南黄海陆架沉积物中褶皱的形态及成因

更新世以来南黄海陆架具有构造活动性强、沉积厚度大(100~300m)、褶皱变形保存完整等特点,是研究未固结沉积物中褶皱变形的理想“实验室”.高分辨率单道地震剖面揭示了南黄海陆架沉积物中具有不同几何形态的三种褶皱:(1)断层相关褶皱(包括断层扩展褶皱和断层牵引褶皱);(2)横向弯曲褶皱;(3)复合作用褶皱.对褶皱的成因和几何形态的研究表明,控制未固结沉积物中褶皱形成的因素是基底断层及其形成的断块,而不是区域应力场.大量孔隙水可能对沉积物的几何形变具有重要的影响作用.沉积物中断层扩展褶皱和牵引褶皱在形变程度上具有连续性,说明两者在成因上存在联系.断层扩展褶皱可能引发的地震活动和变形带在海洋工程地质评估中应受到重视.     

褶皱调节断裂

褶皱调节断裂是一种在褶皱发育过程中形成的、与构造和地层位置有关的、调节应力变化的二级断裂。最常见的褶皱调节断裂有四种类型。伸出向斜的逆冲断裂和进入背斜的逆冲断裂主要是由褶皱核部不断增加的地层曲率所引起的，虽然层面方向不同级别的差异应力也影响了断裂的断距。根据主要褶皱动力学演化机制的不同，这些逆冲断裂可以沿不对称褶皱的陡翼或缓翼延伸，也可以沿对称褶皱的枢纽延伸。楔状逆冲断裂主要是由于刚性地层中相邻地层之间层面方向的刺穿应力变化而形成的。翼部楔主要表现为断弯褶皱或断倾褶皱的上盘和，或下盘，而枢纽楔则主要表现为趋于加厚刚性较强的地层的多重嵌套断裂。前翼逆冲断裂和后翼逆冲断裂具有一系列的形成机制。前翼空间调节逆冲断裂是一种断距较小的逆冲断裂，它所调节的是由褶皱核部不断增加的地层曲率所引起的应力不连续性。前翼切变逆冲断裂形成于褶皱作用的晚期，主要成因是褶皱陡倾前翼的地层旋转和平行于层面的拉张作用。大多数的后翼逆冲断裂均起源于伸出向斜的逆冲断裂。最终，这些断裂还可以与前翼逆冲断裂一起组成前翼-后翼逆冲断裂。背冲断裂所调节的是断裂相关褶皱形成过程中的上盘应力，它们可以形成于刚性地层之中，还可以以主逆冲断裂的发育速度穿过地层。虽然褶皱调节断裂是一种二级构造，但是，它们却是确定褶皱-逆冲断裂构造中构造圈闭的几何形态及规模的重要因素。因此，在解释褶皱和逆冲断裂带的构造几何形态时，对这些构造进行的准确成图将是非常关键的。     

渤海湾盆地中部428构造带近S-N向走滑断裂的形成时期及其在中生代期间的调节转换作用

渤海湾盆地中部428构造带自印支期以来经历了多期次构造运动叠加改造过程,区域内发育了大量的近S-N向与近EW向褶皱、断层构造,并控制了潜山的形成。然而目前对428构造带的研究仅局限于探索区域内潜山构造成因及其油气圈闭特性,对区域内的断裂系统,尤其是发育的大量近S-N向断裂的形成时期及其后期演化过程中所起到的调控作用尚不明确。鉴于此,为明确其形成时期、探索其对区域构造格局演化模式所产生的影响,基于前人的研究成果,以石臼坨凸起东侧428构造带为主要研究对象,通过对该区域典型的地震剖面进行精确解析,对其展开了系统性的研究。研究结果表明：(1) 428构造带与石臼坨凸起东侧连接处存在一条近S-N向走滑断裂;(2)该走滑断裂的形成最早可追溯至印支期。根据古生界褶皱和薄底构造的分布特征可知,该走滑断裂最初为近E-W向逆冲推覆断裂的侧向断坡;(3)近S-N向走滑断裂阻挡了燕山期NWW向的逆冲推覆作用,从而控制古生界和中生界大量协调褶皱的发育。而近E-W向断裂表现为压扭性质,控制了中生界雁列式褶皱的形成。基于以上认识,认为该近S-N向走滑断裂在印支-燕山期均起到了重要的调控作用,是一个重要的调节转换带...     

渤海湾盆地大歧口凹陷变换构造与板内变形差异

以大歧口凹陷大面积高精度三维地震资料为基础,并结合前人的研究成果,系统分析了大歧口凹陷变换构造与板内其他块体间的变形差异。从对不同级别构造的控制作用分析,大歧口凹陷的变换构造带可以划分为3个级别:(1)近南北向的主变换带(也称一级变换带),自西向东依次为孔店东变换带、沿岸变换带和羊二庄变换带,分别对应了大歧口凹陷西部、沿岸和羊二庄3条基底走滑断裂带。这3个主变换带起到了协调大歧口凹陷东西两侧构造样式差异的作用。(2)近东西向的次变换带(也称二级变换带),自北向南依次对应大歧口凹陷的汉沽、海河-新港和歧中3条控凹断裂。这3条近东西向的控凹断裂起到了调节黄骅坳陷北、中、南三区变形差异的作用,致使大歧口凹陷主变换构造带近南北向的发育。(3)三级变换带,一般垂直于主控断裂发育,起到传递断裂之间伸展量的作用。大歧口凹陷变换构造带主要有边界主控断层的影响、先期基底构造的控制和新生代不均匀伸展作用的影响3个成因。变换构造带的存在和发育使大歧口凹陷内部不同时期的不同块体存在时空上的差异变形,造成了凹陷内部构造样式的差异。受太平洋板块后退式俯冲和印度-欧亚板块挤压碰撞作用的影响,黄骅坳陷新生代以来处于右旋拉张应力场作用下,表现出早期裂陷、后期拉分断陷的特征;其区域主构造应力场由孔店-沙四期的WNW—ESE向拉伸变为沙三-东营期的NW—SE向拉伸,到新近纪又发展为近N—S向拉伸,总体呈顺时针旋转,而这样一个构造演化过程正好可以用黄骅坳陷内大歧口凹陷的发育和演化拉分模式来成功解释。     

南黄海构造样式的特征及含油气性

南黄海不同构造层内发育各具特色及多类型的构造样式，主要表现有压缩，伸展和反转构造样式，分别对应基底卷入型的压性断块和冲断构造，挤压背斜构造，潜山构造，穹隆构造，张性断块构造以及断层扩展反转褶皱构造，盖层滑脱型褶皱反转构造，单条冲断系负反转构造等，认为这些构造样式是地壳挤压，伸展和走滑联合作用的结果，并探讨与油气赋存的规律。     

西非被动大陆边缘重力滑脱构造体系下的塑性构造

论述了西非被动大陆边缘深水环境下的重力滑脱构造体系中的塑性构造。研究发现塑性地层在整个西非被动大陆边缘都有分布,且盐岩塑性层主要分布在西非被动大陆边缘的西南部和西北部,发育层位为过渡期(J-K)构造层之内;中部尼日尔三角洲等塑性层主要为泥岩塑性层,发育层位为古近系和新近系。根据重力滑脱构造体系发育特征可划分为:以正断裂和塑性焊接构造为主的上部重力滑脱伸展构造、以底辟构造为主的中部重力滑脱底辟构造、以冲断裂、塑性褶皱和塑性冲断构造为主的下部重力滑脱冲断构造。根据塑性构造上覆地层的变形过程,塑性构造演化主要经历了后生变形期和同生变形期。塑性构造变形机制主要受基底掀斜作用和上覆地层的沉积速率控制。塑性构造中的底辟、褶皱、冲断及塑性焊接构造对油气成藏的控制作用依次减弱。     

尼日尔三角洲中深水褶皱与逆冲断裂带的构造样式

深水尼日尔三角洲中包含有两个大型的褶皱和逆冲断裂带，它们是由显示有复合类型的逆冲作用的大陆架上的重力拉张作用所引起的压缩作用的产物。这些压缩构造形成于Akata组超压页岩中的多滑脱（水平）面之上。使用生长沉积作用模式、褶皱形态、断面地震反射和一般断弯褶皱及切变断弯褶皱原理等，我们描述并模拟了组成这些（构造）带的断裂相关褶皱和叠瓦状逆冲断裂系统的构造类型和运动学特征。单个断裂相关褶皱，包括前裂逆冲断裂和后裂逆冲断裂都是以倾角小于相关断面斜坡的长平后翼为特征的，其后翼上生长地层倾角向上变小的特征则反映了持续的翼部旋转成分。前翼要短于后翼，但是，生长地层则具有更为一致的倾角，反映了由膝折带的迁移所引起的褶皱作用成分。因此，我们使用了一种结合了一般断弯褶皱原理和切变断弯褶皱原理的方法来描述这些构造，包括超压页岩中的一个弱基底滑脱带的影响。我们详细地论述了这些原理，并进行了叠瓦状逆冲断裂系统的运动学模拟，结果显示了与该三角洲中空间和时间变化有关的逆冲断裂作用的复杂历史。使用褶皱生长地层的区域图形，我们定义了包括单滑脱面和多滑脱面的前裂、后裂和同代逆冲断裂。并定义了两种主要的叠瓦状逆冲断裂系统类型：Ⅰ型系统具有一个底部滑脱面，Ⅱ型叠瓦状逆冲断裂系统则具有多个底部滑脱面，并会造成Akata组明显的构造加厚以及浅层逆冲断片的再褶皱。通过对穿过这些系统的两条区域横剖面进行的层序恢复，我们分辨出了构造类型、逆冲断裂的活动时间及次序、及区域地层缩短量，而这些信息则与深水尼日尔三角洲中的烃类成熟和油气充注等之间有着重要的联系。     

南海裂陷盆地中斜向伸展及其油气勘探意义

利用海上钻井、地震等资料,重新认识南海珠江口盆地文昌B凹陷控凹边界南断裂构造变形史及动力学机制,探讨油气勘探意义。研究表明,渐新世—中新世,南断裂具有斜向伸展性质,在倾向剖面,断裂带发育挤压褶皱和破碎主位移带的构造样式;在走向剖面,相关地层呈"厚薄相间"分布。平面上,发育雁列式背斜与洼地共生、"马尾状"断裂体系和右阶斜列阶步断裂体系。斜向伸展动力学机制受控于区域伸展构造应力场与先存南断裂走向。南断裂渐新世—中新世斜向伸展变形,控制和影响了油气成藏要素、流体相态。     

雪峰陆内构造系统燕山期构造变形特征和动力学

通过分析雪峰陆内构造系统燕山期褶皱-断裂的构造特征和时空演化,得出研究区雪峰山西侧构造样式具有明显的块断效应,各次级构造单元的边界断裂对构造样式具有强烈的控制作用。时序上,燕山期有两期褶皱变形,早期褶皱轴向总体为NE向,晚期褶皱轴向为S—N向或NNE向;动力学上,雪峰陆内构造系统在NW—SE向的缩短作用下,其中的雪峰山隆升带的前寒武纪基底垂向推挤隆升,且不同块体平面上表现为复杂的走滑逃逸:以怀化-新晃断裂为界,以南的块体向SW向挤出。结合古太平洋板块在燕山期的俯冲规律,古太平洋板块NW向和W向的两次俯冲可能控制了燕山期两幕褶皱和逆冲作用。     

南冲绳海槽岩石圈构造动力作用机制探讨

由最新获得的重磁、地震和多波束地形数据 ,结合多尺度的地幔流动力分析 ,展示了南冲绳海槽岩石圈构造动力的多样性特征和其内在的联系。从上新世开始的三幕张性断陷活动是在以前的压性断裂构造的基础上发展起来的 ,向岛弧侧迁移 ,岩浆、火山活动主要集中在正断层与平移断层的交汇处。深部动力源可归结为上地幔对流产生的菲律宾海板块俯冲 ,引起岛弧岩石圈挤压褶皱而向海沟旋张掀斜 ,产生弧后岩石圈的张性构造 ;进一步引起弧后软流圈挤压隆起 ,岩石圈与软流圈耦合作用导致海槽断陷张裂、岩浆活动。冲绳海槽仍是一个软流圈在汇聚的弧后盆地。全球性左旋压扭滑移背景 ,琉球海沟南段俯冲受阻小、强度大 ,台湾—吕宋的北向挤压 ,使海槽表现为剪张性 ,由平移断层调控使张性断裂左旋雁行排列 ,整个海槽张性构造由北往南推进 ,张应力方向由NW过渡到NNW。     

Structural architecture and tectonic evolution of the Yelleg inverted half graben,northern Sinai,Egypt

The Gebel Yelleg area includes a number of folds belonging to the northern Sinai Syrian Arc structures. Detailed surface structural mapping and subsurface (seismic and borehole) data show that the Gebel Yelleg structures are related to Late Cretaceous-Early Tertiary inversion of a Jurassic asymmetric (or half) graben formed during the opening of Neotethys. The inversion structures include a large (45-km long) asymmetric fold (Yelleg Anticline) with a steep flank overlying the southeastern (main) bounding fault of the inverted half graben as well as some right-stepped en echelon folds overlying the northwestern bounding fault of the half graben. The large inversion anticline is dissected by a large number of long, nearly orthogonal normal faults whereas the en echelon folds are dissected by transverse normal faults and two sets of oblique-slip faults. Inversion of the northern Sinai extensional basins is related to Africa-Eurasia convergence and was probably transpressional with a small component of dextral slip. This study shows that the magnitude of inversion in the northern Sinai fold belt decreases toward the southern boundary of the Jurassic extensional province.     

宁镇地区的限制性断层

宁镇山脉的褶皱带被一系列横断层分割为褶断段。横断层相邻的断块,无论是褶皱的形态、纵断层的数目、规模和断距等特征沿纵向跨越横断层均存在不连续性的跃变,表明这些横断层是早于褶皱或与之伴生的纵断层而存在,并对各断块内发育的地质构造起到限制作用。因横断层作为较早的边界,后期的挤压在被分割的各块段内可以是有差异的,导致宁镇褶皱带在总体上的一致性,分段上的有特殊性。     

北黄海盆地褶皱分布与成因类型

北黄海盆地为叠置在华北地台上的中新生代断陷盆地,在地史上经受了多期区域构造运动的改造,地层变形强烈,褶皱构造相当发育,分为伸展型、压缩型、重力型和热力型4大成因类型。其中,与张性正断层相关的伸展型褶皱分布范围最广,可进一步划分为牵引褶皱、逆牵引褶皱、滚动褶皱、翘倾褶皱、补偿性挤压背斜和断层-位移褶皱;形成于区域挤压应力场的压缩型褶皱包括非反转挤压褶皱和反转褶皱,在东部和中部坳陷表现明显;重力型褶皱以发育于古潜山之上的披覆背斜比较常见;由岩浆活动引起的热力型褶皱不甚发育,目前仅见于东部坳陷。     

论反转构造

反转构造指同一断裂面出现两期力学性质和运动方向都相反的构造组合。依反转构造的尺度有断层的反转，盆地的反转及盆地系的反转。负反转包括三类型式，发生在裂谷期的正反转有三类型式，发生在后裂谷期的有四种型式。反转构造的成因有应力型，重力型的热力型。大型的负反转与裂陷作用复合可以使地壳厚度显著减薄。     

Salt tectonics and tear faulting in the central part of the Zagros Fold-Thrust Belt,Iran

The central part of the Zagros Fold-Thrust Belt is characterized by a series of right-lateral and left-lateral transverse tear fault systems, some of them being ornamented by salt diapirs of the Late Precambrian–Early Cambrian Hormuz evaporitic series. Many deep-seated extensional faults, mainly along N–S and few along NW–SE and NE–SW, were formed or reactivated during the Late Precambrian–Early Cambrian and generated horsts and grabens. The extensional faults controlled deposition, distribution and thickness of the Hormuz series. Salt walls and diapirs initiated by the Early Paleozoic especially along the extensional faults. Long-term halokinesis gave rise to thin sedimentary cover above the salt diapirs and aggregated considerable volume of salt into the salt stocks. They created weak zones in the sedimentary cover, located approximately above the former and inactive deep-seated extensional faults. The N–S to NNE–SSW direction of tectonic shortening during the Neogene Zagros folding was sub-parallel with the strikes of the salt walls and rows of diapirs. Variations in thickness of the Hormuz series prepared differences in the basal friction on both sides of the Precambrian–Cambrian extensional faults, which facilitated the Zagros deformation front to advance faster wherever the salt layer was thicker. Consequently, a series of tear fault systems developed along the rows of salt diapirs approximately above the Precambrian–Cambrian extensional faults. Therefore, the present surface expressions of the tear fault systems developed within the sedimentary cover during the Zagros orogeny. Although the direction of the Zagros shortening could also potentially reactivate the basement faults as strike-slip structures, subsurface data and majority of the moderate-large earthquakes do not support basement involvement. This suggests that the tear fault systems are detached on top of the Hormuz series from the deep-seated Precambrian–Cambrian extensional faults in the basement.     

The impact of syn- and post-extension prograding sedimentation on the development of salt-related rift basins and their inversion: Clues from analogue modelling

Various studies have demonstrated the intrinsic interrelationship between tectonics and sedimentation in salt-related rift basins during extension as well as during their inversion by compression. Here, we present seven brittle–ductile analogue models to show that the longitudinal or transverse progradation of sediment filling an elongate extensional basin has a substantial impact on the growth of diapirs and their lateral geometrical variations. We use five extensional models to reveal how these prograding systems triggered diapir growth variations, from proximal to distal areas, relative to the sedimentary source. In the models, continuous passive diapir walls developed, after a short period of reactive–active diapiric activity, during syn-extensional homogeneous deposition. In contrast, non-rectilinear diapir walls grew during longitudinal prograding sedimentation. Both longitudinal and transverse post-extensional progradation triggered well-developed passive diapirs in the proximal domains, whereas incipient reactive–active diapirs, incipient roller-like diapirs, or poorly developed diapirs were generated in the distal domains, depending on the modelled sedimentary pattern. Two models included final phases of 6% and 10% shortening associated with basin inversion by compression, respectively, to discriminate compressional from purely extensional geometries. With the applied shortening, the outward flanks of existing diapir walls steepened their dips from 8°–17° to 30°–50°. Likewise, 6% of shortening narrowed the diapir walls by 32%–72%, with their fully closing (salt welds) with 10% of shortening. We compare our results with the distribution of salt walls and minibasins of the Central High Atlas diapiric basin in Morocco, which was infilled with a longitudinally prograding mixed siliciclastic and carbonatic depositional sequence during the Early–Middle Jurassic with a minimum thicknesses of 2.5–4.0 km.     

Cenozoic structural deformation and dynamic processes of the Bohai Bay basin province,China

Cenozoic structures in the Bohai Bay basin province can be subdivided into eleven extensional systems and three strike-slip systems. The extensional systems consist of normal faults and transfer faults. The normal faults predominantly trend NNE and NE, and their attitudes vary in different tectonic settings. Paleogene rifting sub-basins were developed in the hanging walls of the normal faults that were most likely growth faults. Neogene–Quaternary sequences were deposited in both the rifting sub-basins and horsts to form a unified basin province. The extensional systems were overprinted by three NNE-trending, right-lateral strike-slip systems (fault zones). Although the principal displacement zones (PDZ) of the strike-slip fault zones are developed only in the basement and lower basin sequences in some cross sections, the structural deformation characteristics of the upper basin sequences also indicate that they are basement-involved, right-lateral strike-slip fault zones. According to the relationships between faults and sedimentary sequences, the extensional systems were mainly developed from the middle Paleocene to the late Oligocene, whereas the strike-slip systems were mainly developed from the Oligocene to the Miocene. Strike-slip deformation was intensified as extensional deformation was weakened. Extensional deformation was derived from horizontal tension induced by upwelling of hot mantle material, whereas strike-slip deformation was probably related to a regional stress field induced by plate movement.     

Origin of transverse folds in an extensional growth-fault setting: Evidence from an extensive seismic volume in the western Gulf of Mexico

Growth faults in gravity-driven extensional provinces are dominated by coast-parallel trends, but coast-perpendicular (transverse) trends are far less documented. The Clemente–Tomas fault in the inner Texas shelf has corrugations that are transverse to the fault and that plunge downdip. A large (8500 km²), high-quality, 3D seismic survey allows a uniquely encompassing perspective into hanging-wall deformation above this corrugated fault surface. Synextensional strata in the hanging wall are folded into alternating transverse ridges and synclines, typically spaced 10 km apart. Forward modelling in dip profiles of an extensional fault having three ramps produces ramp basin-rollover pairs that compare with the seismically revealed ridges and synclines. As they translated down the undulose fault plane, ramp basins and rollovers were juxtaposed along strike, forming the hanging-wall ridges and synclines observed offshore Texas. Fault-surface corrugations correlate broadly with footwall structure. We infer that corrugations on the Clemente–Tomas fault formed by evacuation of an allochthonous salt canopy emplaced in the late Eocene to early Oligocene. Early salt evacuation (Oligocene) created an undulose topography that influenced incipient Clemente-Tomas fault segments as they merged to form an inherently undulose fault. Late salt evacuation (early Miocene) further deformed this fault surface.     

Different expressions of rifting on the South China Sea margins

Rifting of continental margins is generally diachronous along the zones where continents break due to various factors including the boundary conditions which trigger the extensional forces, but also the internal physical boundaries which are inherent to the composition and thus the geological history of the continental margin. Being opened quite recently in the Tertiary in a scissor-shape manner, the South China Sea (SCS) offers an image of the rifting structures which varies along strike the basin margins. The SCS has a long history of extension, which dates back from the Late Cretaceous, and allows us to observe an early stretching on the northern margin onshore and offshore South China, with large low angle faults which detach the Mesozoic sediments either over Triassic to Early Cretaceous granites, or along the short limbs of broad folds affecting Palaeozoic to Early Cretaceous series. These early faults create narrow troughs filled with coarse polygenic conglomerate grading upward to coarse sandstone. Because these low-angle faults reactivate older trends, they vary in geometry according to the direction of the folds or the granite boundaries. A later set of faults, characterized by generally E–W low and high angle normal faults was dominant during the Eocene. Associated half-graben basement deepened as the basins were filling with continental or very shallow marine sediments. This subsequent direction is well expressed both in the north and the SW of the South China Sea and often reactivated earlier detachments. At places, the intersection of these two fault sets resulting in extreme stretching with crustal boudinage and mantle exhumation such as in the Phu Khanh Basin East of the Vietnam fault. A third direction of faults, which rarely reactivates the detachments is NE–SW and well developed near the oceanic crust in the southern and southwestern part of the basin. This direction which intersects the previous ones was active although sea floor spreading was largely developed in the northern part, and ended by the Late Miocene after the onset of the regional Mid Miocene unconformity known as MMU and dated around 15.5 Ma. Latest Miocene is marked by a regional basement drop and localized normal faults on the shelf closer to the coast. The SE margin of the South China Sea does not show the extensional features as well as the Northern margin. Detachments are common in the Dangerous Grounds and Reed Bank area and may occasionally lead to mantle exhumation. The sedimentary environment on the extended crust remained shallow all along the rifting and a large part of the spreading until the Late Miocene, when it suddenly deepened. This period also corresponds to the cessation of the shortening of the NW Borneo wedge in Palawan, Sabah, and Sarawak. We correlate the variation of margin structure and composition of the margin; mainly the occurrence of granitic batholiths and Mesozoic broad folds, with the location of the detachments and major normal faults which condition the style of rifting, the crustal boudinage and therefore the crustal thickness.     

Geometries and mechanism of folds in sediments on the southern Huanghai Sea shelf

1Intraduction Foldsinconsolidatedstrataareoftendocumen ted.Butfoldsinloosely consolidatedsedimentsare rarelydiscussed,probablybecauseofthefollowings:(1)folddeformationsinloosely consolidatedsedi mentsareweakortheyhavebeendestroyed;(2)tectonicactivityhasbe…