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1.
The planform patterns of meandering submarine channels and subaerial fluvial bends show many similarities that have given rise to strong analogies concerning the fluid dynamics of these channel types. Existing models of helical motion in open‐channel bends depict flow that is characterized by surface flow towards the outer bank, and basal flow towards the inner bank. This paper investigates and compares, through an analytical model and physical experiment, flows within fluvial meanders, and submarine channel bends that contain density‐driven gravity currents. The results indicate that the sense of helical motion can be reversed in submarine bends that contain density currents when compared with fluvial bends, and that the orientation of the helical flow is dependent on the vertical distribution of downstream velocity. Specifically, the sense of helical motion is reversed in bends when the maximum downstream velocity is near the bed, resulting in near‐bed flow towards the outer bank. These findings suggest that the dynamics of sediment transport and deposition in curved channels with such velocity profiles will be fundamentally different to those currently assumed from sinuous open‐channels.  相似文献   

2.
Three‐dimensional seismic data were used to infer how bottom currents control unidirectional channel migration. Bottom currents flowing towards the steep bank would deflect the upper part of sediment gravity flows at an orientation of 1° to 11° to the steep bank, yielding a helical flow circulation consisting of a faster near‐surface flow towards the steep bank and a slower basal return flow towards the gentle bank. This helical flow model is evidenced by the occurrence of bigger, muddier (suggested by low‐amplitude seismic reflections) lateral accretion deposits and gentle channel wall with downlap terminations on the gentle bank and by smaller, sandier (indicated by high‐amplitude seismic reflectors) channel fills and steep channel walls with truncation terminations on the steep bank. This helical flow circulation promotes asymmetrical depositional patterns with dipping accretion sets restricted to the gentle bank, which restricts the development of sinuosity and yields unidirectional channel migration. These results aid in obtaining a complete picture of flow processes and sedimentation in submarine channels.  相似文献   

3.
An air‐gun survey, conducted over a total distance of 4356 km in the western end of the Kurile Arc offshore, has revealed the architecture and evolution of the Kushiro submarine canyon and Tokachi submarine channels of the Tokachi‐oki forearc basin. The Kushiro submarine canyon, which runs along the eastern margin of the forearc basin, is characterized by an entrenchment of up to several hundred metres in depth. The Tokachi submarine channels, by contrast, occupy the centre of the basin and consist of small, branching and levéed channels. The Kushiro submarine canyon is not connected to the Tokachi River, which has the largest drainage area in eastern Hokkaido, with a catchment area of approximately 9010 km2 that includes high mountains and a volcanic region. Instead, the Kushiro submarine canyon exhibits an offset connection/quasi‐connection (probably having been connected during a prior sea‐level lowstand) with the Kushiro River (drainage area of 2500 km2) which contains the Kushiro Swamp at its mouth. To understand this unusual arrangement of rivers and submarine channels, acoustic facies analysis was undertaken to establish the seismic stratigraphy of the area. Subsurface strata can be divided into six seismic units of Miocene to Recent age. Analyses of seismic facies and isopach maps indicate that: (i) the palaeo‐Kushiro submarine canyon, which was ancestral to the Kushiro submarine canyon, was an aggradational levéed channel; and (ii) the palaeo‐Tokachi submarine channel was much larger than the present‐day channel and changed its course several times. Both the palaeo‐Kushiro submarine canyon and palaeo‐Tokachi submarine channel were fed predominantly by the ancestral Tokachi River, whereas the present‐day channels are no longer connected or quasi‐connected to the Tokachi River. Entrenchment of the Kushiro submarine canyon began in its distal reaches during the Early Pleistocene and propagated landward over time, which was possibly caused by base‐level fall (i.e. subsidence of the trench floor) or uplift of the forearc basin. Entrenchment of the upper part of the Kushiro submarine canyon began during the Middle Pleistocene, which may have been related to: (i) depositional progradation; (ii) uplift of the coastal area; or (iii) a change in source area from the ancestral Tokachi River to the Kushiro River.  相似文献   

4.
DONALD R. LOWE 《Sedimentology》2012,59(7):2042-2070
Deposits of submarine debris flows can build up substantial topography on the sea floor. The resulting sea floor morphology can strongly influence the pathways of and deposition from subsequent turbidity currents. Map views of sea floor morphology are available for parts of the modern sea floor and from high‐resolution seismic‐reflection data. However, these data sets usually lack lithological information. In contrast, outcrops provide cross‐sectional and lateral stratigraphic details of deep‐water strata with superb lithological control but provide little information on sea floor morphology. Here, a methodology is presented that extracts fundamental lithological information from sediment core and well logs with a novel calibration between core, well‐logs and seismic attributes within a large submarine axial channel belt in the Tertiary Molasse foreland basin, Austria. This channel belt was the course of multiple debris‐flow and turbidity current events, and the fill consists of interbedded layers deposited by both of these processes. Using the core‐well‐seismic calibration, three‐dimensional lithofacies proportion volumes were created. These volumes enable the interpretation of the three‐dimensional distribution of the important lithofacies and thus the investigation of sea floor morphology produced by debris‐flow events and its impact on succeeding turbidite deposition. These results show that the distribution of debris‐flow deposits follows a relatively regular pattern of levées and lobes. When subsequent high‐density turbidity currents encountered this mounded debris‐flow topography, they slowed and deposited a portion of their sandy high‐density loads just upstream of morphological highs. Understanding the depositional patterns of debris flows is key to understanding and predicting the location and character of associated sandstone accumulations. This detailed model of the filling style and the resulting stratigraphic architecture of a debris‐flow dominated deep‐marine depositional system can be used as an analogue for similar modern and ancient systems.  相似文献   

5.
底流在陆缘深水环境下广泛存在,可对深水沉积过程及砂体分布产生重要影响。前人对重力流与底流的交互作用机制及沉积产物开展了大量研究,但目前有关底流改造型的海底扇储层构型模式仍然研究不够深入。东非鲁伍马盆地是当前重力流—底流交互作用研究的热点地区,文中以其代表性的下始新统海底扇水道体系为例,综合岩心、测井及三维地震资料开展储层构型精细表征,建立重力流—底流交互作用下的海底扇水道体系构型模式。研究表明,目标水道体系内部发育水道、溢岸及朵叶3种构型要素,其中水道可分为水道复合体、单一水道及其内部不同级次的构型单元。底流对细粒物质的搬运可形成非对称的溢岸沉积,导致水道复合体之间呈逆底流侧向迁移叠置样式,其间泥岩隔层容易保存; 单一水道之间呈顺水道纵向迁移或逆底流侧向迁移样式,其中纵向迁移部位水道切叠连通,而侧向迁移部位容易保存泥质侧向隔挡体。受重力流沉积演化的影响,单一水道内部充填由砂泥交互型逐渐演化为富砂型,且在水道弯曲段的轴部砂体最为发育。  相似文献   

6.
Submarine external levées are constructional features that develop outside slope channel systems, and are a volumetrically significant component of continental margins. However, detailed observations of their process sedimentology and depositional architecture are rare. Extensive exposures of external levées at multiple stratigraphic intervals and well‐constrained palaeogeographic positions in the Fort Brown Formation, Karoo Basin, South Africa, have been calibrated with research boreholes. This integrated data set permits their origin, evolution and anatomy to be considered, including high‐resolution analysis of sedimentary facies distribution and characterization of depositional sub‐environments. An idealized model of the stratigraphic evolution and depositional architecture of external levées is presented, and variations can be attributed to allogenic (for example, sediment supply) and autogenic (for example, channel migration) factors. Initiation of external levée construction is commonly marked by deposition of a basal sand‐rich facies with sedimentary structures indicating rapid deposition from unconfined flows. These deposits are interpreted as frontal lobes. Propagation of the parent channel, and resultant flow confinement, lead to partial erosion of the frontal lobe and development of constructional relief (levées) by flow overspill and flow stripping. Overall fining‐upwards and thinning‐upwards profiles reflect increased flow confinement and/or waning flow magnitude through time. Identification of a hierarchy of levée elements is not possible due to the absence of internal bounding surfaces or sharp facies changes. The down‐slope taper in levée height and increasing channel sinuosity results in increasing numbers of crevasse lobe deposits, and is reflected by the increased occurrences of channel avulsion events down‐dip. External levées from the Fort Brown Formation are silt‐rich; however their stratigraphic evolution and the distribution of many components (such as sediment waves and crevasse lobe) share commonalities with mud‐rich external levées. This unique integrated data set has permitted the first high‐resolution characterization of external submarine levée systems.  相似文献   

7.
The Lucia Chica channel system is an avulsion belt with four adjacent channels that progressively avulsed to the north‐east from a single, upslope feeder channel. Avulsion occurred from underfilled channels, leaving open channels that were reactivated by flows stripped from younger, adjacent channels. Differences in relief (height from channel thalweg to levée crest), sinuosity and levée stratigraphy between adjacent channels correspond to relative channel age, and indicate a change in channel morphology and architecture with time. Potential triggers for the change over time include differences in gradient, flow behaviour and characteristics, and channel evolution. Gradient does not appear to be a major control on channel formation and avulsion because adjacent channels formed on the same gradient. Based on available ultra‐high‐resolution remote imaging obtained with an Autonomous Underwater Vehicle, differences in adjacent channel morphology are interpreted to be primarily a result of differences in channel maturity. The interpreted sequence of channel maturity involves erosional channel inception through scouring and incipient channels (defined by linear trains of scours) prior to development of continuous thalwegs. Channel narrowing, formation and growth of levées, increasing channel relief and development of sinuosity occurred as channels evolved. The evolutionary sequence interpreted from the high‐resolution Lucia Chica dataset provides a unique perspective on intrinsic controls of architecture for single channel elements. In addition to helping bridge the gap between outcrop and industry‐standard reflection‐seismic data resolutions and scopes, interpretations in this study also expose potential problems with hierarchical classifications in three‐dimensional imaging of distributary systems, and provide potentially important analogues for evolutionary morphologies not resolved in other deep‐water channel systems.  相似文献   

8.
The Miocene Gorgoglione Flysch Formation records the stratigraphic product of protracted sediment transfer and deposition through a long‐lived submarine channel system developed in a narrow and elongate thrust‐top basin of the Southern Apennines (Italy). Channel‐fill deposits are exposed in an outcrop belt approximately 500 m thick and 15 km long, oriented oblique to the palaeoflow, which was roughly south‐eastward. These exceptional exposures of channel‐fill strata allow the stacking architectures and the evolution of the channel system to be analyzed at multiple scales, enabling the effects of syn‐sedimentary thrust tectonics and basin confinement on the depositional system development to be deciphered. Two end‐member types of elementary channel architecture have been identified: high‐aspect‐ratio, weakly‐confined channels, and low‐aspect‐ratio, incisional channels. Their systematic stacking results in a complex pattern of seismic‐scale depositional architectures that determines the stratigraphic framework of the deep‐water system. From the base of the succession, two prominent channel complex sets have been recognized, namely CS1 and CS2, consisting of amalgamated incisional channel elements and weakly‐confined channel elements. These channelized units are overlain by isolated incisional channels, erosional into mud‐prone slope deposits. The juxtaposition of different channel architectures is interpreted to have been governed by regional thrust‐tectonics, in combination with a high subsidence rate that promoted significant aggradation. In this scenario, the alternating ‘in sequence’ and ‘out of sequence’ tectonic pulses of the basin‐bounding thrusts controlled the activation of coarse‐clastic inputs in the basin and the resulting stacking architectures of channelized units. The tectonically‐driven confinement of the depositional system limited the lateral offset in channel stacking, preventing large‐scale avulsions. This study represents an excellent opportunity to analyze the stratigraphic evolution of a submarine channel system in tectonically‐active settings from an outcrop perspective. It should find wide applicability in analogous depositional systems, whose stratigraphic architecture has been influenced by tectonically‐controlled lateral confinement and associated lateral tilting.  相似文献   

9.
Alluvial fans develop their semi‐conical shape by quasi‐cyclic avulsions of their geomorphologically active sector from a fixed fan apex. On debris‐flow fans, these quasi‐cyclic avulsions are poorly understood, partly because physical scale experiments on the formation of fans have been limited largely to turbidite and fluvial fans and deltas. In this study, debris‐flow fans were experimentally created under constant extrinsic forcing, and autogenic sequences of backfilling, avulsion and channelization were observed. Backfilling, avulsion and channelization were gradual processes that required multiple successive debris‐flow events. Debris flows avulsed along preferential flow paths given by the balance between steepest descent and flow inertia. In the channelization phase, debris flows became progressively longer and narrower because momentum increasingly focused on the flow front as flow narrowed, resulting in longer run‐out and deeper channels. Backfilling commenced when debris flows reached their maximum possible length and channel depth, as defined by channel slope and debris‐flow volume and composition, after which they progressively shortened and widened until the entire channel was filled and avulsion was initiated. The terminus of deposition moved upstream because the frontal lobe deposits of previous debris flows created a low‐gradient zone forcing deposition. Consequently, the next debris flow was shorter which led to more in‐channel sedimentation, causing more overbank flow in the next debris flow and resulting in reduced momentum to the flow front and shorter runout. This topographic feedback is similar to the interaction between flow and mouth bars forcing backfilling and transitions from channelized to sheet flow in turbidite and fluvial fans and deltas. Debris‐flow avulsion cycles are governed by the same large‐scale topographic compensation that drives avulsion cycles on fluvial and turbidite fans, although the detailed processes are unique to debris‐flow fans. This novel result provides a basis for modelling of debris‐flow fans with applications in hazards and stratigraphy.  相似文献   

10.
Abstract Thickness variations across‐levee and downchannel in acoustically defined depositional sequences from six submarine channel‐levee systems show consistent and quantifiable patterns. The thickness of depositional sequences perpendicular to the channel trend, i.e. across the levee, decreases exponentially, as characterized by a spatial decay constant, k. Similarly, the thickness of sediment at the levee crest decreases exponentially down the upper reaches of submarine channels and can be characterized by a second spatial decay constant, λ. The inverse of these decay constants has units of length and defines depositional length scales such that k?1 is a measure of levee width and λ?1 is a measure of levee length. Quantification of levee architecture in this way allowed investigation of relationships between levee architecture and channel dimensions. It was found that these measures of levee e‐folding width and levee e‐folding length are directly related to channel width and relief. The dimensions of channels and levees are thus intimately related, thereby limiting the range of potential channel‐levee morphologies, regardless of allocyclic forcing. A simple sediment budget model relates the product of the levee e‐folding width and e‐folding length to through‐channel volume discharge. A classification system based on the quantitative downchannel behaviour of levee architecture allows identification of a ‘mid‐channel’ reach, where sediment is passively transferred from the through‐channel flow to the levees as an overspilling flow. Downstream from this reach, the channel gradually looses its control on guiding turbidity currents, and the resulting flow can be considered as an unconfined or spreading flow.  相似文献   

11.
深水水道是陆坡沉积的重要组成单元,深水水道储层受到广泛关注。基于高分辨率三维地震资料,利用地震属性、分频技术等研究穆尼盆地第四纪深水弯曲水道的沉积构型、成因及沉积过程,主要取得以下3个方面的成果:(1)建立了深水弯曲水道沉积构型模式。弯曲深水水道由水道和堤岸组成。堤岸脊将堤岸分成内堤岸和外堤岸两部分。水道由底部粗粒滞留沉积、深海泥质披覆沉积以及滑块组成。(2)深水水道早期为低弯曲水道,后期逐渐演化为高弯曲水道。(3)建立了深水弯曲水道沉积的岩相模式,深水弯曲水道由垂向加积水道和侧向迁移水道组成。顺重力流方向,侧向迁移带,内弯带以沉积作用为主,外弯带以侵蚀作用为主。垂向加积带,水道底部粗粒滞留沉积往往表现为垂向加积特征。深水弯曲水道岩相模式的建立对深水浊积水道储层准确预测具有重要的理论指导意义。  相似文献   

12.
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13.
《Sedimentology》2018,65(6):1947-1972
Submarine channels convey turbidity currents, the primary means for distributing sand and coarser sediments to the deep ocean. In some cases, submarine channels have been shown to braid, in a similar way to rivers. Yet the strength of the analogy between the subaerial and submarine braided channels is incompletely understood. Six experiments with subaqueous density currents and two experiments with subaerial rivers were conducted to quantify: (i) submarine channel kinematics; and (ii) the responses of channel and bar geometry to subaerial versus submarine basin conditions, inlet conditions and the ratio of ‘flow to sediment’ discharge (Q w/Q s). For a range of Q w/Q s values spanning a factor of 2·7, subaqueous braided channels consistently developed, were deeper upstream compared to downstream, and alternated with zones of sheet flow downstream. Topographic analyses included spatial statistics and mapping bars and channels using a reduced‐complexity flow model. The ratio of the estimated depth‐slope product for the submarine channels versus the subaerial channels was greater than unity, consistent with theoretical predictions, but with downstream variations ranging over a factor of 10. For the same inlet geometry and Q w/Q s, a subaqueous experiment produced deeper, steeper channels with fewer channel threads than its subaerial counterpart. For the subaqueous cases, neither slope, nor braiding index, nor bar aspect ratio varied consistently with Q w/Q s. For the subaqueous channels, the timescale for avulsion was double the time to migrate one channel width, and one‐third the time to aggrade one channel depth. The experiments inform a new stratigraphic model for submarine braided channels, wherein sand bodies are more laterally connected and less vertically persistent than those formed by submarine meandering channels.  相似文献   

14.
Much of our understanding of submarine sediment‐laden density flows that transport very large volumes (ca 1 to 100 km3) of sediment into the deep ocean comes from careful analysis of their deposits. Direct monitoring of these destructive and relatively inaccessible and infrequent flows is problematic. In order to understand how submarine sediment‐laden density flows evolve in space and time, lateral changes within individual flow deposits need to be documented. The geometry of beds and lithofacies intervals can be used to test existing depositional models and to assess the validity of experimental and numerical modelling of submarine flow events. This study of the Miocene Marnoso Arenacea Formation (Italy) provides the most extensive correlation of individual turbidity current and submarine debris flow deposits yet achieved in any ancient sequence. One hundred and nine sections were logged through a ca 30 m thick interval of time‐equivalent strata, between the Contessa Mega Bed and an overlying ‘columbine’ marker bed. Correlations extend for 120 km along the axis of the foreland basin, in a direction parallel to flow, and for 30 km across the foredeep outcrop. As a result of post‐depositional thrust faulting and shortening, this represents an across‐flow distance of over 60 km at the time of deposition. The correlation of beds containing thick (> 40 cm) sandstone intervals are documented. Almost all thick beds extend across the entire outcrop area, most becoming thinly bedded (< 40 cm) in distal sections. Palaeocurrent directions for flow deposits are sub‐parallel and indicate confinement by the lateral margins of the elongate foredeep. Flows were able to traverse the basin in opposing directions, suggesting a basin plain with a very low gradient. Small fractional changes in stratal thickness define several depocentres on either side of the Verghereto (high) area. The extensive bed continuity and limited evidence for flow defection suggest that intrabasinal bathymetric relief was subtle, substantially less than the thickness of flows. Thick beds contain two distinct types of sandstone. Ungraded mud‐rich sandstone intervals record evidence of en masse (debrite) deposition. Graded mud‐poor sandstone intervals are inferred to result from progressive grain‐by‐grain (turbidite) deposition. Clast‐rich muddy sandstone intervals pinch‐out abruptly in downflow and crossflow directions, in a fashion consistent with en masse (debrite) deposition. The tapered shape of mud‐poor sandstone intervals is consistent with an origin through progressive grain‐by‐grain (turbidite) deposition. Most correlated beds comprise both turbidite and debrite sandstone intervals. Intrabed transitions from exclusive turbidite sandstone, to turbidite sandstone overlain by debrite sandstone, are common in the downflow and crossflow directions. This spatial arrangement suggests either: (i) bypass of an initial debris flow past proximal sections, (ii) localized input of debris flows away from available sections, or (iii) generation of debris flows by transformation of turbidity currents on the basin plain because of seafloor erosion and/or abrupt flow deceleration. A single submarine flow event can comprise multiple flow phases and deposit a bed with complex lateral changes between mud‐rich and mud‐poor sandstone.  相似文献   

15.
在岩心观察的基础上,结合录井及多种分析化验资料,对吐哈盆地鲁克沁地区二叠系梧桐沟组沉积相标志、物源方向、沉积相展布及沉积模式进行研究。结果表明,梧桐沟组沉积时期,鲁克沁地区湖盆经历了由断陷湖盆向坳陷湖盆转换的过程。梧桐沟组一段沉积时期,研究区东西两侧发育水下扇沉积,扇中水道形成多期叠置的厚层泥质砂砾岩沉积,砂砾岩分布面积大,物性较差。梧桐沟组二段和三段沉积时期,湖盆水体变浅,湖岸坡度变缓,研究区东西两侧发育扇三角洲沉积,前缘水下分流河道形成了几套厚10~15 m的砂砾岩沉积,分选性好于水下扇形成的砂砾岩,物性相对较好。相比较而言,扇三角前缘水下分流河道砂体和水下扇砂体顶部的含砾砂岩是较好的储集体。该研究成果将对鲁克沁稠油聚集带储集层预测及区带优选具有指导意义。  相似文献   

16.
海底水道不但是沉积物搬运过程中从源到汇的关键环节,而且由于其中常常发育可作为良好油气储层的砂岩,近年来已成为深水沉积学研究的热点之一.基于莺歌海盆地乐东区新采集的三维地震资料和钻井资料,在建立了该区莺歌海组一段四级层序地层格架基础上,深入剖析了每个四级层序低位体系域内海底水道发育特征及其影响因素,构建了海底水道演化模式.研究结果表明,该区由于构造稳定、物源供给充足,高频海平面变化得以被沉积物记录下来,因此,可被识别出体系域发育齐全的多个四级层序,且在每个四级层序低位体系域内都发育了大量海底水道,具体包括斜坡水道和轴向水道两种类型,它们总体具有汇聚型特征.海底水道演化过程中受相对海平面变化、构造活动和沉积作用过程影响,呈现出数量逐渐减少、规模逐渐变小的特征.这些被快速沉积速率所记录下来的高频海平面变化及海底水道演化特征,为更好地理解可作为良好油气储层的海底水道的成因机制及其控制因素提供了良好的范例.   相似文献   

17.
《Sedimentology》2018,65(5):1590-1610
Downstream variation in grain size associated with changes in river pattern is a topic that interests multiple disciplines. How grain size varies between adjacent reaches with strongly contrasting river pattern is an outstanding question. This study presents a combined field and numerical modelling investigation of a river with a downstream planform change from single channel to anabranching, where the planform is controlled by a change in underlying lithology. This approach enabled exploration of the controls on sedimentology in a river for which there is very limited opportunity to collect flow and sediment transport data. This study shows that the surficial grain size decreases as a result of the downstream change in planform. This is because of a decrease in flow velocity and shear stress associated with a decrease in channel depth related to the planform change. Channel geometries in both the field and modelling data fit into distinct groups based on channel depth, the deepest being the single channel reach and the shallowest being the anabranching. This downstream reduction in channel dimension (depth) is caused because the total discharge is split from one channel into multiple channels. The coarsest grain sizes (cobble) are deposited at the terminus of the single channel and in the distributary channels; anabranching channels contain sand‐size sediments. This study shows that, in a transition from single channel to anabranching, the channel dimensions decrease as the number of channels increases, resulting in a decrease in bed shear stress and the fining of bed material downstream.  相似文献   

18.
Submarine turbidity currents are one of the most important processes for moving sediment across our planet; they are hazardous to offshore infrastructure, deposit petroleum reservoirs worldwide, and may record tsunamigenic landslides. However, there are few studies that have monitored these submarine flows in action, and even fewer studies that have combined direct monitoring with longer‐term records from core and seismic data of deposits. This article provides one of the most complete studies yet of a turbidity current system. The aim here is to understand what controls changes in flow frequency and character along the turbidite system. The study area is a 12 km long delta‐fed fjord (Howe Sound) in British Columbia, Canada. Over 100 often powerful (up to 2 to 3 m sec?1) events occur each year in the highly‐active proximal channels, which extend for 1 to 2 km from the delta lip. About half of these events reach the lobes at the channel mouths. However, flow frequency decreases rapidly once these initially sand‐rich flows become unconfined, and only one to five flows run out across the mid‐slope each year. Many of these sand‐rich, channelized, delta‐sourced flows therefore dissipated over a few hundred metres, once unconfined, rather than eroding and igniting. Upflow migrating bedforms indicate that supercritical flow dominated in the proximal channels and lobes, and also across the unconfined mid‐slope. These supercritical flows deposited thick sand beds in proximal channels and lobes, but thinner and finer beds on the unconfined mid‐slope. The distal flat basin records far larger volume and more hazardous events that have a recurrence interval of ca 100 years. This study shows how sand‐rich delta‐fed flows dissipate rapidly once they become unconfined, that supercritical flows dominate in both confined and unconfined settings, and how a second type of more hazardous, and much less frequent event is linked to a different scale of margin failure.  相似文献   

19.
盐构造与深水水道的交互作用--以下刚果盆地为例   总被引：2，自引：1，他引：1  
在被动大陆边缘盆地,水道作为深水油气的主要储集体,是深水油气勘探的重要目标。在下刚果盆地,由于盐构造的多期活动导致对水道砂体的展布规律认识不清。研究水道和盐构造的交互作用方式有利于预测含盐盆地中水道砂体的平面分布。利用三维地震资料,在盐构造与深水水道广泛发育的下刚果盆地研究盐构造与深水水道的交互作用,建立了盐构造与水道的交互作用模式。盐构造与水道的交互作用方式主要有6种,分别为限制、改向、封堵、侵蚀、迁移和剥蚀。盐构造的活动时期与水道形成演化时期的先后关系、水道中重力流的侵蚀能力决定了盐构造与水道的交互作用方式。水道经过早期发育的盐构造且水道中重力流侵蚀能力较弱多发生限制和改向;若水道中重力流侵蚀能力很强,可发生水道对盐构造的侵蚀;若盐构造的规模较大,其可阻止水道向下游输送沉积物并造成水道中重力流的回流,形成朵体沉积。若水道与盐构造同时活动多发生水道的迁移。晚期活动的盐构造可导致其上方的水道沉积体遭受剥蚀。  相似文献   

20.
《Sedimentology》2018,65(5):1447-1481
  相似文献   

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