【作者】 张路；

【导师】 曲国胜；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2008， 博士

【摘要】 在我国大陆东部地区,福建沿海现今的构造活动十分引人注目,很多学者对福建沿海的第四纪构造活动进行了研究,包括:断层活动性、地震活动性以及二者关系,沿海盆地的沉积、构造与地震活动性,沿海沉积与地壳升降和海平面变化关系等。福建东南沿海地区的构造由北东向和北西向两组断裂控制,北东向断裂带有政和—大埔断裂带、长乐—诏安断裂带和滨海断裂带3条深大断裂带;北西向为韩江断裂带、九龙江断裂带、永安—晋江断裂带、兴化湾断裂带和闽江断裂带等断裂带。长乐—诏安断裂带是本区重要的深大断裂带,主要活动时期在更新世中期之前,更新世晚期以来活动强度大为减弱。长乐—诏安断裂带现代的地震活动较频繁,但无论是在强度上还是在空间密度和时间频度上,均要比滨海断裂带弱。滨海断裂带是一条海域深大断裂带,是华南陆区正常型陆壳与海区减薄型陆壳的分界地壳断裂,可能是新生代强烈沉陷的台湾海峡西边界断裂;它是本地区最重要的现代地震发生带。在福建沿海地区北西向断裂是一组较新的、活动性强烈的左旋张性断裂带,它们的切割深度可能不及北东向断裂,但它们几乎切割错断了其它所有方向的断裂;该断裂组分布比较规则(方向一致、排列等距),且地震活动强度向南递增,强震一般发生在北东向和北西向断裂交汇部位。福建东南沿海地区基岩以燕山期花岗岩、侏罗纪和白垩纪的陆相碎屑—火山碎屑建造为主,第四纪沉积主要分布于东部沿海花岗岩基底的盆地、平原中。沿长乐—诏安断裂带分布有混合岩化、花岗岩化的动力变质带。长乐—诏安断裂带南部漳浦—龙海一带分布有新近纪以来的玄武岩,该火山在晚更新世有活动。福建沿海地区新生代沉积较浅,主要是第四纪沉积,更新统划分为下更新统天宝组、中更新统同安组、更新统上部龙海组和东山组,全新统主要为长乐组。该区第四纪沉积由长乐—诏安断裂带及北西向断裂控制,主要分布于福州盆地、长乐平原、莆田平原、泉州盆地、同安平原、漳州盆地和龙海平原等地区,这些盆地一般位于长乐—诏安断裂带和北两向断裂的交汇处。福建沿海地区尽管已取得了大量对第四纪盆地和构造的研究成果,但对盆地形成发展、大区域第四纪构造演化及其动力学模式深入研究较少。为深入探测和研究福建沿海的断裂及其活动性,近年来陆续开展了福州、漳州、厦门和泉州等城市活断层探测与地震危险性评价项目。本文利用该项目获得的资料和福建沿海、台湾海峡以及更大区域资料,结合作者对几个城市断层的野外调查,对福建沿海第四纪盆地构造及其运动规律进行了综合性分析,获得该地区第四纪地壳运动、动力学成因更进一步认识,论文在以下方面取得了进展:1.研究方法研究本区古海平面的标志层位,分析其测年和高程,对比盆地的海侵层位,确认盆地的构造沉降。论文在总结该区大量沉积和构造及其构造活动时空关系的研究成果基础上,充分了解国际相关领域的研究进展,对盆地的沉积深度、时间及相关构造活动的对应演化关系进行了深入分析,根据现有资料和盆地沉积特点,提出了利用钻孔资料进行沉积深度—时代(D-T)分析方法,从而更有效直观地判断第四纪盆地断层的活动性,分析盆地内不同位置、不同时期构造活动之幅度和强度的时空变化。2.盆地构造分析沿研究区的两组深大断裂分布的历史地震和多数现代小震说明了断裂的活动性,这些断裂的深部活动引发地表沉降,是盆地形成的重要成因。根据盆地地貌、海平面升降和海侵层位等特征,确认盆地的构造属性,阐明盆地形成的阶段性——从早期“断陷”到晚更新世以来“拗陷沉积”。根据闽南各城市活断层探测结果获得了市区及其附近地区大量钻探和年代学研究资料,本文利用盆地钻探获得的钻孔测年数据对各个钻孔进行沉积的深度—时代对比分析(D-T分析),进一步判断盆地的断层活动性和沉积规律,确认盆地构造的发展趋势。(1)盆地断层活断层探测及研究表明,福建沿海几个北西向盆地(福州、漳州和泉州)内的断裂均为高倾角正断层,并且倾向盆地中心;盆地内北西向较活动的断裂位于盆地西南侧或中部盆地沉积最深处:福州盆地的闽侯—南屿断裂是福州盆地最具发生中等—中强地震潜势的相对危险断层,其次为五虎山北麓断裂,盆地内其余断层为一般危险性断层,盆地内2条相对危险断裂均位于盆地西南侧。泉州盆地的寺角—晋江断裂最新活动时代在更新世晚期;本文根据D-T沉积—构造分析认为紫帽山—乌石山断裂在更新世晚期有活动。寺角—晋江断裂在盆地中部最深处,紫帽山—乌石山断裂在盆地西南侧。其余断裂在第四纪早期或以前有活动。漳州盆地的古塘—大梅溪断裂和九龙江断裂北支最新活动时代可能在更新世晚期,是相对危险断裂,九龙江断裂北支是位于漳州市小区西南侧的北西向断裂;在珩坑—天宝小区西南侧的岱山岩—珩坑断裂要比珠坑断裂更活动一些。厦门岛的筼筜港断陷盆地内只有北东向筼筜港断裂可能有晚更新世活动,岛上其余断裂活动更早。(2)盆地沉积福建沿海几个盆地内的第四纪沉积较新,一般为更新世以来沉积,盆地的D-T沉积—构造分析发现,盆地沉积的中心都有由北东向南西迁移的趋势:福州盆地东北部可能在近千年来无沉积或有过剥蚀,在40～8ka时段高沉积速率位置向西转移,福州盆地的沉积中心有由北东向南西迁移的趋势。泉州盆地的东北部最早沉积(近80ka左右);30ka盆地中部开始沉积,并成为沉积中心;而在最近千年,盆地中部的沉积变为高速并成为最高速沉降区。自盆地形成开始,盆地的沉积中心就有从北东向盆地中部迁移的趋势。漳州盆地:珩坑—天宝小区的东北部沉积较早,但更新世晚期以来,东北部沉积深度和速率小于南西部,表明盆地中心有随时间向南西迁移的规律;同样,漳州市小区的沉积中心也有向南迁移的趋势。厦门岛筼筜港断陷盆地内的沉积有向南西迁移的趋势。通过上述盆地断裂和沉积的综合分析可以认为,福建东南沿海福州、泉州和漳州3个由北西向断裂控制的盆地中,北西向较活动断裂发育在盆地西南侧或中部最深处,盆地的沉积均有由北东向南西的迁移趋势,盆地有向南西方向掀斜的特征。3.区域构造运动模型福建东南沿海地区的第四纪构造运动模型建立在①几个北西向盆地内的断裂和沉积所表现的盆地向南西方向掀斜特征、②盆地第四纪沉积事件的时间序列和③该区地壳结构的分析基础上。福建沿海几个沉积盆地以及龙海平原、广东省沿海潮汕平原和珠江三角洲的第四纪钻探与年代学研究表明:滨海盆地第四纪起始沉积年代早于内陆盆地,厦门岛比龙海平原早,龙海平原比漳州盆地早;其它几个沉积事件也具有相同特征。在内陆,漳州盆地起始沉积最早,沿南西和向北东2个方向各盆地起始沉积时代均分别逐渐变新:其中厦门—漳州盆地形成的时代最早,福州盆地、珠江口盆地形成时代最晚。福建省沿海内陆盆地的其它几个沉积事件也有从漳州向北东变新的趋势。利用该区几条深部地震勘探结果建立的区域地壳结构模型表明:本区的地壳较薄,在上地壳底部存在低速层;低速层底面在滨海断裂带和台湾海峡明显上隆,在漳州—厦门一线沿九龙江断裂上隆,在泉州一带也有部分区域上隆;上地幔顶面的深度图像和低速层底面类似,沿北西向九龙江断裂带和永安—晋江断裂带的上隆更明显。通过各个盆地内部构造运动趋势研究,对比盆地之间的沉积序列,结合地壳结构分析,给出该区的构造运动模型:在第四纪早期或前第四纪,北东向的拉张作用使漳州南西侧深部的上地幔发生隆起,随后,伸展作用向北东扩展,伴随该区两组断裂的活动,陆续形成漳州、泉州和福州盆地;向南西扩发展同样陆续形成潮汕平原和珠江口盆地;该伸展作用的持续发展,形成福建东南沿海第四纪的构造格局。4.区域构造动力学分析本文由大区域到小区域逐步分析了西太平洋板块和菲律宾板块的第四纪运动方式,着眼于直接作用于该区的西菲律宾板块西缘的构造,论述沿海、台湾和菲律宾等海域的构造及其活动,结合南海板块对该区构造影响的讨论,给出如下构造运动及其动力学解释:对西太平洋洋盆的演化分析表明,中生代晚期库拉板块NNW向俯冲、中生代和新生代太平洋板块南北两洋脊先后俯冲到亚洲板块东南缘之下、新生代太平洋板块运动方向的改变和菲律宾板块北西向俯冲等大事件,对闽台地区构造的形成和发展起着重要的作用。论文讨论了巴士构造系的形成机理:菲律宾板块北西方向运动,北侧沿琉球沟弧盆系俯冲消亡,西侧在台湾纵谷以弧—陆碰撞带与欧亚板块左旋逆走滑断层接触,而与南中国海次板块以马尼拉海沟相邻,南中国海次板块在马尼拉海沟向东俯冲作用于菲律宾板块。这两个板块的共同作用下,势必在台湾南端巴士海峡一带产生沿NWW—SEE一线的左旋拉伸,形成巴士构造系。分析表明:在菲律宾板块的北西向挤压作用下,福建东南沿海及滨海地区表现为隆升和北东向拉伸。菲律宾板块的运动在巴士构造系产生左旋拉张作用,巴士构造系在陆地的延伸位于漳州南西侧,它的活动引发地幔隆升,成为本区伸展构造运动的触发点。拉张作用从漳州—厦门一带分别向北东和南西扩展,引发福建东南沿海各个盆地的沉积和升降运动。菲律宾板块的运动是韵律式的,它在巴士构造系引发的左旋拉张作用是多期的,福建东南沿海各个盆地的运动也是多期的。5.岩石圈的多层圈构造解释论文从岩石圈多层构造思想分析讨论了东南沿海地区地壳伸张、破裂的成因,解释该区第四纪构造运动。岩石圈的上层(上地壳)为脆性、中脆性层,岩石在岩石圈上层受力时的主要变形方式是脆性破裂,断层破裂和地震多发生于此;岩石圈下层(下地壳和上地幔)是半延性、延性的塑性层,厚度要比上层大得多,是岩石圈主要的受力、传力层,它的主要变形方式是塑性蠕变。在巴士构造—漳州一线的岩石圈接受引张作用时,岩石圈变形所表现出的伸展作用从受力端向另一端传播,持续的引张力作用在该区形成等距的正断层组,可能是导致由九龙江断裂带向两侧第四纪盆地依次发展的深部构造原因。更多还原

【Abstract】 Present-day tectonic activities are obvious and intensive in the eastern coast area of Fujian province, mainland of China. Many researchers have studied Quaternary tectonics of coast areas of Fujan province. These studies involve activity of faults, earthquakes and the relationship between them; sediments, tectonics and earthquake activity in coastal basins; and relationship of coastal sediment to crustal vertical movement or to sea level change.The tectonics of coastal area of southeastern Fujian is controlled by two groups of faults: northeast and northwest strike faults. The northeast strike faults are the Zhenghe-Dapu fault zone, Changle-Zhao’an fault zone and Seashore fault zone. The northwest strike faults are the Hanjiang fault zone, Jiulongjiang fault zone, Yong’an-Jinjiang fault zone, Xinghuawan fault zone and Minjiang fault zone. The Changle-Zhao’an fault zone is an important great deep fault zone, it was active mainly before mid Pleistocene and has been weakened since late Pleistocene. The Changle-Zhao’an fault zone has some present earthquakes, but its intensity is weaker than the Seashore fault zone either in space-density or in time-frequency. The Seashore fault zone is a great deep marine fault zone and may be the west-boundary fault of the Taiwan strait which has been subsided greatly since Cenozoic. This fault zone is the most important present earthquake active zone. The northwest strike fault zones are a group of newer and more active sinistral tensile fault zones. Their depths may be less than the northeast trending fault zones, but nearly has cut all the northeast strike fault zones. This fault groups are distributed regularly (equal strike direction and distance), it’s intensity of earthquake activity increases southwards, and the strong earthquakes took place at the cross site of the northeast strike fault zones and northwest strike fault zones generally.Geologically, Yanshan granite, Jurassic and Cretaceous terrestrial-pyroclastic tephra sedimentary formation are dominant in southeastern coastal areas of Fujian province. Quaternary sediments are distributed in eastern coastal basins and plains. There are magmatic and granitization dynamometamorphic rocks along the Changle-Zhao’an fault zone. Basalt younger than Neogene appears in southern part of the Changle-Zhao’an fault zone in Zhangpu and Longhai city. The volcano was active in late Pleistocene.In the Fujian coast area, the Cenozoic sediment is shallow, mainly is Quaternary. Pleistocene is divided into lower Pleistocene Tianbao formation, middle Pleistocene Tong’an formation and upper Pleistocene Longhai and Dongshan formation. Holocene is Changle formation mainly. In this area the Quaternary sedimentation is controlled by the Changle fault zone and the northwest strike fault group, the sediment is mainly located in the Fuzhou basin, Changle plain, Putian plain, Quanzhou basin, Tong’an plain, Zhangzhou basin and Longhai plain. These basins are located at the cross sites of the Changle fault zone and the northwest strike fault mainly.There is a lot of research achievements about Quaternary basins and tectonics in the Fujian coastal area. But there is less profound research about formation and tectonic development of basins, evolvement of big regional Quaternary tectonics and the dynamical model of this area. For deeper studying the faults and their activity in this area, recently the projects of active faults detection in big cities and earthquake possibility assessment have been carried out successively in Fuzhou, Quanzhou, Zhangzhou and Xiamen cities recently. Using the information of these data and correlative results of other studies in the Fujian coastal area, Taiwan strait and other regions, combining the author’s exploration of faults in the cities, this thesis analyzes synthetically tectonics and its movement of the Quaternary basins in the southeastern coastal area of Fujian province and has acquired more understanding of Quaternary tectonic movement and its dynamic cause of this region.The progresses of the research are as follows:1. Studying methodBy studying symbolic strata of ancient sea level, analyzing their geochron and elevation, comparing strata of ingression of basins, this thesis has determined the basins’ tectonic subsidence.Summarizing a lot of study achievements of sediment, tectonics and space-time relation of tectonic activity in the area, comprehending the international progress of this study field, according to present data and the character of the basins’ sediment, the thesis proposes the depth-time (D-T) method which analyzes basins using drilling data. Applying this method we can efficiently and visually assess activity of faults of basins and analyze the tectonic activity of basins at different locations and times in Quaternary.2. Analysis of basin structureThe historic earthquakes and the most current small earthquakes are located along two groups of deep fault zones that indicate the fault zones are active. The deep action of these faults makes decline of surface and is important cause of formation of basins in the Fujian eastern coast area. According the geomorphology of the basins, the movement of historical sea level and the strata of ingression in this area, the thesis has affirmed tectonic attribute of these basins and illustrated the phasic development of these basins: from early fault subsidence to later Pleistocene down-warped sedimentation.According to the drilling data and geochronometry data of active fault detection project in all cities of this area, the paper analyzes and compares depth-time relation of each drilling data (D-T analysis), judges fault activity and sedimentation behaviors in the basins and determines the development trend of basin tectonics.(1) Faults in basinsIn the northwest trending basins (Fuzhou, Quanzhou and Zhangzhou basins) in the mainland, all faults are steep sloped and dipping to centers of basins. The northwest strike faults, which are more active, are located at the deepest portions of basins and at southwest or centers of basins.In the Fuzhou basin the Minhou-Nanyu fault is most possible to produce medium-major earthquakes and is relatively unsafe, Wuhushan fault is secondly. Other faults in the basin are generally safe. The two relatively unsafe faults lie at southwest of the basin.In the Quanzhou basin the Sijiao-Jinjiang fault was active in late Pleistocene. According to the sediment D-T analysis the thesis considers the Zimaoshan-Wushishan fault was active in late Pleistocene. The Sijiao-Jinjiang fault is located at the center of the Quanzhou basin. The Zimaoshan-Wushishan fault lies at southwest of the basin. Other faults were active in early Quaternary or earlier.In the Zhangzhou basin the Gutang-Dameixi fault and north-Jiulongjiang fault were active in late Pleistocene, are relatively unsafe faults. The North-Jiulongjiang fault is northwestern strike in southwest of Zhangzhou urban subarea. The Daishanyan-Hangkeng fault in southwest of the basin is more active than the Zhukeng fault in the Hangkeng-Tianbao subarea of the Zhangzhou basin.On the Xiamen island, the Yuandanggang fault in the northeastern strike fault basin was active in the early stages of late Pleistocene, other faults were active earlier.(2) Sediment in basinsThe sediment in these basins is newer than Pleistocene generally. The sediment D-T analysis of the northwest trending basins in the mainland reveals that the sedimentary center of basins has moved from northeast to southwest.The erosion maybe took place in recent hundreds of years in northeastern part of the Fuzhou basin; the place where the sedimentary speed is higher had moved southwestward during the time 40ka to 8ka. The sedimentary center of the Fuzhou basin has moved from northeast to southwest.In northeastern part of the Quanzhou basin the sediment is earliest (about 80 ka). In 30ka the sediment occurred in middle part of the basin which became the sedimentary center of the basin then. In recent thousands years the sediment in southwestern part of the basin has became speedy, and has be most speedy. The sedimentary center of the basin has moved from northeast to southwest since formation of the basin.In the Zhangzhou basin, the sediment was earlier in northeastern part of Hangkeng-Tianbao subarea, but later its sedimentary speed was lower than in southwestern part of the subarea. Thus the sedimentary center of the basin was in northeastern part early, then moved southwards, had arrived at southwest of the subarea. In the Zhangzhou urban subarea the sediment has had the trend of moving southwards likewise.The sediment of the Yuandanggang basin on the Xiamen Island has had the trend of moving southwards too.According to synthetic analysis of faults and sediments of these basins, the conclusions are as follows: The three northwestern trending basins in the mainland are northwestern strike fault basins; the more active northwest strike faults are located at the center or southwest of basins (i.e. the deepest place); the sedimentary centers of basins have moved from northeast to southwest. The basins are tilting toward southwest.3. The model of regional tectonic movementThe model of Quaternary tectonic movement of southeastern coastal areas of Fujian province is established according to①basins’ property of tilting to southwest shown by the faults and sediment in mainland basins of this area,②the serial events of sediment in these basins and③regional crustal structure.The drilling-exploration and geochronology studies of these basins in Fujian province and other collected data in Chaoshan plain and Zhujiang delta of Guangdong province show the following features.The initial Quaternary sediment in the inland area is older than in the coastal areain the Xiamen island older than in Longhai plain and in Longhai plain older than in Zhangzhou basin. In the mainland area, the initial Quaternary sediment in the Zhangzhou basin is oldest, it becomes newer gradually respectively in two directions to northeast and to southwest _ it is the oldest in Xiamen-Zhangzhou basin and it is the newest in the Fuzhou basin and in the Zhujiang delta. Other sedimentary events of mainland basins in Fujian coastal areas are newer gradually northeastward.Using the result of deep seismic prospectings in this region, the model of regional crustal structure is established. The model shows the following features. The crust in this region is relatively thin. There is a low velocity layer in the bottom of the upper crust. The undersurface of the low velocity layer was upheaved notably around the Seashore faults zone and Taiwan strait, was upheaved around Jiulongjiang faults zone too, was upheaved partially around Quanzhou city. The depth image of superface of upper mantle is like this, but the upheaval is more apparent around the Jiulongjiang fault zone and Yong’an-Jinjiang fault zone.According to the study of tectonic movement trend of these basins, comparing serial sediment in the basins and analyzing crust structure of this region, the model of regional tectonic movement is established:In early Quaternary or pre-Quaternary, a northeastern tension made the upper mantle at southwest to Zhangzhou upheaved, then the tension expanded northeastward, the two groups of faults developed, then the Zhangzhou basin, Quanzhou basin and Fuzhou basin had formed successively; the tension expanded southwestward, then the Chaoshan plain and Zhujiang delta had formed successively too. The tension developed continually and had shaped the Quaternary structural pattern of southeastern coastal area of Fujian province.4. Regional tectonic dynamics analysisAnalyzing the manner of Quaternary movement of the adjacent West Pacific Plate and Philippine Plate carefully (mainly tectonic movement of the west edge of the West Philippine Plate), studying the structure and tectonic movement of the adjacent marine area, Taiwan area and Philippine sea area, discussing the influence of the South Chinese Sea Plate on structure of this region, the paper suggests a reasonable dynamic explanation of tectonic movement of this region.The analysis of evolution of the Pacific basin shows that subduction of the Kula Plate towards NNW , subduction of two oceanic ridges of Pacific Plate under southeastern edge of the Euro-Asia Plate step by step, change of movement direction of Pacific Plate and subduction of Philippine Plate westward _ these important events have effects on formation and evolution of structure of the Fujian-Taiwan area.The Philippine Plate has moved northwestward. Its north edge has subducted under the Ryukyu trench. Its west edge has contacted the Euro-Asia Plate in the Taiwan collision by left-lateral strike slip faults and has contacted South China Sea Plate by the Manila trench. In the Manila trench the South China Sea Plate has subducted under the Philippine Plate. The cooperating action of these two sub-plate has made left-lateral tension around the Bashi strait certainly and has made Bashi tectonic system.Under northwestern compression of Philippine Plate the Fujian eastern costal and seashore areas show uplifted and tension movement. Movement of the Philippine Plate has made left-lateral tension on the Bashi tectonic system. The Bashi tectonic system extends to southwest of Zhangzhou city, is a trigger site of tectonic movement of coastal and circumlittoral areas of Fujian province. The tension stretches from the Zhangzhou-Xiamen area northeastward and southwestward and makes sediment and vertical movement of all basins in the southeastern coast of Fujian province. The movement of the Philippine Plate is rhythmic, so the left-lateral tension made by the movement is multi-episode, the tectonic movement of basins in the southeastern coast area of Fujian province is multi-episode too5. The explanation by multi-layer structure of lithosphereThe causes of crustal extension and fracture are analyzed and discussed by the multi-layer lithosphere tectonic theory. The Quaternary structural movement of this area is explained by the theory.Upper layer of lithosphere (upper crust) is brittle, or mid-brittle. The brittle fracture is the deformation style of rock in upper lithosphere mainly, where fault ruptures and earthquakes happen. The lower layer of lithosphere (lower crust and upper mantle) is ductile, mid-ductile layer or which thickness is bigger than upper layer. The lower layer of lithosphere is the layer which bears the stress and through which the stress translates. Deformation of the lower layer is plastic creep mainly. When lithosphere is subjected to the tension along the Bashi structure, tensional deformation shown by lithosphere deformation spreads from forced end to another end, and the continuous tension formed groups of normal faults in this region. This is a possible cause of deep structure for ordinal development of Quaternary basins in the study area from the Jiulongjiang fault zone in two directions.更多还原