响产生的克拉通边缘压陷的构造演化过程中,西秋构造带处于"跷跷板"式地壳升降运动的"支点"部位,发育古隆起和基底卷入高角度断层,晚期南天山隆升向南斜向推挤的挤压剪切应力场使古隆起边界断层复活,基底断裂活动并在新生界之下形成冲断隆起。     

论胶东地区中生代岩石圈减薄的证据及其动力学机制

胶东地区可划分为两个大地构造单元：胶北断块和胶南造山带。前者为华北板块组成部 分，后者为华北和扬子板块的碰撞拼合带。五莲－青岛－海阳－牟平深断裂构成上述两个构造单 元的边界。本文从地质（陆壳隆升、构造岩浆活动与断陷盆地形成）和地球物理（重、磁异常与地震 测深）两个方面论述了胶东地区中生代经历了两个不同构造演化时期：前期（Ｔ３－Ｊ２）陆壳隆升和后 期（Ｊ－Ｋ）陆壳拉伸。我们认为，岩石圈减薄的动力学条件是与库拉－太平洋板块以不同边界类型 向欧亚大陆俯冲以及郯庐断裂以不同方式的强烈活动密切相关。在综合分析基础上建立了胶东地 区岩石圈减薄的动力学模式。     

Sedimentary Basins in the Western White Nile, Sudan, as Indicated by a Gravity Survey

An academic geophysical research as a regional gravity survey was made during 1994 in the Western White Nile to infer the shallow crustal structures in the area. The result of the survey was compiled as a Bouguer anomaly map with a contour interval of 2 ×10-5m/s2. It is found that the negative residual anomalies are related to the Upper Cretaceous sediments (Nubian Sandstone Formation) filling all depressions in the Basement complex surface while the positive residual anomalies are attributed to the relatively shallow or outcropping Basement rocks and the steep gravity gradients are resulting from the sharp contacts between the sedimentary infill and the Basement rocks. To define the geological structures in the area, 9 profiles were studied. For each of the profiles, measured and computed Bouguer gravity anomalies, crustal density model, subsurface geology evaluation were performed. A G-model computer program was applied in the gravity modeling, which is based on the line-integral method of gravity computation. A geological/structural map was proposed showing inferred sedimentary basins, faulting troughs and uplifted Basement block and tectonic trends. The basins are believed to be fault-controlled which developed by extensional tectonics (pull-apart mechanism). As for the mechanism and cause of faulting, the area is considered as a part of the Central Sudan rift system which had been subjected to several tectonic events since Early Cambrian to Tertiary times which resulted in the formation of several fracture systems associated with block subsidence, rifting and basin formation.