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1.
Facies model for a coarse‐grained,tide‐influenced delta: Gule Horn Formation (Early Jurassic), Jameson Land,Greenland 
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下载免费PDF全文 Christian Haug Eide John A. Howell Simon J. Buckley Allard W. Martinius Bjørn Terje Oftedal Gijs A. Henstra 《Sedimentology》2016,63(6):1474-1506
Tide‐dominated deltas have an inherently complex distribution of heterogeneities on several different scales and are less well‐understood than their wave‐dominated and river‐dominated counterparts. Depositional models of these environments are based on a small set of ancient examples and are, therefore, immature. The Early Jurassic Gule Horn Formation is particularly well‐exposed in extensive sea cliffs from which a 32 km long, 250 m high virtual outcrop model has been acquired using helicopter‐mounted light detection and ranging (LiDAR). This dataset, combined with a set of sedimentological logs, facilitates interpretation and measurement of depositional elements and tracing of stratigraphic surfaces over seismic‐scale distances. The aim of this article is to use this dataset to increase the understanding of depositional elements and lithologies in proximal, unconfined, tide‐dominated deltas from the delta plain to prodelta. Deposition occurred in a structurally controlled embayment, and immature sediments indicate proximity to the sediment source. The succession is tide dominated but contains evidence for strong fluvial influence and minor wave influence. Wave influence is more pronounced in transgressive intervals. Nine architectural elements have been identified, and their internal architecture and stratigraphical distribution has been investigated. The distal parts comprise prodelta, delta front and unconfined tidal bar deposits. The medial part is characterized by relatively narrow, amalgamated channel fills with fluid mud‐rich bases and sandier deposits upward, interpreted as distributary channels filled by tidal bars deposited near the turbidity maximum. The proximal parts of the studied system are dominated by sandy distributary channel and heterolithic tidal‐flat deposits. The sandbodies of the proximal tidal channels are several kilometres wide and wider than exposures in all cases. Parasequence boundaries are easily defined in the prodelta to delta‐front environments, but are difficult to trace into the more proximal deposits. This article illustrates the proximal to distal organization of facies in unconfined tide‐dominated deltas and shows how such environments react to relative sea‐level rise. 相似文献
2.
平沟矿区山西组潮控三角洲—河流沉积及聚煤特点 总被引：3，自引：0，他引：3
通过野外和室内研究,提出山西组形成于河流—潮控三角洲环境。河流沉积包括辫状曲流河和高弯度曲流河。潮控三角洲以潮汐沉积发育为标志,潮汐沙坝、潮河道构成其沉积骨架,揭示了沉积期仍受海水内泛影响。煤聚积发生在河道岸后边缘沼泽环境、废弃潮汐沙坝上发育起来的潮坪环境及分流间湾充填变浅形成的泥炭沼泽环境。总结了不同沉积环境的聚煤特点。 相似文献
3.
The upper Hawkesbury River, New South Wales, Australia: a Holocene example of an estuarine bayhead delta 总被引：1，自引：0，他引：1
Holocene deposits of the Hawkesbury River estuary, located immediately north of Sydney on the New South Wales coast, record the complex interplay between sediment supply and relative sea-level rise within a deeply incised bedrock-confined valley system. The present day Hawkesbury River is interpreted as a wave-dominated estuarine complex, divisible into two broad facies zones: (i) an outer marine-dominated zone extending 6 km upstream from the estuary mouth that is characterized by a large, subtidal sandy flood-tidal delta. Ocean wave energy is partially dissipated by this flood-tidal delta, so that tidal level fluctuations are the predominant marine mechanism operating further landward; (ii) a river-dominated zone that is 103 km long and characterized by a well developed progradational bayhead delta that includes distributary channels, levees, and overbank deposits. This reach of the Hawkesbury River undergoes minor tidal level fluctuations and low fluvial runoff during baseflow conditions, but experiences strong flood flows during major runoff events. Fluvial deposits of the Hawkesbury River occur upstream of this zone. The focus of this paper is the Hawkesbury River bayhead delta. History of deposition within this delta over the last c. 12 ka is interpreted from six continuous cores located along the upper reaches of the Hawkesbury River. Detailed sedimentological analysis of facies, whole-core X-ray analysis of burrow traces and a chronostratigraphic framework derived from 10 C-14 dates reveal four stages of incised-valley infilling in the study area: (1) before 17 ka BP, a 0–1 m thick deposit of coarse-grained fluvial sand and silt was laid down under falling-to-lowstand sea level conditions; (2) from 17 to 6·5 ka BP, a 5–10 m thick deposit composed of fine-grained fluvial sand and silt, muddy bayhead delta and muddy central-basin deposits developed as the incised valley was flooded during eustatic sea-level rise; (3) during early highstand, between 6·5 and 3 ka BP, a 3–8 m thick bed of interbedded muddy central-basin deposits and sandy river flood deposits, formed in association with maximum flooding and progradation of sandy distributary mouth-bar deposits commenced; (4) since 3 ka BP, fluvial deposits have prograded toward the estuary mouth in distributary mouth-bar, interdistributary-bay and bayhead-delta plain environments to produce a 5–15 m thick progradational to aggradational bayhead-delta deposit. At the mouth of the Hawkesbury estuary subaqueous fluvial sands interfinger with and overlie marine sands. The Hawkesbury River bayhead-delta depositional succession provides an example of the potential for significant variation of facies within the estuarine to fluvial segment of incised-valley systems. 相似文献
4.
LUIS A. BUATOIS NUBIA SANTIAGO MEYLIN HERRERA PIRET PLINK‐BJÖRKLUND RON STEEL MARÍA ESPIN KAOLU PARRA 《Sedimentology》2012,59(5):1568-1612
Analysis of Neogene cores from the Eastern Venezuela Basin along 65 km of a west–east trending shoreline allows characterization of the sedimentological and ichnological signatures of wave, river and tidal processes. The area displays deltas prograding northward from the Guyana Shield. Twenty‐three facies are defined and grouped into four categories (wave‐influenced, river‐influenced, tide‐influenced and basinal). Wave‐dominated deltaic deposits occur mostly in the Tácata Field. The delta plain was characterized by tide‐influenced distributary channels separated by interdistributary bays. Fluvial discharge in the delta front and prodelta was repeatedly interrupted by storm‐wave reworking and suspended sediment fallout. Delta‐front and prodelta deposits contain some ichnotaxa that typically do not occur in brackish water (for example, Chondrites and Phycosiphon). Amalgamated storm deposits are unburrowed or contain vertical Ophiomorpha. Lateral (especially on the updrift side) to the river mouths, waves caused nearly continuous accretion of the associated strandplains. These deposits are the most intensely bioturbated, and are dominated by the estenohaline echinoid‐generated ichnogenus Scolicia. River‐dominated deltaic deposits are present in the Santa Bárbara, Mulata, Carito and El Furrial Fields. Low‐sinuosity rivers characterized the alluvial plain, whereas the subaerial delta plain was occupied by higher‐sinuosity rivers. The subaqueous delta plain includes distributary channels and tide‐influenced interdistributary bays. Further seaward, successions are characterized by terminal distributary‐channel and distributary mouth‐bar deposits, as well as by delta‐front and prodelta deposits showing evidence of sediment gravity‐flow and fluid‐mud emplacement. Delta‐front and prodelta deposits are unbioturbated to sparsely bioturbated, suggesting extreme stress, mostly as a result of high fluvial discharge and generation of sediment gravity flows. Tidal influence is restricted to interdistributary bays, lagoons and some distributary channels. From an ichnological perspective, and in order of decreasing stress levels, four main depositional settings are identified: river‐dominated deltas, tide‐influenced delta plains, wave‐dominated deltas and wave‐dominated strandplain–offshore complexes. 相似文献
5.
笔者对钻井和测井资料综合分析认为：陇东华池油田延长组长3油层组形成于湖盆逐渐萎缩、三角洲沉积不断向湖盆进积期,主要发育有三角洲平原分流河道、洪泛平原、三角洲前缘水下分流河道、河口坝、复合式坝、远砂坝和分流间湾等沉积微相,沉积环境由三角洲前缘演变为三角洲平原,储层砂体主要为三角洲前缘的水下分流河道、河口坝和复合式坝砂岩。沉积微相对城华地区延长组长3油层组含油气性的控制主要表现在3个方面：①沉积微相控制着生储盖的组合;②沉积微相控制着储层砂体的展布;③沉积微相影响着储层的储集性能。 相似文献
6.
Recognition criteria,characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation,Argentina) 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 Marcello Gugliotta Stephen S. Flint David M. Hodgson Gonzalo D. Veiga 《Sedimentology》2016,63(7):1971-2001
The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes, a tract known as the fluvial to marine transition zone, which varies between systems due to the relative strength of these processes. To understand how fluvial and tidal process interactions and the fluvial to marine transition zone are preserved in the rock record, large‐scale outcrops of deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated. Fluvial–tidal indicators consist of cyclically distributed carbonaceous drapes in unidirectional, seaward‐oriented cross‐stratifications, which are interpreted as the result of tidal modulation of the fluvial current in the inner part of the fluvial to marine transition zone. Heterolithic deposits with decimetre‐scale interbedding of coarser‐grained and finer‐grained facies with mixed fluvial and tidal affinities are interpreted to indicate fluvial discharge fluctuations (seasonality) and subordinate tidal influence. Many other potential tidal indicators are argued to be the result of fluvial–tidal interactions with overall fluvial dominance or of purely fluvial processes. No purely tidal or tide‐dominated facies were recognized in the studied deposits. Moreover, fluvial–tidal features are found mainly in deposits interpreted as interflood (forming during low river stage) in distal (delta front) or off‐axis (interdistributary) parts of the system. Along major channel axes, the interpreted fluvial to marine transition zone is mainly represented by the fluvial‐dominated section, whereas little or no tide‐dominated section is identified. The system is interpreted to have been hyposynchronous with a poorly developed turbidity maximum. These conditions and the architectural elements described, including major and minor distributary channels, terminal distributary channels, mouth bars and crevasse mouth bars, are consistent with an interpretation of a fluvial‐dominated, tide‐influenced delta system and with an estimated short backwater length and inferred microtidal conditions. The improved identification of process interactions, and their preservation in ancient fluvial to marine transition zones, is fundamental to refining interpretations of ancient deltaic successions. 相似文献
7.
The lower part of the Cretaceous Sego Sandstone Member of the Mancos Shale in east‐central Utah contains three 10‐ to 20‐m thick layers of tide‐deposited sandstone arranged in a forward‐ and then backward‐stepping stacking pattern. Each layer of tidal sandstone formed during an episode of shoreline regression and transgression, and offshore wave‐influenced marine deposits separating these layers formed after subsequent shoreline transgression and marine ravinement. Detailed facies architecture studies of these deposits suggest sandstone layers formed on broad tide‐influenced river deltas during a time of fluctuating relative sea‐level. Shale‐dominated offshore marine deposits gradually shoal and become more sandstone‐rich upward to the base of a tidal sandstone layer. The tidal sandstones have sharp erosional bases that formed as falling relative sea‐level allowed tides to scour offshore marine deposits. The tidal sandstones were deposited as ebb migrating tidal bars aggraded on delta fronts. Most delta top deposits were stripped during transgression. Where the distal edge of a deltaic sandstone is exposed, a sharp‐based stack of tidal bar deposits successively fines upward recording a landward shift in deposition after maximum lowstand. Where more proximal parts of a deltaic‐sandstone are exposed, a sharp‐based upward‐coarsening succession of late highstand tidal bar deposits is locally cut by fluvial valleys, or tide‐eroded estuaries, formed during relative sea‐level lowstand or early stages of a subsequent transgression. Estuary fills are highly variable, reflecting local depositional processes and variable rates of sediment supply along the coastline. Lateral juxtaposition of regressive deltaic deposits and incised transgressive estuarine fills produced marked facies changes in sandstone layers along strike. Estuarine fills cut into the forward‐stepped deltaic sandstone tend to be more deeply incised and richer in sandstone than those cut into the backward‐stepped deltaic sandstone. Tidal currents strongly influenced deposition during both forced regression and subsequent transgression of shorelines. This contrasts with sandstones in similar basinal settings elsewhere, which have been interpreted as tidally influenced only in transgressive parts of depositional successions. 相似文献
8.
Fluvial to tidal transition in proximal,mixed tide‐influenced and wave‐influenced deltaic deposits: Cretaceous lower Sego Sandstone,Utah, USA 下载免费PDF全文
下载免费PDF全文 Marijn van Cappelle Stephen Stukins Gary J. Hampson Howard D. Johnson 《Sedimentology》2016,63(6):1333-1361
Facies models for regressive, tide‐influenced deltaic systems are under‐represented in the literature compared with their fluvial‐dominated and wave‐dominated counterparts. Here, a facies model is presented of the mixed, tide‐influenced and wave‐influenced deltaic strata of the Sego Sandstone, which was deposited in the Western Interior Seaway of North America during the Late Cretaceous. Previous work on the Sego Sandstone has focused on the medial to distal parts of the outcrop belt where tides and waves interact. This study focuses on the proximal outcrop belt, in which fluvial and tidal processes interact. Five facies associations are recognized. Bioturbated mudstones (Facies Association 1) were deposited in an offshore environment and are gradationally overlain by hummocky cross‐stratified sandstones (Facies Association 2) deposited in a wave‐dominated lower shoreface environment. These facies associations are erosionally overlain by tide‐dominated cross‐bedded sandstones (Facies Association 4) interbedded with ripple cross‐laminated heterolithic sandstones (Facies Association 3) and channelized mudstones (Facies Association 5). Palaeocurrent directions derived from cross‐bedding indicate bidirectional currents which are flood‐dominated in the lower part of the studied interval and become increasingly ebb‐directed/fluvial‐directed upward. At the top of the succession, ebb‐dominated/fluvial‐dominated, high relief, narrow channel forms are present, which are interpreted as distributary channels. When distributary channels are abandoned they effectively become estuaries with landward sediment transport and fining trends. These estuaries have sandstones of Facies Association 4 at their mouth and fine landward through heterolithic sandstones of Facies Association 3 to channelized mudstones of Facies Association 5. Therefore, the complex distribution of relatively mud‐rich and sand‐rich deposits in the tide‐dominated part of the lower Sego Sandstone is attributed to the avulsion history of active fluvial distributaries, in response to a subtly expressed allogenic change in sediment supply and relative sea‐level controls and autocyclic delta lobe abandonment. 相似文献
9.
早更新世晚期(加拉米洛亚时开始到松山时结束)，中国东部陆架发生海侵。随着海侵的推进，在南黄海中部出现了较厚的三角洲沉积。在沉积层的垂直序列上，发现了分流河口沙坝、分流河道和分流河口间湾等三角洲前缘沉积亚相的交替。这是一个海侵序列的三角洲层序。在海侵进程中三角洲的进积速率与海水进侵速率基本平衡。南黄海晚松山时古长江三角洲的发现，从一个侧面证明了浙闽隆起带在早期第四纪仍然是继承晚第三纪的一个构造上的隆起及地貌上的屏障，它制约着古长江流向东北方向。 相似文献
10.
This paper presents examples of various large tidal sandbodies from the Eocene Roda Sandstone in the southern Pyrenees and the Late Pleistocene and Early Holocene in the East China Sea. An attempt is made to summarize the geometric variability of these large tidal sandbodies in relation to the sediment supply and tidal discharge of the depositional system. Transverse sand bars were developed in low-sinuosity, high-gradient channels with high influxes of coarse sediments and water from fluvial systems. Tidal point bars were formed in meandering low-gradient estuarine channel where tidal influence was stronger and sediment was finer than those of the transverse sand bar. A tidal delta complex was built up at the estuary mouth with an abundant sediment supply and an increased tidal discharge. Tidal sand ridges were formed when relict fluvial or deltaic sands were eroded and reworked by strong tidal currents during subsequent sea-level rise.
Since the sediment supply and the tidal discharge of the depositional system were closely related to the eustatic sea-level change and basin subsidence, i.e. the relative sea-level change, special attention will be given to the relationship between geometric variability of tidal sandbodies and the sequence stratigraphic framework in which various sandbodies occurred. Three orders of eustatic sea-level fluctuations can be recognized. The third-order eustatic sea-level cycle, together with basin subsidence, controlled the development of systems tracts and the occurrence of different tidal sandbodies, such as estuary and tidal flat facies during the late stage of a LSW systems tract (type 1 sequence) or a SM systems tract (type 2 sequence); tidal point bar facies, tidal delta facies or tidal sand-ridge facies during a TR systems tract; estuary facies during an early HS systems tract; and fluvial sand bar facies in a late HS systems tract and the early stage of a SM or LSW systems tract. There are also the fourth-order and fifth-order eustatic fluctuations, which are superimposed on the third-order eustatic changes and have important control on the build-up, abandonment and preservation of composite and single tidal sandbodies, respectively.
Since the deposition of tidal sandbodies is very sensitive to eustatic sea-level changes, recognition of various tidal sandbodies is important in sequence stratigraphy analyses of sedimentary basins and in the facies prediction of clastic sediments in basin modelling. 相似文献
11.
The interaction of river and marine processes in the fluvial to marine transition zone fundamentally impacts delta plain morphology and sedimentary dynamics. This study aims to improve existing models of the facies distribution, stratigraphic architecture and preservation in the fluvial to marine transition zone of mixed-process deltas, using a comprehensive sedimentological and stratigraphic dataset from the Middle Miocene Lambir Formation, Baram Delta Province, north-west Borneo. Eleven facies associations are identified and interpreted to preserve the interaction of fluvial and marine processes in a mixed-energy delta, where fluvial, wave and tidal processes display spatially and temporally variable interactions. Stratigraphic successions in axial areas associated with active distributary channels are sandstone-rich, comprising fluvial-dominated and wave-dominated units. Successions in lateral areas, which lack active distributary channels, are mudstone-rich, comprising fluvial-dominated, tide-dominated and wave-dominated units, including mangrove swamps. Widespread mudstone preservation in axial and lateral areas suggests well-developed turbidity maximum zones, a consequence of high suspended-sediment concentrations resulting from tropical weathering of a mudstone-rich hinterland. Within the fluvial to marine transition zone of distributary channels, interpreted proximal–distal sedimentological and stratigraphic trends suggest: (i) a proximal fluvial-dominated, tide-influenced subzone; (ii) a distal fluvial-dominated to wave-dominated subzone; and (iii) a conspicuously absent tide-dominated subzone. Lateral areas preserve a more diverse spectrum of facies and stratigraphic elements reflecting combined storm, tidal and subordinate river processes. During coupled storm and river floods, fluvial processes dominated the fluvial to marine transition zone along major and minor distributary channels and channel mouths, causing significant overprinting of preceding interflood deposits. Despite interpreted fluvial–tidal channel units and mangrove influence implying tidal processes, there is a paucity of unequivocal tidal indicators (for example, cyclical heterolithic layering). This suggests that process preservation in the fluvial to marine transition zone preserved in the Lambir Formation primarily records episodic (flashy) river discharge, river flood and storm overprinting of tidal processes, and possible backwater dynamics. 相似文献
12.
以最新钻取的SE2孔沉积物为重点研究对象,对晚第四纪以来钱塘江下切河谷充填物的沉积特征和沉积相进行了精细研究,重建了研究区地层结构和层序地层格架,总结了强潮型钱塘江河口湾和下切河谷的沉积模式。钱塘江下切河谷充填物自下而上依次发育河床、河漫滩、古河口湾、近岸浅海和现代河口湾5种沉积相类型,表现为一个较完整的Ⅰ型层序,其内部层序界面、初始海泛面、最大海泛面、海侵和海退潮流侵蚀面、体系域内海侵面发育。钱塘江下切河谷充填物自海向陆可划分为海向段、近海段、近陆段和陆向段4段,各段沉积序列和海陆相互作用程度不同。在钱塘江下切河谷充填物中海陆过渡部位首次明确划分出了古河口湾相,并对其沉积特征和分布模式进行了初步探讨;其形成时间在9000 a BP左右,具有与现代河口湾不同的沉积特征,表现为中部为潮道砂体沉积,向陆渐变为受潮流影响的河流沉积,两侧被潮坪或盐沼沉积包围,沉积物在平面上自陆向海呈现粗-细-粗的分布模式。现代河口湾平面上自陆向海依次发育受潮流影响的河流沉积、粉砂质砂坎、潮道-潮流砂脊复合体和湾口泥质沉积区,沉积物呈现粗-细-粗-细的分布模式,与大多数河口湾常见的粗-细-粗的分布格局明显不同。 相似文献
13.
鄂尔多斯盆地神木地区太原组是在北隆南倾的古地形背景下形成的以浅水三角洲为主的充填沉积。携带沉积物的河流进入海水后,由于河水与海水之间存在着较大的密度差异、侧向扩散较少,其三角洲前缘沿着海底继续向前快速推进,使水下分流河道延伸较远。研究区地形坡度平缓、水体浅,三角洲平原向前推进并进一步降低了地形坡度,从而减弱了携带沉积物的流体的动能,使得大部分沉积物在三角洲平原的分流河道中沉积下来。同时因水体浅,河口坝、席状砂等前缘沉积物常遭受进积的水下分流河道的冲刷和侵蚀而难以保存。研究区三角洲平原分流河道沉积极为发育,前三角洲相对不发育,三角洲前缘也以水下分流河道沉积为主。分流河道、水下分流河道常对下伏沉积物强烈冲刷,切割先期的沉积物乃至包括海相沉积物在内的深水沉积物。在三角洲废弃期,三角洲前缘沉积物常被潮汐作用改造。三角洲平原分流河道及三角洲前缘水下分流河道砂体呈带状分布,是天然气勘探的有利目标。 相似文献
14.
The Mono estuary is an infilled, microtidal estuary located on the wave-dominated Bight of Benin coast which is subject to very strong eastward longshore drift. The estuarine fill comprises a thick unit of lagoonal mud deposited in a ‘central basin’between upland fluvial deposits and estuary-mouth wave-tide deposits. This lagoonal fill is capped by organic-rich tidal flat mud. In addition to tidal flat mud, the superficial facies overlying the ‘central basin’fill include remnants of spits resting on transgressive/washover sand, an estuary-mouth association of beach, shoreface, flood-tidal delta and tidal inlet deposits, and a thin sheet of fluvial sediments deposited over tidal flat mud. After an initial phase of spit intrusion over the infilled central basin east of the present Mono channel, the whole estuary mouth became bounded by a regressive barrier formed from sand supplied by the Volta Delta during the middle Holocene eustatic highstand. Barrier progradation ceased late in the Holocene following the establishment of an equilibrium plan-form shoreline alignment that allowed through-drift of Volta sand to sediment sinks further downdrift. Over the same period, accretion, from fluvially supplied sediments, of the estuarine plain close to the limit of spring high tides, or, over much of the lower valley, into a fluvial plain no longer subject to tidal flooding, induced marked meandering of the Mono and its tidal distributaries in response to confinement of much of the tidal prism to these channels. The process resulted in erosion of spit/washover and regressive barrier sand, and in reworking of the tidal flat and floodbasin deposits. The strong longshore drift, equilibrium shoreline alignment and the year-round persistence of a tidal inlet maintained by discharge from the Mono and from Lake Ahémé have resulted in a stationary barrier that is reworked by a mobile inlet. The Mono example shows that advanced estuarine infill may result in considerable facies reworking, obliteration of certain facies and marked spatial imbrication of fluvial, estuarine and wave-tide-deposited facies, and confirms patterns of sedimentary change described for microtidal estuaries on wave-influenced coasts. In addition, this study shows that local environmental factors such as sediment supply relative to limited accommodation space, and strong longshore drift, which may preclude accumulation of sediments in the vicinity of the estuary mouth, may lead to infilled equilibrium or near-equilibrium estuaries that will not necessarily evolve into deltas. 相似文献
15.
东营凹陷古近系沙河街组碎屑岩储集层非均质性与油气意义 总被引：4，自引：3，他引：1
从宏观和微观两方面分析了东营凹陷古近系沙河街组碎屑岩储集层的非均质性特征。沙河街组碎屑岩储集砂体类型多样,通过统计分析宏观物性参数,不同成因类型储集砂体的渗透率和孔隙度分布差别较大,其中河流相、（扇）三角洲前缘水下分流河道及河口坝砂体储集质量最好;不同沉积微相的孔隙度基本上均呈正态分布,其中三角洲河口坝砂体及水下分流河道砂体孔隙度峰值较高。非均质参数表明,（扇）三角洲前缘水下分流河道非均质程度最强。通过对各种微观非均质性参数的综合研究,将储集层孔隙结构分为5种类型,其中大孔较粗喉及大孔中细喉为好的储集层,常见于（扇）三角洲水下分流河道砂体下部和河口砂坝主体的中细砂岩中。非均质性研究的结果与油田试油结果对比吻合较好,表明该项研究对下一步油气勘探与后期注水开发具有重要的指导意义。 相似文献
16.
KARL CHARVIN GARY J. HAMPSON KERRY L. GALLAGHER RICHARD LABOURDETTE 《Sedimentology》2010,57(3):760-785
Although modern wave‐dominated shorelines exhibit complex geomorphologies, their ancient counterparts are typically described in terms of shoreface‐shelf parasequences with a simple internal architecture. This discrepancy can lead to poor discrimination between, and incorrect identification of, different types of wave‐dominated shoreline in the stratigraphic record. Documented in this paper are the variability in facies characteristics, high‐resolution stratigraphic architecture and interpreted palaeo‐geomorphology within a single parasequence that is interpreted to record the advance of an ancient asymmetrical wave‐dominated delta. The Standardville (Ab1) parasequence of the Aberdeen Member, Blackhawk Formation is exposed in the Book Cliffs of central Utah, USA. This parasequence, and four others in the Aberdeen Member, record the eastward progradation of north/south‐trending, wave‐dominated shorelines. Within the Standardville (Ab1) parasequence, distal wave‐dominated shoreface‐shelf deposits in the eastern part of the study area are overlain across a downlap surface by southward prograding fluvial‐dominated delta‐front deposits, which have previously been assigned to a separate ‘stranded lowstand parasequence’ formed by a significant, allogenic change in relative sea‐level. High‐resolution stratigraphic analysis of these deposits reveals that they are instead more likely to record a single episode of shoreline progradation characterized by alternating periods of normal regressive and forced regressive shoreline trajectory because of minor cyclical fluctuations in relative sea‐level. Interpreted normal regressive shoreline trajectories within the wave‐dominated shoreface‐shelf deposits are marked by aggradational stacking of bedsets bounded by non‐depositional discontinuity surfaces. Interpreted forced regressive shoreline trajectories in the same deposits are characterized by shallow incision of fluvial distributary channels and strongly progradational stacking of bedsets bounded by erosional discontinuity surfaces that record enhanced wave‐base scour. Fluvial‐dominated delta‐front deposits most probably record the regression of a lobate delta parallel to the regional shoreline into an embayment that was sheltered from wave influence. Wave‐dominated shoreface‐shelf and fluvial‐dominated delta‐front deposits occur within the same parasequence, and their interpretation as the respective updrift and downdrift flanks of a single asymmetrical wave‐dominated delta that periodically shifted its position provides the most straightforward explanation of the distribution and relative orientation of these two deposit types. 相似文献
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Optimizing sampling strategy for radiocarbon dating of Holocene fluvial systems in a vertically aggrading setting 总被引：1，自引：0，他引：1
TORBJÖRN E. TÖRNQVIST GEO J. VAN DIJK 《Boreas: An International Journal of Quaternary Research》1993,22(2):129-145
In this paper we address the question of how to determine the period of activity (sedimentation) of fossil (Holocene) fluvial systems in vertically aggrading environments. Our data base consists of almost 100 14 C ages (partly AMS) from the Rhine–Meuse delta in the central Netherlands. Radiocarbon samples from the tops of lithostratigraphically correlative organic beds underneath overbank deposits (sample type 1) yield consistent ages, indicating a synchronous onset of overbank deposition over distances of at least up to 20 km along channel belts. Similarly, 14 C ages from the base of organic residual channel fills (sample type 3) generally indicate a clear termination of within-channel sedimentation. In contrast, 14 C ages from the base of organic beds overlying overbank deposits (sample type 2), commonly assumed to represent the end of fluvial sedimentation, show a large scatter reaching up to 1000 14 C years. This setting usually produces 14 C ages significantly younger than residual channels of the same fluvial system, indicating the presence of non-depositional unconformities. These usually occur on top of slightly elevated sediment bodies (especially natural levee deposits), which often contain palaeosols. Such hiatuses appear to be much more abundant than hitherto supposed. We conclude that a combination of sample types 1 and 3 generally yields a satisfactory delimitation of the period of activity of a fossil fluvial system. The problems associated with 14 C samples of type 2 may also be present in coastal areas with an alternation of tidal deposits and organic beds. 相似文献
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The role of tidal,wave and river currents in the evolution of mixed‐energy deltas: Example from the Lajas Formation (Argentina) 下载免费PDF全文
下载免费PDF全文 Many modern deltas show complex morphologies and architectures related to the interplay of river, wave and tidal currents. However, methods for extracting the signature of the individual processes from the stratigraphic architecture are poorly developed. Through an analysis of facies, palaeocurrents and stratigraphic stacking patterns in the Jurassic Lajas Formation, this paper: (i) separates the signals of wave, tide and river currents; (ii) illustrates the result of strong tidal reworking in the distal reaches of deltaic systems; and (iii) discusses the implications of this reworking for the evolution of mixed‐energy systems and their reservoir heterogeneities. The Lajas Formation, a sand‐rich, shallow‐marine, mixed‐energy deltaic system in the Neuquén Basin of Argentina, previously defined as a tide‐dominated system, presents an exceptional example of process variability at different scales. Tidal signals are predominantly located in the delta front, the subaqueous platform and the distributary channel deposits. Tidal currents vigorously reworked the delta front during transgressions, producing intensely cross‐stratified, sheet‐like, sandstone units. In the subaqueous platform, described for the first time in an ancient outcrop example, the tidal reworking was confined within subtidal channels. The intensive tidal reworking in the distal reaches of the regressive delta front could not have been predicted from knowledge of the coeval proximal reaches of the regressive delta front. The wave signals occur mainly in the shelf or shoreface deposits. The fluvial signals increase in abundance proximally but are always mixed with the other processes. The Lajas system is an unusual clean‐water (i.e. very little mud is present in the system), sand‐rich deltaic system, very different from the majority of mud‐rich, modern tide‐influenced examples. The sand‐rich character is a combination of source proximity, syndepositional tectonic activity and strong tidal‐current reworking, which produced amalgamated sandstone bodies in the delta‐front area, and a final stratigraphic record very different from the simple coarsening‐upward trends of river‐dominated and wave‐dominated delta fronts. 相似文献
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通过露头沉积学与岩石学分析,在湘西北龙山、永顺地区下志留统龙马溪组中首次发现完整的潮控型三角洲沉积,也是华南地区龙马溪组中存在三角洲相的首次报道。识别出前三角洲、三角洲前缘和三角洲平原3个亚相及10个微相。前三角洲亚相以滨外泥页岩为主,并发育低密度浊积岩,主要见于龙马溪组底部和下部;三角洲前缘亚相包括席状砂、分流间湾、河口砂坝和远砂坝等;三角洲平原亚相包括分流河道、分流间湾、天然堤和决口扇等,主要见于龙马溪组中部、上部。通过分析剖面垂向序列及其指示的沉积环境变化,提出本区龙马溪组三角洲相碎屑岩是构造挤压背景下“雪峰隆起”开始形成的重要沉积响应。该三角洲沉积的发现,对于理解扬子东南缘早志留世构造-古地理转型的时限与过程具有特殊意义。 相似文献