南海北部珠江口外峡谷体系沉积特征、演化及其控制因素

深水海底峡谷内部的粗粒碎屑沉积物不仅可以作为良好的油气储层,也可以较为完整地记录海洋地质环境变迁的相关信息,是目前海洋地质领域研究的热点.为揭示南海北部珠江口外峡谷体系沉积演化过程及其控制因素,利用多波束测深和高分辨率二维多道地震数据,对珠江口外峡谷体系地形特征、沉积充填特征、形成发育过程和控制因素进行研究.研究发现珠江口外峡谷呈三段式发育：上段为NW-SE走向,宽度超过30 km,侵蚀强度不大,横截面为不规则形态;中段为E-W走向,宽度开始变窄（25～30 km）,横截面呈U型;下段为NW-SE走向,宽度达到最大（25～45 km）,横截面呈U型,中段和下段以沉积作用为主.珠江口外峡谷体系沉积演化主要分为3个阶段：早期阶段（23～15.5 Ma）,水道-海底扇阶段（15.5～11.6 Ma）和峡谷-海底扇/块体流阶段（11.6～0 Ma）.揭示了该峡谷珠江口外峡谷体系的发育和演化主要受构造运动、海平面变化和沉积物供给的控制作用,通过以上分析,将对南海北部海洋灾害地质、深水沉积体系研究及油气资源勘探有重要的指导意义.     

南海海盆盆西峡谷的形态与结构及形成演化

盆西峡谷是南海中建南盆地中东部的一条大型峡谷,整体呈NW向,水深介于2 850~4 300 m,全长约188 km,宽为1.5~14.5 km,起始于中建南盆地,延伸到西南次海盆,对其进行形态、结构和形成演化的研究,为后续西南次海盆浊积扇的研究奠定了基础,对深入了解浊流沉积物的搬运模式提供科学依据.利用高分辨率多波束测深、单道和多道地震的最新资料,研究盆西峡谷的形态特征和结构及形成演化,结果表明盆西峡谷具有"分段性"特征,剖面形态从WN向ES依次表现为上段U型、中上段V型、中下段下V上U型和下段U型4段形态;上段以沉积作用为主,发育多期下切河道充填沉积,厚度可达1 200 m;中上段以侵蚀-沉积过渡作用为主,发育浊积水道砂体;中下段以冲刷作用为主,发育内堤岸和块体流沉积;下段发育块体流和滑塌体沉积.研究表明,盆西峡谷的形成受古地貌条件、侵蚀-沉积作用、海平面变化、构造运动和岩浆活动等多方面的影响,其中侵蚀-沉积作用、断裂活动和海平面变化为主控因素.揭示出盆西峡谷沉积演化可分为3个演化阶段:中中新世的峡谷蕴育阶段、晚中新世的峡谷侵蚀-充填阶段和上新世-第四纪的峡谷"回春"阶段.      

中建海底峡谷地貌及沉积特征的分段性

中建海底峡谷具有分段性,但分段的关键地貌特征、各段沉积充填及其控制因素缺乏精细描述和系统论证.综合利用高分辨率二维和三维地震资料,结合水深地貌数据,对中建海底峡谷地貌及沉积特征进行了详细分析,总结了其南北段沉积过程的主控因素.中建海底峡谷呈NW向顺直展布于广乐隆起与西沙隆起之间,以华光礁附近的地貌高点为拐点被分为南北两...     

台湾东部海域台东峡谷沉积特征及其成因

台湾东部峡谷的研究程度较低,对其沉积特征及成因缺乏系统的论述.利用近年来在台湾东部海域获得的地震剖面,对台东峡谷的形态特征、沉积充填以及成因进行了详细的分析.台东峡谷主体位于花东海盆,该部分水深在4 000~5 500 m范围内,以NE方向为主,长度约为160 km,宽度为0.2~14 km.根据峡谷的平面延伸特征,可以将台东峡谷分为3个区段:上游段为NE-NEE走向段、中游段为NE-NNW走向段、下游段为NE走向段直到峡谷嘴部;下切谷剖面形态从上游段的"V"型、中游段的复合形态（"UV"并行）逐渐过渡到下游段的"U"型.台东峡谷上游段-中游段滑塌构造发育,峡谷转弯处的侧翼可见波状沉积,其下游段则以沉积充填为主.台东峡谷的成因与构造作用、地形特征和深水沉积作用关系密切.受西南高东北低的地形特征及基底隐伏断裂控制,峡谷总体呈现NE向延伸;重力流作用为峡谷的下切侵蚀和充填提供了动力与物质来源,峡谷从上游段到下游段下切侵蚀能力减弱,谷底充填增厚;峡谷中游段受海山的阻挡,发生转向;峡谷下游段因多条峡谷携带的沉积物汇入和"喇叭状"地形的影响,输送的沉积物在出加瓜脊末端后,形成了大型深水扇.      

南大西洋西非岸盆地群构造、沉积演化对比

非洲西部海岸盆地群经历了裂谷期、同裂谷期和漂移期构造演化阶段,构造演化和沉积充填有一定的相似性,但是由于后期局部构造和差异沉积的影响,现今盆地发育的构造样式和沉积建造有一定区别,导致勘探效果有较大的差异.本文通过对比南大西洋赤道段转换型、中段含泥型、中段含盐型和南段火山型盆地的综合柱状图,加上对尼日尔三角洲盆地和下刚果...     

孟加拉盆地东部褶皱带差异构造变形及成因

基于野外地质调查和地震资料分析,证实了孟加拉盆地东部褶皱带发育底部和中部两套滑脱层。底部滑脱层在整个褶皱带均发育,而中部滑脱层仅发育于北段—中段的陆上和陆架区,在中段的陆坡-洋盆区及南段则不发育。中部滑脱层的发育受古陆坡富泥沉积控制。北段—中段主要发育滑脱褶皱及被断层突破的滑脱褶皱,而南段主要发育泥底辟和泥火山构造。孟加拉盆地东部褶皱带滑脱层系及构造样式的差异变形特征主要受区域挤压作用、沉积作用以及地层流体超压等方面存在着差异的共同影响。     

北美东部被动大陆边缘盆地的分段性与油气勘探

北美东部被动大陆边缘是世界上最古老的完整被动大陆边缘之一,是研究被动大陆边缘发育演化的天然实验室。本文在大量国外研究成果的基础上,应用盆地构造解析方法,深入研究了北美东部被动大陆边缘盆地群的地质结构和构造演化特征,并揭示了盆地群的油气地质规律。研究认为,北美东部盆地群沉积充填和不整合面发育具有明显的分段性和差异性。以区域不整合面为界,不同段盆地可划分为不同的构造层:南段盆地可划分为两套构造层;中段南部盆地可划分为3套构造层;中段北部盆地可划分为4套构造层;而北段盆地可划分为5套构造层。盆地群整体经历了陆内裂谷—陆间裂谷—被动大陆边缘的演化过程,但不同段盆地的构造演化具有明显的分段性和迁移性:晚三叠世沉降中心位于南段盆地;早侏罗世初期迁移至中段盆地,南段大陆开始裂解;中侏罗世逐渐迁移至北段盆地,中段大陆开始裂解;早白垩世晚期,北段大陆开始裂解。受持续的抬升剥蚀及大西洋岩浆活动省的联合作用,南段盆地和中段大多数盆地缺乏油气保存条件;斯科舍盆地和大浅滩盆地是主要的含油气盆地,以上侏罗统烃源岩为主,主要发育断层—背斜圈闭和盐体刺穿圈闭,整体表现为“自生自储”和“下生上储”的特征。     

南海构造变形分区及成盆过程

为了系统认识新生代南海沉积盆地形成演化过程和成盆机制, 在对南海及其周缘区域构造和沉积研究进展调研的基础上, 利用覆盖南海主要盆地新近采集和重处理的地震剖面开展详细的构造-地层分析.基于盆地结构构造、演化特征和成盆动力学的差异性, 以红河-越东-Lupar线大型走滑构造带为界, 将南海及其周缘沉积盆地划分为古南海俯冲拖拽构造区沉积盆地群和挤出-逃逸构造区沉积盆地群, 前者主要是古南海俯冲及其所引起的区域构造变形形成的盆地, 包括北部湾、琼东南、珠江口、曾母、北康、文莱-沙巴和礼乐等盆地, 后者是印度-欧亚大陆碰撞导致印支地块挤出和旋转形成的盆地, 如莺歌海、湄公、中建南、万安等盆地.最后, 结合周缘板块动力学事件和本次对盆地构造研究的成果, 特别是盆地中重要界面属性的重新厘定, 建立了南海及其周缘沉积盆地演化过程.      

台湾峡谷中段沉积特征及流体机制探讨

海底峡谷、高弯度水道等深水沉积单元中的流体活动方式是人们关注的热点.本次研究利用高分辨地震资料,结合地形地貌特征对台湾峡谷中段的沉积特征及流体活动方式进行初步探讨.台湾峡谷中段发育内堤岸(inner levee),它成层性好、地层产状倾斜,地震反射特征与峡谷西岸和下覆滑塌体明显不同,内部结构表现为逐级上超的特征,以侧向加积为主.曲流河和深水高弯度水道的点坝均发育于河(水)道拐弯处,由于离心力作用,沉积物在凸岸堆积形成点坝.该内堤岸位于峡谷中段直线型地段,不具备形成点坝的地形地貌条件,综合分析认为该内堤岸是由垂直于峡谷轴向、自西向东的底流与沿峡谷向下的重力流交互作用形成的.     

中国南海西北次海盆西北陆缘洋陆过渡区深水沉积体系特征

高分辨率二维地震资料显示中国南海西北次海盆西北陆缘（水深1 000 m及以下）发育如下深水沉积体系:珠江口盆地南部隆起区缓坡带（水深约1 000~1 500 m、坡度<1.2°）出露神狐南海山,该海山附近发育“海山相关等深流沉积体系”,可能受南海中层水循环（自西向东）底流控制;神狐南海山以南水深约1 500~2 500 m的陆坡区（坡度>2°）普遍发生坡移,发育“重力流滑塌体系”和“峡谷体系”,鲜见等深流沉积;下陆坡区（水深>2 500 m,坡度稍缓<2°）滑塌现象明显减少,主要发育“峡谷体系”以及“席状等深流沉积体系”,席状等深流沉积体系可能受分散的、流速较低的南海深层水循环底流控制。地震沉积记录显示,神狐南海山附近等深流侵蚀特征最早出现于晚中新世早期,其后至现今该区较稳定发育等深流沉积/侵蚀的加积序列,说明南海西北次海盆西北陆缘的稳定底流沉积/侵蚀可追溯至晚中新世早期。     

南海西沙海域东岛北峡谷体系形态、演化及其成因机制

海底峡谷是全球大陆边缘分布较广泛的地貌单元,是地形地貌、深水沉积和海洋地质灾害领域研究的重要内容。本研究基于高分辨率多波束测深和二维地震资料,以南海西沙东部海域为研究区,深入剖析了东岛北海底峡谷体系。东岛北海底峡谷分布在水深1000～3150 m范围,长度137 km,下切深度70～400 m,表现出西高东低的地形特征,总体由一条主峡谷和4条分支峡谷构成。峡谷上游有东岛西北部Ⅰ区和永兴海台东部Ⅱ区的沉积物供给,峡谷中游加入了东岛东北部Ⅲ区供给的沉积物。3个物源区的沉积物供应以线状的峡谷、水道和面状的块体流沉积类型为主。主峡谷北坡周缘分布有大量的海底麻坑,侧壁呈阶梯状不断后撤垮塌,因重力驱动作用和水流侵蚀,使峡谷壁外缘发育呈不规则小型“枝杈”状水道;主峡谷南岸因浊流作用,发育沉积物波。NE走向主断裂,控制着主干峡谷NE方向延伸,而峡谷南岸分布海山和海丘地形、岩浆底辟,影响主峡谷各分段的转向;同时峡谷和周缘下部地层发育的断层,控制峡谷侧壁向谷底呈阶梯状下降。     

Sediment dispersal system in the Taiwan–South China Sea collision zone along a convergent margin: A comparison with the Papua New Guinea collision zone of the western Solomon Sea

Through a large-scale examination of the morpho-sedimentary features on sea floors in the Taiwan–Luzon convergent margin, we determined the main sediment dispersal system which stretches from 23°N to 20°N and displays as an aligned linear sediment pathway, consisting of the Penghu Canyon, the deep-sea Penghu Channel and northern Manila Trench. The seafloor of South China Sea north of 21°N are underlain by a triangle-shaped collision marine basin, resulting from oblique collision between the Luzon Arc and Chinese margin, and are mainly occupied by two juxtaposed slopes, the South China Sea and Kaoping Slopes, and a southward tilting basin axis located along the Penghu Canyon. Two major tributary canyons of the Formosa and Kaoping and small channels and gullies on both slopes join into the axial Penghu Canyon and form a dendritic canyon drainage system in this collision marine basin. The canyon drainage system is characteristic of lateral sediment supply from flank slopes and axial sediment transport down-canyon following the tilting basin axis. The significance of the collision marine basin in term of source to sink is that sediments derived from nearby orogen and continental margins are transported to and accumulated in the collision basin, serving as a temporary sediment sink and major marine transport route along the basin axis. The comparison of the Taiwan–South China Sea collision zone with the Papua New Guinea collision zone of the western Solomon Sea reveals remarkable similarities in tectonic settings and sedimentary processes that have resulted in similar sediment dispersal systems consisting of (1) a canyon drainage network mainly in the collision basin and (2) a longitudinal sediment transport system comprising a linear connection of submarine canyon, deep-sea channel and oceanic trench beyond the collision marine basin.     

南海北部神狐海域新近系以来沉积相及水合物成藏模式

广州海洋地质调查局自2000年以来在南海北部陆坡区相继开展了多个航次的天然气水合物资源的调查及研究工作, 取得了非常丰富的地震资料.在对这些地震资料精细解释的基础上, 识别出了6种典型的地震相: 透镜状前积相、丘状前积相、V字型充填相、席状平行相、底辟—气烟囱状杂乱相、丘状杂乱相; 并由此分析出3种类型的沉积相: 深水浊积相、滑塌相、峡谷水道相.结合似海底反射(BSR) 在研究区范围内的分布, 研究BSR与各沉积相之间的空间位置关系, 由此分析出了3种水合物成藏模式: 断层沟通浊积扇体成藏模式、断层沟通峡谷水道成藏模式、断层沟通峡谷水道及滑塌扇体成藏模式.      

Late Proterozoic Patsy Springs Canyon,Adelaide Geosyncline: submarine or subaerial origin?

A significant aspect of Late Proterozoic sedimentation in the Adelaide Geosyncline, South Australia, is the presence of kilometre-deep erosional incisions which have been termed canyons. These structures were formerly described to be of submarine origin, cut and filled in an inferred basin-slope setting by subaqueous processes. Subsequent detailed research, particularly on a specific incision known as Patsy Springs Canyon, indicates that sedimentary structures within some of the canyon-filling sediments are indicative of deposition above fair weather wave base. In addition, an unusual carbonate unit, which is observed to veneer upper portions of canyon shoulders and to contribute to carbonate breccias interbedded with canyon-fill, has a stable isotope signature which may imply a non-marine origin. The presence of the carbonate veneer, where it is in situ, suggests that at least upper portions of the canyons could have been emergent during the canyon-filling phase. Considering these observations, and combining them with regional stratigraphical relationships, an alternative model for canyon genesis is proposed involving subaerial erosion and subsequent filling by coastal onlap. Such a model requires base-level changes of the order of 1 km, in order to account for observed canyon cutting and filling. Vertical movements associated with halokinesis, or thermally-induced uplift of the order of 1 km, could have resulted in the observed erosional events. Alternatively, a Messinian-style evaporitic lowering of base-level is currently receiving serious attention. With present knowledge this mechanism most satisfactorily explains all observations.     

Submarine origin for the Neoproterozoic Wonoka canyons,South Australia

An examination of the deeply incised Ediacaran Wonoka canyons in the Adelaide Geosyncline (most recently interpreted as subaerial valleys) demonstrates their submarine origin, and confirms them as some of the best examples of ancient outcropping submarine canyons in the world. The entire canyon-fill succession is interpreted to be of deep-water (below wave base) origin, consisting of calcareous shale and siltstone together with a variety of mass-flow deposits including turbidites, grain flows and debris flows. The canyon fill lacks definitive shallow-water structures (e.g. mud cracks, fenestral fabrics or wave ripples) at all stratigraphic levels. Canyon-lining carbonate crusts that have previously been interpreted as non-marine calcretes or tufas (and used to suggest a non-marine origin for the canyons) are argued to be of deep-water, marine, microbial origin. Extremely negative carbon isotope values from the canyon-fill and canyon-lining crusts have a primary marine origin. Previously interpreted deepening upward trends in the canyon fill (used as evidence of a subaerial erosion episode followed by drowning) are suggested to be fining upward trends, caused by the transition from canyon cutting to canyon filling, with the majority of the fill being of deep-water slope origin. The basal conglomeratic canyon-fill sediments represent the last vestiges of the high-energy, deep-water, canyon-erosion environment in which the incisions formed. A deep-water origin for the canyons is consistent with all previous stratigraphic observations of the Wonoka canyons, including the conspicuous lack of regional unconformities in the lower Wonoka Formation, and their emanation from the deep-water facies of the Wonoka Formation. A submarine canyon origin also removes the need for extreme (~ 1 km) relative sea level fluctuation and associated problems (i.e. an enclosed basin with Messinian-style evaporative drawdown or thermal uplift above a migrating mantle plume) required by the subaerial valley hypotheses.     

南海西北次海盆构造演化的沉积响应

通过对南海西北次海盆新获得的地震资料进行综合解释和层序地层分析,揭示了海盆中的沉积对构造演化阶段的响应。始新世-早渐新世陆缘裂陷期,盆地以对称裂谷形式,发育地堑裂谷层序,沉积以近物源为特征,相变大,发育了冲积扇-扇三角洲-湖相沉积,沉积体系的配置受同沉积断裂控制明显,快速沉降和充分的物源供给决定了沉积体系的构成特征。晚渐新世海底扩张期,岩石圈破裂,陆缘进一步拉开并开始海底扩张,出现海相沉积,来自陆坡的陆架边缘三角洲越过陆坡进入海盆,在海盆内沉积了一套向海盆中部逐渐减薄的楔状地层,并伴有大量的火山碎屑沉积物。早-中新世以来热沉降期,随着构造沉降增大,相对海平面总体不断上升,进入深水盆地,形成陆架陆坡体系,大量的碎屑物质以重力流、深水底流等深水作用方式进入海盆;沉降晚期陆架-陆坡物源供应减弱,琼东南中央峡谷成为其主要的物质供应来源通道,在此期间二次海平面下降、回升的综合作用下,海盆内发育了多期以下切水道为特征的低水位域沉积体系。     

Seismic stratigraphy and development of Avon canyon in Benin (Dahomey) basin, southwestern Nigeria

Interpretation of a grid of high resolution seismic profiles from the offshore eastern part of the Benin (Dahomey) basin in southwestern Nigeria area permitted the identification of cyclic events of cut and fill associated with the Avon canyon. Seismic stratigraphic analysis was carried out to evaluate the canyon morphology, origin and evolution. At least three generations of ancient submarine canyons and a newly formed submarine canyon have been identified. Seismic reflection parameters of the ancient canyons are characterized by transparent to slightly transparent, continuous to slightly discontinuous, high to moderate amplitude and parallel to sub-parallel reflections. Locally, high amplitude and chaotic reflections were observed. The reflection configurations consist of regular oblique, chaotic oblique, progradational and parallel to sub-parallel types. These seismic reflection characteristics are probably due to variable sedimentation processes within the canyons, which were affected by mass wasting. Canyon morphological features include step-wise and spoon-shaped wall development, deep valley incision, a V-shaped valley, similar orientation in the southeast direction, and simple to complex erosion features in the axial floor. The canyons have a composite origin, caused partly by lowering of the sea level probably associated with the formation of the Antarctic Ice Sheet about 30 Ma ago and partly by complex sedimentary processes. Regional correlation with geological ages using the reflectors show that the canyons cut through the Cretaceous and lower Tertiary sediments while the sedimentary infill of the canyon is predominantly Miocene and younger. Gravity-driven depositional processes, downward excavation by down slope sediment flows, mass wasting from the canyon walls and variation in terrigenous sediment supply have played significant roles in maintaining the canyons. These canyons were probably conduits for sediment transport to deep-waters in the Gulf of Guinea during their period of formation.     

南海边缘海减薄陆壳成因剖析

南海中央海盆南、北两侧陆缘分布着面积较广的减薄陆壳,正确认识海盆减薄陆壳的成因是研究南海构造演化的重要一环.通过分析基于地壳伸展因子公式计算的南海地壳拉张伸展特征和解释中生代以来的陆壳隆升特征等,证实晚中生代以来至渐新世末,该区不仅发生了地壳拉张伸展作用,还发生了较长期的地壳隆升挤压作用,致使酸性侵入岩出露地表,减薄陆壳区的上地壳厚薄分布不均.始新世南海南部发育海陆过渡相和海相沉积、北部仅为陆相沉积,暗示始新世南海古地理格局是南、北陆缘具有不同沉积环境的盆地群,二者之间应该被隆起所隔.这些地质现象说明该区地壳隆升剥蚀与地壳拉张伸展活动时间有较长的重叠.南海中央海盆两侧减薄陆壳的成因不仅仅是地壳拉张伸展所致,而是拉张伸展与隆升剥蚀共同作用的结果,因此可以认为在曾经发生了地壳隆升挤压而遭受长期剥蚀的区域,如果用全地壳伸展因子的公式来估算地壳拉张伸展程度,将得出错误的结论.