珠江口盆地白云凹陷北坡上新世—第四纪陆架边缘沉积体系特征

运用珠江口盆地新采集的高分辨率多道地震资料,结合前人在本区的钻井、岩心、测井曲线及地震的综合资料,建立了白云凹陷北坡上新世—第四纪的等时地层格架,在此基础上分析了陆架边缘典型沉积体系,并初步探讨了其控制因素。研究表明,上新世—第四纪地层内识别出T0(海底)、T1(1.8Ma)和T2(5.3Ma)3个三级层序界面,划分出A、B2个三级层序。研究区地震相主要有席状平行—亚平行地震相、帚状前积地震相、透镜状前积地震相、谷状充填地震相,不同的地震相及其组合代表特定的沉积体系。地震相特征分析表明,研究区上新世—第四纪发育大规模的陆架边缘三角洲和深切水道群,深切水道是沉积物向下陆坡—深海盆输送的通道。白云凹陷北坡上新世—第四纪沉积体系的发育受陆架边缘的地形、海平面升降、沉积物供给等因素的控制。     

白云凹陷北坡珠江组下段陆架边缘三角洲特征及其主控因素

为了明确白云凹陷北坡珠江组下段陆架边缘三角洲的形成演化阶段及其主要控制因素,采用地震沉积学、层序地层学的相关理论和方法,结合钻测井数据、地震反射结构特征和均方根振幅属性等资料,在前人研究的基础上对该陆架边缘三角洲的识别特征、演化模式和控制因素进行了重新认识和探讨分析。结果表明:陆架边缘三角洲在顺物源方向具有高角度斜交型前积反射,缺乏顶积层的海岸平原相,其前端发育盆底扇沉积;垂向沉积序列以多期反旋回的前三角洲、席状砂、河口沙坝和水下分流河道的叠置为特征,发育陆坡区常见的生物扰动、泥质条带变形和滑塌、滑动现象;珠江组下段陆架边缘三角洲形成于强制海退体系域时期,并伴随着盆底扇的发育,而低位体系域时期主要发育斜坡扇和低位楔状体;构造活动促使白云凹陷北坡在珠江组下段时期形成稳定分布的陆架坡折带,珠江组下段时期古珠江携带的充沛物源和该时期强烈的海平面下降使碎屑沉积物能够进积至陆架边缘,甚至陆坡地区形成陆架边缘三角洲沉积。     

南海南部表层沉积物粒度分布特征及其影响因素

对取自南海南部的153个表层沉积物样品,进行了粒度、粒度参数计算和Q型聚类分析,探讨了表层沉积物的粒度分布特征、沉积类型及影响因素。结果表明,研究区沉积物主要粒级组分为黏土和粉砂,底质类型主要为泥,还有粉砂质砂、砂质粉砂和粉砂,平行于等深线基本呈带状分布;结合Q型聚类分析结果,研究区沉积物可分为外陆架及陆架坡折区粗粒沉积物(砂和粉砂)和陆坡区细粒沉积物(泥)两类,500m等深线是两类沉积物的分界线;对比粒度分析结果,判定两类沉积物属于不同成因类型,外陆架及陆架坡折区是现代沉积和残留沉积的混合沉积,陆坡区是现代沉积;影响南海南部表层沉积物粒度分布的主要因素是物源、水动力条件、水深与地形及洋流。     

琼东南盆地陵水研究区海底地质灾害类型、分布和成因机制

琼东南盆地陵水研究区位于西沙海槽北部的陆架边缘和陆坡区,地质灾害广泛分布。利用三维反射地震数据,在琼东南盆地陵水研究区识别了海底滑坡、麻坑、丘状体、流体管道、天然气水合物(BSRs)、活动断层等海底地质灾害体,并分析了各类地质灾害体的地震反射特征和分布规律。结合区域构造和沉积演化过程,分析了地质灾害体的成因机制。研究表明,灾害体的分布面积总计超过2000km~2,各类灾害体相互叠置。构造断层活动、充足物源供给和海平面变化是导致该地区海底地质灾害广泛分布的重要原因。第四纪晚期高沉积速率导致陆架边缘和陆坡区沉积了较厚地层,有机质丰富,为水合物成藏提供了潜在气源。陆坡区的滑坡主要分布在加积层序较发育的陡坡区。在陆架边缘和滑坡不太发育的陆坡缓坡区,超压流体释放形成流体管道、丘状体和麻坑。高沉积速率、埋藏的古滑坡和区域的构造不稳定性是诱发超压流体释放的重要因素。     

珠江口盆地白云凹陷北坡第四纪层序地层和沉积体系演化及其控制因素

结合地震、测井及微体古生物等资料,研究了珠江口盆地白云凹陷北斜坡区第四纪的沉积体系、层序地层及控制因素。研究区第四系发育以巨厚的高角度前积层为特征的大陆斜坡沉积体系,可将其划分为4个三级层序。层序的构成包括低位、海进及高位域,沉积体系包括下切谷、北东向单向迁移斜坡水道、陆架边缘三角洲、斜坡扇及高角度陆架边缘前积体系等。随着海平面下降及物源供应,三角洲体系推进至陆架坡折形成巨厚的陆架边缘三角洲和斜坡扇体系。更新世大陆斜坡沉积体系不断从番禺隆起向白云凹陷推进,陆架坡折带向海迁移;陆架区下切谷向上不断发育,在SB3和SB2界面上最密集;而冰后期至今的全新世高位三角洲被局限在内陆架地区。大陆斜坡沉积体系的演化主要受海平面变化、构造作用、气候变化以及沉积供给变化的共同控制。     

南海北部陆架第四系边缘三角洲地震反射特征

陆架边缘三角洲因其具有面积广、厚度大、储层发育等特点,在世界上已成为重要的油气勘探目标。运用高分辨率单道地震资料,对南海北部珠江口盆地番禺低隆起陆架边缘三角洲第四系地震相和沉积特征进行了详细分析,认为第四系陆架边缘三角洲主要为三角洲平原、三角洲前缘和前三角洲沉积。三角洲平原主要以水道—天然堤相组合为局部特征,频繁发生水道下切与改道。三角洲前缘主要以大型的前积地震相为主,随着海平面升降及物源供给变化,前缘带不断进积,由陆架向陆坡方向生长,三角洲前缘砂体前积受控于坡折带。前三角洲特征不明显。综合分析表明,研究区第四纪以来相对海平面经历了多次缓慢下降再迅速上升的旋回,形成了慢速海退和快速海侵交替进行的陆架边缘三角洲沉积。     

南海北部双峰南陆坡区的构造层序及沉积充填过程

利用高分辨率二维地震反射剖面及钻井资料,对南海北部双峰南陆坡区的构造层序及沉积充填特征进行了研究。根据地震不整合界面、构造发育特征及地层组合情况,将研究区地层从下至上划分为下、中、上三个构造层序。研究分析表明,构造活动、海盆扩张、相对海平面变化、火山活动及物源供给等因素在不同阶段因时而异地共同控制着各构造层序的沉积充填过程及演化。下构造层(Tg—T6)形成于一系列的半地堑结构断陷盆地,在湖泊相的沉积环境下,沉积体系受同沉积断裂控制明显,发育了冲积扇—扇三角洲—半深湖相沉积;中构造层(T6—T4)形成于西北次海盆扩张沉降构造背景,在陆坡缓慢沉降和火山喷发的双重影响下,造就了陆坡区特殊的几何形态结构,影响着沉积体系的发育,陆坡区中上部为浅海陆架边缘三角洲沉积,在陆坡区则以斜坡扇等相关沉积为主;上构造层(T4—T0)形成于相对海平面总体上升、西北次海盆由缓慢进入相对快速的沉降阶段,沉积作用受控于物质供应充分程度和深水作用,发育了以深水水道和滑塌体为沉积特征的深水沉积体系。     

南海白云凹陷东南部两种不同类型块体搬运沉积体系的地震响应及成因分析

文章利用三维地震数据揭示了南海白云凹陷东南部两种不同类型的块体搬运沉积体系的内部反射特征、外部形态及运动指示标志, 并且探讨了其成因机制。结果表明, 自晚中新世以来研究区共发育4种地震相: 弱振幅水平状连续地震相、强振幅波状连续地震相、弱振幅半透明杂乱反射地震相和中-强振幅丘状连续反射地震相。通过地震相分析可知, 研究区自晚中新世以来共发育两种不同类型的块体搬运沉积体系: 1) 多期块体搬运沉积复合体, 主要由弱振幅半透明杂乱反射地震相组成, 边界模糊; 2) 单期块体搬运沉积体, 主要由弱振幅半透明杂乱反射地震相和中-强振幅丘状连续反射地震相组成, 边界清晰明显。另外, 研究结果发现高沉积速率和地震活动使得研究区的块体搬运沉积体系表现出内部运动指示特征发育程度低的特征, 而东沙构造活动导致该块体搬运沉积体系具有频发性。     

南海西北部晚第四纪典型地震相—沉积相特征

南海西北部地形变化大,水深由近岸几十米变化至深海盆区的3 500m,跨越了陆架、陆坡、深海盆、岛礁等地貌单元。南海西北部也是深水油气的重要勘探地区。利用高分辨率单道地震资料,采用地震相分析方法,对研究区晚第四纪典型地震相—沉积相分布特征开展深入分析。研究区内的主要地震相包括：①席状、亚平行、强振幅、低连续、中频地震相;②披盖状、波状、中振幅、中—低连续、中低频地震相;③披盖状、平行—亚平行、中—弱振幅、中连续、中—低频地震相;④披盖状、平行、强振幅、高连续、中—高频地震相;⑤席状、平行、中—弱振幅、高连续、中—低频地震相;⑥披盖状、波状、弱振幅、低连续、低频地震相;⑦前积相;⑧下切充填地震相;⑨杂乱地震相;⑩条带状、波状、中—弱振幅、中—低连续、低频地震相;瑏瑡披盖状、平行、强振幅、高频、高连续地震相共11种。对地震相—沉积相及其分布特征的分析结果认为,区内晚第四纪主要发育有三角洲相、河道相、滨浅海相、浅海相、半深海相、深海相、滑塌相、斜坡相、浊流相、生物礁相等沉积相,其分布主要受海底地形地貌、构造运动等多种因素所控制。     

北康-曾母盆地中中新世以来层序地层样式特征探讨

开展地震资料解释,分析上超、下超、顶超等地震反射终止关系、不整合面以及沉积趋势,识别出北康-曾母盆地中中新世以来14个三级层序界面。在层序界面内部,通过层序地层内幕结构刻画和原形剖面恢复,并结合地层堆砌方式,在北康-曾母盆地中中新世以来的层序地层内,划分了海进、高位正常海退、强制海退和低位正常海退4种成因单元。通过进一步研究该4种成因单元内地层结构和相分布关系,提出北康-曾母盆地中中新世以来的3种层序地层样式,即陆架边缘富砂型三角洲进积楔、退积型生物礁和陆架边缘富砂-富泥型退积楔,其中,沉积物源供应量充足且可容空间减小时,发育富砂的三角洲进积楔,陆架边缘-斜坡-盆地区域发育含砂深水扇;而可容空间增量远大于沉积物供应量时,发育退积型生物礁和富砂-富泥退积楔,斜坡-盆地区域含砂深水扇欠发育。     

莘县凹陷下第三系层序地层学分析

根据地震反射特征、古生物组合、湖水面变化及构造变动，应用层序地层学原理，对下第三系进行层序划分，分析了地震相类型，总结出主要的沉积体系特征及其展布规律     

冲绳海槽西部陆坡地震相模式与沉积体系

对冲绳海槽西部陆坡上两个航次(95航次和99航次)共计2000多公里的单道地震资料进行分析和解译，对斜坡沉积环境下沉积体系发育、分布特征进行了研究。结果表明：a)冲绳海槽西部斜坡环境下，上新世以来的沉积层均不同程度的变形和错动；b)存在两种斜坡相地震反射模式——退覆模式和叠覆模式，这两种模式都反映了冲绳海槽西部陆坡得到充足的沉积物供给；c)斜坡环境下主要发育陆架边缘三角洲、重力流沉积和水道充填等沉积体系；d)沉积层发育特征表明，冲绳海槽西部陆坡具有北段坡度缓、沉积物供应丰富、构造相对不活跃，中段坡度陡、沉积物供应充足、构造活动强烈，南段坡度陡、沉积供应相对较少、构造和火山活动十分强烈3种主要沉积环境。西部陆坡的沉积特征也揭示了东海陆架向陆坡提供了大量碎屑沉积物质。     

Growth patterns of a proximal terrigenous margin offshore the Guadalfeo River, northern Alboran Sea (SW Mediterranean Sea): glacio-eustatic control and disturbing tectonic factors

The shelf-upper slope stratigraphy offshore and around the Guadalfeo River on the northern continental margin of the Alboran Sea, Western Mediterranean Basin, has been defined through the interpretation of a grid of Sparker seismic profiles. We tried to identify evolutionary trends in shelf growth, as well as to determine the regional/local factors that may modify the influence of glacio-eustatic fluctuations. Four major depositional sequences are identified in the sedimentary record by a detailed seismic interpretation, which defines three significant intervals of shelf-upper slope progradation, dominated by deposition of shelf-margin wedges, which resulted in uniform patterns of shelf-margin growth in response to significant sea-level falls. In contrast, the record of transgressive intervals is more variable, mainly as the result of distinct patterns of regressive-to-transgressive transitions. Major progradational wedges are internally composed of seaward-prograding, landward-thinning wedges, interpreted to represent shelf-margin deltaic deposits. In contrast, the last aggradational interval is composed of shelf-prograding wedges that show distinct characteristics, in terms of seismic facies, morphology and distribution when compared with previous shelf-margin wedges. These shelf wedges are thought to represent the particular case of Regressive Systems or Shelf Margin Systems Tracts, and their development seems to be controlled by a drastic change in main depocenter location, which moved from the upper slope to the shelf during the Pleistocene. The stacking pattern of seismic units, the shallowness of the acoustic basement and the migration of the shelf break are used to infer spatial and temporal changes in tectonic subsidence-uplift rates, which interact with low-order glacio-eustatic changes. For much of the Pliocene-Quaternary, uplifted sectors alternated laterally with sectors experiencing more subsidence. Subsequently, a significant change from lateral outgrowth to vertical accretion is recognised. This stratigraphic change could be related to the combined influence of increased subsidence rates on the shelf and the onset of higher-frequency glacio-eustatic cyclicity after the Mid Pleistocene Revolution that occurred around 1 Ma.     

辽东湾南部下第三系地震地层学研究

本文依据地震地层学原理,结合层速度和砂岩百分比的研究,描述了辽东湾南部下第三系地震相和沉积相类型及特征,确定出近岸水下扇沉积体系、三角洲—滑塌浊积扇沉积体系、滨浅湖—滩坝沉积体系和深湖—深水浊积扇沉积体系,指出这些沉积体系的平面分布具有不对称性,垂向演化具有继承性和新生性的特点。最后预测了有利勘探地区。     

Sedimentary evolution of the northwestern Alboran Sea during the Quaternary

Five depositional bodies occur within the Quaternary deposits of the northwestern Alboran Sea: Guadalmedina-Guadalhorce prodelta, shelf-edge wedges, progradational packages, Guadiaro channel-levee complex, and debris flow deposits. The sedimentary structure reflects two styles of margin growth characterized: 1) by an essentially sediment-starved outer, shelf and upper slope and by divergent slope seismic facies; 2) by a prograding sediment outer shelf, and parallel slope seismic facies. Eustatic oscillations, sediment supply, and tectonic tilting have controlled the type of growth pattern, and the occurrence of the depositional bodies. Debris flows were also controlled locally by diapirism.     

Post-Calabrian sequence stratigraphy of the northwestern Alboran Sea (southwestern Mediterranean)

The post-Calabrian sedimentary column of the northwestern Alboran Sea comprises three depositional sequences. The two older depositional sequences are defined by lowstand systems tracts (shelf-margin deltas, slope, base-of-slope, and basin deposits, and the Guadiaro channel-levee complex). In contrast, the most recent depositional sequence also includes transgressive (relict shelf facies) and high-stand (the Guadalmedina-Guadalhorce prodelta and hemipelagic facies) systems tracts. The stratigraphic architecture of these depositional sequences is controlled by the synchronism between high frequency sea-level changes, variations in sediment supply, and sedimentary processes. The configuration of the depositional sequences is variable and their distribution is complex, as a result of the relative importance played by sea-level changes and tectonism through the area.

The sequence boundaries are represented by polygenetic surfaces in the proximal margin, and by monogenetic surfaces in the distal margin and basin. Each polygenetic surface results from the interaction between the sequence boundary with the lowstand erosional truncation surface and the transgressive surface, both developed during the previous sea-level cycle. The monogenetic surfaces correspond to unconformities and their correlative conformities, formed during sea-level lowstands. This pattern of depositional sequences developed in the margin and basin of the northwestern Alboran Sea shows differences with the Exxon Sequence Stratigraphy Model as traditionally applied: sea-level change control is essentially recognized through lowstand systems tracts, and sequence boundary coincides with lowstand erosional truncation surface and transgressive surface, both developed during the previous sea-level cycle.     

Sequence architecture and depositional evolution of the Late Miocene to quaternary northeastern shelf margin of the South China Sea

Based on an integrated analysis of seismic, well logging and paleontological data, the sequence architecture and depositional evolution of the northeastern shelf margin of the South China Sea since Late Miocene are documented. The slope deposits of the Late Miocene to Quaternary can be divided into two composite sequences (CS1 and CS2) bounded by regional unconformities with time spans of 3–7 Ma, and eight sequences defined by local unconformities or discontinuities with time spans of 0.8–2.3 Ma. Unconformities within CS1 feature shelf-edge channel erosion, while in CS2 they form truncations at the top of the shelf margin as prograding complexes and onlap contacts against the slope.Depositional systems recognized in the slope section include unidirectionally migrating slope channels, slope fans or aprons, shelf-edge deltas and large-scale slope clinoforms. CS1 (Late Miocene to Pliocene) is characterized by development of a series of shelf-margin channels and associated slope fan aprons. The shelf-margin channels, oriented mostly NW-SE, migrate unidirectionally northeastwards and intensively eroded almost the entire shelf-slope zone. Two types of channels have been identified: (1) broad, shallow and unconfined or partly confined outer-shelf to shelf-break channels; and (2) deeply incised and confined unidirectionally migrating slope channels. They might be formed by gravity flow erosion as bypassing channels and filled mostly with along-slope current deposits. Along the base of the shelf slope, a series of small-scale slope fans or fan aprons are identified, including three depositional paleo-geomorphological elements: (1) broad or U-shaped, unconfined erosional-depositional channels; (2) frontal splays-lobes; and (3) non-channelized sheets. CS2 (Quaternary) consists mainly of a set of high-angle clinoforms, shelf-margin deltas and lower slope unidirectionally migrating channels.The relative sea level changes reflected in the sequence architecture of the study area are basically consistent with Haq's global sea level curve, but the development of regional unconformities were apparently enhanced by tectonic uplift. The development of high-angle (thick) clinoforms in the Quaternary may be attributed to a high sediment supply rate and rapid tectonic subsidence. The formation of the unidirectionally migrating channels appears to have resulted from the combined effects of the northeastward South China Sea Warm Current (SCSWC) and downslope gravity flow. The formation of the slope channels in the outer-shelf to shelf-break zone may be predominately controlled by bottom current, whereas those developed along the middle to lower slope zone may be dominated by gravity flow.     

珠江口盆地白云凹陷早中新世深水层序模式

近年来深水勘探已成为寻找油气的重要领域,白云凹陷在早中新世经历了复杂的构造沉积环境,解剖深水层序模式有利于揭示深水沉积演化规律。通过井震结合及属性分析对白云凹陷早中新世层序地层进行研究,识别出3个层序界面:ZJSB1(23.8 Ma),ZJSB2(22Ma),ZJSB3(21Ma)。其中ZJSB1、ZJSB3为重大不整合面,ZJSB2为水道下切侵蚀面。与之对应的界面发育3套层序:ZJSQ1,ZJSQ2,ZJSQ3。由于白云凹陷构造运动及古地貌的差异性,总结了2套深水层序模式:水道—深海披覆泥层序模式与块状搬运复合体—砂质碎屑流深海扇—水道—深海泥层序模式,在不同的演化阶段,前者主要受海平面的变化控制,而后者是受构造和海平面双重影响的。而同一地质时期古地貌又控制了沉积发育,高地势区发育下切水道,而低洼区发育深海披覆泥岩。因此,深水层序模式下研究深海沉积单元,对指导深水沉积和油气勘探具有极其重要的意义。     

Stratigraphic evolution of Eocene clinoforms from northern Santos Basin,offshore Brazil: Evaluating controlling factors on shelf-margin growth and deep-water sedimentation

In order to assess the controlling factors on the evolution of a shelf margin and the timing of sediment transfer to deep waters, a seismic stratigraphic investigation was carried out in the Eocene interval of northern Santos Basin, offshore Brazil. The studied succession configures a complex of prograding slope clinoforms formed in a passive margin and encompasses five seismic facies and their respective depositional settings: shelf-margin deltas/shorefaces, oblique slope clinoforms, sigmoidal slope clinoforms, continental to shelfal deposits and mass-transport deposits. These are stratigraphically arranged as seven depositional sequences recording a total shelf-edge progradation of about 35 km and a progradation rate of 1,75 km/My. Two main types of sequences can be recognized, the first one (type A) being dominated by oblique slope clinoforms and shelf-margin deltas/shorefaces in which shelf-edge trajectories were essentially flat to descending and extensive sandy turbidites were deposited on the foreset to bottomset zones. Sequences of this type are dominated by forced-regressive units deposited during extensive periods of relative sea-level fall. Type B comprises an upper part represented by aggradational shelfal deposits and a lower part composed of mass-transport deposits and high-relief sigmoidal clinoforms with descending shelf-edge trajectory. Steep slump scars deeply cut the shelfal strata and constitutes the boundary between the two intervals observed in type B sequences. Sandy turbidites occur at the same frequency in both forced- and normal-regressive units but are more voluminous within forced-regressive clinoforms associated with shelf-margin deltas/shorefaces. Major slope failures and mass-transport deposits, by the other hand, occurred exclusively in type B sequences during the onset of sea-level fall and their volume are directly related to the thickness of the shelfal sediments formed during the pre-failure normal regressions.