A discussion and classification of subaqueous mass-transport with particular application to grain-flow,slurry-flow,and fluxoturbidites

Sediments will remain at rest on the sea-floor provided forces of shear resistance exceed the downslope shear stress imposed by gravity. The shear resistance of granular water-saturated sediments is discussed within the constraints imposed by the Coulomb model of shear failure, and the phenomena of thixotropy, liquefaction, retrogressive flow sliding and fluidization are discussed as mechanisms for producing the mass-mobilisation of sediment. Processes of laminar mass-flow (= inertia flow) are broadly divided into those involving water as the interstitial fluid (grain-flow) and those having an interstitial fluid of enhanced viscosity (slurry-flow). Recent and experimental examples of inertia-flow are summarised and discussed under the headings grain-fall, grain-flow, slump-creep and fluxoturbidites. It is concluded that grain-flow and slump-creep deposits may be more widespread in the sedimentary record than present reports indicate. It is recommended that the term fluxoturbidite be restricted to its original sense, to describe the deposits of proximal turbidites in which the immediately pre-depositional transport was by inertia-flow. A suggested terminology for subaqueous mass-transport processes and their products is summarised in the form of a flow-chart, terminological distinction being drawn between the processes of mobilisation, transport and deposition of the sediment, and between the various sedimentary beds or facies that result from emplacement by mass-transport.     

Sedimentology of the Middle Marker (3.4 Ga), Onverwacht Group,Transvaal, South Africa

The Middle Marker is a thin (3–6 m) sedimentary unit at the base of the Hooggenoeg Formation in the 3.4 Ga old Onverwacht Group, Barberton Mountain Land, South Africa. The original sediments consisted largely of current-deposited volcaniclastic detritus now represented by green to buff-colored silicified volcaniclastic rock and fine-grained gray chert. Black chert, possibly formed by the silicification of a non-volcaniclastic precursor, makes up a significant part of the unit. The Middle Marker is underlain and overlain by mafic and commonly pillowed volcanic flowrock. Although the original sediment has been replaced by and/or recrystallized to a microquartz, chlorite, sericite, carbonate and iron oxide mosaic under lower greenschist-grade metamorphism, sedimentary textures and structures are remarkably well preserved. Textural pseudomorphs indicate the primary volcaniclastic sediment consisted of a mixture of crystal, vitric and lithic debris. Middle Marker sediments were deposited as a prograding, cone-flanking volcaniclastic sedimentary platform in a relatively-shallow and locally current/wave-influenced subaqueous sedimentary environment. Available paleocurrent data indicate a largely bimodal, orthogonal distribution pattern which is quite similar to both ancient and modern shallow marine/shelf systems. Diagnostic evidence for tidal activity is lacking. As felsic volcanic activity waned, an extensive airfall blanket of fine-grained volcanic ash and dust was deposited in a low-energy subaqueous environment. The sedimentary cycle was terminated with a renewal of submarine mafic volcanism. Middle Marker volcaniclastic sediments accumulated in an anorogenic basin removed or isolated from the influence of continental igneous and metamorphic terranes. Although compositionally dominated by a volcanic source, Middle Marker sediments owe their final texture and sedimentary structures to subaqueous sedimentary rather than volcanogenic processes.     

Triassic carbonate submarine fans along the Arabian platform margin, Sumeini Group, Oman

ABSTRACT The Sumeini Group formed along the passive continental margin slope that bounded the northeastern edge of the Arabian carbonate platform. With the initial development of this passive continental margin in Oman during Early to Middle Triassic time (possibly Permian), small carbonate submarine fans of the C Member of the Maqam Formation developed along a distally steepened slope. The fan deposits occur as several discrete lenticular sequences of genetically related beds of coarsegrained redeposited carbonate (calciclastic) sediment within a thick interval of basinal lime mudstone and shale. Repeated pulses of calciclastic sediment were derived from ooid shoals on an adjacent carbonate platform and contain coarser intraclasts eroded from the surrounding slope deposits. Sediment gravity flows, primarily turbidites with lesser debris flows and grain flows, transported the coarse sediments to the relatively deep submarine fans. Channel erosion was a major source of intraformational calcirudite. Two small submarine fan systems were each recurrently supplied with calciclastic sediment derived from point sources, submarine canyons. The northern fan system retrogrades and dies out upsection. The southern fan system was apparently longer-lived; calciclastic sediments in it are more prevalent and occur throughout the section. The proximal portions of this fan system are dominated by channelized beds of calcirudite which represent inner- to mid-fan channel complexes. The distal portions include mostly lenticular, unchannelized beds of calcarenite, apparently mid- to outer-fan lobes. Carbonate submarine fans appear to be rare in the geological record in comparison with more laterally continuous slope aprons of coarse redeposited sediment. The carbonate submarine fans of the C Member apparently formed by the funnelling of coarse calciclastic sediment into small submarine canyons which may have developed due to rift and/or transform tectonics. The alternation of discrete sequences of calciclastic sediment with thick intervals of ‘background’ sediment resulted from either sea-level fluctuations or pulses of tectonic activity.     

A large-scale meandering submarine canyon: outcrop example from the late Proterozoic Adelaide Geosyncline, South Australia

The late Proterozoic Adelaide Geosyncline, along with overlying Cambrian strata, comprises a thick sequence of sediments and sparse volcanics which accumulated in a major rift and passive margin setting. During late syn-rift or early post-rift phases, large volumes of terrigenous and carbonate sediments of the late Proterozoic Umberatana and Wilpena Groups and Cambrian Hawker Group filled the rift. Submarine canyon development was related to at least four of these depositional cycles, the most notable of which resulted in incision and subsequent filling of the major (several kilometres in width and up to 1.5 km deep) submarine canyons by the Wonoka Formation. The Wonoka Formation canyons are not obviously fault controlled. They are interpreted to have been eroded by turbidity currents during a relative low-stand of sea-level. They were subsequently filled by a fining-upwards suite of sediments which reflects subsequent relative rise of sea-level and carbonate platform development. Ultimately the canyon complex was buried by north-westerly progradation of overlying fluvial and slope sequences (Billy Springs Beds and possibly correlative upper Pound Subgroup). It is considered likely that more distal elements of this prograding clastic wedge provided the necessary material for canyon erosion, prior to canyon filling and ultimate burial by what may have been elements of the same depositional cycle. It is considered possible that the series of isolated outcrops of canyon cross-sections within the Wonoka Formation are sections of a single canyon thalweg developed within a considerably broader zone of slope degradation. If this interpretation is correct, then the gorge-like Patsy Springs Canyon lies in more proximal regions of the basin-slope, whereas 40 km to the north-east the lower slope is cut by the Fortress Hill Canyon Complex. Palaeocurrent analyses of channel-fill turbidites within the canyons imply that the Fortress Hill Complex is in fact the outcropping western edge of a sinuous, incised canyon thalweg. The Wonoka Formation canyons, containing basal sedimentary breccias but only minor conglomerates, are considered typical of passive margin canyon development. They are contrasted with the generally highly conglomeratic channel-fills observed in outcropping Tertiary and Cretaceous examples of active margin canyons and upper fan valleys.     

川西盐边群的优地槽岩石组合

<正> 古优地槽岩石组合往往难以得到完整保存的记录。蛇绿岩的上冲作用使得蛇绿岩的岩石层序受到破坏;消减作用又常使消减带的复理石岩系变形,成为关系复杂、断裂交错的冲断席;最后的弧带造山作用或碰撞造山作用(Coleman,1975;Dickinson,1977)又进一步使这些岩石褶曲、断裂,于是,原来的层序和面貌便难以辨认。     

Sedimentary processes in a submarine canyon excavated into a temperate‐carbonate ramp (Granada Basin,southern Spain)

During the Late Tortonian, shallow‐water temperate carbonates were deposited in a small bay on a gentle ramp linked to a small island (Alhama de Granada area, Granada Basin, southern Spain). A submarine canyon (the ‘Alhama Submarine Canyon’) developed close to the shoreline, cross‐cutting the temperate‐carbonate ramp. The Alhama Submarine Canyon had an irregular profile and steep slopes (10° to 30°). It was excavated in two phases reflected by two major erosion surfaces, the lowermost of which was incised at least 50 m into the ramp. Wedge‐shaped and trough‐shaped, concave‐up beds of calcareous (terrigenous) deposits overlie these erosional surfaces and filled the canyon. A combination of processes connected to sea‐level changes is proposed to explain the evolution of the Alhama Submarine Canyon. During sea‐level fall, part of the carbonate ramp became exposed and a river valley was excavated. As sea‐level rose, river flows continued along the submerged, former river‐channel, eroding and deepening the valley and creating a submarine canyon. At this stage, only some of the transported conglomerates were deposited locally. As sea‐level continued to rise, the river mouth became detached from the canyon head; littoral sediments, transported by longshore and storm currents, were now captured inside the canyon, generating erosive flows that contributed to its excavation. Most of the canyon infilling took place later, during sea‐level highstand. Longshore‐transported well‐sorted calcarenites/fine‐grained calcirudites derived from longshore‐drift sandwaves poured into and fed the canyon from the south. Coarse‐grained, bioclastic calcirudites derived from a poorly sorted, bioclastic ‘factory facies’ cascaded into the canyon from the north during storms.     

Sedimentologic and stratigraphic constraints on emplacement of the Star Kimberlite, east–central Saskatchewan

Diamond-bearing kimberlites in the Fort à la Corne region, east–central Saskatchewan, consist primarily of extra-crater pyroclastic deposits which are interstratified with Lower Cretaceous (Albian and Cenomanian) marine, marginal marine and continental sediments. Approximately 70 individual kimberlite occurrences have been documented. The Star Kimberlite, occurring at the southeastern end of the main Fort à la Corne trend, has been identified as being of economic interest, and is characterized by an excellent drill core database. Integration of multi-disciplinary data-sets has helped to refine and resolve models for emplacement of the Star Kimberlite. Detailed core logging has provided the foundation for sedimentological and volcanological studies and for construction of a regionally consistent stratigraphic and architectural framework for the kimberlite complex. Micropaleontologic and biostratigraphic analysis of selected sedimentary rocks, and U–Pb perovskite geochronology on kimberlite samples have been integrated to define periods of kimberlite emplacement. Radiometric age determination and micropaleontologic evidence support the hypothesis that multiple kimberlite eruptive phases occurred at Star. The oldest kimberlite in the Star body erupted during deposition of the predominantly continental strata of the lower Mannville Group (Cantuar Formation). Kimberlites within the Cantuar Formation include terrestrial airfall deposits as well as fluvially transported kimberlitic sandstone and conglomerate. Successive eruptive events occurred contemporaneous with deposition of the marginal marine upper Mannville Group (Pense Formation). Kimberlites within the Pense Formation consist primarily of terrestrial airfall deposits. Fine- to medium-grained cross-stratified kimberlitic (olivine-dominated) sandstone in this interval reflects reworking of airfall deposits during a regional marine transgression. The location of the source feeder vents of the Cantuar and Pense kimberlite deposits has not been identified. The youngest and volumetrically most significant eruptive events associated with the Star Kimberlite occur within the predominantly marine Lower Colorado Group (Joli Fou and Viking Formations). Kimberlite beds, which occur at several horizons within these units, consist of subaerial and marine fall deposits, the latter commonly exhibiting evidence of wave-reworking. Black shale-encased resedimented kimberlite beds, likely deposited as subaqueous debris flows and turbidites, are particularly common in the Lower Colorado Group. During its multi-eruptive history, the Star Kimberlite body is interpreted to have evolved from a feeder vent and overlying positive-relief tephra ring, into a tephra cone. Initial early Joli Fou volcanism resulted in formation of a feeder vent (200 m diameter) and tephra ring. Subsequent eruptions, dominated by subaerial deposits, partly infilled the crater and constructed a tephra cone. A late Joli Fou eruption formed a small (70 m diameter) feeder pipe slightly offset to the NW of the early Joli Fou feeder vent. Deposits from this event further infilled the crater, and were deposited on top of early Joli Fou kimberlite (proximal to the vent) and sediments of the Joli Fou Formation (distal to the vent). The shape of the tephra cone was modified during multiple marine transgression and regression cycles coeval with deposition of the Lower Colorado Group, resulting in wave-reworked kimberlite sand along the fringes of the cone and kimberlitic event deposits (tempestites, turbidites, debris flows) in more distal settings.     

Geochemistry and petrology of metamorphosed submarine basic ashes in the Edough Massif (Cap de Garde,Annaba, northeastern Algeria)

The study presents the first evidence of metamorphosed submarine ashes in the Edough Massif, in northeastern Algeria. It occurs below the greenschist-facies Tellian units that represent the thrusted Mesozoic to Eocene passive paleomargin of northern Africa deposited on thinned continental crust. The metamorphic complex consists of tectonically superposed units composed of gneisses (lower unit) and micaschists (upper unit). At the Cap de Garde, these units enclose an “intermediate unit” composed of micaschists and meter-thick layers of marbles, which are sometimes intercalated with amphibolites. The latter occur as discontinuous small lenses and layers. The amphibolites are parallel to the primary bedding of the marbles and the main foliation. Chemical markers and field observations indicate that they are metamorphic equivalents of basic igneous rocks. The lenticular character, low thickness and multiple intercalations with marine sediments and the unusual high lithium concentrations suggest subaqueous near-source basaltic ash-fall deposits in a marine environment.     

弯曲海底峡谷中浊流的三维流动及沉积的初步研究

海底浊流的运动及其沉积,是目前浊流研究的热点之一。根据经过验证的基于雷诺平均纳维尔-斯托克斯方程及浮力项修正 k-ε 湍流模型的三维数值计算模型模拟了海底弯曲圆弧形峡谷内的浊流的流动和沉积,结果表明:（1）浊流在运动过程中由于对环境水体的夹带厚度不断增加,浊流厚度一般会超过峡谷深度,溢出峡谷,使浊流产生密度和动量损失;（2）浊流到达弯道部分后,由于离心力的作用会产生剥离,溢出更多的浊流至漫滩区域。浊流剥离的最大处为弯道顶点外岸下游处,其过量密度可达入流的37.5%;（3）对于模拟的横剖面为圆弧型的峡谷内的浊流来说,弯道顶点处的二次流在底部形成一个顺时针的循环圈,靠近峡谷底部从外岸指向内岸;（4）在峡谷中间及弯道顶点内岸下游处形成沉积,在弯道顶点外岸下游处形成侵蚀。这些特征对根据浊流的沉积观察推测其形成环境及油气储层的调查等方面有一定的参考意义。     

孟加拉湾若开盆地深水沉积体系结构单元类型及演化模式

利用多个地震数据体的地震反射特征,分析了孟加拉湾若开盆地深水沉积体系的不同沉积结构单元类型(峡谷、水道及水道复合体、天然堤—漫溢沉积、朵体以及块体搬运沉积)的典型地震响应特征、及其发育的位置,构建了研究区陆架—陆坡—盆底的沉积结构单元演化模式。研究表明,一个深水沉积体系垂向上自下而上的组合样式为:底部块体搬运沉积及厚层大规模朵体沉积,上覆水道复合体沉积,之后为水道—天然堤复合体沉积、以及一些小规模朵体沉积,顶部为薄层深海泥岩沉积。横向上自陆架向深海盆地的发育模式表现为:陆架/上陆坡峡谷—上陆坡侵蚀型水道—下陆坡侵蚀沉积型水道—沉积型水道—盆地朵体。     

Architecture and evolution of the Kushiro submarine canyon in the Kurile Trench forearc slope,North‐western Pacific

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

鄂尔多斯盆地神木地区下二叠统太原组浅水三角洲沉积特征

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。     

Depositional model for lacustrine nearshore subaqueous fans in a rift basin: The Eocene Shahejie Formation,Dongying Sag,Bohai Bay Basin,China

The origin of the fourth member of the Eocene Shahejie Formation in the northern steep slopes of the Minfeng Sub‐sag, Dongying Sag, China, was investigated by integrating core studies and flume tank depositional simulations. A non‐channelized depositional model is proposed in this paper for nearshore subaqueous fans in steep fault‐controlled slopes of lacustrine rift basins. The deposits of nearshore subaqueous fans along the base of steep border‐fault slopes of rift basins are typically composed of deep‐water coarse‐grained sediment gravity‐flow deposits directly sourced from adjacent footwalls. Sedimentation processes of nearshore subaqueous fans respond to tectonic activities of boundary faults and to seasonal rainfall. During tectonically active stages, subaqueous debris flows triggered by episodic movements of border‐faults dominate the sedimentation. During tectonically quiescent stages, hyperpycnal flows generated by seasonal rainfall‐generated floods, normal discharges of mountain‐derived rivers and deep‐lacustrine suspension sedimentation are commonly present. The results of a series of flume tank depositional simulations show that the sediments deposited by subaqueous debris flows are wedge‐shaped and non‐channelized, whereas the sediments deposited by hyperpycnal flows generated by sporadic floods from seasonal rainfall are characterized by non‐channelized, coarse‐grained lobate depositional bodies which switch laterally because of compensation sedimentation of hyperpycanal flows. The hyperpycnal‐flow‐deposited non‐channelized lobate depositional bodies can be divided into a main body and lateral edges. The main body can be further subdivided into a proximal part, middle part and frontal part. Normal mountain‐derived river‐discharge‐deposited sediments are characterized by thin‐bedded, fine‐grained sandstones and siltstones with a limited distribution range. Normal mountain‐derived river‐discharge‐deposited sediments and deep‐lacustrine mudstones are commonly eroded in the area close to boundary faults. A nearshore subaqueous fan can be divided into three segments: inner fan, middle fan and outer fan. The inner fan is composed of debrites and the proximal part of the main body. The middle fan consists of the middle part of the main body and lateral edges, normal mountain‐derived river‐discharge‐deposited fine‐grained sediments and deep‐lacustrine mudstones. The outer fan comprises the frontal part of the main body, lateral edges, and deep‐lacustrine mudstones. Based on the non‐channelized depositional model for nearshore subaqueous fans, criteria for stratigraphic subdivision and correlation are discussed and applied.     

尼日利亚海上区块近海底深水水道体系地震响应特征与沉积模式

利用高分辨率三维地震资料,对西非尼日利亚海上OML130地区近海底深水沉积进行了研究.剖析了深水水道体系各沉积单元地震反射特征,详细论述了水道与堤岸单元的外形几何特征及内部充填特征,即单一水道在剖面上为V字型,下部地震反射为强反射、低连续,代表相对粗颗粒碎屑沉积,顶部为中强振幅、连续性强、水平层状地震反射特征,反映了水道发育晩期废弃充填的特点,平面形态为高弯度条带状.在分析水道下切侵蚀与充填特征的基础之上,总结了水道体系内水道之间的3种叠置样式,研究表明平面上类似曲流河沉积体系的水道体系内,后期单一水道的发生不一定是在前期水道基础之上直接侧向迁移与顺流演化,而可能是另一个新的沉积过程,因而在不同位置展现不同的水道叠置样式.通过分析水道体系形成演化的主要影响因素,结合研究区浅层与深层资料,提出了被动大陆边缘深水水道体系的沉积模式.研究认为,在陆坡上某一区域,在物源供给及海平面变化,尤其是流域地形(构造或沉积所致)影响下,使得水道体系、朵叶体系既可以同时出现,也可以在顺流方向交替出现.借助近海底的高分辨率三维地震资料对深水沉积进行研究,可以揭示沉积单元特征,从而建立研究区内适性强的沉积演化模式,为深水油气勘探与开发提供更为成功的服务.     

An ancient submarine canyon in the Oligocene-Miocene of the western Niger Delta

ABSTRACT
An anomalous sequence of thick fossiliferous marine shale of late Oligocene-early Miocene age, here termed the Opuama Shale Member, occurs within the paralic Agbada Formation in the subsurface of the western Niger Delta. The Opuama Shale fills a deep palaeochannel which was cut into Eocene-early Oligocene paralic beds. Planktonic and benthic foraminifera suggest that deposition in the channel began in the late Oligocene-early Miocene at outer shelf-slope depths, and that by the late early Miocene the channel had filled to shallow neritic depths. The channel, which is believed to be of submarine origin, is termed the Opuama canyon. The Opuama canyon originated during the pronounced early-Middle Oligocene drop in sea-level, and was cut by turbidity currents. It was filled, during the major late Oligocene-early Miocene rise of sea-level.
The location of the Opuama canyon in the western re-entrant of the Niger Delta supports Burke's (1972) conclusion that the western and eastern (where ancient submarine canyon fills are known) re-entrants of the delta are potential sites for ancient submarine canyons. Burke based his conclusion on the observation that the eastern and western re-entrants of the modern delta are areas where opposing longshore drifts converge and generate turbidity currents which cut submarine canyons.     

Sedimentary architecture of detached deep‐marine canyons: Examples from the East Coast Basin of New Zealand

Submarine canyons are conduits for the distribution of sediment across continental margins. Although many canyons connect directly with fluvial or marine littoral system feeders, canyons detached from direct hinterland supply are also recognized. The fill of detached canyons remains enigmatic, because their deep‐water setting restricts analysis of their evolution and stratigraphic architecture. Therefore, this study aims to investigate the sedimentary processes that infilled deep‐water canyons and the resulting architecture. Miocene outcrops of an exhumed deep‐water system from the East Coast Basin, New Zealand, are documented and compared with the morphology and seismic scale architecture of a modern detached canyon system on the same convergent margin. The outcropping system preserves the downstream margin of a sub‐basin deposited at palaeo‐water depths >700 m. A 6 km wide by 430 m deep incision is filled by heterogeneous siliciclastic sediments, 50% of which comprise graded thin‐beds with traction structures, interpreted to result from oscillatory flows. These are intercalated with concave‐up lenses, up to 15 m thick, of sigmoidally‐bedded, amalgamated sandstones, which preserve ripple casts on bed bases, interpreted as deposits at the head of a deep‐marine canyon. Palaeo‐flow was eastward, into the sub‐basin margin. On the adjacent margin of the sub‐basin down‐dip, stacked and amalgamated sandstones and conglomerates represent the fill of a submarine channel complex, at least 3 km wide. The channels are inferred to have been fed by the up‐dip canyon, which traversed the intervening structural high; similar relationships are seen in the bathymetry data. Seismic studies on this margin demonstrate that multiple phases of canyon cut and fill may occur, with downstream architectural evolution comparable to that seen at outcrop, demonstrating that detached canyons may act as sediment conduits. Breaching of developing sea‐floor structures by detached canyons can modify tortuous sediment pathways, supplying sediment to otherwise starved areas of the slope.     

琼东南盆地中央峡谷深水天然堤—溢岸沉积

中央峡谷位于琼东南盆地深水区,发育面积较广,内部天然堤—溢岸沉积发育。深水天然堤—溢岸可作为良好的油气储集体,深受油气工业界的关注。为了指导中央峡谷的油气勘探,利用三维地震资料,结合地震剖面以及均方根振幅属性对中央峡谷内部天然堤—溢岸沉积的形态和控制因素进行了分析,总结了天然堤—溢岸的沉积模式,并对其油气勘探前景进行了...     

Late Proterozoic Patsy Springs Canyon,Adelaide Geosyncline: submarine or subaerial origin?

A significant aspect of Late Proterozoic sedimentation in the Adelaide Geosyncline, South Australia, is the presence of kilometre-deep erosional incisions which have been termed canyons. These structures were formerly described to be of submarine origin, cut and filled in an inferred basin-slope setting by subaqueous processes. Subsequent detailed research, particularly on a specific incision known as Patsy Springs Canyon, indicates that sedimentary structures within some of the canyon-filling sediments are indicative of deposition above fair weather wave base. In addition, an unusual carbonate unit, which is observed to veneer upper portions of canyon shoulders and to contribute to carbonate breccias interbedded with canyon-fill, has a stable isotope signature which may imply a non-marine origin. The presence of the carbonate veneer, where it is in situ, suggests that at least upper portions of the canyons could have been emergent during the canyon-filling phase. Considering these observations, and combining them with regional stratigraphical relationships, an alternative model for canyon genesis is proposed involving subaerial erosion and subsequent filling by coastal onlap. Such a model requires base-level changes of the order of 1 km, in order to account for observed canyon cutting and filling. Vertical movements associated with halokinesis, or thermally-induced uplift of the order of 1 km, could have resulted in the observed erosional events. Alternatively, a Messinian-style evaporitic lowering of base-level is currently receiving serious attention. With present knowledge this mechanism most satisfactorily explains all observations.     

新疆奇台地区下石炭统扇三角洲沉积特征

新疆奇台地区下石炭统地层中发现一套冲积扇进积到湖泊中而形成的扇三角洲沉积体。三角洲层序完整，清楚地显示出湖退又湖进的沉积序列；其中，扇三角洲平原部分主要以泥石流成因的块状砂砾岩为主，夹扇面河道沉积的含砾砂岩、中粗粒砂岩透镜体及中薄层状漫流沉积；扇三角洲前缘以碎屑流沉积的块状砂砾岩为主，夹水下分流河道沉积的砂岩透镜体。前三角洲以深灰色泥岩、粉砂质泥岩为主．沉积体中含丰富的植物化石。     

南海北部狭窄陆架-断裂陆坡控制的大型深水扇体系

南海北部狭窄陆架-断裂陆坡控制的深水沉积体系研究程度极低.以“源-渠-汇”耦合思想为指导,基于岩石学特征、测井相、地震相分析,刻画了揭阳凹陷珠海组深水扇砂体的垂向叠置和横向迁移特征,并将其形成演化划分为珠海组四段初始形成期、珠海组三段-二段发展扩大期、珠海组一段萎缩消亡期.揭阳凹陷珠海组大型盆底扇的形成受控于易剥蚀的中生界物源、多期的相对海平面快速下降、狭窄陆架-断裂陆坡的有利地貌这3个关键因素的耦合作用;在区域三级相对海平面快速下降的背景下,揭阳凹陷北侧东沙隆起富砂的下白垩统快速剥蚀,沉积物直接沿狭窄陆架区的侵蚀下切谷或小型陆架边缘三角洲的水下分流河道搬运,顺断裂坡折带或构造转换带调节,以重力流形式经峡谷水道继续搬运至下陆坡盆地形成大型海底扇.