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Quaternary sea-level fluctuations and steady state bathymetric profile for Fuji basin. (A) Apparent sea level curve (eustasy plus water loading) showing eccentricity-dominated signature, 100-k.y. cycles (Miller et al., 2005). Timing uncertainties in sea level curve are approximately ±5 k.y., whereas amplitude errors range from ±10% (low stands) to +20% (high stands) (K. G. Miller, 2007, personal communication). (B) Evolution of the Fuji basin, showing ponded basin fill (top) to perched slope fill (middle) to complete bypass (bottom), following Beaubouef and Friedmann (2000). Note that the Fuji basin profile is taken from present-day bathymetry, whereas the dip of the regional profile was taken from Prather et al. (1998). P. lacunosa = Pseudoemiliania lacunosa ; S. antillea = Stilostomella antillea.
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Three-dimensional seismic data from the Fuji basin, as alt- controlled intraslope minibasin in north-central Green Can- yon, Gulf of Mexico, reveal complex interactions between gravity- and suspension-driven sedimentation. Seismic vol- umes for late Pleistocene (∼470 ka) to Holocene fill within the Fuji basin consist of approximately 45% mass trans...
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The characteristics of coastal zones are controlled by the geological structure and properties of rock and soil mass, and accordingly they can be classified into several categories. In this paper, six important problems confronted in coastal geological environment were discussed: (1) earthquake and tsunami; (2) seawater invasion; (3) coast erosion...
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... Ponded or confined turbidite systems are documented from small (up to several kilometres across) intra-slope basins with fault or saltcontrolled geometries (e.g. Madof et al., 2009;Prather et al., 2012;Cumberpatch et al., 2021), as well as successions deposited in structurallycontrolled foredeep basin-plain settings with dimensions from kilometres to tens of kilometres across (e.g. Pickering & Hiscott, 1985;Haughton, 1994Haughton, , 2000Kneller et al., 1997;Sinclair, 2000;Remacha et al., 2005;Amy et al., 2007;Tinterri & Muzzi Magalhaes, 2011;Fonnesu et al., 2018;Tinterri & Piazza, 2019;Patacci et al., 2020). ...
This study demonstrates the effectiveness of sedimentological–statistical multivariate analysis of one‐dimensional‐section in the unravelling depositional processes and sedimentation patterns recorded in a contained and partially ponded succession. Turbidite deposition of a 100 m thick mud‐rich Oligocene‐age sequence at Szczawa, the Polish Outer Carpathians, was primarily controlled by topographic confinement and magnitude of incoming flows. Only the largest turbidite flows were subjected to the true flow ponding, while in smaller volume flows the silty/sandy part behaved as unconfined flow and only muddy suspension cloud developed a ponded character. True ponding of low‐density turbidity currents is interpreted for sandstones that show sedimentary structures attesting to flow reflections and combined‐flow processes and are associated with abnormally thick co‐genetic mudstones, which in turn results in low sandstone‐to‐mudstone ratio, irrespective of turbidite bed thickness. These features testify to pronounced interaction of flows with confining topography. Tractional structures associated with a considerable proportion of fines, namely banded structure and heterolithic bedding, are interpreted as produced during transitional (turbulent to laminar) flow phase in the condition of mud‐rich turbidite flow confinement. These structures are also considered here as indicators of proximity to source area and location on the slope. The co‐occurrence of banded sandstones, hybrid event megabeds and an olistostrome resulted from flows‐trapping, confined basin geometry, which precluded downslope propagation and further transformation of large‐volume flows. Therefore, a structurally‐controlled contained intraslope mini‐basin is proposed here as the most likely depositional setting. This work provides robust field and statistical evidence for ponding processes of low‐density turbidity currents in a structurally‐controlled mini‐basin. The results of this study are consistent with experimental data and recent field studies on ponded turbidites. Therefore, the Szczawa succession may serve as a new reference example of containment processes of low‐density turbidity currents and represents a valuable depositional model for intraslope turbidite succession.
... Attached submarine failure deposits tend to be regionally extensive and can be divided into shelf-attached from remobilized shelf sediments linked to shelf-edge deltaic systems, and slope-attached from remobilized slope sediments . Detached submarine failure deposits are geometrically smaller and associated with localized instabilities such as diapirism/halokinetics (Madof et al., 2009;Wu et al., 2020) or oversteepening in thrusts belts anticlines (Moscardelli and Wood, 2008;Ortiz-Karpf et al., 2018) (Fig. 2). ...
Mass transport complexes and their associated mass transport deposits—both referred to here as submarine failure deposits—are virtually ubiquitous in the modern and ancient sedimentary record of many deepwater basins. As exploration expands to new frontiers, submarine failure deposits are being identified as components of the petroleum system in numerous prospects. Although such deposits were historically considered facies to avoid from a viewpoint of petroleum exploration, it is now recognized that they can act as source, reservoir, or seal elements. In this paper, we set out to investigate the role of submarine failure deposits as effective seals in the petroleum system using published data and propose a methodology to risk some first-order factors at a macro-, meso-, and micro-scale that influence the seal quality of these submarine failure deposits. We accomplish this by discussing the properties intrinsic to submarine failure deposits that affect the seal quality at different scales. Based on published literature, at least six offshore fields from the Gulf of Mexico and NW Borneo are reported to have a submarine failure deposit as an effective seal. These fields combined account for ∼0.9 billion barrels of oil equivalent of cumulative discovered reserves globally and prove the potential of submarine failure deposits as effective seals and a future undervalued play concept. We use three case studies to illustrate our methodology. Our methodology can be further customized using datasets from industry and public records. The seal risk matrix presented here is based on more than a decade of research and has been already used by several exploration companies with encouraging feedback. We acknowledge the limitations of the methodology, but future interdisciplinary research and integration of new datasets and results will improve the de-risking of submarine failure deposits in exploration. Additionally, this methodology can potentially be applied to assessing seal potential of submarine failure deposits for carbon capture sequestration and storage projects.
... Most examples involve simple aggradation of confined turbidites against stable slopes that are either bare of sediment or draped by mud. Less is known about onlap settings where the onlap is inherently unstable and the slope/base of slope is modified by episodic slope failures, although this situation is likely to be common in basins on active substrates, such as slope minibasins in the Gulf of Mexico and elsewhere (Madof et al., 2009;Beaubouef and Abreu, 2010) or thrust-top basins (Tinterri and Tagliaferri, 2015). Onlaps associated with the Alfaro sub-basin are instructive on a number counts: ...
The Neogene Tabernas Basin, SE Spain, provides important evidence at outcrop for the interplay between tectonic deformation of the sea floor, slope instability and turbidity current behaviour. Dextral-oblique strike-slip faults and associated folds propagated along the basin axis to deform the palaeo-sea floor, creating structurally-controlled depressions in which turbidity currents were trapped and ponded. EW-trending syn-depositional faults define a narrow sub-basin that subsided asymmetrically as a negative flower structure. The sub-basin contains an expanded succession (>300 m of ponded turbidite sheets, debrites and slumps) along its northern margin flanked by the principal fault strand defined by a wide zone of sheared and calcite-veined marl. A narrower fault zone with a smaller displacement marks the southern margin of the sub-basin and the fill close to it is thin with internal discordances, evidence of local failure and southward thinning of sandstone sheets. Both northern and southern faults ‘died’ at the same stratigraphic level and were overstepped by basin floor turbidites showing evidence of weaker and longer-range topographic confinement. As turbidites healed and aggraded out of the sub-basin to progressively onlap the southern margin of the basin, major gravity failures occurred emplacing thick (>100 m) mass-transport complexes. The first initially reworked the southern part of the sub-basin fill together with the early onlap wedge, the second remobilised the onlap wedge, and the third records failure of the upper part of the slope well above the wedge. The first two were toe-confined failures, the third and furthest travelled was confined by basin axis topography. All three failures are lateral to or directly overlain by ‘megabed’ sheets on the basin floor, implying either a common trigger (earthquakes) or slope instability following reflection of large volume flows. Tabernas turbidites highlight the role of basin tectonics (as opposed to up-dip supply and sea level fluctuations) in directly impacting on deep-water processes and stratigraphy. Small deep-water transtensional sub-basins opened up along long transfer faults accommodating regional extension.
... Three mud-dominated condensed sections with draping geometries bound two stratigraphic units that consist of turbidites and mass-transport deposits (Fig. 10C). Brazos-Trinity basin 4 is an example of a salt-withdrawal minibasin with a relatively large proportion of sandy channelized and lobe architectural elements; other minibasins can have much larger proportions of muddy mass-transport deposits and hemipelagites (e.g., the Fuji Basin consists of only ~5% sandy channelized turbidites; Madof et al., 2009). The seismic-stratigraphic character of these salt-withdrawal minibasins is more layered than that of our study area in the Campos Basin. ...
Submarine channels are conduits for sediment delivery to continental margins, and channel deposits can be sandy components of the fill in tectonically active salt basins. Examples of salt-withdrawal basin fill commonly show successions of sandy channelized or sheet-like systems alternating with more mud-rich mass-transport complexes and hemipelagites. This alternation of depositional styles is controlled by subsidence and sediment-supply histories. Salt-basin fill comprising successions of largely uninterrupted meandering-channel deposition are less commonly recognized. This begs the questions: can sediment supply be large enough to overwhelm basin subsidence and result in a thick succession of channel deposits, and, if so, how would such a channel system evolve? Here, we use three-dimensional seismic-reflection data from a >1500 km2 region with salt-influenced topography in the Campos Basin, offshore Brazil, to evaluate the influence of salt diapirs on an Upper Cretaceous–Paleogene giant meandering submarine-channel system (channel elements >1 km wide; meander wavelengths several kilometers to >10 km). The large scale of the channels in the Campos Basin suggests that sediment discharge was large enough to sustain the meandering channel system in spite of large variability in subsidence across the region. We interpreted 22 channel centerlines to reconstruct the detailed kinematic evolution of this depositional system; this level of detail is akin to that of recent studies of meandering fluvial channels in time-lapse Landsat satellite images. The oldest channel elements are farther from salt diapirs than many of the younger ones; the centerlines of the older channel elements exhibit a correlation between curvature and migration rate, and a spatial delay between locations of peak curvature and maximum migration distance, similar to that observed in rivers. As many of the younger channel centerlines expanded toward nearby salt diapirs, their migration pattern switched to downstream translation as a result of partial confinement. Channel segments that docked against salt diapirs became less mobile, and, as a result, they do not show a correlation between curvature and migration rate. The channel migration pattern in the Campos Basin is different compared to that of a tectonically quiescent continental rise where meander evolution is unobstructed. This style of channelized basin filling is different from that of many existing examples of salt-withdrawal minibasins that are dominated by overall less-channelized deposits. This difference might be a result of the delivery of voluminous coarse sediment and high discharge of channel-forming turbidity currents to the Campos Basin from rivers draining actively uplifting coastal mountains of southeastern Brazil. Detailed kinematic analysis of such well-preserved channels can be used to reconstruct the impact of structural deformation on basin fill.
... Architecture of the study area consists of the stacking of different types of seismic units classically encountered in similar slope and turbidite environments (e.g. Twichell et al., 1991;Piper et al., 1997;Droz et al., 2003;Madof et al., 2009) and already identified in the Danube Fan (Zander et al., 2017;Hillman et al., 2018;Winguth et al., 2000;Popescu et al., 2004;). The majority of these units are the channel/ levee systems and MTDs. ...
... It is generally considered that during sea-level falls, migration of the river-mouth to the shelf edge and rapid deltaic sedimentation leads to an increase in sedimentation load, overstepping and overpressuring in the prodelta and slope sediments, resulting in sediment failure, MTD formation, and canyon development (Weimer, 1990;Posamentier and Kolla, 2003;Madof et al., 2009). A link between the MTDs, the scarp Fig. 3B) shows the characteristics of the eastern side of channel complex B with the staircase shape of the erosional surface, the internal levee overlying the MTD resulting from the collapse of levee B3. ...
The upper continental slope offshore Romania is a complex area hosting turbidite deposits, multiple types and ages of deep-seated faults, gas hydrates, gas-escape features, and numerous Mass Transport Deposits (MTDs). Multi-scale seismic data sets (2D-high-resolution and near-bottom very high-resolution) were used to study the interaction between such disparate geological features and determine their impact on slope stability.
At least five main paleo-valleys have been identified in the north of the Viteaz (Danube) canyon/valley. The most recent channelized systems linked to these valleys formed over a basal layer of MTDs. These MTDs are associated with an unconformity corresponding to the Base Neoeuxinian Sequence Boundary formed during the last major sea-level fall. This erosional surface shows scarp alignments that coincide with underlying faults. We argue that gravity-driven fault reactivation, with possible upward gas/fluid migration along these faults, is a determinant factor controlling sedimentary instabilities. Numerous MTDs are also observed during channel-levees building and reveal local sediment instabilities related to localized erosional process in the canyon. Finally, MTDs recorded within the upper draping unit, suggest that sediment instability also occurred during recent sea level highstand. Sediment pulse, seismicity, and gas hydrate dynamics can also play a determinant role in sediment instability throughout the sediment record.
... Over the western study area two sets of chaotic weak reflections with internal block rotation are observed in GU2 and GU3 (Figure 12a), representing mass-transport deposits (MTDs) (e.g., Gong et al., 2014;Morley, 2009;Moscardelli & Wood, 2008). These MTDs are assumed to be of intrabasinal origin (e.g., Heinio et al., 2006;Madof et al., 2009) with short distance of sliding and slumping, associated with the remobilization of unconsolidated deposits trigged by intense structural uplift of the detachment fold. ...
This paper presents a three‐dimensional (3D) seismic‐based case study (∼1,200 km²) from the deepwater Niger Delta to examine the role of shale deformation in the structural development of a deepwater gravitational system. Tectono‐stratigraphic interpretation reveals that this system consists of two sets of major fold‐thrusts laterally separated by a central oblique detachment fold. A prominent shale thick beneath these structures is believed to have originated from tectonic deformation rather than a pretectonic thick, due to its complex internal structures. Seismic mapping of the growth units indicates synchronous initiation of the oblique detachment fold with the main thrusts and gradual growth in response to thickening shales. Downslope gravitational contraction is not considered the direct cause for the oblique shale‐detachment fold. Evidence from the 3D shale distribution and deformation styles within the shale unit reveals that shales that were squeezed out of adjacent shale‐thinning areas “flowed” laterally into the detachment‐fold core. Based on the spatial variation in structural deformation and growth strata distribution, this study proposes a model that considers differential contraction and differential loading from syntectonic sediments as two key factors leading to the 3D shale redistribution which ultimately determines the deformation styles and evolution history within the overburden. Additionally, seismic imaging within the shale unit recognizes various internal structures ranging from hundreds to thousands of meters in scale, and confirms what has been suggested in previous studies, that redistribution of shales occurred through a combination of multiscale brittle failures, ductile folding, and plastic flows.
... Over the last two decades, significant progress has been made in the understanding of (1) the large-scale stratigraphic architecture and evolution of salt-withdrawal minibasins (Mahaffie, 1994;Pratson and Ryan, 1994;Winker, 1996;Prather et al., 1998;Badalini et al., 2000;Beaubouef and Friedmann, 2000;Booth et al., 2000;Winker and Booth, 2000;Meckel et al., 2002;Sinclair and Tomasso, 2002;Booth et al., 2003;Smith, 2004;Beaubouef and Abreu, 2006;Mallarino et al., 2006;Madof et al., 2009;Pirmez et al., 2012;Prather et al., 2012a, b) and (2) the behavior of turbidity currents entering the basins and the resulting fine-scale depositional features (Brunt et al., 2004;Lamb et al., 2004Lamb et al., , 2006Smith and Joseph, 2004;Toniolo et al., 2006a, b;Khan and Imran, 2008;Viparelli et al., 2012). However, these studies have largely focused on sedimentary processes, and the effects of basin subsidence on the stratigraphic architecture have received limited attention. ...
Intraslope basins, or minibasins, are topographic features of the continental slope that can be filled with sediment transported by submarine flows. These deposits may contain important hydrocarbon reservoirs. Here we present results of two-dimensional numerical simulations of multiple turbidity currents entering two linked minibasins. The numerical model accounts for the non-uniformity of sediment grain size in the flow and the resulting deposit. Model results reasonably reproduce the evolution of linked minibasins illustrated in the field based “fill-and-spill” conceptual model. The conceptual model was developed for the Brazos–Trinity system from field observations. Further, simulations of two linked minibasins show that the upstream basin traps most of the coarse sediment. This material is deposited in the proximal zone of the basin and fine sediment is transported farther downslope, resulting in the formation of a weak pattern of downstream fining. Model results with different initial and boundary conditions reveal that minibasin geometry and turbidity-current characteristics are important controls on the deposit shape and grain-size distribution.
... The Sollube basin is of a similar size and geometry to previously reported subsurface minibasins ( Fig. 13; e.g., Pratson and Ryan 1994;Booth et al. 2003;Madof et al. 2009;Doughty-Jones et al. 2017). Therefore, this rare, exhumed example of a halokinetically influenced deep-water succession provides an excellent exposure of fine-scale minibasin depositional architecture, providing an analogue for subsurface minibasins. ...
... 8,10,13). As the basin developed, thicker-bedded sandstones representing channel fills and lobes were deposited in topographic lows (basin axis), consistent with subsurface analogues (e.g., Booth et al. 2003;Madof et al. 2009;Mayall et al. 2010;Doughty-Jones et al. 2017) and numerical models (e.g., Sylvester et al. 2015;Wang et al. 2017). Towards the flanks, the lower-density parts of the flows responsible for the thickbedded sandstones may run up topography, depositing thin-bedded sandstones. ...
... Before this study, most understanding of halokinetically-influenced deep-water systems came from subsurface datasets (e.g., Booth et al. 2003;Madof et al. 2009;Carruthers et al. 2013;Doughty-Jones et al. 2017). Features that are common across several depositional settings where halokinetic movements are observed include multi-scalar thinning and onlap, growth faulting, pebble conglomerates, mixed siliciclastic-carbonate lithologies, MTDs, variable paleocurrents, angular unconformities, and abrupt facies variability (Dalgarno and Johnson 1968;Dyson 1999;Kernen et al. 2012Kernen et al. , 2018Carruthers et al. 2013;Counts and Amos 2016;Counts et al. 2019). ...
Behavior of sediment gravity flows can be influenced by seafloor topography associated with salt structures; this can modify the depositional architecture of deep-water sedimentary systems. Typically, salt-influenced deep-water successions are poorly imaged in seismic reflection data, and exhumed systems are rare, hence the detailed sedimentology and stratigraphic architecture of these systems remains poorly understood.
The exhumed Triassic (Keuper) Bakio and Guernica salt bodies in the Basque–Cantabrian Basin, Spain, were active during deep-water sedimentation. The salt diapirs grew reactively, then passively, during the Aptian–Albian, and are flanked by deep-water carbonate (Aptian–earliest Albian Urgonian Group) and siliciclastic (middle Albian–Cenomanian Black Flysch Group) successions. The study compares the depositional systems in two salt-influenced minibasins, confined (Sollube basin) and partially confined (Jata basin) by actively growing salt diapirs, comparable to salt-influenced minibasins in the subsurface. The presence of a well-exposed halokinetic sequence, with progressive rotation of bedding, beds that pinch out towards topography, soft-sediment deformation, variable paleocurrents, and intercalated debrites indicate that salt grew during deposition. Overall, the Black Flysch Group coarsens and thickens upwards in response to regional axial progradation, which is modulated by laterally derived debrites from halokinetic slopes. The variation in type and number of debrites in the Sollube and Jata basins indicates that the basins had different tectonostratigraphic histories despite their proximity. In the Sollube basin, the routing systems were confined between the two salt structures, eventually depositing amalgamated sandstones in the basin axis. Different facies and architectures are observed in the Jata basin due to partial confinement.
Exposed minibasins are individualized, and facies vary both spatially and temporally in agreement with observations from subsurface salt-influenced basins. Salt-related, active topography and the degree of confinement are shown to be important modifiers of depositional systems, resulting in facies variability, remobilization of deposits, and channelization of flows. The findings are directly applicable to the exploration and development of subsurface energy reservoirs in salt basins globally, enabling better prediction of depositional architecture in areas where seismic imaging is challenging.
... Development of slope fans is associated with a change in bathymetric gradient between the base of the contemporaneous continental slope and upper portion of the basin floor Browne et al., 2005). Ponded fans develop due to confined sediment gravity flows where the slope has bowl-shaped and completely closed basins (Badalini et al., 2000;Pirmez et al., 2000;Prather, 2003;Madof et al., 2009;Gamberi and Rovere, 2011). In areas characterized by a normal downslope gradient decrease, turbidity currents freely spread in the basin plain and develop basin-floor fans in a lobate form with broad spatial extent King et al., 1994;Johnson et al., 2001;Saller et al., 2004;Yang and Kim, 2014). ...
The sediment budget of the Northwest Sub-basin, South China Sea since the Late Miocene (11.6 Ma, average thickness > 1000 m) accounts for more than two-thirds of the total infill since the initial ocean spreading of the sub-basin (32 Ma). The sediment sources and architectural pattern of these deposits, however, are poorly known. Using high-resolution 2D reflection seismic data with age constraint from IODP boreholes, we have documented two interdigitating basin-floor fan systems that developed since the Late Miocene. These were fed by two of the largest deep-water canyon systems worldwide, from the west (the Central Canyon Xisha Trough) and the northeast (the Pearl River Canyon), as well as from smaller headless canyons and gullies across the surrounding slopes. Based on careful analysis of seismic facies, their geometry and occurrence, we identify the principal deep-water architectural elements, including the multi-scale channels, channel-levee complexes, lobes, sheets and drapes, mass-transport deposits, volcanic intrusions, turbidity-current sediment-wave fields, and a contourite drift/terrace. Tentative reconstructions show that the development of these Late Miocene-Quaternary basin-floor fan systems was dominated by changes of sediment supply. The Xisha fan reached its largest extent during the Late Miocene, while the Pearl River fan was most active during the Late Miocene to Quaternary. During the Late Miocene, both the conduits of the Central Canyon and the Pearl River Canyon were active with abundant sediment supply, generating the two incipient fan systems. Sediment supply from the west via the Central Canyon persisted throughout the Late Miocene, being coarser-grained than that of the Pearl River fan. With the demise of the Central Canyon during the Pliocene and consequent sharp decrease in sediment supply, the Xisha fan size reduced significantly. By contrast, supply of mud-rich sediments from the Pearl River and northern slope increased through the Pliocene and into the Quaternary, leading to the modern sedimentary pattern of interdigitating basin-floor fans. Insights into the evolution of sediment supply and fan development through time derived in this study contribute to a better understanding of how source to sink systems feed marginal oceanic basins such as the South China Sea.
... On a slope with a simple topography, i.e. with a gradually decreasing downslope gradient, the slope channels transition into depositional lobes that spread onto the basinal plain. In contrast, in areas where intra-slope basins develop due to seafloor deformation, sediment gravity flows can be confined, leading to the development of ponded fans (Prather, 2003;Madof et al., 2009). ...
Analyses of high-resolution seismic reflection, drilling, and well-log data were combined to identify and investigate deepwater fans developed in the eastern part of the Qiongdongnan Basin, South China Sea, during the Middle Miocene and their relationship to slope morphology. We identified three types of deepwater fans that developed on the northern continental margin of the South China Sea during the Middle Miocene: (1) those consisting of small canyons and depositional lobes; (2) those consisting of large canyons and depositional lobes; and (3) those consisting of distributary channels without depositional lobes. Sourced from deltaic sediments deposited on the northern continental shelf margin, the lithologies of the sediments in all fans are dominated by siltstone. The scale of development and the internal features are mainly controlled by the slope topography. The deepwater fans consisting of small canyons and depositional lobes developed on slopes with low gradient, caused by the continuous progradation of the shelf-edge towards the basin centre due to sediment transport in high-speed flows. The canyon heads developed in this setting are located below the shelf-break; these canyons are narrower, shallower, and shorter than those of the deepwater fans consisting of large canyons. Thus, the scale of the depositional lobes deposited by gravity flow through such canyons is smaller than that of deepwater fans with large depositional lobes. Deepwater fans consisting of large canyons and depositional lobes developed on steep narrow slopes, caused by rising shelf-edge trajectories due to the equilibrium between the sediment supply and subsidence rates. The canyon heads developed in this setting are located upon the shelf-break and extend toward the toe of the slope, incising the shelf-break; these canyons are wider, deeper, and longer than those of the deepwater fans consisting of small canyons. The scale of the depositional lobes deposited by gravity flows transported through such canyons is correspondingly larger than that of deepwater fans with small depositional lobes. Deepwater fans consisting of distributary channels without depositional lobes developed on gentler and wider slopes than slopes where small canyons and depositional lobes formed, owing to the low sediment supply. The deepwater distributary channels have a long transportation distance and wider distribution area, enabling the formation of large-scale deepwater fans. Depositional models for all three types of deepwater fans were postulated.
