在发育盐构造的被动大陆边缘盆地中,明确盐构造活动与深水重力流事件的沉积耦合特征是该类盆地相对优质储层和甜点区预测、评价的基础.通过综合钻井、岩心分析和三维地震精细解释,对墨西哥湾Sureste盆地中新统深水重力流沉积与盐构造之间的作用方式及响应进行研究,并探讨不同作用方式的成因及油气地质意义.研究表明,Sureste盆地陆坡区发育一系列与盐构造活动相关的微盆、地形坡折、局部凸起和弯曲通道等地貌单元;在这种复杂陆坡地貌背景下,早期和同沉积期盐构造既可以疏导或限制重力流,形成导向、限定、局限和侧向迁移等多种作用类型,也可以被重力流侵蚀形成不整合,后期盐构造活动对深水重力流沉积的改造表现为截切和变形两种样式;不同作用方式和匹配关系受重力流的性质、侵蚀能力与盐构造的规模、数量、走向以及活动时间和强度的控制,局限、侵蚀和截切对应了盐构造与深水重力流沉积相互作用的三个端元;早期和同沉积期盐构造活动影响深水碎屑岩储层的质量和分布,后期盐构造活动对构造、构造—岩性圈闭的形成至关重要.

Post-rift volcanisms and fault activities are significant for understanding the tectonic-sedimentary evolution of rifted continental margins and associated hydrocarbon entrapments. In this study, a series of post-rift fault-associated volcanic activities have been found in the northern continental margin of the South China Sea (SCS). However, their episodes and relationships with the progressive continental breakup are still doubtful. Here, new 2D/3D seismic, borehole, dating, and biostratigraphic data are used to investigate the characteristics of the postrift volcanism and fault activities in the Baiyun Sag (BYS), Pearl River Mouth Basin. The newly-found fault-associated volcanic complexes include thirteen submarine volcanic mounds and associated lava flows, together with igneous sills that are mainly composed of basalts and tuffs. Seismic stratigraphic analysis combined with K-Ar dating from cores confirms that post-rift volcanism in the BYS climaxed along with the breakup of the SCS mainly in three episodes: (1) the first episode near Oligocene/Miocene boundary (23.3 Ma); (2) the second at the middle Early Miocene (17.6 Ma); and (3) the new-found third episode at the late Early Miocene (17.1 Ma). Also, fifty-three syn-sedimentary faults are interpreted, which are characterized by a WNW trending normal fault group separated by an ENE trending transcurrent fault group. And there is evidence that these fifty-three faults were long-lived from ca. 32-17.1 Ma and served as important conduits for the upward migration of the magma. The three episodes of volcanism and tectonic fault activities are related to the progressive continental breakup in the northern SCS margin, and they represent the tectonic signature of the early stage of the post-rift subsidence after the lithospheric breakup which extends to the top of a hypothetical breakup sequence (32-17.1 Ma) in the BYS. Furthermore, this study proves that the diachronous continental breakup in the SCS margin can result in corresponding changes in depositional architectures, along with a breakup sequence characterized by the deposition of a 'sandstone-carbonate-shale' regressive-transgressive cycle. The sedimentological changes and associated tectonic features recorded in the Baiyun Sag suggest an exceptionally active tectonic setting in the time of the formation of the breakup sequence (Early Oligocene-Early Miocene) along the northern SCS margin.

中央峡谷是南海西北部重要的沉积体之一,物源问题一直是其研究的焦点问题,并且至今没有统一的认识.为了解决中央峡谷物源问题,本文利用重矿物、稀土元素以及锆石年龄等物源分析方法,通过与潜在物源区进行对比,确定了中央峡谷的主要物源,探讨了其成因意义.研究结果表明:①红河是中央峡谷的主要物源,对中央峡谷的形成起到主导作用;②红河水系在历史时期曾经发生重大改变,这种改变可能发生在3.6 Ma至今的某个时期;③中央峡谷源于红河,其形成与大河注入相关,并在琼东南盆地中央凹陷带形成大型储集体,为其成为深水油气勘探目标提供了物质基础.

以珠江口盆地区域二维地震资料、钻井资料为基础,结合南海扩张演化历史,重点研究了盆地内部重要不整合面、盆地演化以及对珠江沉积体系演化的控制作用,旨在为南海北部珠江沉积体系深水油气勘探提供支持和参考.研究结果表明:珠江口盆地除基底外,发育三个重要的不整合面,即破裂不整合、陆坡跃迁不整合和陆坡坡度突变不整合;据此将珠江口盆地珠江沉积体系演化划分为四个阶段:裂陷期主要发育河流、湖泊相沉积;断陷陆坡期主要发育陆架边缘三角洲沉积(前积层较陡);拗陷缓陆坡期发育陆架边缘三角洲沉积(前积层较缓);拗陷陡陆坡期主要为三角洲—海底峡谷—海底扇沉积.断陷陆坡期与拗陷缓坡期陆架边缘三角洲的勘探,应沿陆架坡折横向去勘探;而拗陷陡陆坡期三角洲—海底峡谷—海底扇,应采取纵向勘探的思路,垂直于陆架坡折方向寻找油气.

The longitudinal morphology of continental slopes contains significant geological information,and the variations in morphology have been related with the long-term interaction of sedimentary and erosional processes.Basing on a series of 2Dseismic profiles crossing the margin of the northern South China Sea,we have utilized a curve fitting procedure to investigate the morphology of continental slopes and recognized three types of continental slopes:concave-up,planar,and sigmoidal.Concave-up slopes develop within the Yinggehai-western Qiongdongnan area and are thought to be dominated by rapid sediment supply.The central Pear River Mouth area also has concave-up slopes,but they are mostly attributed to the progradation of shelf-edge deltas as well as the erosion of a giant submarine canyon.The sigmoidal slopes are mainly distributed on the two flanks of the Pearl River Mouth area,which resulted from the shaping process of ocean currents and internal waves.A certain type of continental slope tends to have its own stratal stacking pattern,shelf-edge trajectory trend and characteristic depositional systems.Investigation of modern slope morphology can help build up the conduit-sink models,thus providing useful guidance for deep-water hydrocarbon exploration on ancient buried slopes.

Integration of 2D and 3D seismic data from the Qiongdongnan Basin along the northwestern South China Sea margin has enabled the seismic stratigraphy, seismic geomorphology and emplacement mechanisms of eight separate, previously undocumented, mass–transport complexes (MTCs) to be characterized. These eight MTCs can be grouped into two types: (1) Localized detached MTCs, which are confined to submarine canyons and cover hundreds of km2, consist of a few tens of km3 remobilized sediments and show long striations at their base. They resulted from small-scale mass-wasting processes induced by regional tectonic events and gravitational instabilities on canyon margins. (2) Regional attached MTCs, which occur within semi-confined or unconfined settings and are distributed roughly perpendicular to the strike of the regional slope. Attached MTCs occupy hundreds to thousands of km2 and are composed of tens to hundreds of km3 of remobilized sediments. They contain headwall escarpments, translated blocks, remnant blocks, pressure ridges, and basal striations and cat-claw grooves. They were created by large-scale mass-wasting processes triggered by high sedimentation rates, slope oversteepening by shelf-edge deltas, and seismicity. Our results show that MTCs may act as both lateral and top seals for underlying hydrocarbon reservoirs and could create MTC-related stratigraphic traps that represent potential drilling targets on continental margins, helping to identify MTC-related hydrocarbon traps.

红河沉积体系的研究对南海北部油气勘探具有重要的意义.为了进一步明确晚中新世至上新世红河深水沉积体系组成、演化和探讨油气勘探意义.本文在前人研究的基础上,从物源分析入手,首先明确了红河深水沉积体系的物源确定其组成,然后总结展布演化特征,最终探讨了其油气勘探意义.研究结果表明:①晚中新世晚期东方地区的海底扇以及上新世莺琼盆地发育的中央峡谷均属于红河沉积体系;②晚中新世至上新世,红河沉积体系演化可划分为红河海底扇、中央峡谷阶以及衰弱三个演化阶段;③红河沉积体系平面上主要沿着中央凹陷带呈条带状发育,为南海西北部浅水区和深水区提供了重要的储层条件.

Quaternary deep water contourites were studied based on seismic data in northern South China Sea(NSCS).Giant elongated drifts,confined drifts,slope sheeted drifts and sediment waves were found between about 1200 m and 3000 m water depth in NSCS.Giant drifts showed mounded morphology with moats on the landward flank.Confined drifts were developed in the negative relief among topography prominences,where were relative flat and with moats.Slope sheet drifts displayed with sheet morphology.Large scale of sediment waves were generated partially associated to drifts.When deep water contour current moved from northeastern to southwestern,because of relatively obvious topographical change and Coriolis force,helical contour current was produced and secondary circulation appeared in further and formed giant elongated drifts and confined drifts in the upper-middle slope.However,tabular contour current may produce slope sheet drifts for flat and unrestricted environment in middle-low slope.This study was not only helpful to improve the recognition of deep water contourite,but also was beneficial to serve the hydrocarbon exploration.

When reservoir prediction is carried out in a deep-water carbonate-distributing area without any exploration well,it is commonly not only easy to judge reservoir-free bioherms erroneously as real organic reefs only according to the mound seismic reflection configuration that is considered as the proof of reef existence but also easy to ignore the shoal flats without the feature of mound seismic reflection which are likely to be reservoirs.Contrasting seismic reflection with seismic velocity in feature,it is shown that some deference and correlation exist among reefs,bioherms and shoal flat bodies.A reef is characteristic of the mound reflection configuration with high velocity,and a bioherm is of same mound reflection configuration but with low velocity while a shoal flat(body) is of high velocity without the mound reflection configuration.Based on such features,a new method is built for predicting reef reservoirs and shoal flat reservoirs in deep-water areas.This method is applied to predict once more the middle Miocene Meishan carbonate reservoir in some deep-water area of Qiongdongnan Basin.The re-prediction gives a different result that a large part of reefs that were predicted before into "reefs" are reclassified into bioherms and meanwhile shoal flats with a such large area nearly as the distribution area of the reefs are unexpectedly discovered.It is proved that it is an accurate method for predicting carbonate reservoirs in deep-water area.

In the northwest of South China Sea,a huge far source Sedimentary System which is called Red River Sedimentary System has been discovered recently.The Red River depositional system refers to a genetically related combination of a series of deltas,submarine canyon infillings,submarine fans and fine-grained suspension deposits deriving from the terrestrial clastics of the Red River in Neocene.The main body of this depositional system comprises the Red River delta,the Red River submarine fan and the Central Canyon.In order to understand the identify standard and distributing in the plan view,a great deal of 2D seismic profiles has been used.The paper mainly focuses on the system which is developed during late Miocene to Pliocene.Base on the distributing in the plan view,the development history of the Red River Sedimentary system can be understood.The results show that deltas,channels,submarine canyon,channel-levee complex and lobes can be identified in the Red River Sedimentary system based on the seismic reflection characteristics.According to the combination and spatial distribution features of the Red River sedimentary system,the development history of the system can be subdivided into three stages: SQ1-SQ2,the formation period of Red River submarine fan,which is characterized by huge submarine fan;SQ3-SQ4,the development period of the confined submarine fan-Central Canyon,which is characterized by a confined submarine fan developed before the central Canyon;and SQ5-SQ6,the weakening period of the Red River depositional system,which is characterized by Red River Sedimentary System fading out in the research area,instead of Hainan slope's growing.Red River Sedimentary System derives from Qinghai-Tibetan Plateau uplift.The research is not only beneficial for ascertaining Oil and gas prospecting,but also helpful for rebuilding uplift history of Qinghai-Tibetan Plateau,and answering the question whether Red River capture occurred or not.

Based on the interpretation of seismic profiles,slices and attributes,lateral accretion packages(LAPs) were found in Dongfang 1-1 area of the Yinggehai Basin in northern South China Sea.According to their sinuosity,LAPs can be categorized into high or low sinuous types,which are both characterized by a series of shingled reflections on seismic profiles.However,in the plan view,the high sinuous type is represented by a scroll-bar pattern while the low sinuous type is ribbon-like.The LAPs are suggested to be formed by multiple stages of "cut- fill"as well as the subsequent lateral migration.The lower part of LAPs are consisted of coarse-grained reservoir resulting from the amalgamation of channel axis bottom deposits,which have good lateral connectivity and reservoir potential.However,it turns upwards into the combination of sandstones interbeded with mudstones,leading to a low lateral connectivity and quality.The discovery of the LAPs is significant to understand the nature of the deep-water gravity-flow systems and also provides potential targets for the hydrocarbon exploration in the study area.

Based on the study of Pearl River Mouth basin and Niger Delta Basin,making use of high-resolution 3-D seismic data,drilling and logging data as well as regional geological data,the sedimentary architectures of the MTDs were discussed.The results show that three type MTDs are identified;slide blocks originated from the failures of continental slope(type-Ⅰ),slide blocks of submarine channel wall(type-Ⅱ) and slide-debris flow deposits complex(type-Ⅲ).The same type MTDs have certain similarities in geometry,internal texture,physical property,and stacking pattern.Type-I displays a lobate form.There is listric slump escarpment at the tail of the slide.Rotated blocks lie above a detachment surface.Listric fans are observed within the rotated blocks.The geometry and internal texture of the type-Ⅱ are same with the type-Ⅱ.But they have different distribution range,slide direction,and strike of the slump escarpment.The linear basal scars of the type-Ⅱ represent the stronger erosion capability.The rough topography of the MTDs is caused by the inner deformation which is indicated by thrust faults.

Analyses of a large amount of 2D and 3D seismic data permit a systematical investigation of the along-strike variations in the morphology and sedimentation of the northern margin of the South China Sea (SCS). Our results show that the studied margin can be divided into five sectors along depositional strike, which overlay the Yinggehai and western Qiongdongnan Basin (Sector 1), eastern Qiongdongnan Basin (Sector 2) and Pearl River Mouth Basin (Sector 3, 4 and 5). Each displays distinct characteristics in their relief, slope morphology, canyon development, and sequence stacking pattern as well as the resulting deposits. In general, the along-strike variability of the morphology and sedimentation of the northern SCS margin can be attributed to the regional and local structural style, sediment supply and marine extrinsic processes.

The Plio-Quaternary unidirectionally migrating channels (UMCs) and contourites in the northern slope of the South China Sea were investigated in this paper using seismic data. The UMCs include thalweg deposits (TDs) and laterally migrating deposits (LMDs), which result from the interaction between gravity flow and contour current. The LMDs migrating directions are northeast (NE) and west-southwest (WSW) and also display weak seismic reflection and obvious multi-stages. By contrast, the TDs show high seismic reflection and lateral aggradation.

The Quaternary continental slope of the Baiyun Sag in northern South China Sea is characterized by a complex topography and abundant gravity flow sedimentation. High-resolution 3-D seismic data in this area allow for a detailed study of the seismic geomorphology and deep-water gravity flow depositional process. The Quaternary continental slope in the northern South China Sea is an above-graded slope. An intraslope basin lies within the above-grade continental slope. Slump, erosion, and deposition processes tend to develop a gentle topography and consequently a graded slope. The upper continental slope, which is above the slope equilibrium profile, is dominated by erosion and slumping. Slides, slumps and erosional channels are developed within this continental slope. The intraslope basin is located below the slope equilibrium profile and is potential accommodation space where sediments transported by gravity flows could be deposited, forming lobe aprons. Under the influence of gravity flow supply, gravity flow duration, continental slope topography, equilibrium profile, and accommodation, a slump-erosional channel-lobe depositional system is developed in the Quaternary continental slope in the Baiyun Sag. The deep-water gravity flow depositional process and the distribution of gravity flow sediments are greatly influenced by the continental slope topography, while the continental slope topography at the same time is reshaped by deep-water gravity flow depositional process and its products. The study of the interplay between the continental slope and gravity flow is helpful in predicting the distribution of the deep-water gravity flow sediments and the variation of sediment quality.

By interpretation of the 3D seismic data,observation and analysis of the drilling,well logging and core data from Baiyun sag in Pearl River Mouth Basin,the characteristics,sedimentary model and controlling factors of deep-water fans in 21Ma were researched.The results indicate that several kinds of gravity-flow structures are discovered in the core such as normally graded bedding,Bouma sequence and slump deformation bedding,all of which indicate a kind of gravity flow deposits in bathyal environment.In seismic profile,typical sedimentary architectures of the fans are recognized,which include channels,channel-levee complex and lobes.In 21Ma,the Baiyun sag developed the kind of shelf-margin delta-valley-submarine fan sedimentary model is mainly controlled by tectonic framework,relative sea-level changes,slope break belt evolution,formation of faults as well as the material supply of the Pearl River delta.

Based on a large amount of drill,core and seismic data from the eastern Baiyun Sag,by the analysis of seismic attributes,seismic facices as well as drilling sedimentary facies,it is proved that in Baiyun Sag there is not only the north provenance but also the eastern depositional system which is derived from the Dongsha Uplift in early Miocene,and this discovery will lead to the expansion of the exploration scope for the deepwater clastic deposits of Baiyun Sag. The Eastern Depositional System is mainly developed in SQ23.8,with the bottom boundary SB23.8.Previous studies reported that the ＂Baiyun Movement＂ occurred in 23.8 Ma B.P.results in tremendous changes of Baiyun sag,causing the thermal subsidence of the sag,making the shelf neritic environment transform into slope deepwater environment,and SB23.8 is the interface of the shelf break belt migrating from the south of Baiyun sag to north.In 23.8 Ma B.P.the relative sea level fell to the lowest,which made the Panyu Low Uplift in the north and the Dongsha Uplift in the east be in a state of exposure.The formers＇ study has confirmed that the Panyu Low Uplift provides debris for the deep water of Baiyun sag,and then,whether the Dongsha Uplift which was also exposed in SQ23.8 can serve as the provenance for Baiyun sag is the breakthrough point of this paper. The erosion area of Dongsha uplift during early Miocene is about 20 000 km2,which is close to Baiyun sag,and considering such a great erosion area the uplift should provide materials for Baiyun sag.Besides,on the image of 3D seismic RMS amplitude slices present an abnormally high amplitude in the east of Baiyun sag,and the graph of sandstone/strata contour of SQ23.8 also presents high values in the east.In addition,on seismic,a wedge-shaped progradational reflection configuration with the direction from Dongsha Uplift to Baiyun sag in SQ23.8 is developed.Therefore,according to the above analysis,it is concluded that the Dongsha Uplift is one of the provenances of Baiyun sag during the period of SQ23.8 deposition. On seismic,the deposits characterized by wedge-shaped progradational reflection configuration are interpreted as the deposits of deltas for their developed location,and the deposits in front characterized by high-amplitude,good continuity,progradational reflection on the trend seismic profile,a hummocky bidirectional progradation configuration on the cross profile,are interpreted as the submarine fan.Through observation of the core it is found that the carbonate content is fairly high in the core of SQ23.8,indicating that the sediments come from Dongsha Uplift,because during the period of SQ23.8 deposition,only Dongsha Uplift developed carbonate,also,again confriming the viewpoint that Dongsha Uplift is the provenance of Baiyun sag.Besides,a variety of gravity flow sedimentary structures are found in the core,such as normal graded bedding,Bouma sequence and slump-deformation bedding and so on,indicating a kind of gravity flow deposits in bathyal environment.The sediments of the core are identified as submarine fan deposits. Based on the sequence division result by integrating well and seismic data,SQ23.8 can be divided into three system tracts： LST,TST and HST.Combining the sequence stratigraphic analysis and the study of the sedimentary facies,the sedimentary and evolution model of the eastern sedimentary system has been established.In this depositional system,the lowstand system tracts（LST） are represented by submarine fans,and the trangressive system tracts（TST） are dominated by the mixed deposits of clastic and carbonate rock,while in the highstand system tracts（HST） the deltaic deposits are well developed.The deposits and sedimentary model are mainly controlled by the change of relative sea level and material supply.

Deepwater gravity flow deposits are one of the main depositional types on the slope of the northern South China Sea.Based on high-resolution 3D seismic data,drilling data and logging data,and integrated with geophysical date interpretation and geological analysis,we identified,interpreted and forecasted a 21 Ma deepwater depositional system developed in Baiyun sag,northern South China Sea.The results showed that three types of deepwater gravity-flow deposits were identified,i.e.mass-transport,channel-levee complex and lobate deposits.The mass-transport deposit(MTD) has a chaotic seismic reflection with basal erosion scratches.The channel-levee complex deposit is characteristic of a "gull-wing" seismic reflection,of which the former(channel) shows a low-amplitude U-or V-shaped seismic reflection and acts as a main pathway for deepwater gravity-flow deposits,while the latter(levee) formed by the overflow of gravity flow is of a high-amplitude wedge-shaped reflection.A high-amplitude parallel to sub-parallel seismic reflection is interpreted to represent the lobate deposit,which is located in front of the channel and comes in a lobe-like shape on plane.Gradual evolution from the mass-transport deposit to the channel,channel-levee complex or labate deposit is often accompanied with a reciprocal transformation of various flow patterns of deepwater gravity flow.The research integrated geophysics,sedimentology and marine geology with the observation of the 21 Ma deepwater gravity-flow depositional system in Baiyun sag,northern South China Sea to establish a deepwater sedimentary model,which is of the theoretic significance in studying various depositional processes of deepwater gravity flow.

Based on a large amount of seismic, drilling and core data, the characteristics of the early-middle Miocene submarine fans in the Baiyun Sag, northern South China Sea are investigated. By analyzing the sedimentary processes of submarine fans in SQ21 (SQ21 refers to the 3rd-order sequence with its bottom boundary 21 Ma), a sedimentary model of the sand-rich fans is established and the main factors controlling fan deposition are detailed. The results indicate that from early to middle Miocene the Pearl River Mouth Basin developed seven 3rd-order sequences in all, with each lowstand systems tract (LST) of the sequence corresponding to submarine fans. However, only the fans in SQ13.8 and SQ21 are sand-rich fans, the others being mud-rich fans. The cores reveal that the submarine fans in the Pearl River Mouth Basin developed five lithofacies: (1) mud clast-bearing sandstone, interpreted as channel deposits; (2) typical turbidite sandstones, also interpreted as channel deposits; (3) thin-bedded sandstone and mudstone, interpreted as channel-levee complex deposits; (4) massive sandstones, interpreted as lobe deposits; (5) massive mudstone, interpreted as hemipelagic mud. The sand-rich submarine fans in the Pearl River Mouth Basin mainly developed in LST, and in LST reverse faults were active, which led to the formation of accommodation on the shelf. Different from the theory of classic sequence stratigraphy, the accommodation on the shelf captures terrigenous debris transported by the Pearl River, and the uplift at the edge of shelf serves as a “Linear Source” for the deep water area instead of the Pearl River. Therefore, the fans mainly derived from the eroded debris from the uplift. Factors controlling fan deposition include the basin’s tectonic framework, the evolution of the slope break, relative sea-level changes as well as the evolution of the fault system, and the fans are formed under the combination of the above factors.