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1.
Subaqueous liquefied and fluidized sediment flows and their deposits   总被引：3，自引：0，他引：3  
A clear distinction must be made between liquefied and fluidized systems. In liquefied beds and flows, the solids settle downward through the fluid, displacing it upward, whereas, in fluidized beds, the fluid moves upward through the solids, which are temporarily suspended without net downward movement. Many recent references to fluidized sediment gravity flows refer, in fact, to flows of liquefied debris. Most uniformly liquefied beds of well-sorted sand- or gravel-sized sediment will resediment as simple two-layer systems. Liquefied flows can originate either by liquefaction followed by failure, as in many retrogressive flow slides, or by failure followed by liquefaction, as in the case of some slumps. Empirical and theoretical estimates of flow velocity, thickness, and travel distance suggest that natural laminar liquefied flows of fine-grained sand will generally resediment after moving a kilometre or less. Laminar flows of coarse-grained sand will resediment after moving only a few metres. Grain dispersive pressure is thought to be of little significance in the development or maintenance of liquefied flows. Many surficial submarine sand beds are apparently susceptible to liquefaction, including submarine canyon and continental rise deposits. Within submarine canyons and narrow fjords, steep slopes and channels promote the evolution of liquefied flows from slumps by liquefaction after failure and of high density turbidity currents from liquefied flows by the development of turbulence. Upon moving into the lower parts of submarine canyons or into proximal fan channels, liquefied flows will resediment and high density turbidity currents will tend to decline to flows transitional between liquefied flows and turbidity currents. The liquefied, coarser detritus within such transitional flows will be deposited while finer-grained debris will remain in suspension and continue downslope as dilute turbidity currents. Resedimentation of the liquefied portions of such flows may be responsible for the deposition of the A-subdivision of many turbidites and many thick, structureless ‘proximal turbidites’ or ‘fluxoturbidites’. Similar units can originate by liquefaction of the traction deposits of normal turbidity currents. Fluidized flows are probably uncommon, thin, and, where formed, originate through fluidization of the fine-grained tops of liquefied graded beds.  相似文献   

2.
Status and Trends in Research on Deep-Water Gravity Flow Deposits   总被引：3，自引：0，他引：3  
Deep-water gravity flows are one of the most important sediment transport mechanisms on Earth. After 60 years of study,significant achievements have been made in terms of classification schemes,genetic mechanisms,and depositional models of deep-water gravity flows. The research history of deep-water gravity flows can be divided into five stages: incipience of turbidity current theory; formation of turbidity current theory; development of deep-water gravity flow theory; improvement and perfection of deep-water gravity flow theory; and comprehensive development of deep-water gravity flow theory. Currently,three primary classification schemes based on the sediment support mechanism,the rheology and transportation process,and the integration of sediment support mechanisms,rheology,sedimentary characteristics,and flow state are commonly used.Different types of deep-water gravity flow events form different types of gravity flow deposits. Sediment slump retransportation mainly forms muddy debris flows,sandy debris flows,and surge-like turbidity currents. Resuspension of deposits by storms leads to quasi-steady hyperpycnal turbidity currents(hyperpycnal flows). Sustainable sediment supplies mainly generate muddy debris flows,sandy debris flows,and hyperpycnal flows. Deep-water fans,which are commonly controlled by debris flows and hyperpycnal flows,are triggered by sustainable sediment supply; in contrast,deep-water slope sedimentary deposits consist mainly of debris flows that are triggered by the retransportation of sediment slumps and deep-water fine-grained sedimentary deposits are derived primarily from finegrained hyperpycnal flows that are triggered by the resuspension of storm deposits. Harmonization of classification schemes,transformation between different types of gravity flow deposit,and monitoring and reproduction of the sedimentary processes of deep-water gravity flows as well as a source-to-sink approach to document the evolution and deposition of deep-water gravity flows are the most important research aspects for future studies of deep-water gravity flows study in the future.  相似文献   

3.
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   

4.
The deeply dissected Southwest Grand Banks Slope offshore the Grand Banks of Newfoundland was investigated using multiple data sets in order to determine how canyons and intercanyon ridges developed and what sedimentary processes acted on glacially influenced slopes. The canyons are a product of Quaternary ice‐related processes that operated along the margin, such as ice stream outwash and proglacial plume fallout. Three types of canyon are defined based on their dimensions, axial sedimentary processes and the location of the canyon head. There are canyons formed by glacial outwash with aggradational and erosional floors, and canyons formed on the slope by retrogressive failure. The steep, narrow intercanyon ridges that separate the canyons are composite morphological features formed by a complex history of sediment aggradation and degradation. Ridge aggradation occurred as a result of mid to late Quaternary background sedimentation (proglacial plume fallout and hemipelagic settling) and turbidite deposition. Intercanyon ridge degradation was caused mainly by sediment removal due to local slump failures and erosive sediment gravity flows. Levée‐like deposits are present as little as 15 km from the shelf break. At 30 km from the shelf, turbidity currents spilled over a 400 m high ridge and reconfined in a canyon formed by retrogressive failure, where a thalweg channel was developed. These observations imply that turbidity currents evolved rapidly in this slope‐proximal environment and attained flow depths of hundreds of metres over distances of a few tens of kilometres, suggesting turbulent subglacial outwash from tunnel valleys as the principal turbidity current‐generating mechanism.  相似文献   

5.
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   

6.
The Storegga Slide, which occurred ～8100 years ago, is one of the world's largest and best studied exposed submarine landslides. In this study we use novel geomorphometric techniques to constrain the submarine mass movements that have shaped the north-eastern Storegga Slide, understand the link between different forms of failure, and propose a revised development model for this region. According to this model, the north-eastern part of the Storegga Slide has developed in four major events. The first event (event 1) was triggered in water depths of 1500–2000 m. In this event, the surface sediments were removed by debris flows and turbidity currents, and deposited in the Norwegian Sea Basin. Loading of the seabed by sediments mobilised by the debris flows and turbidity currents resulted in the development of an evacuation structure. Loss of support associated with this evacuation structure, reactivation of old headwalls and seismic loading activated spreading in the failure surface of event 1 up to the main headwall (event 2). In some areas, spreading blocks have undergone high displacement and remoulding. Parts of the spreading morphology and the underlying sediment have been deformed or removed by numerous debris flows and turbidity currents (event 3). We suggest that the higher displacement and remoulding of the spreading blocks, and their removal by debris flows and turbidity currents, was influenced by increased pore pressures, possibly due to gas hydrate dissolution/dissociation or by lateral variability in the deposition of contourite drifts in palaoeslide scars. The fourth event entailed a large, blocky debris flow that caused localised compression and transpressive shearing in the southern part of the spreading area.  相似文献   

7.
Overlapping gravity accumulation bodies were formed on the northwestern steep slope of the Shuangyang Formation in the Moliqing fault depression of northeast China. This study analyzed in detail the spatial distribution of the lithofacies and lithofacies associations of these accumulation bodies based on more than 600 m of core sections, and summarized 12 major types of lithofacies and three types of lithofacies associations: (1) the proximal zone consists of gravelly debris flows dominated by alluvial channel conglomerates; (2) the middle zone is dominated by various gravity flow deposits and traction flow deposits; and (3) the distal zone is dominated by mudstones with intercalations of sandy debris and turbidites. Combining with the grain size cumulative probability curves analysis, we determined the transformation of debris flows to sandy debris flows and to turbidity currents in the slope zone of the basin margin, and further proposed a lacustrine slope apron model that is characterized by (1) an inconstant multiple source (line source), (2) an alternation of gravity flow deposits and traction flow deposits dominated by periodical changes in a source flood flow system, and (3) the transformation of sandy debris flow deposits into distal turbidity current deposits. This sedimentary model may be applicable to other fault depressions for predicting reservoir distribution.  相似文献   

8.
ABSTRACT The Wagwater Trough is a fault-bounded basin which cuts across east-central Jamaica. The basin formed during the late Palaeocene or early Eocene and the earliest sediments deposited in the trough were the Wagwater and Richmond formations of the Wagwater Group. These formations are composed of up to 7000 m of conglomerates, sandstones, and shales. Six facies have been recognized in the Wagwater Group: Facies I-unfossiliferous massive conglomerates; Facies II—channelized, non-marine conglomerates, sandstones, and shales; Facies III-interbedded, fossiliferous conglomerates and sandstones; Facies IV—fossiliferous muddy conglomerates; Facies V—channelized, marine conglomerates, sandstones, and shales; and Facies VI—thin-bedded sheet sandstones and shales. The Wagwater and Richmond formations are interpreted as fan delta-submarine fan deposits. Facies associations suggest that humid-region fan deltas prograded into the basin from the adjacent highlands and discharged very coarse sediments on to a steep submarine slope. At the coast waves reworked the braided-fluvial deposits of the subaerial fan delta into coarse sand and gravel beaches. Sediments deposited on the delta-front slope were frequently remobilized and moved downslope as slumps, debris flows, and turbidity currents. At the slope-basin break submarine fans were deposited. The submarine fans are characterized by coarse inner and mid-fan deposits which grade laterally into thin bedded turbidites of the outer fan and basin floor.  相似文献   

9.
Some of the Earth's largest submarine debris flows are found on the NW African margin. These debris flows are highly efficient, spreading hundreds of cubic kilometres of sediment over a wide area of the continental rise where slopes angles are often <1°. However, the processes by which these debris flows achieve such long run‐outs, affecting tens of thousands of square kilometres of seafloor, are poorly understood. The Saharan debris flow has a run‐out of ≈700 km, making it one of the longest debris flows on Earth. For its distal 450 km, it is underlain by a relatively thin and highly sheared basal volcaniclastic layer, which may have provided the low‐friction conditions that enabled its extraordinarily long run‐out. Between El Hierro Island and the Hijas Seamount on the continental rise, an ≈25‐ to 40‐km‐wide topographic gap is present, through which the Saharan debris flow and turbidites from the continental margin and flanks of the Canary Islands passed. Recently, the first deep‐towed sonar images have been obtained, showing dramatic erosional and depositional processes operating within this topographic `gap' or `constriction'. These images show evidence for the passage of the Saharan debris flow and highly erosive turbidity currents, including the largest comet marks reported from the deep ocean. Sonar data and a seismic reflection profile obtained 70 km to the east, upslope of the topographic `gap', indicate that seafloor sediments to a depth of ≈30 m have been eroded by the Saharan debris flow to form the basal volcaniclastic layer. Within the topographic `gap', the Saharan debris flow appears to have been deflected by a low (≈20 m) topographic ridge, whereas turbidity currents predating the debris flow appear to have overtopped the ridge. This evidence suggests that, as turbidity currents passed into the topographic constriction, they experienced flow acceleration and, as a result, became highly erosive. Such observations have implications for the mechanics of long run‐out debris flows and turbidity currents elsewhere in the deep sea, in particular how such large‐scale flows erode the substrate and interact with seafloor topography.  相似文献   

10.
碎屑流与浊流的流体性质及沉积特征研究进展   总被引：5，自引：1，他引：4  
受浊流沉积模式(即鲍马序列和浊积扇模式)的驱动和浊积岩思维定势的影响,自1970s浊流与浊积岩的概念逐渐扩大,特别是通过"高密度浊流"术语的引入,以及将水下浊流与陆上河流的错误类比,使得一部分碎屑流与底流的沉积被认为是浊积岩。随着现代观测设备的应用以及详细的岩芯观察,碎屑流(特别是砂质碎屑流)和浊流被重新认识。浊流是一种具牛顿流变性质和紊乱状态的沉积物重力流,其沉积物支撑机制是湍流。碎屑流是一种具塑性流变性质和层流状态的沉积物重力流,其沉积物支撑机制主要是基质强度和颗粒间的摩擦强度。浊流沉积具特征的正粒序韵律结构,底部为突变接触而顶部为渐变接触;碎屑流沉积一般具上、下两层韵律结构,即下部发育具平行碎屑结构的层流段,上部发育具块状层理的"刚性"筏流段。但当碎屑流被周围流体整体稀释改造且改造不彻底时,强碎屑流可变为中—弱碎屑流,相应自下而上可形成逆—正粒序的沉积韵律结构,其中发育有呈漂浮状的石英颗粒和泥质撕裂屑等碎屑颗粒,明显区别于浊流沉积单一的正粒序韵律结构特征。碎屑流沉积顶、底部均为突变接触。浊流的沉积模式为简单的具平坦盆底的坡底模式,而碎屑流则为复杂的斜坡模式。  相似文献   

11.
The dynamic interpretation of most current-structure sequences derives directly from experiments on the succession of bedforms produced by flows in flumes. The results of these and related studies have been used to construct stability field diagrams in which the fields of individual bedforms are usually expressed as a function of flow intensity (power, velocity, bed shear stress, etc.) and grain size. The data underlying existing stability-field diagrams were collected largely from the study of flows carrying coarse-grained sediment entrained through particle-by-particle bed erosion. Many flows, however, do not entrain sediment through simple bed erosion. Most turbidity currents originate by the development of turbulence in slumps, slides, and other slope failures. Such flows generally form with highly concentrated suspended loads and their bed-load layers derive sediment from the collapsing suspended-sediment clouds. Because the collapse properties of such clouds may be related as much to suspended particle concentration, size distribution, particle interactions, and other factors as to flow intensity, the stability fields of bedforms developed beneath such flows may differ in flow intensity-grain-size relationships from those beneath flows deriving sediment from bed erosion alone. Useful stability-field diagrams for turbidity currents must include suspended-load fallout rate as a third variable, independent of flow intensity and mean grain size. A preliminary stability-field diagram of this type indicates that Bouma Tabc sequences may theoretically form with essentially no velocity variation of the attendant flow. This type of analysis may have considerable relevance to the interpretation not only of turbidites but also of other deposits formed where bed-load layers are fed from above rather than below. These include shallow-shelf storm units deposited from highly concentrated flows and volcaniclastic layers formed where pyroclastic debris falls directly into moving water.  相似文献   

12.
在详细野外剖面工作的基础上,通过岩性特征、沉积构造及沉积序列等的系统观察研究,发现济源盆地下侏罗统鞍腰组重力流沉积由滑塌沉积、砂质碎屑流沉积和浊流沉积构成。滑塌沉积以砂岩和泥岩的混杂、岩层的滑动变形以及泥岩呈碎块被卷入砂岩层中为特征;砂质碎屑流沉积常呈厚层块状,颗粒分选和磨圆较差,杂基较多,可见漂浮于层内的石灰岩砾石;常见的浊流沉积分为2种类型: 具有明显正粒序结构的浊流沉积和砂泥岩薄互层的浊流沉积,可用鲍马序列来描述。鞍腰组重力流沉积可划分为3个沉积序列: 序列A记录了滑塌沉积→砂质碎屑流沉积→浊流沉积→深湖沉积的转换过程;序列B表现为砂质碎屑流与浊流沉积的叠覆;序列C由浊流及湖泊沉积构成,并经历了由序列A→序列B→序列C的沉积演化过程。重力流的形成受秦岭造山带于早侏罗世沿三门峡—鲁山—舞阳断裂发生逆冲推覆作用的控制,其沉积演化指示了秦岭造山带造山作用由强到弱的过程。  相似文献   

13.
L. J. STRACHAN 《Sedimentology》2008,55(5):1311-1332
The process by which slumps transform into other flow types is an understudied phenomenon; generally, sedimentologists have assumed that this is how many debris flows and turbidity currents form, yet there is a paucity of information relating to the specific processes involved. This paper aims to redress this imbalance and investigates the processes of slump flow transformation using a well‐exposed example, where the precursor slump and flows to which it was transforming have been preserved in the outcrop. A detailed field investigation of the Lower Miocene, Little Manly Slump, located within the Waitemata Basin, New Zealand, reveals a complex bi‐partite deposit, comprised of a lower slump‐debrite unit and an upper turbidite unit, separated from one another by an impersistent contact. Reconstruction of slump evolution, from preserved strain indicators, shows that slump motion was unsteady and non‐uniform, and that the slump arrested rapidly. Flow transformation is directly linked to slump evolution and progressed through the multiple processes of body transformation, fluidization transformation and surface transformation. The resultant flow comprised a very dense lower unit with slump and debris flow phases overlain by a turbidity current. This study shows that flow transformation did not result in en masse transformation to a debris flow by a single process, but rather it was characterized by partial transformation of the slump to generate a three‐phase flow. Density is thought to be the key parameter in controlling flow transformation efficiency, which appears to have varied rapidly as a function of slump unsteadiness and non‐uniformity.  相似文献   

14.
Experiments were carried out in a 10 × 6 m basin to simulate turbidity currents generated by the Horgen Slumping Events of 1875. The conditions for kinematic similarity were satisfied and the experiments gave further insight into the mechanics of transport triggered by the Horgen slumps. The experimental turbidity currents laid down thick deposits on a subaqueous fan, and thin sheets of turbidite on the floor of the elongate basin through longitudinal transport, comparable with the simulated deposits in Lake Zurich. It is concluded that longitudinal transport is a general phenomenon of turbidity currents.  相似文献   

15.
Mass transport deposits, up to 3·9 m thick, have been identified from piston cores collected from canyon floors and inter-canyon ridges on the central Scotian Slope. These deposits are characterized by four distinct mass-transport facies – folded mud, dipping stratified mud, various types of mud-clast conglomerate, and diamicton. Commonly, the folded and stratified mud facies are overlain by mud-clast conglomerate, followed by diamicton and then by turbidity current deposits of well-sorted sand. Stratified and folded mud facies were sourced from canyon walls. Overconsolidation in clasts in some mud-clast conglomerates indicates that the source sediment was buried 12–33 m, much deeper than the present cored depth, implying a source in canyon heads and canyon walls. The known stratigraphic framework for the region and new radiocarbon dating suggests that there were four or five episodes of sediment failure within the past 17 ka, most of which are found in more than one canyon system. The most likely mechanism for triggering occasional, synchronous failures in separate canyons is seismic ground shaking. The facies sequence is interpreted as resulting from local slides being overlain by mud-clast conglomerate deposits derived from failures farther upslope and finally by coarser-grained deposits resulting from retrogressive failure re-mobilizing upper slope sediments to form debrisflows and turbidity currents.  相似文献   

16.
为探讨陆相断陷湖盆陡坡带构造活动控制下水下粗碎屑岩沉积特征、搬运机制及其演化规律,以滦平断陷盆地陡坡带下白垩统西瓜园组为研究对象,采用无人机倾斜摄影、实测剖面、砾石定向性定量表征等技术方法,从沉积背景、岩相类型、沉积单元及相序特征等方面开展野外露头解剖工作.滦平盆地西瓜园组沉积时期,近岸水下扇沉积于构造沉降速率大、湖平面上升、深水、古地貌陡峭环境,洪水携带粗碎屑沉积沿陡坡带入湖,底部发育与地震活动相关的砾质碎屑流,伴随发育滑动—滑塌沉积,上部发育高密度浊流.随着沉积物不断供给,斜坡坡度逐渐减小;随着粗碎屑沉积搬运距离不断增加,砂砾质碎屑流中砾石表现出明显定向性,高密度浊流所占厚度比例增加;末端以低密度浊流为主.扇三角洲沉积于构造沉降速率相对较低、水深相对较浅、古地貌相对平缓的环境,发育相对成熟的供源体系,汇水系统长度较长,扇三角洲前缘粗碎屑岩由碎屑流向高密度浊流、牵引流、低密度浊流转换.   相似文献   

17.
Maar eruptions form small initially steep‐walled basins that contain important archives for the climatic and palaeoenvironmental history in continental areas. The two Ukinrek Maars in south‐western Alaska erupted between 30 March and 9 April 1977 and are the best‐documented maars that have erupted in historical time. This study presents a preliminary analysis of geomorphology, hydrology, magnetic susceptibility, geochemistry and sedimentology data of a field study in August 2004. These results, photographs and topographic surveys are combined for reconstructing the post‐eruptive evolution of Ukinrek East Maar. Within less than 30 years the initially polygonal shape of the crater with nearly vertical crater walls has developed into an almost elliptic form with slopes of 35° inclination on debris fans between a few escarpments. The water table and the crater floor have risen significantly and the crater diameter:depth ratio increased from 3·4 to 5·7, whereas the average height of the crater rim remained almost constant. The main sub‐aerial resedimentation process is formation of rock falls, rock slumps and scree resulting in debris flows and turbidites within the lake that is ice‐covered throughout about half of the year. Distal lake sediments consist of laminated minerogenic clayey‐sandy silts that document frequent turbidity currents. From the linear sedimentation rate of only ca 5 mm year?1 in 17 cm long cores it may be concluded that the largest portion of the crater sediments formed within the first few months of the maar history, however, this has to be confirmed by future studies.  相似文献   

18.
Near Williams Lake, in the central interior of British Columbia, the Fraser River exposes long sections of late Pleistocene glaciolacustrine sediments selectively preserved within a bedrock trough. The dominant facies types are thick, normally graded gravels and sands that occupy steeply dipping multistorey channels up to 300 m wide and several tens of metres deep. Channels appear to have been simultaneously cut and filled by high density turbidity currents in a glacial lake floored by stagnant ice. Fining upward sediment gravity flow sequences up to 50 m thick may be the product of quasi-continuous ‘surging’ turbidity flows triggered by catastrophic meltwater discharges into the trough or retrogressive failure of ice-cored sediments. Large-scale post-depositional deformation structures, such as synclinal folds, normal faults, sedimentary dyke swarms and dewatering structures, record gravitational foundering of sediment and pore-water expulsion caused by the melt of underlying glacier ice. Melting of buried ice masses along the floor of the trough appears to have controlled the flow paths of turbidity currents by producing sub-basins within the overlying sediment pile. An idealized model of ‘supraglacial’ lacustrine sedimentation is developed that may be applicable to other glaciated areas with similar bedrock topography.  相似文献   

19.
本文在总结前人对浊流沉积研究的基础上,分析前人对浊流与浊积岩、浊流沉积与浊流相模式的对应关系之间的认识,并对鲍马序列进行重新审视。在海底扇研究过程中,鲍马序列已经不能充分反映浊流沉积的全过程。鲍马序列所反应的沉积模式其实是由碎屑流、浊流、底流等多种形式流体组合和改造后的结果,海底扇沉积模式不能笼统归结为浊流沉积作用的结果。在完善重力流、底流等沉积作用的同时,建立一个与沉积作用相互联系的深海沉积系统,以对深海研究提供更好地指导和预测。  相似文献   

20.
Various deep-water deposits developed in the Yinggehai Basin and Qiongdongnan Basin(Ying-Qiong Basin)in the northern South China Sea,making the two basins significantly hydrocarbon-producing areas and ideal for studying the genetic mechanism and sedimentary characteristics of deep-water clastic rocks.Using cores,image well logging,heavy mineral assemblages,and seismic data,we thoroughly studied the geometry,tectonic background,driving mechanism and source-to-sink process of deep-water deposits in the study area.The results showed that:(1)there were five genetic mechanisms of deep-water clastic rock,i.e.,slides,slumps,debris flows,turbidity currents,and bottom currents.(2)The sliding deposits were distributed from the delta front to the continental slope toe.The slumping deposits were mainly distributed at the continental slope toe or the basin’s central area,far from the delta front The turbidity deposits were widely developed in the deep-water area,but with huge differences in thickness.The bottom currents mainly reworked previous deposits far from the slope.(3)Slip and extension along the preexisting fault zone were the main structural factors that drive the axial channel formation at the slope foot.(4)The sand-rich gravity sediment flows in the Ying-Qiong basin were primarily caused by the direct supply of terrigenous debris into the marine environment over the slope break.  相似文献   

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