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1.
琼东南盆地第四纪块体搬运体系的地震特征   总被引：4，自引：0，他引：4  
第四纪以来,琼东南盆地的陆坡区域广泛发育深水块体搬运体系。深水块体搬运体系是广泛发生在外陆架/上陆坡的一种沉积物搬运机制,包括滑动、滑塌和碎屑流等重力流作用过程。利用深水3D地震资料,提取振幅和相干数据,通过地震剖面、构造图和时间切片分析,揭示块体搬运体系具有丘状外形、波状反射结构、弱振幅和连续性差的地震特征,内部整体比较杂乱,主体发育褶皱,趾部发育逆冲断层,具有塑性流体特征。结合南海构造背景分析,认为研究区第四纪沉积速率高并位于地震多发带,构成了块体搬运体系的形成条件和触发机制。  相似文献   

2.
利用高分辨率三维地震资料、测井和钻井数据,对东非鲁伍马盆地深水沉积特征进行了系统刻画。根据深水沉积体的地震相特征,识别出峡谷、水道、漫溢沉积、朵体、块体搬运沉积(MTDs)和凝缩段等深水沉积单元,建立了地震识别图版。分析总结了水道和朵体的岩性特征、电性特征和储层物性特征,砂岩具有低伽马(GR)和高电阻(RT)特征,厚层砂岩GR曲线呈“箱型”,有泥岩夹层的砂岩段呈叠加的“钟型”特点;储层压实程度弱,发育原生粒间孔隙,具有中—高孔、中—高渗的特征。结合成藏条件研究,认为由水道和朵体浊积砂岩储层、凝缩段和漫溢沉积泥岩盖层、天然堤和MTDs为侧向遮挡等要素构成的油气储、盖配置关系,是研究区油气成藏的一个关键因素,对深水油气勘探具有一定的指导意义。  相似文献   

3.
Triple mass-transport deposits(MTDs) with areas of 625, 494 and 902 km2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic reflection data and multi-beam bathymetric data, the Quaternary MTDs are characterized by typical geometric shapes and internal structures. Results of slope analysis showed that they are developed in a steep slope ranging from 5° to 35°. The head wall scarps of the MTDs arrived to 50 km in length(from headwall to termination). Their inner structures include well developed basal shear surface, growth faults, stepping lateral scarps, erosion grooves, and frontal thrust deformation. From seismic images, the central deepwater channel system of the Xisha Trough has been filled by interbedded channel-levee deposits and thick MTDs. Therefore, we inferred that the MTDs in the deepwater channel system could be dominated by far-travelled slope failure deposits even though there are local collapses of the trough walls. And then, we drew the two-dimensional process model and threedimensional structure model diagram of the MTDs. Combined with the regional geological setting and previous studies, we discussed the trigger mechanisms of the triple MTDs.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
Subsurface mass-transport deposits (MTDs) commonly have a chaotic seismic-reflection response. Synthetic seismic-reflection profiles, created from a precise lithological model, are used to interpret reflection character and depositional geometries at multiple frequencies. The lithological model was created from an outcrop of deep-water lithofacies where sandstone deposition was influenced by mass-transport deposit topography. The influence of MTD topography on sandstone distribution should be considered in reservoir characterization and modeling when MTDs underlie the reservoir, especially if the reservoir is thin relative to the scale of the topography. MTD topography up to several tens of meters in both the horizontal and vertical dimensions (relative to local elevation) compartmentalizes significant quantities of sandstone and is not resolved at lower seismic-reflection frequencies. The resolvability of thick (up to 70 m) sandstone packages is hindered when they are encased in MTDs of at least equivalent thickness. Lateral and vertical changes in seismic-reflection character (e.g., amplitude, polarity, geometry) of sandstone packages in the synthetic profiles are due to lithology changes, tuning effects, resolution limits, and depositional geometries, which are corroborated by the lithological model. Similar reflection-character changes are observed in an actual seismic-reflection profile, of comparable scale to the synthetic profiles, from the Gulf of Mexico, which demonstrates similar lithofacies distributions. Synthetic profiles, when constrained by a precise lithological model, are particularly useful analogues for interpretation of lithofacies relationships, and depositional geometries, in complicated depositional environments, such as deep-water slope deposits.  相似文献   

7.
The Neogene and Quaternary sediments of the Faeroe-Shetland Channel and West Shetland shelf and slope rest upon a major regional unconformity, the Latest Oligocene Unconformity (LOU), and have been deposited through the interaction of downslope and parallel-to-slope depositional processes. The upper to middle continental slope is dominated by mass-transport deposits (debris flows), which progressively diminish downslope, and were largely generated and deposited during glacial cycles when ice sheets supplied large quantities of terrigeneous sediment to the upper slope and icebergs scoured sea-floor sediments on the outer shelf and uppermost slope. Large-scale sediment failures have also occurred on the upper slope and resulted in deposition of thick, regionally extensive mass-transport deposits on portions of the lower slope and channel floor. In contrast, large fields of migrating sediment waves and drift deposits dominate most of the middle to lower slope below 700 m water depth and represent deposition by strong contour currents of the various water masses moving northeastward and southwestward through the channel. These migrating sediment waves indicate strong northeastward current flow at water depths shallower than 700 m and strong southwestward current flow at water depths from 700 to >1,400 m. These flow directions are consistent with present-day water-mass flow through the Faeroe-Shetland Channel. The Faeroe-Shetland Channel floor is underlain by thin conformable sediments that appear to be predominantly glacial marine and hemipelagic with less common turbidites and debris flows. No evidence is observed in seismic or core data that indicates strong contour-current erosion or redistribution of sediments along the channel floor.  相似文献   

8.
西沙海域碳酸盐台地周缘水道沉积体系   总被引：3，自引：1，他引：2  
高分辨率地震资料显示,南海北部西沙海域碳酸盐台地周缘广泛发育水道沉积体系。礁缘水道底界面表现出强反射特征,内部充填弱-强、连续性好的地震相,可见底部杂乱反射特征;斜坡水道在地震剖面上表现为横向上连续发育的"V"型特征,且下切深度较浅。西沙隆起与广乐隆起之间的南北向低洼地带发育大型深水水道,并且受古地貌高点影响,水道分为南北两个分支。北分支水道可分为5期,且水道迁移现象明显;南分支水道可分为4期,水道以充填强振幅、连续性好的浊流沉积体和弱振幅、杂乱的块体搬运体系(Mass Transport Deposits,MTDs)为特征,每期水道均表现出侵蚀-充填-废弃的旋回性。分析认为西沙碳酸盐台地周缘水道沉积物源来自西沙隆起和广乐隆起的碳酸盐台地和生物礁碎屑及由火成作用产生的火成岩碎屑。西沙-广乐碳酸盐台地水道相互贯通,构成台地-斜坡-深水的水道沉积体系,为碳酸盐岩、生物礁及火山碎屑向台地周缘输送提供了良好的通道。  相似文献   

9.
The effect of Cenozoic mass-transport deposits (MTDs) on the morphology of the Late Neogene to Quaternary seafloor is investigated using a 3D seismic volume from offshore Brazil. The studied MTD shows large remnant blocks deforming the seafloor several Ma after a principal instability event marking the base of the investigated strata. Remnant blocks formed during this latter instability event were quickly buried, with differential compaction between individual blocks and adjacent debrites triggering: a) seafloor instability on the flanks of uncompacted (remnant) blocks, b) the incision of submarine channels between seafloor highs formed by buried remnant blocks, c) local uplifted areas on the seafloor that may form potential triggers for future slope instabilities. The interpreted data show that palaeo-seafloor scarps reached more than 120 m in height, with flanking strata to remnant blocks reaching angles of 15°. Angles of this magnitude caused local collapse of seafloor strata and, in some intervals, the confinement of younger MTDs sourced from the upper slope. The statistical data presented here indicate that differential compaction over heterogeneous MTDs continued well after early burial, still deforming the seafloor c. 15 Ma after the main instability event. In addition, significant structural traps are formed by forced folds on remnant blocks that not experienced substantial compaction. Therefore, we conclude that MTDs on passive margins can control seafloor topography after early burial, at the same time contributing to the formation of significant structural traps in post-MTD successions.  相似文献   

10.
The seismic geomorphology and seismic stratigraphy of a deep-marine channel-levee system is described. A moderate to high-sinuosity channel trending southeastward across the northeastern Gulf of Mexico basin floor, and associated depositional elements are well imaged using conventional 3D multi-channel seismic reflection data. Depositional elements described include channels, associated levees, a channel belt, avulsion channels, levee crevasses, frontal splays, sediment waves, and mass transport complexes. Distinguishing morphologic and stratigraphic characteristics of each depositional element are discussed. These deposits are presumed to be associated with repeated deep-marine turbidity flows and other mass transport processes.  相似文献   

11.
In the Nile deep-sea turbidite system (NDSTS), the province fed by the Rosetta branch of the Nile delta is characterised by the recurrent activity of gravity processes. Seven mass-transport deposits (MTDs) were recognised from the upper to the mid slope, downstream from imbricated scars (~ 30 km-long, ~ 200 m high) running along the shelf edge nearby the Rosetta canyon. Extending on surfaces between 200 and 5000 km2, with estimated volumes from 3 to 500 km3, these MTDs represent about 40% (up to 90% locally) of the total Pleistocene–Holocene sedimentary thickness. Three types of MTDs can be distinguished on the basis of their scale. Each has also a distinctive internal configuration and distribution within the Rosetta depositional setting. Age estimates of two MTDs point towards relationships between climate and submarine mass failures through sea-level changes, sediment supply, or a combination of both. Additionally, the presence of gas in the sediment and earthquake shaking may have concurred to trigger large-scale failures on the low slope angles (1°–2°) of the Rosetta area.  相似文献   

12.
This study focuses on the interpretation of stratigraphic sequences through the integration of biostratigraphic, well log and 3D seismic data. Sequence analysis is used to identify significant surfaces, systems tracts, and sequences for the Miocene succession.The depositional systems in this area are dominantly represented by submarine fans deposited on the slope and the basin floor. The main depositional elements that characterize these depositional settings are channel systems (channel-fills, channel-levee systems), frontal splays, frontal splay complexes, lobes of debrites and mass-transport complexes.Five genetic sequences were identified and eleven stratigraphic surfaces interpreted and correlated through the study area. The Oligocene-lower Miocene, lower Miocene and middle Miocene sequences were deposited in bathyal water depths, whereas the upper Miocene sequences (Tortonian and Messinian) were deposited in bathyal and outer neritic water depths. The bulk of the Miocene succession, from the older to younger deposits consists of mass-transport deposits (Oligocene-lower Miocene); mass transport deposits and turbidite deposits (lower Miocene); debrite deposits and turbidite deposits (middle Miocene); and debrite deposits, turbidite deposits and pelagic and hemipelagic sediments (upper Miocene). Cycles of sedimentation are delineated by regionally extensive maximum flooding surfaces within condensed sections of hemipelagic mudstone which represent starved basin floors. These condensed sections are markers for regional correlation, and the maximum flooding surfaces, which they include, are the key surfaces for the construction of the Miocene stratigraphic framework. The falling-stage system tract forms the bulk of the Miocene sequences. Individual sequence geometry and thickness were controlled largely by salt evacuation and large-scale sedimentation patterns. For the upper Miocene, the older sequence (Tortonian) includes sandy deposits, whereas the overlying younger sequence (Messinian) includes sandy facies at the base and muddy facies at the top; this trend reflects the change from slope to shelf settings.  相似文献   

13.
冲绳海槽西部陆坡地震相模式与沉积体系   总被引：8，自引：3，他引：5  
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。  相似文献   

14.
冲绳海槽西部陆坡碎屑沉积物的搬运方式:滑塌和重力流   总被引：9，自引：3，他引：6  
通过对冲绳海槽2000多公里的实测单道地震资料(95和99航次)和沉积物柱状样(92航次)分析,认为滑塌和重力流是冲绳海槽西部陆坡(东海陆坡)碎屑沉积物向海槽搬运的重要方式;分析结果表明,西部陆坡这两种作用是广泛存在的。陆坡沉积物堆积速率、地形坡度和构造活动、地震、海啸等因素造成了陆坡南、北和中段之间的滑塌和重力流发育程度存在差异。海底滑塌和重力流这两种作用可以同时发生,也可以单独发生,但柱状样揭示重力流发生得更频繁。从空间分布上看,海底滑塌主要分布于上陆坡的断裂带附近,平行海槽呈带状延伸;而重力流沉积主要分布于断裂带向下一直到槽底的部位。重力流沉积主要有4种表现形式：1)沉积物重力蠕动;2)浊积平原;3)透镜状浊积体;4)沿斜坡的碎屑流沉积。上述研究表明,滑塌和重力流不仅是陆架向海槽输送物质的重要方式,也对陆坡沉积结构的塑造起了重要的作用。  相似文献   

15.
The ˜4000 m thick and ∼20 Myr deep-water sedimentary fill of the Upper Cretaceous Magallanes Basin was deposited in three major phases, each with contrasting stratigraphic architecture: (1) the oldest deep-water formation (Punta Barrosa Formation) comprises tabular to slightly lenticular packages of interbedded sandy turbidites, slurry-flow deposits, and siltstone that are interpreted to record lobe deposition in an unconfined to weakly ponded setting; (2) the overlying, 2500 m thick and shale-dominated Cerro Toro Formation includes a succession of stacked conglomeratic and sandstone channel-fill deposits with associated finer-grained overbank deposits interpreted to record deposition in a foredeep-axial channel-levee system; (3) the final phase of deep-water sedimentation is characterized by sandstone-rich successions of highly variable thickness and cross-sectional geometry and mudstone-rich mass transport deposits (MTDs) that are interpreted to record deposition at the base-of-slope and lower slope segments of a prograding delta-fed slope system. The deep-water formations are capped by shallow-marine and deltaic deposits of the Dorotea Formation.These architectural changes are associated with the combined influences of tectonically driven changes and intrinsic evolution, including: (1) the variability of amount and type of source material, (2) variations in basin shape through time, and (3) evolution of the fill as a function of prograding systems filling the deep-water accommodation. While the expression of these controls in the stratigraphic architecture of other deep-water successions might differ in detail, the controls themselves are common to all deep-water basins. Information about source material and basin shape is contained within the detrital record and, when integrated and analyzed within the context of stratigraphic patterns, attains a more robust linkage of processes to products than stratigraphic characterization alone.  相似文献   

16.
Based upon 2D seismic data, this study confirms the presence of a complex deep-water sedimentary system within the Pliocene-Quaternary strata on the northwestern lower slope of the Northwest Sub-Basin, South China Sea. It consists of submarine canyons, mass-wasting deposits, contourite channels and sheeted drifts. Alongslope aligned erosive features are observed on the eastern upper gentle slopes (<1.2° above 1,500 m), where a V-shaped downslope canyon presents an apparent ENE migration, indicating a related bottom current within the eastward South China Sea Intermediate Water Circulation. Contourite sheeted drifts are also generated on the eastern gentle slopes (~1.5° in average), below 2,100 m water depth though, referring to a wide unfocused bottom current, which might be related to the South China Sea Deep Water Circulation. Mass wasting deposits (predominantly slides and slumps) and submarine canyons developed on steeper slopes (>2°), where weaker alongslope currents are probably dominated by downslope depositional processes on these unstable slopes. The NNW–SSE oriented slope morphology changes from a three-stepped terraced outline (I–II–III) east of the investigated area, into a two-stepped terraced (I–II) outline in the middle, and into a unitary steep slope (II) in the west, which is consistent with the slope steepening towards the west. Such morphological changes may have possibly led to a westward simplification of composite deep-water sedimentary systems, from a depositional complex of contourite depositional systems, mass-wasting deposits and canyons, on the one hand, to only sliding and canyon deposits on the other hand.  相似文献   

17.
The Plio-Pleistocene stratigraphic record of the Peri-Adriatic basin (eastern central Italy) is well exposed along the uplifted western margin of the basin and consists of a series of coarse-grained slope canyon fills encased in a thick succession of hemipelagic mudstones. This study deals with the detailed sedimentology, stratal architecture, and sequence-stratigraphic interpretation of two of these submarine canyon-fills (namely CMC1 and CMC2) exposed at Colle Montarone. These strata contain widespread evidence of gravity-driven sedimentation processes, with high- and low-density turbidity currents, slumps and cohesive debris flows being responsible for most of the sediment transport and deposition. Beds are organised into four recurrent lithofacies, each corresponding to a specific deep-water depositional element: (i) clast-supported conglomerates (channel complexes); (ii) thin-bedded sandstones and mudstones (levee-overbank); (iii) very thinly-bedded mudstones (tributary channels); (iv) pebbly mudstones and chaotically bedded mudstones (mass-transport complexes).  相似文献   

18.
 The stratal architecture of the Gulf of Cádiz continental margin (SW Spain) has been analyzed by using single-channel, very high-resolution seismic reflection profiles. An evolutionary scheme of asymmetrical depositional sequences is proposed that was governed by the Late Pleistocene–Holocene sea-level fluctuations. Stratigraphic analysis defined 14 seismic units, that are configured into two major type-1 depositional sequences related to 4th-order eustatic sea level changes (100–110 ka). Within these sequences, minor asymmetrical depositional sequences have been recognized related to 5th-order eustatic cycles (22–23 ka) superimposed and modulated by the regressive trends of 4th-order cycles. In 5th-order depositional sequences, the forced regressive and lowstand deposits are volumetrically dominant. They cause the main progradation of the margin in such a way that they form the margin structure almost entirely. Received: 6 April 1995 / Revision received: 8 March 1996  相似文献   

19.
Recently, as oil exploitation has become focused on deepwater slope areas, more multi-channel high resolution 2D and 3D seismic data were acquired in the deepwater part of the Qiongdongnan Basin, northern South China Sea. Based on 3D seismic data and coherence time slice, RMS and 3D visualization, a series of deepwater channels were recognized on the slope that probably developed in the late Quaternary period. These channels trend SW–NE to W–E and show bifurcations, levees, meander loops and avulsions. High Amplitude Reflections (HARs), typical for channel–levee complexes, are of only minor importance and were observed in one of the channel systems. Most of the detected channels are characterized by low-amplitude reflections, and so are different from the typical coarse-grained turbidite channels that had been discovered worldwide. The absence of well data in the study area made it difficult to determine the age and lithology of these channels. Using a neighboring drill hole and published data about such depositional systems worldwide, the lithology of these channels is likely to be dominated by mudstones with interbedded thin sandstones. These channels are formed by turbidity currents originated from the little scale mountain river of mid-Vietnam in SW direction and were probably accompanied by a relative sea level drop in the last glacial age. These channels discovered on the northern South China Sea slope are likely to be fine-grained, mud-dominant and low N:G deposits in a deepwater paleogeographic setting.  相似文献   

20.
High-resolution multichannel 2-D and 3-D seismic data, primarily from upper fan reaches of near-seafloor channel-levee systems on the Niger Delta slope and in the Arabian Sea, reveal a high level of detail and architectural complexity. Several architectural elements are common to each system examined in this study. They include inner levees, outer levees, erosional fairways, channel-axis deposits, rotational slumps blocks, and mass transport deposits. Although the scale of individual systems varies significantly, similarities in first-order architectural elements and their configurations suggest that common depositional processes are involved regardless of scale differences.Most of the channel-levee systems examined in this study are characterized by a basal erosional fairway that is bordered by outer levees of varying thickness. Together these elements define the base and margins of the channel-belt, where channel-axis deposits and inner levees are the dominant architectural elements. Vertical, sub-vertical, and lateral stacking patterns of sinuous and/or meandering channels create seismic facies that range from narrow to wide zones of high amplitude reflections (HARs) with chaotic to continuous and shingled to horizontal reflections. Some HARs appear as isolated or stacked asymmetric to symmetric u- and v-shaped reflections, referred to here as channel-forms. Channel-belts evolve within the confines of the scalloped erosional fairway walls (flanked by outer levee), and are similar in morphology to meander-belts in fluvial systems, but commonly have a greater component of vertical aggradation. Detailed study of one particular channel-levee system on the Niger Delta slope shows a period of incision followed by three distinct phases of channel development during its aggradational history. Each fill phase corresponds to a different channel stacking architecture, planform geometry, and nature of terrace development, with important implications for reservoir architecture. In some cases, multiple phases of inner levee growth are observed, each intimately linked to the channel migration and aggradation history. Channel sinuosity evolves dynamically, with some meander loops undergoing periods of accelerated meander growth at the same time that others show little lateral migration.  相似文献   

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