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1.
《Sedimentology》2018,65(3):952-992
Hybrid event beds comprising both clean and mud‐rich sandstone are important components of many deep‐water systems and reflect the passage of turbulent sediment gravity flows with zones of clay‐damped or suppressed turbulence. ‘Behind‐outcrop’ cores from the Pennsylvanian deep‐water Ross Sandstone Formation reveal hybrid event beds with a wide range of expression in terms of relative abundance, character and inferred origin. Muddy hybrid event beds first appear in the underlying Clare Shale Formation where they are interpreted as the distal run‐out of the wakes to flows which deposited most of their sand up‐dip before transforming to fluid mud. These are overlain by unusually thick (up to 4·4 m), coarse sandy hybrid event beds (89% of the lowermost Ross Formation by thickness) that record deposition from outsized flows in which transformations were driven by both substrate entrainment in the body of the flow and clay fractionation in the wake. A switch to dominantly fine‐grained sand was accompanied initially by the arrest of turbulence‐damped, mud‐rich flows with evidence for transitional flow conditions and thick fluid mud caps. The mid and upper Ross Formation contain metre‐scale bed sets of hybrid event beds (21 to 14%, respectively) in (i) upward‐sandying bed set associations immediately beneath amalgamated sheet or channel elements; (ii) stacked thick‐bedded and thin‐bedded hybrid event bed‐dominated bed sets; (iii) associations of hybrid event bed‐dominated bed sets alternating with conventional turbidites; and (iv) rare outsized hybrid event beds. Hybrid event bed dominance in the lower Ross Formation may reflect significant initial disequilibrium, a bias towards large‐volume flows in distal sectors of the basin, extensive mud‐draped slopes and greater drop heights promoting erosion. Higher in the formation, hybrid event beds record local perturbations related to channel switching, lobe relocations and extension of channels across the fan surface. The Ross Sandstone Formation confirms that hybrid event beds can form in a variety of ways, even in the same system, and that different flow transformation mechanisms may operate even during the passage of a single flow. 相似文献
2.
Hybrid event beds dominated by transitional‐flow facies: character,distribution and significance in the Maastrichtian Springar Formation,north‐west Vøring Basin,Norwegian Sea 
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下载免费PDF全文 Sarah J. Southern Ian A. Kane Michał J. Warchoł Kristin W. Porten William D. McCaffrey 《Sedimentology》2017,64(3):747-776
Hybrid event beds comprising clay‐poor and clay‐rich sandstone are abundant in Maastrichtian‐aged sandstones of the Springar Formation in the north‐west Vøring Basin, Norwegian Sea. This study focuses on an interval, informally referred to as the Lower Sandstone, which has been penetrated in five wells that are distributed along a 140 km downstream transect. Systematic variations in bed style within this stratigraphic interval are used to infer variation in flow behaviour in relatively proximal and distal settings, although individual beds were not correlated. The Lower Sandstone shows an overall reduction in total thickness, bed amalgamation, sand to mud ratio and grain size in distal wells. Turbidites dominated by clay‐poor sandstone are at their most common in relatively proximal wells, whereas hybrid event beds are at their most common in distal wells. Hybrid event beds typically comprise a basal clay‐poor sandstone (non‐stratified or stratified) overlain by banded sandstone, with clay‐rich non‐stratified sandstone at the bed top. The dominant type of clay‐poor sandstone at the base of these beds varies spatially; non‐stratified sandstone is thickest and most common proximally, whereas stratified sandstone becomes dominant in distal wells. Stratified and banded sandstone record progressive deposition of the hybrid event bed. Thus, the facies succession within hybrid event beds records the longitudinal heterogeneity of flow behaviour within the depositional boundary layer; this layer changed from non‐cohesive at the front, through a region of transitional behaviour (fluctuating non‐cohesive and cohesive flow), to cohesive behaviour at the rear. Spatial variation in the dominant type of clay‐poor sandstone at the bed base suggests that the front of the flow remained non‐cohesive, and evolved from high‐concentration and turbulence‐suppressed to increasingly turbulent flow; this is thought to occur in response to deposition and declining sediment fallout. This research may be applicable to other hybrid event bed prone systems, and emphasizes the dynamic nature of hybrid flows. 相似文献
3.
应用深水沉积学和地震沉积学的相关理论,通过岩心观察描述、钻测井资料分析及平面沉积相编图,对下刚果盆地A区块白垩系Pointe Indienne组深水重力流的类型、沉积特征、垂向沉积组合及沉积模式进行了探讨分析,指出该地区发育砂质碎屑流、泥质碎屑流、浊流及与重力流形成过程相关的滑动—滑塌沉积,并总结了该深水重力流的沉积模式。结果表明:砂质碎屑流沉积以块状层理细砂岩为主,含大型漂浮泥砾和泥岩撕裂屑;泥质碎屑流沉积以泥级碎屑为主,含有少量的暗色泥岩碎屑和砂质团块,见“泥包砾”结构;浊流沉积以发育完整或不完整的鲍马序列为特征;滑动—滑塌沉积具有明显的剪切滑移面,可见旋转火焰构造、砂岩扭曲杂乱分布及褶皱变形层;纵向上可识别出4种类型的重力流沉积垂向组合,以多期砂质碎屑流沉积叠置和砂质碎屑流沉积与浊流沉积叠置最为常见;研究区深水重力流沉积可分为上部扇、中部扇和外部扇3部分,上部扇以主水道沉积为主;中部扇以辫状水道和溢岸沉积为主,砂体厚度较大;外部扇以朵叶体沉积和薄层浊积岩为主,砂体厚度相对较薄。 相似文献
4.
鄂尔多斯晚三叠世湖盆异重流沉积新发现 总被引：15，自引：4，他引：11
水下重力流沉积作为重要的油气储层,已成为当前学术研究和油气工业共同关注的焦点.在鄂尔多斯盆地南部延长组长7~长6油层组深湖相沉积中,发现一种不同于砂质碎屑流沉积和滑塌浊积岩的重力流成因砂岩.其沉积特征为一系列向上变粗的单元(逆粒序层)和向上变细的单元(正粒序层)成对出现;每一个粒序层组合内部的泥质含量变化(高-低-高)与粒度变化一致;上部正粒序层与下部逆粒序层之间可见层内微侵蚀界面;砂岩与灰黑色纯泥岩、深灰色粉砂质泥岩互层;粉砂质泥岩层内也表现出类似的粒度变化特征.通过岩芯观察和薄片鉴定,认为该岩石组合形成于晚三叠世深湖背景下的异重流(hyperpycnal flow)沉积.其沉积产物--hyperpycnite(异重岩?)以发育逆粒序和层内微侵蚀面而区别于其它浊积岩,逆粒序代表洪水增强期的产物,上部的正粒序层为洪水衰退期的沉积,逆粒序-正粒序的成对出现代表一次洪水异重流事件沉积旋回;层内微侵蚀面是洪峰期流速足以对同期先沉淀的逆粒序沉积层侵蚀造成的.鄂尔多斯盆地延长组异重岩的发现,不仅为探索陆相湖盆环境下的异重流沉积提供了一个范例,而且对于深水砂体成因研究、储层预测和油气勘探具有理论和现实意义. 相似文献
5.
重力流混合事件层在陆相湖盆广泛发育,其形成和分布对理解重力流沉积演化过程及重力流沉积常规与非常规油气勘探开发意义重大.以涠西南凹陷流沙港组一段和鄂尔多斯盆地延长组7段重力流沉积为研究对象,分析湖盆重力流混合事件层的沉积特征、类型、成因及沉积模式,并进一步探讨其地质意义.湖盆主要发育滑动、滑塌重力驱动块体搬运沉积和砂质碎屑流、泥质碎屑流、高密度浊流和低密度浊流等重力流流体沉积,同时广泛发育重力流混合事件层沉积.湖盆重力流混合事件层包含多层结构、双层结构和频繁互层三种大的类型;其中,双层结构的重力流混合事件层进一步根据上下两个沉积单元厚度的差异可细分为两个亚类.多层结构的混合事件层主要为流体侵蚀或砂体液化成因,多发育于混合事件层沉积近端;双层结构与频繁互层结构的混合事件层主要为流体减速膨胀、泥质碎屑流中碎屑颗粒的差异沉降成因,多发育于混合事件层沉积远端.相同沉积单元组成的沉积层在垂向上的规律叠置是岩芯中识别重力流混合事件层沉积的可靠依据;在未明确其沉积过程的情况下可能会导致沉积信息的错误解读.同时,重力流混合事件层的发育会导致重力流沉积非均质性增强,不利于常规油气的储集;但是,重力流混合事件层形成的细粒沉积物是非常规油气"甜点"区发育的优势沉积岩相组合类型. 相似文献
6.
鄂尔多斯盆地上三叠统延长组长7段深水重力流沉积类型 总被引：1，自引：0，他引：1
以鄂尔多斯盆地上三叠统延长组长7段取芯段为主要研究对象,以详细的岩芯观察为基础,以Z43井为例,研究鄂尔多斯盆地延长组长7段深水重力流沉积类型及其特征。研究结果表明,研究区主要发育砂质碎屑流沉积、低密度浊流沉积及混合事件层三种沉积类型。砂质碎屑流沉积整体呈块状,岩性为中—细砂岩,内部可见多个接触面,为多套砂质碎屑流沉积垂向叠置形成。低密度浊流沉积中大部分为中—薄层的正粒序砂岩垂向叠置而成,部分泥质含量较高,表现出砂泥互层的特征。混合事件层主要由下部干净的块状细砂岩与上部富含变形泥岩撕裂屑的砂质泥岩或泥质砂岩成对组合形成,其成因为浊流流动过程中侵蚀泥质基底,黏土物质或泥质碎屑的混入导致浊流向泥质碎屑流转化,最终形成下部浊流沉积上部泥质碎屑流沉积的混合事件层。相近位置不同深度不同类型的深水重力流沉积垂向叠置,指示了复杂多变的重力流流体演化过程。对重力流沉积类型的准确认识,能进一步促进对深水重力流流体转化过程的理解,明确深水重力流沉积分布,为鄂尔多斯盆地深水重力流沉积及常规与非常规油气勘探与开发提供理论指导。 相似文献
7.
The Marnoso‐arenacea Formation in the Italian Apennines is the only ancient rock sequence where individual submarine sediment density flow deposits have been mapped out in detail for over 100 km. Bed correlations provide new insight into how submarine flows deposit sand, because bed architecture and sandstone shape provide an independent test of depositional process models. This test is important because it can be difficult or impossible to infer depositional process unambiguously from characteristics seen at just one outcrop, especially for massive clean‐sandstone intervals whose origin has been controversial. Beds have three different types of geometries (facies tracts) in downflow oriented transects. Facies tracts 1 and 2 contain clean graded and ungraded massive sandstone deposited incrementally by turbidity currents, and these intervals taper relatively gradually downflow. Mud‐rich sand deposited by cohesive debris flow occurs in the distal part of Facies tract 2. Facies tract 3 contains clean sandstone with a distinctive swirly fabric formed by patches of coarser and better‐sorted grains that most likely records pervasive liquefaction. This type of clean sandstone can extend for up to 30 km before pinching out relatively abruptly. This abrupt pinch out suggests that this clean sand was deposited by debris flow. In some beds there are downflow transitions from turbidite sandstone into clean debrite sandstone, suggesting that debris flows formed by transformation from high‐density turbidity currents. However, outsize clasts in one particular debrite are too large and dense to have been carried by an initial turbidity current, suggesting that this debris flow ran out for at least 15 km. Field data indicate that liquefied debris flows can sometimes deposit clean sand over large (10 to 30 km) expanses of sea floor, and that these clean debrite sand layers can terminate abruptly. 相似文献
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9.
The Lower Cretaceous Britannia Formation (North Sea) includes an assemblage of sandstone beds interpreted here to be the deposits of turbidity currents, debris flows and a spectrum of intermediate flow types termed slurry flows. The term ‘slurry flow’ is used here to refer to watery flows transitional between turbidity currents, in which particles are supported primarily by flow turbulence, and debris flows, in which particles are supported by flow strength. Thick, clean, dish‐structured sandstones and associated thin‐bedded sandstones showing Bouma Tb–e divisions were deposited by high‐ and low‐density turbidity currents respectively. Debris flow deposits are marked by deformed, intraformational mudstone and sandstone masses suspended within a sand‐rich mudstone matrix. Most Britannia slurry‐flow deposits contain 10–35% detrital mud matrix and are grain supported. Individual beds vary in thickness from a few centimetres to over 30 m. Seven sedimentary structure division types are recognized in slurry‐flow beds: (M1) current structured and massive divisions; (M2) banded units; (M3) wispy laminated sandstone; (M4) dish‐structured divisions; (M5) fine‐grained, microbanded to flat‐laminated units; (M6) foundered and mixed layers that were originally laminated to microbanded; and (M7) vertically water‐escape structured divisions. Water‐escape structures are abundant in slurry‐flow deposits, including a variety of vertical to subvertical pipe‐ and sheet‐like fluid‐escape conduits, dish structures and load structures. Structuring of Britannia slurry‐flow beds suggests that most flows began deposition as turbidity currents: fully turbulent flows characterized by turbulent grain suspension and, commonly, bed‐load transport and deposition (M1). Mud was apparently transported largely as hydrodynamically silt‐ to sand‐sized grains. As the flows waned, both mud and mineral grains settled, increasing near‐bed grain concentration and flow density. Low‐density mud grains settling into the denser near‐bed layers were trapped because of their reduced settling velocities, whereas denser quartz and feldspar continued settling to the bed. The result of this kinetic sieving was an increasing mud content and particle concentration in the near‐bed layers. Disaggregation of mud grains in the near‐bed zone as a result of intense shear and abrasion against rigid mineral grains caused a rapid increase in effective clay surface area and, hence, near‐bed cohesion, shear resistance and viscosity. Eventually, turbulence was suppressed in a layer immediately adjacent to the bed, which was transformed into a cohesion‐dominated viscous sublayer. The banding and lamination in M2 are thought to reflect the formation, evolution and deposition of such cohesion‐dominated sublayers. More rapid fallout from suspension in less muddy flows resulted in the development of thin, short‐lived viscous sublayers to form wispy laminated divisions (M3) and, in the least muddy flows with the highest suspended‐load fallout rates, direct suspension sedimentation formed dish‐structured M4 divisions. Markov chain analysis indicates that these divisions are stacked to form a range of bed types: (I) dish‐structured beds; (II) dish‐structured and wispy laminated beds; (III) banded, wispy laminated and/or dish‐structured beds; (IV) predominantly banded beds; and (V) thickly banded and mixed slurried beds. These different bed types form mainly in response to the varying mud contents of the depositing flows and the influence of mud on suspended‐load fallout rates. The Britannia sandstones provide a remarkable and perhaps unique window on the mechanics of sediment‐gravity flows transitional between turbidity currents and debris flows and the textures and structuring of their deposits. 相似文献
10.
Shallow-water gravity-flow deposits, Chapel Island Formation, southeast Newfoundland, Canada 总被引：3，自引：0，他引：3
A remarkable suite of shallow-water, gravity-flow deposits are found within very thinly-bedded siltstones and storm-generated sandstones of member 2 of the Chapel Island Formation in southeast Newfoundland. Medium to thick siltstone beds, termed unifites, range from non-graded and structureless (Type 1) to slightly graded with poorly developed lamination (Type 2) to well graded with lamination similar to that described for fine-grained turbidites (Type 3). Unifite beds record deposition from a continuum of flow types from liquefied flows (Type 1) to turbidity currents (Type 3). Calculations of time for pore-fluid pressure dissipation support the feasibility of such transitions. Raft-bearing beds consist of siltstone with large blocks or‘rafts’ of thinly bedded strata derived from the underlying and adjacent substrate. Characteristics suggest deposition from debris flows of variable strength. Estimates of debris strength and depositional slope are calculated for a pebbly mudstone bed using measurable and assumed parameters. An assumed density of 2.0 g cm-1 and a compaction estimate of 50% gives a strength estimate of 79.7 dyn cm-2 and a depositional slope estimate of 0.77°. The lithologies and sedimentary structures in member 2 indicate an overall grain-size distribution susceptible to liquefaction. Inferred high sediment accumulation rates created underconsolidated sediments (metastable packing). Types of sediment failure included in situ liquefaction (‘disturbed bedding’), sliding and slumping. Raft-bearing debrites resulted from sliding and incorporation of water. Locally, hummocky cross-stratified sandstone directly overlies slide deposits and raft-bearing beds, linking sediment failure to the cyclical wave loading associated with large storms. The gravity flows of the Chapel Island Formation closely resemble those described from the surfaces of modern, mud-rich, marine deltas. Details of deltaic gravity-flow deposition from this and other outcrop studies further our understanding of modern deposits by adding a third dimension to studies primarily carried out with side-scan sonar. 相似文献
11.
B.Z. Xian J.H. Wang J.P. Liu Y.L. Dong C.L. Gong Z.Y. Lu 《Australian Journal of Earth Sciences》2018,65(1):135-151
Sediment avalanche from delta ramp is one of the significant development mechanisms for a turbidite system in a lacustrine basin. To advance our understanding of deep-water sedimentary processes in a lacustrine delta ramp, delta-fed turbidites in the Eocene Dongying depression of the Bohai Bay Basin were studied using core data, 3-D seismic data and well log data. Sandy debris flows, muddy debris flows, mud flows, turbidity currents, slides, sandy slumps and muddy slumps were interpreted based on the identification of lithofacies. Data indicates that deep-water sedimentary processes in the study area were dominated by debris flows and slumps, which accounted for ～68% and 25% (in thickness) of total gravity flow deposits, respectively; turbidity-current deposits only accounted for ～5%. Mapping of turbidites showed that most were deposited after short-distance transportation (<20 km), restricted by the scale of deep-water areas and local topography. Channels, depositional lobes, debris flow tongues, muddy turbiditic sheets, slides and slumps were identified in a delta-fed ramp system. Slides and slumps were dominant at the base of slopes or at the hanging walls of growth faults with strong tectonic activity. Channels and depositional lobes developed in gentle, low-lying areas, where sediments were transported longer distances. Sand-rich sediment supply, short-distance transportation and local topography were crucial factors that controlled sedimentation of this ramp system. Channels generally lacked levees and only produced scattered sandstones because of possible hydroplaning of debris flow and unstable waterways. In addition to lobes, debris flow tongues could also be developed in front of channels. These findings have significant implications for hydrocarbon exploration of deep-water sandstone fed by deltas in a lacustrine basin. 相似文献
12.
《Sedimentology》2018,65(1):151-190
This study documents the character and occurrence of hybrid event beds (HEBs) deposited across a range of deep‐water sub‐environments in the Cretaceous–Palaeocene Gottero system, north‐west Italy. Detailed fieldwork (>5200 m of sedimentary logs) has shown that hybrid event beds are most abundant in the distal confined basin‐plain domain (>31% of total thickness). In more proximal sectors, hybrid event beds occur within outer‐fan and mid‐fan lobes (up to 15% of total thickness), whereas they are not observed in the inner‐fan channelized area. Six hybrid event bed types (HEB‐1 to HEB‐6) were differentiated mainly on basis of the texture of their muddier and chaotic central division (H3). The confined basin‐plain sector is dominated by thick (maximum 9·57 m; average 2·15 m) and tabular hybrid event beds (HEB‐1 to HEB‐4). Their H3 division can include very large substrate slabs, evidence of extensive auto‐injection and clast break‐up, and abundant mudstone clasts set in a sandy matrix (dispersed clay ca 20%). These beds are thought to have been generated by highly energetic flows capable of delaminating the sea floor locally, and carrying large rip‐up clasts for relatively short distances before arresting. The unconfined lobes of the mid‐fan sector are dominated by thinner (average 0·38 m) hybrid event beds (HEB‐5 and HEB‐6). Their H3 divisions are characterized by floating mudstone clasts and clay‐enriched matrices (dispersed clay >25%) with hydraulically fractionated components (mica, organic matter and clay flocs). These hybrid event beds are thought to have been deposited by less energetic flows that underwent early turbulence damping following incorporation of mud at proximal locations and by segregation during transport. Although there is a tendency to look to external factors to account for hybrid event bed development, systems like the Gottero imply that intrabasinal factors can also be important; specifically, the type of substrate available (muddy or sandy) and where and how erosion is achieved across the system producing specific hybrid event bed expressions and facies tracts. 相似文献
13.
沉积物重力流流体转化沉积-混合事件层 总被引：3，自引：2，他引：1
随着浊流和碎屑流理论体系日臻成熟,重力流的流体转化过程逐渐受到重视,而与其相关联的混合事件层概念也应运而生。混合事件层是单次碎屑流或浊流流体转化中的沉积记录,是多种流变学特征的垂向沉积组合。典型混合事件层沉积序列具有五段式的特征（即纯净砂岩段H1、条带状砂岩段H2、黏性碎积岩段H3、波状层理段H4、块状泥岩段H5）,其内部通常存在岩性突变界面。混合事件层发育于粗粒三角洲内部、海底扇和水道与舌状体过渡区、舌状体侧缘、远端及限制性的微型盆地边缘地区,其垂向叠置厚度可达数十米。混合事件层的发现对重力流流体转化、重力流沉积物空间流变学性质研究具有重要意义,同时也推动了油气储层构型和非均质性研究,为进一步寻找深水有利储集砂体提供了新思路。混合层地球物理识别方法的建立及其相关概念在湖泊重力流研究中的灵活应用将是下一步的研究方向。 相似文献
14.
随着页岩油气勘探开发和相关领域研究的不断深入,细粒沉积物的搬运和沉积已成为当前沉积学研究的热点问题之一,但中国中生代湖泊环境中的泥质重力流沉积尚未引起应有的关注。通过岩心观察、薄片鉴定等手段及综合研究,分析了鄂尔多斯盆地晚三叠世湖相泥质重力流沉积特征,探讨了其形成机制与成因分类。鄂尔多斯盆地三叠系延长组湖相泥页岩结构类型多样,发育泥质块体流沉积、泥质碎屑流沉积、泥质浊流沉积和泥质异重流沉积等多种重力流沉积类型。按照泥质含量将重力流划分为砂质重力流、泥质重力流和混合重力流3种亚类,并根据成因将重力流划分为滑塌体、碎屑流、浊流及异重流等4种亚类;结合成因和泥质含量,将重力流沉积共划分为12种类型。滑塌岩、碎屑岩分布于三角洲前缘斜坡脚附近;浊积岩、异重岩广泛分布于三角洲斜坡至沉积中心。认为泥质沉积物可以在强水动力条件下搬运-沉积;重力流沉积细粒物质在湖相沉积中占据很大的比例;泥质重力流对泥页岩中的碎屑物质、黏土矿物及有机质的搬运和沉积起到重要作用,因而对于页岩油气的生烃、储集性能和压裂工艺研究具有重要意义。 相似文献
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On the basis of detailed sedimentological investigation, three types of hybrid event beds (HEBs) together with debrites and turbidites were distinguished in the Lower Cretaceous sedimentary sequence on the Lingshan Island in the Yellow Sea, China. HEB 1, with a total thickness of 63–80 cm and internal bipartite structures, is characterised by a basal massive sandstone sharply overlain by a muddy sandstone interval. It is interpreted to have been formed by particle rearrangement at the base of cohesive debris flows. HEB 2, with a total thickness of 10–71 cm and an internal tripartite structure, is characterised by a normal grading sandstone base, followed by muddy siltstone middle unit and capped with siltstones; the top unit of HEB 2 may in places be partly or completely eroded. The boundary between the lowest unit and the middle unit is gradual, whereas that between the middle unit and the top unit is sharp. HEB 2 may be developed by up-dip muddy substrate erosion. HEB 3, with a total thickness up to 10 cm and an internal bipartite structure, is characterised by a basal massive sandstone sharply overlain by a muddy siltstone interval. The upper unit was probably deposited by cohesive debris flow with some plant fragments and rare mud clasts. HEB 3 may be formed by the deceleration of low-density turbidity currents. The distribution of HEBs together with debrites and turbidites implies a continuous evolution process of sediment gravity flows: debris flow → hybrid flow caused by particle rearrangement → high-density turbidity current → hybrid flow caused by muddy substrate erosion → low-density turbidity current → hybrid flow caused by deceleration. 相似文献
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页岩油气的勘探开发推动了泥页岩沉积机理研究的快速发展,使得细粒物质的搬运和沉积成为当今沉积学界和油气工业界共同关注的焦点。尽管海洋环境下的泥质重力流沉积研究成果频见报道,但有关我国新生代湖泊环境中的泥质重力流沉积尚未引起沉积学界的关注。故本文在国内外相关文献调研基础上,以岩芯观察和薄片鉴定为重点,分析了渤海湾盆地东营凹陷古近系沙河街组三段湖相泥质重力流沉积特征;探讨了湖相泥质重力流沉积的形成机制;以期为湖泊沉积学研究和陆相页岩油气开发提供参考。研究发现,东营凹陷古近系沙河街组三段发育泥质块体流、泥质碎屑流、泥质浊流及泥质异重流等多种重力流沉积类型;泥质滑塌岩、泥质碎屑岩、泥质浊积岩和泥质异重岩在时空上可以共生共存。认为泥质沉积物可以在动荡水体和较强水动力条件下沉淀;泥质重力流沉积在深水沉积区占有重要地位;泥质重力流对于泥页岩中的粗粒碎屑物质、有机质的搬运和沉积以及有机质的埋藏起到重要作用,因而具有重要的非常规油气地质意义。 相似文献
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利用岩心、粒度、测井信息和重力流沉积理论,系统研究了南堡凹陷东部洼陷带东营组重力流沉积特征和沉积模式。该区重力流沉积砂岩常夹于灰色、灰黑色泥岩中,砂岩相发育,其中正递变层理(含砾)中-细砂岩相(S-3)、粉砂岩相(S-4)和块状层理中-细砂岩相(S-2)发育层数最多,块状层理含砾砂岩相(S-1)次之;S-2沉积厚度最大,S-1和S-3次之。按支撑和沉积机制,将本区重力流分为浊流、砂质碎屑流、颗粒流和液化流,其中砂质碎屑流以基质支撑、冻结块状沉积为特征。不同重力流发育程度有明显差异。从砂岩层数看,浊流最多,砂质碎屑流次之,颗粒流和液化流最少;从单期沉积厚度看,砂质碎屑流最大,平均为1.17m,浊流沉积最小,仅平均为0.25m。为了回避取心的局限性、弱化重力流成因,突出具有油气储集意义的砂层概念,开展了测井岩性解释,结果表明该区重力流沉积为细砂岩或粉砂岩,单层平均厚度2.94m,最大厚度可达9.5m,其中单井中厚度在3m以上的砂体可达22层、累积达107.5m。本区重力流沉积为滑塌成因,除了(扇)三角洲前缘斜坡的自然滑塌外,断层(地震)活动或间歇式火山喷发是其关键的触发机制;断层活动除了提供滑塌的动力外,还影响着其堆积场所和沉积的结构。 相似文献
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Xin Shan Xuefa Shi Peter D. Clift Shuqing Qiao Lina Jin Jianxing Liu Xisheng Fang Taoyu Xu Shunli Li Selvaraj Kandasamy Mengwei Zhao Ying Zhu Hui Zhang Dan Zhang Huawei Wang Yalong Li Zhengquan Yao Sai Wang Jun Xu 《Sedimentology》2019,66(5):1861-1895
The East China Sea Shelf has an unusually wide and low gradient shelf, supplied from sediment‐charged rivers and large river delta systems, with bottom currents sweeping the sea floor and located in the path of strong typhoons. Sediment gravity flow deposits, including four hybrid event beds and a high density turbidite, are identified in a core from the mid‐shelf of the East China Sea. The hybrid event beds typically comprise three or two internal divisions from the base to the top: (i) H1, H3 and H5; or (ii) H3 and H5. Radiocarbon ages of the hybrid event beds were in the range of 3821 to 8526 yr bp . Based on correlation with surrounding cores, the hybrid events may have happened at any time between 1930 yr bp and 3890 yr bp . The δ13C values in hybrid event beds together with bathymetry data suggest local erosion on the shelf. The average δ13C value for the H1 division is similar to the H3 division in the hybrid event beds, implying that the organic matter in the H1 and H3 divisions may come from the same source area. Cross‐plots of upper continental crust normalized rare earth elements in the five units reveal that the sediment source of the four hybrid event beds and the turbidite was ultimately primarily from Korean rivers. Partial transformation from a moderate‐strength debris flow with the additional role of erosional bulking can explain occurrences of hybrid event beds on the East China Sea Shelf. The data indicate that hybrid sediment gravity flow deposits were sourced from intra‐shelf failures and subsequently transformed and deposited as hybrid event beds. The study shows that hybrid sediment gravity flows and turbidity currents may not necessarily indicate proximity to a major fluvial or deltaic system and that intra‐shelf sedimentation can be a sediment source. It is unlikely that the debris flows and turbidity currents were triggered by a hyperpycnal flow or tsunami, because both can carry continental and/or coastal signals which have not been recognized in the core. Typhoons are the probable triggering mechanism. 相似文献