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1.
Pindos foreland basin in west Peloponnesus (Tritea, Hrisovitsi and Finikounda sub‐basins) during Late Eocene to Early Oligocene was an underfilled foreland basin. The basin's geometry was affected by the presence of internal thrusting and transfer faults, causing changes in depth and width. Due to internal thrusting, the foreland basin changed through time from a uniform to non‐uniform configuration, whereas transfer faults have an intensive impact on depositional environments within the basin. Internal thrusting (Gavrovo, internal and middle Ionian thrusts) activated synchronously with the major Pindos Thrust, creating intrabasinal highs that influenced palaeocurrent directions. The transfer faults cross‐cut the intrabasinal highs and produced low relief areas that act as pathways for sediment distribution. The sediments are thicker and sandstone‐rich on the downthrown sides of the transfer faults. In these areas, sandstone reservoirs could be produced. Such tectonically active areas constitute promise for oil and gas reservoirs and traps.  相似文献   

2.
西康群是松潘-甘孜复理石沉积盆地的主体,分布范围广、岩性单调,强烈的构造变形和褶皱叠加导致地层原始的沉积序列、沉积构造破坏殆尽,基于野外露头的沉积学研究较少,巨量复理石的沉积模式也没有合理的解释。详细研究了川西马尔康-金川县一带西康群典型剖面的沉积构造、砂板比、古流向、砂岩粒度及矿物组成,讨论了西康群的沉积环境及沉积模式。认为该区复理石沉积环境属于海底扇扇中-扇端,局部存在砂质碎屑流或等深流的参与和叠加改造;存在两期次的海底扇,其触发机制均为海平面下降,导致三角洲向陆架边缘进积形成海底扇,而随着冲积平原及三角洲复合体的逐渐消耗,沉积物供应量逐渐减小,海底扇的规模及影响范围逐渐缩减,形成两期向岸退积的海底扇沉积。松潘-甘孜盆地复理石建造属于受周缘造山带提供多源或线源,多期次叠加的,以细粒浊积体为主的海底扇,海岸冲积平原及三角洲复合体经过二次搬运使得砾级粗粒沉积物进一步破碎,形成中-细粒砂岩及泥岩为主的扇体沉积。  相似文献   

3.
海底扇是由沉积物重力流形成的海底沉积体。其分类学和相模式研究表明,海底扇主要由海底水道、溢岸及朵叶体等沉积单元构成。然而古代和现代海底扇沉积均无法由单一的通用相模式进行解释。以粒度差异所建立的相模式类型涵盖了多方面信息,相对简单实用。海底扇的触发机制主要包括海底沉积物失稳、洪水型异重流、海洋动力过程及复合成因机制等类型。海底扇的主导流体类型（碎屑流与浊流）、海底地貌形态（限制性与非限制性）及海洋动力条件（底流作用）深刻影响了海底扇的沉积作用、平面形态及空间组合特征,整体上分为三类。其中,浊流沉积主导的海底扇在非限制性海底环境中主要表现为扇状或指状形态,在限制性海底环境中则直接受控于盆地的地貌形态;碎屑流沉积主导的海底扇以块体搬运为特征,平面上表现为舌状和叶状展布形态;底流与重力流共同作用形成的混合型海底扇朵叶体沿底流流向侧向偏转,部分受底流改造沉积形成孤立漂积丘状形态。海底扇沉积物记录了环境信号从“源”到“汇”传输效率和保存程度,对构造变形和古气候变化具有重要的指示作用。人类世以来的现代海底扇沉积物同时也是深海微塑料、陆源有机碳的重要储库,定量评估其丰度特征对于环境评价、污染治理与管控及全球碳循环均具有深远的现实意义。  相似文献   

4.
林畅松  刘景彦  胡博 《沉积学报》2010,28(5):868-874
应用二维层序地层模拟系统开展了构造活动盆地沉积层序的形成过程的动态模拟分析,揭示了同沉积断裂活动、湖平面变化及沉积物供给量变化相互作用对沉积层序形成的控制作用。模拟表明,快速的构造沉降、相对高的湖平面和大量的沉积物供给是形成相对深水扇三角洲的必要条件;而沉积物的供给量变小或构造沉降量加大时有利于形成近岸湖底扇或水下扇。模拟揭示出断陷湖盆陡坡边缘断裂形成的古地貌坡折控制着低水位域浊积扇或湖底扇的发育部位,同时对水进或高位域的三角洲前缘的沉积中心的分布具控制作用。断裂坡折带的构造沉降是控制可容纳空间变化的关键因素。在陆内前陆逆冲构造边缘,层序发育早期（底部）发育冲积扇和河流沉积,但由于相对快的构造沉降形成水进序列;在快速沉降的晚期沉降速率减小,碎屑体系向盆地方向推进,形成广泛河流三角洲沉积。由隐伏逆冲断裂形成的构造坡折带对低位域的分布具控制作用。在构造坡折带下的低位域砂体与上覆的水进域泥岩组合可形成重要的地层油气藏。  相似文献   

5.
J. R. INESON 《Sedimentology》1989,36(5):793-819
The Cretaceous of west James Ross Island, Antarctica represents the proximal fill of a late Mesozoic back-arc basin that was probably initiated by oblique extension during the early development of the Weddell Sea. The succession records sedimentation in two contrasting depositional systems: a laterally persistent slope apron flanking the faulted basin margin interrupted both spatially and temporally by coarse-grained submarine fans. Slope apron deposits are dominated by thinly interbedded turbiditic sandstones and mudstones (mudstone association), interspersed with non-channelized chaotic boulder beds, intraformational slump sheets and isolated exotic blocks representing a spectrum of mass-flow processes from debris flow to submarine gliding. Localized sand-rich sequences (sandstone-breccia association) represent sandy debris lobes at the mouths of active slope chutes. The submarine fan sediments (conglomerate association) are typified by coarse conglomerates and pebbly sandstones, interpreted as the deposits of high-density turbidity currents and non-cohesive debris flows. Three assemblages are recognized and are suggested to represent components of the inner channelled zone of coarse-grained submarine fans, from major fan channels through ephemeral, marginal channels or terraces to levee or interchannel environments. The occurrence of both slope apron and submarine fan depositional systems during the Early and Mid-Cretaceous is attributed to localized input of coarse arc-derived sediment along a tectonically active basin margin. Periods of extensive fan development were probably linked to regional tectonic uplift and rejuvenation of the arc source region; cyclicity within individual fan sequences is attributed to migration or switching of fan channels or canyons. Slope apron sedimentation was controlled largely by intrabasinal tectonics. Local unconformities and packets of amalgamated slide sheets and debris flow deposits probably reflect episodic movement on basin margin faults. Differential subsidence across the basin margin anchored the basin slope for at least 20 Myr and precluded basinward progradation of shallow marine environments.  相似文献   

6.
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   

7.
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   

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.
The Late Cretaceous Gürsökü Formation represents the proximal fill of the Sinop–Samsun Forearc Basin that was probably initiated by extension during the Early Cretaceous. The succession records sedimentation in two contrasting depositional systems: a slope-apron flanking a faulted basin margin and coarse-grained submarine fans. The slope-apron deposits consist of thinly bedded turbiditic sandstones and mudstones, interbedded with non-channelized chaotic boulder beds and intraformational slump sheets representing a spectrum of processes ranging from debris flow to submarine slides. The submarine fan sediments are represented by conglomerates and sandstones interpreted as deposited from high density turbidity currents and non-cohesive debris flows. The occurrence of both slope apron and submarine fan depositional systems in the Gürsökü Formation may indicates that the region was a tectonically active basin margin during the Late Cretaceous.  相似文献   

10.
This paper presents a model of facies distribution within a set of early Cretaceous, deep‐lacustrine, partially confined turbidite fans (Sea Lion Fan, Sea Lion North Fan and Otter Fan) in the North Falkland Basin, South Atlantic. As a whole, ancient deep‐lacustrine turbidite systems are under‐represented in the literature when compared with those documented in marine basins. Lacustrine turbidite systems can form extensive, good quality hydrocarbon reservoirs, making the understanding of such systems crucial to exploration within lacustrine basins. An integrated analysis of seismic cross‐sections, seismic amplitude extraction maps and 455 m of core has enabled the identification of a series of turbidite fans. The deposits of these fans have been separated into lobe axis, lobe fringe and lobe distal fringe settings. Seismic architectures, observed in the seismic amplitude extraction maps, are interpreted to represent geologically associated heterogeneities, including: feeder systems, terminal mouth lobes, flow deflection, sinuous lobe axis deposits, flow constriction and stranded lobe fringe areas. When found in combination, these architectures suggest ‘partial confinement’ of a system, something that appears to be a key feature in the lacustrine turbidite setting of the North Falkland Basin. Partial confinement of a system occurs when depositionally generated topography controls the flow‐pathway and deposition of subsequent turbidite fan deposits. The term ‘partial confinement’ provides an expression for categorising a system whose depositional boundaries are unconfined by the margins of the basin, yet exhibit evidence of internal confinement, primarily controlled by depositional topography. Understanding the controls that dictate partial confinement; and the resultant distribution of sand‐prone facies within deep‐lacustrine turbidite fans, is important, particularly considering their recent rise as hydrocarbon reservoirs in rift and failed‐rift settings.  相似文献   

11.
Flume experiments were performed to study the flow properties and depositional characteristics of high‐density turbidity currents that were depletive and quasi‐steady to waning for periods of several tens of seconds. Such currents may serve as an analogue for rapidly expanding flows at the mouth of submarine channels. The turbidity currents carried up to 35 vol.% of fine‐grained natural sand, very fine sand‐sized glass beads or coarse silt‐sized glass beads. Data analysis focused on: (1) depositional processes related to flow expansion; (2) geometry of sediment bodies generated by the depletive flows; (3) vertical and horizontal sequences of sedimentary structures within the sediment bodies; and (4) spatial trends in grain‐size distribution within the deposits. The experimental turbidity currents formed distinct fan‐shaped sediment bodies within a wide basin. Most fans consisted of a proximal channel‐levee system connected in the downstream direction to a lobe. This basic geometry was independent of flow density, flow velocity, flow volume and sediment type, in spite of the fact that the turbidity currents of relatively high density were different from those of relatively low density in that they exhibited two‐layer flow, with a low‐density turbulent layer moving on top of a dense layer with visibly suppressed large‐scale turbulence. Yet, the geometry of individual morphological elements appeared to relate closely to initial flow conditions and grain size of suspended sediment. Notably, the fans changed from circular to elongate, and lobe and levee thickness increased with increasing grain size and flow velocity. Erosion was confined to the proximal part of the leveed channel. Erosive capacity increased with increasing flow velocity, but appeared to be constant for turbidity currents of different grain size and similar density. Structureless sediment filled the channel during the waning stages of the turbidity currents laden with fine sand. The adjacent levee sands were laminated. The massive character of the channel fills is attributed to rapid settling of suspension load and associated suppression of tractional transport. Sediment bypassing prevailed in fan channels composed of very fine sand and coarse silt, because channel floors remained fully exposed until the end of the experiments. Lobe deposits, formed by the fine sand‐laden, high‐density turbidity currents, contained massive sand in the central part grading to plane parallel‐laminated sand towards the fringes. The depletive flows produced a radial decrease in mean grain size in the lobe deposits of all fans. Vertical trends in grain size comprised inverse‐to‐normal grading in the levees and in the thickest part of the lobes, and normal grading in the channel and fringes of the fine sandy fans. The inverse grading is attributed to a process involving headward‐directed transport of relatively fine‐grained and low‐concentrated fluid at the level of the velocity maximum of the turbidity current. The normal grading is inferred to denote the waning stage of turbidity‐current transport.  相似文献   

12.
日喀则群砂泥质复理石的浊积层序非常发育,包括富泥的粘性高密度浊流、砂质高密度浊流、低密度浊流和Pickering及Hiscott(1986)的限制性泥质高密度浊流的沉积层序。其中,低密度浊流沉积层序的组合与鲍马(Bouma)层序很相似,两者的区别在于沉积的粒度、粒级分布范围、层序厚度和相组合等特征的不同。沉积相序、古流向和物源分析表明,日喀则群复理石盆地的南侧主要发育单向物源的海底扇体系,而盆地北侧以发育双向物源和多种沉积流体的复合沉积为特征。值得指出的是,特殊的浊积类型——限制性泥质高密度浊流沉积的发现为论证日喀则群复理石盆地属残留盆地又提供了一条有力的依据。  相似文献   

13.
Along the West Greenland continental margin adjoining Baffin Bay, bathymetric data show a series of large submarine fans located at the mouths of cross‐shelf troughs. One of these fans, termed here ‘Uummannaq Fan’, is a trough‐mouth fan built largely by debris delivered from a fast‐flowing outlet of the Greenland Ice Sheet during past glacial maxima. Cores from this fan provide the first information on glacimarine sedimentary facies within a major West Greenland trough‐mouth fan and on the nature of Late Weichselian–Holocene glacigenic sediment delivery to this region of the Baffin Bay margin. Glacigenic debris flows deposited on the upper slope and extending to at least 1800 m water depth in front of the trough‐mouth are related to the remobilization of subglacial debris that was delivered onto the upper slope at times when an ice stream was positioned at the shelf edge. In contrast, sedimentary facies from the northern sector of the fan are characterized by hemipelagic and ice‐rafted sediments and turbidites; glacigenic debris flows are notably absent in cores from this region. Quantitative X‐ray diffraction studies of the <2‐mm sediment fraction indicate that the bulk of the sediment in the fan is derived from Uummannaq Trough but there are distinct intervals when sediment from northern Baffin Bay sources dominates, especially on the northern limit of the fan. These data demonstrate considerable variation in the nature of sediment delivery across the Uummannaq Fan when the Greenland Ice Sheet was at the shelf edge. They highlight the variability of glacimarine depositional processes operating on trough‐mouth fans on high‐latitude continental margins during the last glacial maximum and indicate that glacigenic debris flows are just one of a number of mechanisms by which such large depocentres form. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

14.
Climate and tectonics play important roles in controlling processes of transport and deposition on alluvial fans, but the bedrock lithology in the fan catchment area is also a significant, independent factor. Adjacent Oligo-Miocene alluvial fan deposits on the northern margin of the Ebro Basin display contrasting depositional characteristics with one dominated by the deposits of debris flows and the other by deposition from flows of water. A difference in clast compositions indicates that the two studied fans (the Nueno and San Julián fans) had contrasting bedrock lithology in their drainage basins. The proximal facies of the Nueno fan body contains matrix-supported conglomerate beds with up to 80% pebble clasts of gypsum in a matrix of gypsiferous sand, interbedded with gypsarenite beds. The drainage basin of this fan was dominated by Triassic bedrock consisting of beds of gypsum, marl and micritic limestone. The San Julián fan body comprises clast-supported, polymict conglomerate beds containing pebbles from Triassic, Cretaceous and Palaeogene limestone units that are exposed in the adjacent part of the basin margin. The interfingering of the deposits of these two fans demonstrates that they were contemporaneous. Given the consistent climate, the differences in fan depositional processes must therefore be attributed to the contrasting bedrock lithology in their drainage basins. A drainage basin consisting mainly of marl and gypsum bedrock provided sufficient fine-grained material to generate debris flows, whereas more dilute, water-lain processes dominated where the drainage basin was largely limestone strata.  相似文献   

15.
Normark  Piper  & Hiscott 《Sedimentology》1998,45(1):53-70
Hueneme and Dume submarine fans in Santa Monica Basin consist of sandy channel and muddy levee facies on the upper fan, lenticular sand sheets on the middle fan, and thinly bedded turbidite and hemipelagic facies elsewhere. Fifteen widely correlatable key seismic reflections in high-resolution airgun and deep-towed boomer profiles subdivide the fan and basin deposits into time-slices that show different thickness and seismic-facies distributions, inferred to result from changes in Quaternary sea level and sediment supply. At times of low sea level, highly efficient turbidity currents generated by hyperpycnal flows or sediment failures at river deltas carry sand well out onto the middle-fan area. Thick, muddy flows formed rapidly prograding high levees mainly on the western (right-hand) side of three valleys that fed Hueneme fan at different times; the most recently active of the lowstand fan valleys, Hueneme fan valley, now heads in Hueneme Canyon. At times of high sea level, fans receive sand from submarine canyons that intercept littoral-drift cells and mixed sediment from earthquake-triggered slumps. Turbidity currents are confined to ‘underfit’ talweg channels in fan valleys and to steep, small, basin-margin fans like Dume fan. Mud is effectively separated from sand at high sea level and moves basinward across the shelf in plumes and in storm-generated lutite flows, contributing to a basin-floor blanket that is locally thicker than contemporary fan deposits and that onlaps older fans at the basin margin. The infilling of Santa Monica Basin has involved both fan and basin-floor aggradation accompanied by landward and basinward facies shifts. Progradation was restricted to the downslope growth of high muddy levees and the periodic basinward advance of the toe of the steeper and sandier Dume fan. Although the region is tectonically active, major sedimentation changes can be related to eustatic sea-level changes. The primary controls on facies shifts and fan growth appear to be an interplay of texture of source sediment, the efficiency with which turbidity currents transport sand, and the effects of delta distributary switching, all of which reflect sea-level changes.  相似文献   

16.
Calciclastic submarine fans are rare in the stratigraphic record and no bona fide present-day analogue has been described to date. Possibly because of that, and although calciclastic submarine fans have long intrigued deep-water carbonate sedimentologists, they have largely been overlooked by the academic and industrial communities. To fill this gap we have compiled and critically reviewed the existing sedimentological literature on calciclastic submarine fans, thus offering an updated view of this type of carbonate slope sedimentary system.Calciclastic submarine fans range in length from just a few to more than 100 km. Three different types can be distinguished: (1) Coarse-grained, small-sized (< 10 km) fans, which are characterized by the abundance of calcirudites and the scarcity of mud. They have relatively long leveed channels and small radial lobes. (2) Medium-grained, medium-sized fans are typified by the abundance of calcarenites and lesser amounts of calcirudites and mud. They have a tributary network of slope gullies, which merge to form a leveed channel that opens to the main depositional site, characterized by extensive lobes and/or sheets, which eventually pass into basinal deposits through a narrow fan-fringe area. These fans are between 10 and 35 km in length. (3) Fine-grained, large-sized fans are rich in calcarenites and mud, but poor in calcirudites. They have wide and long slope channels that feed very extensive calciturbiditic sheets, the total length always exceeding 50 km and generally being close to 100 km. In terms of grain-size distribution the three fan types compare well with sand/gravel-rich, mud/sand-rich and mud-rich siliciclastic submarine fans, respectively. However, they show notable differences in terms of size and sedimentary architecture, a reflection of the different behaviour of their respective sediment gravity flows.Most calciclastic submarine fans were formed on low-angle slopes and were sourced from distally steepened carbonate ramps subjected to high-energy currents. Under these conditions shallow-water loose grainy sediments were transferred to the ramp slope and eventually funnelled into the submarine fan by sediment gravity flows. These conditions seem to have been more easily met on leeward margins in which the formation of reefs was hampered by cool waters, nutrient enrichment or oligophoty. Another circumstance that contributes to the transfer of shallow-water sediments to the distal ramp slope is a low sea level, forcing the carbonate factory closer to the slope break and destabilizing sediments by increased pore-water pressure. However, the most important factor controlling the development of calciclastic submarine fans was the existence of an efficient funnelling mechanism forcing sediment gravity flows to merge downslope and build up a point-sourced sedimentary accumulation. In most cases this occurred through a major slope depression associated with tectonic structures, an inherited topography, or large-scale mass failures.  相似文献   

17.
Eleven lithofacies and five lithofacies associations were indentified in the Miocene Zhujiang Formation on the basis of detailed core analysis.It could be determined that three depositional types developed,namely submarine fan,basin and deep-water traction current.Six microfacies were further recognized within the fan,including main channels in the inner fan,distributary channels in the middle fan,inter-channels,levees and the outer fan.The lower Zhujiang Formation,mainly sandstone associations,was inner fan and inner-middle fan deposits of the basin fan and the slope fan. The middle part,mainly mudstone associations,was outer fan deposits.With the transgression,the submarine fan was finally replaced by the basinal pelagic deposits which were dominated by mudstone associations,siltstone associations,and deep-water limestone associations.During the weak gravity flow activity,the lower channels,the middle-upper outer fans and basin deposits were strongly modified by the deep-water traction current.The identification of the deep-water traction deposition in Miocene Zhujiang Formation would be of great importance.It could be inferred that the deep-water traction current had been existing after the shelf-break formation since the Late Oligocene (23.8 Ma) in the Baiyun sag,influencing and controlling the sediment composition,the distribution, and depositional processes.It would provide great enlightenment to the paleo-oceanic current circulation in the northern South China Sea.  相似文献   

18.
渤海湾含油气盆地中的浊积岩   总被引：9，自引：1，他引：9  
随着我国对油气藏勘探的深入,在渤海湾含油气盆地中相继发现了一些浊流沉积体--浊积扇。由于浊积扇位于深湖区,插人湖盆腹地生油区,它本身又有较好的储油物性,因此,研究浊积扇的沉积特征及其含油性,对油气勘探具有重要的现实意义。  相似文献   

19.
西藏沙丁、荣布地区三叠系—老第三系沉积地质特征   总被引：1，自引：1，他引：0  
研究区从三叠纪到老第三纪,发育的岩石地层主要有确哈拉群（Ｔ３）、希湖群（Ｊ１－２）、拉贡塘组（Ｊ２－３）、多尼组（Ｋ１）、竟柱山组（Ｋ２）和牛堡组（Ｅ２－３）。在沉积相上,经历了从深水沉积到浅水直至陆相沉积的演变,发育有冲积扇、河流、湖泊、三角洲（潮汐）、障壁海岸、浅海、深海和火山碎屑流沉积。古地理分析表明,研究区晚三叠世古地理轮廓是一个从东南向西北和东北方向由浅水碳酸盐台地及深水陆层海底扇沉积共同发育的沉积盆地;早中侏罗世,演变成为一个由深水砂质浊积岩和细屑浊积岩组成的水下席状体沉积;进入中晚侏罗世,其古地理表现为一个陆屑浅海有障壁海岸;到了晚白垩世,研究区表现为以含煤沉积为特征的三角洲相沉积。  相似文献   

20.
陇东地区上三叠统延长组早中期物源分析与沉积体系   总被引：19，自引：1，他引：18  
利用轻重矿物组合特征、古水流方向、砂岩岩石学特征、水下分流河道砂体空间展布及沉积构造特征等,对鄂尔多斯盆地陇东地区上三叠统延长组长8-长6油层组母岩类型、物源方向以及沉积体系进行研究。古流向参数表明,延长组沉积时期,沉积物从盆地边部向中心搬运。根据轻重矿物组合划分出3个主要物源方向,即西、西南和东北方向。此外,根据古流向判断有南部的次要物源。母岩是盆地周缘的前寒武系石英岩、中基性、中酸性火山岩、变质岩和古生界的浅变质岩、碳酸盐岩和砂砾岩。陇东地区上三叠统延长组长8-长6油层组沉积体系划分为:北东向吴旗-华池三角洲沉积体系和西部环县扇三角洲沉积体系,西南部镇原-泾川辫状河三角洲沉积体系和南部合水-固城川浊积扇沉积体系。在沉积体系划分的基础上,详细阐述了不同沉积体系的岩石学特征、砂体形态和沉积构造及各沉积体系的演化过程。   相似文献   

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