Climbing Ripple Lamination Research Articles

Hyperpycnal flow depositional characteristics and model in an ancient continental basin: a record from the Oligocene Lower Huagang Formation in the Xihu Sag, East China Sea Shelf Basin

Modern observations have determined the presence of hyperpycnal flows; however, their presence in ancient rocks is scarcely reported in the literature, particularly with respect to continental strata. The present study is the first to use core and thin-section analyses and examination of physical reservoir properties to identify hyperpycnal flow sediment from the lower section of the Oligocene Huagang Formation in the central Xihu Sag, East China Sea Shelf Basin. The multiple fine sandy layers are characterized by lower reverse-graded and upper normal-graded bedding with horizontal bedding, climbing-ripple lamination, wavy bedding, and small foreset laminae. Microerosion surfaces are occasionally present between the reverse-graded and normal-graded bedding, and plant fragments are sometimes visible in the deposits. The same grain size sequence changes are observed in the thin sections. This lithologic combination is considered to be related to hyperpycnal flow sedimentation caused by flood events. The lower reverse-graded and upper normal-graded bedding sequences indicate that the flood energy first increased then decreased and the microerosion surfaces were formed through erosion of lower sediments by the flood. Hyperpycnal flows can directly transport deposits from an estuary to a deep-water basin, which distinguishes them from typical turbidity currents. This study also establishes a sedimentary model of the hyperpycnal flow in lacustrine basin, which can be used as a reference for future hyperpycnal deposit studies.

Análise de fácies e petrografia de uma seção do Membro Crato em Nova Olinda (CE): contribuições à história deposicional e diagenética do neoaptiano na Bacia do Araripe

Na Bacia do Araripe, o Membro Crato é uma das mais importantes unidades estratigráficas por seu conteúdo fossilífero, seu contexto análogo ao das “Camadas Pré-Sal” e seu aproveitamento econômico como material de revestimento. Neste trabalho, análises de fácies e petrográficas foram combinadas no estudo de uma seção do Membro Crato em Nova Olinda (CE), com o intuito de investigar sua história deposicional e diagenética. Para tanto, a faciologia de uma seção colunar contínua de cerca de 70 m de espessura foi analisada com a coleta de 13 amostras de rochas carbonáticas, siliciclásticas e evaporíticas. As amostras foram analisadas por petrografia ótica. Foram descritas cinco fácies deposicionais: lamito margoso (Lm), calcilutito laminado (Cl), arenito maciço (Am), siltito com laminação cruzada cavalgante (Scc) e evaporito colunar (Ec). As fácies mais espessas e recorrentes foram interpretadas como lacustres (Lm, Cl), seguidas de sucessões aluviais (Am, Scc) em meio aos intervalos lacustres. A sucessão termina com indícios faciológicos de que condições de extrema aridez (Ec) foram atingidas ao final do intervalo descrito. A petrografia, aqui focada em rochas das fácies Cl, Am e Scc, reforça a ideia de que o intervalo do Aptiano local correspondia a um sistema lacustre árido, eventualmente alimentado por fluxos aluviais imaturos a partir de áreas-fontes próximas. Em particular, o baixíssimo grau de compactação mecânica e cimentação incipiente das rochas terrígenas sugere que a sucessão foi pouco afetada por diagênese após seu soterramento, que foi, por essa razão, pouco profundo. A semelhança dos intervalos terrígenos do Membro Crato com aqueles descritos para a porção final da sotoposta Formação Barbalha sugere contemporaneidade com passagem transicional retrogradante entre as duas unidades.

Geometry and internal organization of hyperpycnites associated with a shelf-margin delta, the Middle Pleistocene Kokumoto Formation on the Boso Peninsula of Japan

Some turbidite beds of the Middle Pleistocene Kokumoto Formation on the Boso Peninsula of Japan exhibit different types of vertical and lateral changes in grain size and sedimentary structures compared with the Bouma model, which is generally interpreted to represent turbidites deposited from surge-type, ephemeral turbidity currents. Some turbidite beds examined by this study are characterized by several repetitions of coarsening-to-fining upward patterns in association with climbing ripple lamination and parallel lamination. Furthermore, these turbidites are not necessarily laterally continuous in the two-dimensional cross section. Two thickest parts are separately observed within the same stratigraphic level. The geometry and internal organization of these turbidites are interpreted to be a product of hyperpycnal flows generated from a multi-source system associated with a shelf-margin delta in an upslope area during falling- and lowstand stages.

Climbing ripple structure and associated storm-lamination from a Proterozoic carbonate platform succession: Their environmental and petrogenetic significance

The Mesoproterozoic Pandikunta Limestone, a shallow water carbonate platform succession in the Pranhita-Godavari Valley, south India, displays well developed climbing ripple lamination and storm deposited structures, such as HCS, wave ripple-lamination, combined-flow ripple-lamination and low angle trough cross-stratification. Different types of stratification developed in calcisiltite with minor amounts of very fine quartz sand and silt. The climbing ripple structures exhibit a complex pattern of superposition of different types (type A, B and S) within cosets pointing to a fluctuating rate of suspension depositionversus bedform migration, and an unsteady character of the flow. Close association of climbing ripple structures, HCS with anisotropic geometry, wavy lamination and combined-flow ripple-lamination suggest that the structures were formed by storm generated combined-flow in a mid-shelf area above the storm wave base. The combined-flow that deposited the climbing ripple structures had a strong unidirectional flow component of variable magnitude. The climbing ripple structure occurs as a constituent of graded stratified beds with an ordered vertical sequence of different types of lamination, reflecting flow deceleration and increased rate of suspension deposition. It is inferred that the beds were deposited from high-density waning flows in the relatively deeper part of the ancient shelf. The structures indicate that the Pandikunta platform was subjected to open marine circulation and intense storm activities.The storm deposited beds, intercalated with beds of lime-mudstone, consist primarily of fine sand and silt size carbonate particles that were hydrodynamically similar to quartz silt. Detrital carbonate particles are structureless and are of variable roundness. The particles were generated as primary carbonate clasts in coastal areas by mechanical disintegration of rapidly lithified beds, stromatolites or laminites, and the finest grade was transported to the offshore areas by storm-generated currents.

Araçatuba Formation: palustrine deposits from the initial sedimentation phase of the Bauru Basin

The Bauru Basin (Upper Cretaceous) accumulated an essentially sandy continental sedimentary sequence. In a first desertic phase the basaltic substratum was covered by a widespread and homogeneous aeolian sand unit with minor loess intercalations. The substratum relief favored the formation of an endorheic drainage system under semi-arid climate, a process that started the development of the Araçatuba Paleoswamp. The palustrine deposits (Araçatuba Formation) comprise siltstone and tipically greenish gray narrow tabular strata of sandstone cemented by carbonate. Moulds and gypsite and dolomite pseudomorphs were identified. The moulds seem to be genetically associated with desiccation cracks, root marks and climbing ripple lamination levels, that, on the whole, indicate calm shallow saline waters undergoing phases of subaerial exposition. At the boundaries of the study area, sand units may exhibit sigmoidal features and convolute bedding structure, which is characteristic of marginal deltaic deposits. The Araçatuba Formation is enclosed in and later overlaid by the aeolian deposits of the Vale do Rio do Peixe Formation.

Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica

Sandstone tempestite beds in the Starshot Formation, cen- tral Transantarctic Mountains, were deposited in a range of shoreline to shelf environments. Detailed sedimentological analysis indicates that these beds were largely deposited by wave-modified turbidity currents. These currents are types of combined flows in which storm-generated waves overprint flows driven by excess-weight forces. The interpreta- tion of the tempestites of the Starshot Formation as wave-dominated turbidites rests on multiple criteria. First, the beds are generally well graded and contain Bouma-like sequences. Like many turbidites, the soles display abundant well-developed flutes. They also contain thick divisions of climbing-ripple lamination. The lamination, however, is dominated by convex-up and sigmoidal foresets, which are geometries identical to those produced experimentally in current-dominated com- bined flows in clear water. Finally, paleocurrent data support a tur- bidity-current component of flow. Asymmetric folds in abundant con- volute bedding reflect liquefaction and gravity-driven movement and hence their orientations indicate the downslope direction at the time of deposition. The vergence direction of these folds parallels paleocur- rent readings of flute marks, combined-flow ripples, and a number of other current-generated features in the Starshot event beds, indicating that the flows were driven down slope by gravity. The wave component of flow in these beds is indicated by the presence of small- to large- scale hummocky cross-stratification and rare small two-dimensional ripples. Wave-modified turbidity currents differ from deep-sea turbidity cur- rents in that they may not be autosuspending and some proportion of the turbulence that maintains these flows comes from storm waves. Such currents are formed in modern shoreline environments by a com- bination of storm waves and downwelling sediment-laden currents. They may also be formed as a result of oceanic floods, events in which intense sediment-laden fluvial discharge creates a hyperpycnal flow. Event beds in the Starshot Formation may have formed from such a mechanism. Oceanic floods are formed in rivers of small to medium size in areas of high relief, commonly on active margins. The Starshot Formation and the coeval Douglas Conglomerate are clastic units that formed in response to uplift associated with active tectonism. Sedi- mentological and stratigraphic data suggest that coarse alluvial fans formed directly adjacent to a marine basin. The geomorphic conditions were therefore likely conducive to rapid fluvial discharge events asso- ciated with storms. The abundance of current-dominated combined- flow ripples at the tops of many Starshot beds indicates that excess- weight forces were dominant throughout deposition of many of these beds.

The Mackenzie Delta: sedimentary processes and facies of a high‐latitude, fine‐grained delta

The Mackenzie Delta is a large fine‐grained delta deposited in a cold arctic setting. The delta has been constructed upon a flooding surface developed on a previous shelf‐phase delta. There are three principal depositional zones: the subaerial delta plain, the distributary channel mouth region and the subaqeous delta. The subaerial delta plain is characterized by an anastomosing system of high‐sinuosity channels and extensive thermokarst lake development. This region is greatly influenced by the annual cycle of seasonal processes including winter freezing of sediments and channels, ice‐jamming and flooding in the early spring and declining river stage during the summer and autumn. Deposition occurs on channel levees and in thermokarst lakes during flood events and is commonly rhythmic in nature with discrete annual beds being distinguishable. In the channel mouth environment, deposition is dominated by landward accretion and aggradation of mouth bars during river‐ and storm surge‐induced flood events. The subaqeous delta is characterized by a shallow water platform and a gentle offshore slope. Sediment bypassing of the shallow‐water platform is efficient as a result of the presence of incised submarine channels and the predominance of suspension transport of fine‐grained sediments. Facies of the shallow platform include silty sand with climbing ripple lamination. Offshore facies are dominated by seaward‐fining fine sand to silt tempestites. Sea‐ice scouring and sediment deformation are common beyond 10 m water depth where bioturbated muds are the predominant facies. The low angle profile of the shallow‐water platform is interpreted to be the combined response of a fine‐grained delta to (1) storm sediment dispersal; (2) autoretreat as a result of the increasing subaerial and subaqeous area of deposition as the delta progrades out of its glacial valley; (3) limited water depth above the underlying flooding surface; and (4) efficient nearshore bypassing of sediment through subice channels at the peak of spring discharge. Several indicators of the cold climate can be used as criteria for the interpretation of ancient successions, including thermokarst lake development, submarine channel scours, freeze–thaw deformation and ice‐scour deformation structures. Permafrost inhibits compaction subsidence and, together with the shallow‐water setting, also limits autocyclic lobe switching. The cold climate can thus influence stratal architecture by favouring the development of regional‐scale clinoform sets rather than multiple, smaller scale lobes separated by autocyclic flooding surfaces.

Grain segregation mechanism in aeolian sand ripples

Many sedimentary rocks are formed by migration of sand ripples. Thin layers of coarse and fine sand are present in these rocks, and understanding how layers in sandstone are created has been a longstanding question. Here, we propose a mechanism for the origin of the most common layered sedimentary structures such as inverse graded climbing ripple lamination and cross-stratification patterns. The mechanism involves a competition between three segregation processes: (i) size-segregation and (ii) shape-segregation during transport and rolling, and (iii) size segregation due to different hopping lengths of the small and large grains. We develop a discrete model of grain dynamics which incorporates the coupling between moving grains and the static sand surface, as well as the different properties of grains, such as size and roughness, in order to test the plausibility of this physical mechanism.

Preservation of pre-vegetational mixed fluvio–aeolian deposits in a humid climatic setting: an example from the Middle Proterozoic Eriksfjord Formation, Southwest Greenland

Sedimentological studies of a 30 m thick coastal cliff section within the Middle Proterozoic Eriksfjord Formation in western South Greenland reveals three distinct types of fluvial sand sheet deposits that reflect perennial streams (Type I), semi-perennial streams (Type II), and ephemeral flash floods (Type III). Perennial river sand sheets are characterised by co-sets of medium-scale trough cross-beds, interbedded with isolated medium- and large-scale, high-angle, tabular cross-beds. Indications of desiccation or subaerial exposure are absent. Semi-perennial fluvial sand sheets consist predominantly of low-angle cross-beds, interbedded with isolated sets of high-angle tabular cross-beds with common reactivation surfaces. Horizontal lamination and climbing ripple lamination form subordinate structures. Associated with the sand sheets are adhesion structures and 0.05–0.4 m thick sets of wind ripple-lamination indicating periods of subaerial exposure and aeolian reworking. High-energy ephemeral flash flood sand sheets consist almost exclusively of planar-parallel lamination and climbing ripple lamination with some isolated sets of low-angle cross-bedding. Scouring and internal truncation surfaces are common. The three types of sand sheets are considered to reflect deposition under changing climatic conditions, varying from humid to arid or semi-arid. Aeolian deposits are preserved within the sand sheets showing characteristics of dominantly perennial flow punctuated by shorter periods of desiccation (Type II), while sand sheets showing features typical of arid and or semi-arid flow conditions (Type III) contain no preserved aeolian deposits. This selective preservation is interpreted to be a result of the combined effect of groundwater table level and fluvial style which in turn are inferred to have been controlled by the climatic regime. The deposits show that during pre-vegetational times the preservation of aeolian deposits, under certain conditions, may be more optimal in fluvial systems formed in a humid climate than in fluvial systems formed under semi-arid or arid circumstances. The occurrence of aeolian deposits within a Precambrian succession of fluvial deposits therefore, need not be an indication of the most arid environmental conditions.

Turbidite Channel/Overbank Deposition in a Lower Devonian Orogenic Shale Basin, Fortin Group of Gaspe Peninsula, Northern Appalachians, Canada

ABSTRACT The Lower Devonian Fortin Group, one of the major stratigraphic units in Connecticut Valley-Gaspe Synclinorium of the Gaspe Peninsula, and its stratigraphic equivalent, the Temiscouata Formation in northwestern New Brunswick and southeastern Quebec, are interpreted as a base-of-slope to deep-basin turbidite succession sandwiched between shallow-marine to nonmarine Siluro-Devonian sediments. The deep-water interpretation is based on a comparison with modern deep-sea turbidite depositional environments and the lower-slope to deep-basinal settings established by previous investigators for equivalent rocks in New England. The monotonous sequences of largely unfossiliferous, well-bedded dark slate, phyllite, and siltstone with intercalated sandstone packets of the Fortin Group and Temiscou ta Formation in the Matapedia and Madawaska/St. John Valley regions, respectively, are interpreted as submarine overbank and channel-fill facies associations. Seven lithofacies have been distinguished: (1) Associations of massive sandstone beds up to 13 m thick and (2) associations of sandstone beds of intermediate (0.5-2.0 m) thickness forming isolated sandstone packets encased in slate and siltstone are the equivalent of modern deep channel-fill deposits. (3-5) Laterally continuous, largely nonbioturbated thin siltstone layers with climbing-ripple lamination (turbidite c division) and parallel lamination (turbidite d division) followed by slate (turbidite e division and hemipelagite) are analogous to muddy spill-over turbidites with interbedded hemipelagites on modern natural levees th t accompany deep channels. Among the fine-grained sediments, a proximal-to-distal facies succession (with respect to presumed lateral distance from channels) consists of (3) siltstone-slate, (4) banded slate, and (5) laminated slate, if found in lateral succession. The same succession may reflect spill-over from progressively deeper channels. The channel/levee interpretation is supported by field observations of (i) a partly exposed channel wall, (ii) truncation of siltstone and slate layers at sandstone contacts, (iii) lag material at the base of massive sandstone layers, and (iv) the chevron pattern of nearly opposing paleocurrent directions in the spill-over facies. (6) Syndepositionally deformed and diamictite facies comprise fine-grained rocks of Facies 3-5. (7) Volumetrically subor inate conglomerates are the coarsest of the redeposited sediments. Siegenian (Praguian)-Emsian turbidite deposition occurred in a deep basin of the Connecticut Valley-Gaspe Trough that developed in response either to wrench tectonics or back-arc spreading related to a volcanic island arc (Piscataquis volcanic belt)/deep-sea trench system (Merrimack-Fredericton Trough).

Sedimentary Regime of Tullock Member of Fort Union Formation, Tullock Creek Type Locality, South-Central Montana: ABSTRACT

The early Paleocene Tullock Member of the Fort Union Formation at its type locality was deposited in a low-gradient riverine system. This interpretation is based on studies of sedimentary structures, geometry, thickness trends, and sand-percent isopach maps. Lithologies consist of interbedded sandstones, siltstones, shales, and thin coal beds. Sandstones 10 m (32.8 ft) thick contain fining-upward, fine-grained, structureless units with erosional bases capped by climbing-ripple lamination. Some sandstones have claystone rip-up clasts at their bases. The sandstones are discrete, highly convex bodies with symmetrical cross sections and flat erosional bases. These sandstone bodies are isolated show no stacking or coalescing, and are concentration in the middle of the Tullock Member. Interbedded calcareous siltstones show ripple cross-laminae and contain elongate calcareous nodules 4 to 16 cm (1.6 to 6.3 in.) long, oriented parallel to the bedding plane. They also contain well-preserved, fragmented leaf impressions. Carbonaceous shale predominates in the upper and lower third of the member. These shales show very thin lamination, contain abundant plant fragments, and have a mottled rooted texture. Thin, discontinuous coal beds are found within the lower third of the Tullock.

Sorting and Wave Abrasion: Controls on Composition and Diagenesis in Lower Frontier Sandstones, Southwestern Wyoming

Lower Frontier sandstones on the Moxa arch were deposited in a wave-dominated, multi-river delta plain which prograded eastward into the Cretaceous Interior seaway; headwaters were in the Sevier thrust belt. Sands were deposited as fluvial units, as marine shoreline sequences, and as offshore sand ridges. Fluvial sandstones, some pebbly, are dominated by trough cross-stratification and by climbing ripple lamination. These sandstones are associated with flood-basin mudstones that contain abundant root traces and lack burrows. Marine shoreline sediments show a transition from burrowed lower shoreface parallel- and hummocky-stratified and ripple-laminated sandstones with mudstones, to surf-generated cross-stratification, to foreshore parallel stratification, and finally to s ructureless backshore sandstones. Offshore sandstones are mostly burrowed, but storm-generated parallel and hummocky stratification is present. Depositional hydrodynamics largely controlled diagenesis. Fluvial sandstones contain a greater percentage of rock fragments and have less quartz than equivalent marine sandstones owing to the combined effects of sorting and wave abrasion. The coarsest sands and gravels, which were trapped on the deltaic plain, were richer initially in rock fragments than finer grained sands that were passed to the shoreline. These latter sands had a significant portion of unstable grains, including chert, destroyed by wave abrasion. Composition significantly influenced diagenesis. Quartz-rich, permeable marine sandstones were cemented early by silica (because quartz overgrowths preferentially form on monocrystalline quartz), whereas primary porosity in quartz-poor fluvial sandstones was largely preser ed through this stage. Fluvial sandstones were affected more by grain dissolution, calcite replacement, calcite precipitation in open pores, and by subsequent carbonate dissolution. Fluvial sandstones generally have the best porosity and permeability mostly due to creation of secondary porosity. Compaction in finer grained sandstones destroyed permeability by squeezing clays into open spaces. Other major diagenetic processes are late-stage growth of kaolinite and continued precipitation of silica.

Middle-fan deposits from the late precambrian kongsfjord formation submarine fan, Northeast Finnmark, Northern Norway

The 3.2 km-thick late Precambrian Kongsfjord Formation Submarine Fan shows well-developed middle-fan facies-associations. Channel deposits are characterised by discrete packets of coarse-grained, medium to thick-bedded, amalgamated sandstone turbidites and other mass-flow deposits, generally 10 to 30 m thick. Individual beds, or packets of beds, wedge out and channel bases cut down by up to 11 m over a lateral distance of 150 m. Channel deposits often comprise a thinning-and-fining-upward sequence although they vary greatly in clarity. Interchannel deposits occur as packets, tens of centimetres to 25 m thick, of thin and very thin bedded Bouma T cde siltstones and mudstones. Palaeocurrents within interchannel deposits commonly diverge from those of adjacent channel sandstones. Within the interchannel deposits, isolated beds or packets of beds occur that are both thicker bedded and coarser grained than the surrounding beds; these unusual deposits are sheet-like or fill small channels, and are interpreted as crevasse splays, lobes and channels. Packets, up to a few metres thick, of laterally discontinuous siltstone turbidites occur immediately above some of the channel sandstones, rarely below, and in some cases within interchannel deposits. These siltstones are thin to medium-bedded, show Bouma T cd, with T c often as climbing-ripple lamination, and commonly show soft-sediment deformation as slides, slumps, liquefaction and fluidisation structures. Palaeoflow within these packets, compared to adjacent channel sandstones, diverges by up to 90°, and in some cases channel sandstones are seen to pass laterally into these deposits with a swing in palaeocurrents from parallel to the inferred channel axis, to perpendicular to it. These deposits are thought to be levees. Channel-margin deposits are most distinctive, and they are recognised by extreme lateral wedging of channel sandstones, with concomitant thinning and fining of individual beds and their amalgamation towards the channel axis. Sliding and slumping of channel margin deposits is common. Throughout the Kongsfjord Formation Submarine Fan, channel sandstone palaeocurrents suggest a sediment-transport direction to the NE quadrant, although some channels funnelled sediment towards the southeast.

Facies sequences and trace fossils in lacustrine/fan delta deposits, Hornelen Basin (M. Devonian), Western Norway

Study of a lacustrine—fan delta succession in a marginal tract of Hornelen Basin shows that occasional lakes were infilled by marginal accretion and progradation of the adjacent fluvial system. The lake deposits are dominantly thin graded rhythmites and thicker massive fine sandstones,both of great lateral extent and formed by fine sediment gravity flows. Wave-generated ripple lamination is also very common whereas current, especially climbing-ripple lamination occurs increasingly towards the southern edge of the lake. Much of the lacustrine sequence is contorted, convoluted or deformed to a lesser degree. Trough cross-stratified sandstones and pebbly sandstones characterised the lowsinuosity stream systems which fed the lakes from the south. In a narrow transitional zone, interpreted in terms of high-sinuosity distributary channels and shoreline, there are significant amounts of planar cross-strata as well as ripple and plane parallel lamination. Eight distinct types of trace fossils, chiefly arthropod tracks, trails and burrows ( Scoyenia ichnofacies) are present in the fine sediments (mudflats, pools and low bars) of this latter zone. Behaviour patterns are dominantly locomotion and resting traces, possibly with some surface feeding but an absence of infaunal feeding or dwelling structures. The repeated progradation and retreat of the sandy fan-delta system into the lakes generated mudstone-bounded sedimentary bodies. These are mainly alluvial coarsegrained, upward coarsening and 5–25 m thick in the proximal areas. They are mainly lacustrine, fine-grained, symmetrical (coarsest in the middle) or uniform and generally less than 5 m thick, distally. In origin these bodies probably represent northward crevassing out of the main westward-flowing axial fluvial system and were possibly triggered by repeated base level changes caused by lowering of the basin floor against the northern fault margin. The trace fossils, described here for the first time in Norway, are also known from several other Devonian alluvial sequences, although the closest comparable ichnofauna occurs in ephemeral lacustrine deposits in south Scotland. The type of arthropod that made the trace fossils cannot be identified at present.

DummyGeometry and internal organization of hyperpycnites associated with a shelf-margin delta, the Middle Pleistocene Kokumoto Formation on the Boso Peninsula of Japan

Some turbidite beds of the Middle Pleistocene Kokumoto Formation on the Boso Peninsula of Japan exhibit different types of vertical and lateral changes in grain size and sedimentary structures compared with the Bouma model, which is generally interpreted to represent turbidites deposited from surge-type, ephemeral turbidity currents. Some turbidite beds examined by this study are characterized by several repetitions of coarsening-to-fining upward patterns in association with climbing ripple lamination and parallel lamination. Furthermore, these turbidites are not necessarily laterally continuous in the two-dimensional cross section. Two thickest parts are separately observed within the same stratigraphic level. The geometry and internal organization of these turbidites are interpreted to be a product of hyperpycnal flows generated from a multi-source system associated with a shelf-margin delta in an upslope area during falling- and lowstand stages.