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1.
Channel-levee systems are frequently interpreted as having a long history of cut-and-fill by channel-shaped features of different scales. Results from a simple geometric model based on a centerline migration algorithm combined with a vertical channel trajectory show that an incising-to-aggrading trajectory of a single channel can produce realistic morphologies similar to systems observed on the seafloor and subsurface, including features such as a basal erosional surface, coeval inner and outer levees, internal erosional boundaries, and terraces draped by inner levee deposits. Channel migration results in composite erosional surfaces that are distinct from topographic surfaces, and their formation does not require larger than usual erosional flows. Many submarine channels interpreted as underfit were probably carved by flows similar to the ones that eroded and deposited the entire channel system. We suggest that the features of most submarine channel-levee systems do not require large temporal variations in flow magnitude but can be explained by a simpler model whereby incision, migration and aggradation of a single channel form over time results in an apparently complex system.  相似文献   

2.
The seismic geomorphology and seismic stratigraphy of a deep-marine channel-levee system is described. A moderate to high-sinuosity channel trending southeastward across the northeastern Gulf of Mexico basin floor, and associated depositional elements are well imaged using conventional 3D multi-channel seismic reflection data. Depositional elements described include channels, associated levees, a channel belt, avulsion channels, levee crevasses, frontal splays, sediment waves, and mass transport complexes. Distinguishing morphologic and stratigraphic characteristics of each depositional element are discussed. These deposits are presumed to be associated with repeated deep-marine turbidity flows and other mass transport processes.  相似文献   

3.
Isaac Channel 3 is a rare outcrop example of a perpendicular cut through a sinuous deep-water channel, and also where levee deposits formed on opposite sides of the channel are well exposed. Strata flanking the outer- and inner-bend margin of the channel show important differences in lithofacies, architecture and association with channel-fill strata. Proximal outer-bend levee deposits are sand-rich (N:G up to 0.68) and comprise medium- to thick-bedded, Ta-d turbidites interstratified with thinly-bedded, Tcd turbidites. The thicker-bedded deposits show lateral variation in grain size and thickness over hundreds of meters whereas thin-bedded strata thin and fine negligibly over similar distances. The distal outer-bend levee (up to 700 m laterally away from the channel) consists predominantly of thin-bedded turbidites interstratified with up to 5 m thick coarse-grained splay deposits. In contrast to the outer-bend, the inner-bend levee deposits are significantly more mud-rich (N:G as low as 0.15) and consist mostly of thin-bedded, Tcd turbidites with less common thicker-bedded, Ta-d turbidites. Lateral thinning and fining trends associated with these less common thicker-bedded deposits occur more rapidly than their outer-bend counterparts.Erosion associated with lateral migration of the channel axis produced a sharp contact along the outer-bend channel margin causing coarse-grained channel-fill deposits to be in erosional contact with levee deposits. This suggests that the crest of the outer-bend levee was elevated above the channel floor and produced a channel margin upon which channel-fill strata onlapped. Positive topography is interpreted to have developed by overspilling processes that deposited abundant sand on the outer-bend levee while the majority of the flow continued through the channel bend and bypassed to areas further downslope. In contrast, some thick-bedded, amalgamated channel-fill deposits in the axial channel area grade laterally over 140 m into thinly-bedded turbidites on the inner-bend levee. The lack of channel-fill on lap relationships implies that topography along the inner bend was sufficiently subtle that at least some flows were able to expand laterally and over the overbank area without becoming separated from the main throughgoing channel flow.Stratal relationships observed in Isaac Channel Complex 3 suggests three main episodes of channel-levee growth that were each initiated by a period of increased levee relief followed by channel filling and distal levee deposition. This consistent depositional history points to the regular variations, in both time and space, of sediment transport and deposition in a deep-marine sinuous channel-levee system.  相似文献   

4.
The Cretaceous Tres Pasos Formation of southern Chile records a slope system characterized by >800 m of paleo-bathymetric relief. Channel deposits are exposed in an outcrop 2.5 km long by 125 m thick and are located in proximity to the toe of a slope clinoform. Exquisite exposures of channel strata offer a unique opportunity for high-resolution analyses of channel stacking patterns and provide insight into the evolution of conduits that transport sediment from continents to the deep ocean.Eighteen slope channels, or channel elements, are present in the strata studied. They are 6–15 m thick and comprised of stacked turbiditic sedimentation units. Channel fills are characterized by a gradational transition from amalgamated sandstone-rich facies in the channel axes to thinly interbedded sandstone and siltstone at the channel margins over distances of 10–30 m. These elements are generally considered to be ∼300 m wide and were formed by punctuated periods of incision and sedimentary bypass, followed by in-filling by collapsing turbidity currents. Out-of-channel deposits consist primarily of fine-grained facies, which are typically covered by vegetation in the study area.The channel strata of the mapped portion of the Tres Pasos Formation can be grouped into three channel complexes 25–70 m thick. Complexes are differentiated based on the preservation of siltstone-dominated deposits (bypass drapes and channel margin), which persist across the entire outcrop belt and coincide with shifts in channel stacking pattern. The oldest four channel elements (channel complex 1) are characterized by the highest lateral offsets, relative to one another. These are interpreted to record the most unconfined channel-stacking pattern present. As the channel system evolved (channel complexes 2 and 3), channel elements began to stack on top of one another, due to the increased confinement imparted on the slope channel system. The amount of vertical offset between successive channel elements preserves the record of channel aggradation as well as erosional degradation. The greatest vertical offset observed is associated with the oldest channels; as the system matured, vertical offset decreased. This decrease in vertical offset is coincident with the decrease in lateral offset of channels. The lateral offset decrease is attributed to establishment of constructional confinement and is the consequence of increased focusing of successive channel-initiating gravity flows. As confinement establishes, channels are predisposed toward underfilled conditions upon abandonment. The capture of channel-initiating currents along channel abandonment relief fairways focused incision and resulted in increased erosion and decreased vertical offset. The consequence of these conditions is an upward increase in channel element amalgamation.The organized stacking of slope channels observed in the Tres Pasos Formation is comparable to that of seismically imaged channel-levee or entrenched slope valley systems. By analogy to these 3-dimentionally constrained systems, a portion of the poorly exposed out-of-channel facies in the Tres Pasos Formation is attributed to aggradational internal levee deposits. The facies insight derived from the studied outcrop provides insight into analogous hydrocarbon-bearing units from numerous continental margins.  相似文献   

5.
Recently, as oil exploitation has become focused on deepwater slope areas, more multi-channel high resolution 2D and 3D seismic data were acquired in the deepwater part of the Qiongdongnan Basin, northern South China Sea. Based on 3D seismic data and coherence time slice, RMS and 3D visualization, a series of deepwater channels were recognized on the slope that probably developed in the late Quaternary period. These channels trend SW–NE to W–E and show bifurcations, levees, meander loops and avulsions. High Amplitude Reflections (HARs), typical for channel–levee complexes, are of only minor importance and were observed in one of the channel systems. Most of the detected channels are characterized by low-amplitude reflections, and so are different from the typical coarse-grained turbidite channels that had been discovered worldwide. The absence of well data in the study area made it difficult to determine the age and lithology of these channels. Using a neighboring drill hole and published data about such depositional systems worldwide, the lithology of these channels is likely to be dominated by mudstones with interbedded thin sandstones. These channels are formed by turbidity currents originated from the little scale mountain river of mid-Vietnam in SW direction and were probably accompanied by a relative sea level drop in the last glacial age. These channels discovered on the northern South China Sea slope are likely to be fine-grained, mud-dominant and low N:G deposits in a deepwater paleogeographic setting.  相似文献   

6.
Two scales of levee confinement are commonly recognised from submarine channel-levee systems on the seafloor and in the subsurface. Large-scale external levees bound the entire system whilst smaller-scale internal levees bound individual thalweg channels within the channel-belt. Although thin beds are commonly identified in core and well logs, their origin, and consequently their stratigraphic significance is currently poorly understood. This knowledge gap stems, in part, from the lack of unambiguously identified outcrop analogues of channel-levees, and in particular the lack of identifiable internal and external levees. Here we report from two exhumed channel-levee systems where both scales of confinement can be recognised: the Rosario Fm. of Baja California, and the Fort Brown Fm. of South Africa. A suite of characteristic sedimentary features are recognised from internal and external levees respectively: internal levees are characterised by structures indicative of complexity in the waxing-waning style of overspill, interactions with topography and flow magnitude variability; in contrast, external levees are characterised by structures indicative of simple surge-like waning flows, relatively uniform flow directions, laterally extensive beds, and a lack of erosive events. Using these observations, together with published literature, we propose a simple nomenclatural scheme for levee sub-environments, and criteria to differentiate between levee sub-environments in core or outcrop.  相似文献   

7.
The Bulgheria canyon-fan system in the eastern Tyrrhenian Sea displays well-developed, small-scale, fluvial-like features and has formed alongside the northern slope of the Sapri peri-Tyrrhenian basin. This study reveals, for the first time, the morphology and course of the present-day system as well as the buried elements based on a Digital Terrain Model and high-resolution seismic profiles interpretation. Two adjacent canyons (Infreschi and Luna) originate in the Cilento outer shelf at a short distance from each other and feed an intraslope basin fan through two main sub-parallel channels that run about 12 and 8 km, respectively. Channel and levee development seems to be controlled primarily by the local slope gradient and by Coriolis forces that induce a faster vertical growth of the right-side features, as is often observed in the Northern Hemisphere. Centrifugal forces, on the other hand, have induced episodic flow-stripping at the meander loops and bends, causing local destruction of the main channel levees rather than new levee growth at the outer bends. Overbank deposits are associated with overspill turbidite deposition in the mid fan where a topographic constraint occurs, whereas large-sediment, low-angle wave fields are mainly developed on the outer fan. Buried features and relict morphologies suggest that the Infreschi channel experienced at least two phases of re-incision since the final stages of the middle Pleistocene. Local re-adjustment of outer lobe growth due to channel avulsion and meander abandonment is possibly a consequence of relative base-level fluctuations. The sedimentary record of the mid and outer fan includes outrun mass wasting deposits from extensive failures of the Sapri slope. Indeed, a marked scar is present on the eastern side of the modern outer lobe that indicates the persistency of mass flow passages up to recent times. In addition to the environmental factors that are currently considered to cause canyon formation on the shelf margin, this study proposes the possibility that the head canyon branch close to the mainland was incised by massive and persistent underground freshwater flow from the adjacent aquifer when the sea-level was lower than at present.  相似文献   

8.
Several laterally offset and aggradational sinuous submarine channels are contained within a 54 km long segment of the Benin-major Canyon. Axial channel deposits produce high amplitude reflections on three-dimensional (3-D) seismic profiles. Some seismic reflections have U- or V-shaped cross-sectional motifs that were correlated with confidence along linear to meandering paths for distances up to 70 km. They are referred to here as channel-forms (CFs), and are believed to be the axial parts of submarine channels preserved during overall channel floor aggradation. A total of 15 separate CFs were mapped allowing thalweg-gradients, dimensions, and morphology to be studied spatially and through time, providing insight into how submarine canyons fill. Their planform geometry evolved predominantly in a stepwise fashion through alternating periods of cut-and-fill, but more gradual channel migrations are also observed. The largest offsets in successive channel floor position occur after periods of significant vertical CF fill (‘thalweg plugging’—with deposits commonly consisting of lower amplitude, transparent to chaotic seismic reflections). The passage of erosive flows after such periods of fill caused abrupt shifts in channel position, particularly at meander bends, with increased potential for the formation of pseudo meander loop cut-offs. Significant spatial differences in the stacking architecture of CFs are attributed to local slope deformation and perhaps also to a recent channel avulsion just west of the study area. Abrupt channel straightening in the western study area coincides with a period of increased valley-gradient associated with amplification of an underlying anticlinal fold. The youngest CFs in this area show limited aggradation and are characterized by repeated episodes of headward erosion causing knickpoint migration as the recent channel floor tried, unsuccessfully, to establish a smooth graded depth profile. This is in stark contrast to the time-equivalent predominantly aggradational CFs in the eastern study area that show a progressive increase in sinuosity through time.  相似文献   

9.
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10.
The Mississippi Fan is a large, mud-dominated submarine fan over 4 km thick, deposited in the deep Gulf of Mexico during the late Pliocene and Pleistocene. Analysis of 19,000 km of multifold seismic data defined 17 seismic sequences, each characterized by channel, levee, and associated overbank deposits, as well as mass transport deposits. At the base of nine sequences are a series of seismic facies consisting of mounded, hummocky, chaotic, and subparallel reflections, which constitute 10–20% of the sediments in each the sequences. These facies are externally mounded and occur in two general regions of the fan: (1) in the upper and middle fan they are elongate in shape and mimic the channel's distribution; (2) in the middle fan to lower fan they are characterized by a fan-shaped distribution, increasing in width downfan. These facies are interpreted to have formed as disorganized slides, debris flows, and turbidites (informally called “mass transport complexes”). Overlying this basal interval, characteristic of all sequences, are well-developed channel-levee systems that constitute 80–90% of the fan's sediments. Channels consist of high amplitude, subparallel reflections, whereas the flanking levee sediments appear as subparallel reflections that have high amplitudes at the base changing upward to low amplitude. The vertical change in amplitude may reflect a decrease in grain size and bed thicknesses. Overbank sediments are characterized by interbedded subparallel to hummocky and mounded reflections, suggesting both turbidites from the channel, as well as slides and debris flows derived both locally and from the slope updip.  相似文献   

11.
The study of many slope channel systems has led to the development of rules in the form of observations, measurements, and hypotheses. For example, we hypothesize that high abandonment relief can strongly influence the location of the subsequent channel element and will result in an organized channel stacking pattern in which the path of the younger channel element approximates the path of the former element. The rules were developed with the objective of constructing forward models of petroleum reservoirs that are internally consistent, reproducible, and quantifiable. Channelized turbidite deposits can be interpreted to be the product of multiple cycles of waxing-waning flow energy at multiple scales. Systematic changes in the volume and caliber of turbidity flows through time trigger a fall of the equilibrium profile, which drives erosion and sediment bypass across the slope, followed by a rise of the equilibrium profile, which allows deposition on the slope of increasingly mud-rich sediments through time. In most turbidite successions, at least three scales of waxing-waning cyclicity can be interpreted: element, complex set, and sequence. The stacking pattern of channel elements within a complex set-scale cycle tends to be sequential: (1) erosion and sediment bypass; (2) amalgamation of channel elements associated with a low rate of aggradation; (3) a disorganized stacking pattern of channel elements associated with a moderate rate of aggradation; and (4) an organized stacking pattern of channel elements associated with a high rate of aggradation. Stages 1 and 2 may be absent or minor in mud-rich systems but prominent in sand-rich systems. Conversely, stage 4 may be prominent in mud-rich systems but absent in sand-rich systems. Event-based forward modeling, utilizing rules, can produce realistic architectures, such as the four stages described above. Multiple realizations and multiple alternative models can be constructed to quantitatively examine the probability of specific parameters of interest such as pore volume and connectivity.  相似文献   

12.
There are three major fan valleys on upper Monterey fan. Deep-tow geophysical profiles and 40 sediment cores provide the basis for evaluation of the sedimentation histories of these valleys. Monterey fan valley leads from Monterey canyon to a major suprafan and is bounded by levees that crest more than 400 m above the valley floor. The valley passes through a large z-bend or meander. Monterey East fan valley joins Monterey fan valley at the meander at about 150 m above the valley floor, and marks an earlier position of the lower Monterey fan valley. Ascension valley, a hanging contributary to the Monterey fan valley, appears to have once been the shoreward head of the lower part of the present Monterey fan valley. The relief of Monterey fan valley appears from deep-tow profiles to be erosional. The valley is floored with sand. Holocene turbidity currents do not overtop the levees 400 m above the valley floor, but do at times overflow and transport sand into Monterey East valley, producing a sandy floor. An 1100 m by 300 m dune field was observed on side scan sonar in Monterey East valley.Ascension fan valley was floored with sand during glacial intervals of lowered sea level, then was cut off from its sand source as sea level rose. A narrow (500 m), erosional, meandering channel was incised into the flat valley floor; the relief features otherwise appear depositional, with a hummocky topography perhaps produced in the manner of a braided riverbed. The sand is mantled by about 6 m of probable Holocene mud. Hummocky relief on the back side of the northwestern levees of both Ascension and Monterey valleys is characteristic of many turbidite valleys in the northeast Pacific. The hummocky topography is produced by dune-like features that migrate toward levee crests during growth.  相似文献   

13.
The present paper highlights the sequence development within the Mesoproterozoic Koldaha Shale Member of the Kheinjua Formation, Vindhyan Supergroup which records the occurrence of a forced regressive wedge and associated discontinuity surfaces at the base of the wedge. Nine lithofacies have been identified within the study area that are grouped into three lithofacies associations varying in depositional setting from outer shelf, through shoreface-foreshore-beach to continental braidplain. The outer shelf sediments are aggradational to slightly progradational representing highstand systems tract. The rapidly progradational, wedge-shaped shoreface to foreshore-beach succession occurs sharply or erosively above the outer shelf sediments and is bounded by a regressive surface of marine erosion (RSME) at the base and by a subaerial unconformity at the top. This, along with its downstepping trajectory, supports deposition of this sedimentary wedge during falling sea level. A laterally extensive soft sediment deformation zone occurs at the base of the wedge.The forced regressive wedge is incised by fluvial braidplain deposits that rest on an erosive surface representing a sequence boundary. The thin braidplain deposits are the product of aggradation during a subsequent early rise in relative sea level, and thus, they are inferred to represent a lowstand systems tract. The constituent architectural elements that characterize the braidplain deposits are downstream accretion elements and small channel elements. Further landward, the base and top of the shoreface wedge merge to form an unconformity across deposits that rest directly on the outer shelf sediments. The identification of forced regressive wedges has significant economic importance in view of the potential occurrence of hydrocarbons within the Proterozoic formations.  相似文献   

14.
The Ebro Fan System consists of en echelon channel-levee complexes, 50×20 km in area and 200-m thick. A few strong reflectors in a generally transparent seismic facies identify the sand-rich channel floors and levee crests. Numerous continuous acoustic reflectors characterize overbank turbidites and hemipelagites that blanket abandoned channel-levee complexes. The interlobe areas between channel complexes fill with homogeneous mud and sand from mass flow and overbank deposition; these exhibit a transparent seismic character. The steep continental rise and sediment “drainage” of Valencia Trough at the end of the channel-levee complexes prevent the development of distributary channels and midfan lobe deposits.  相似文献   

15.
The Ebro Fan System consists of en echelon channel-levee complexes, 50×20 km in area and 200-m thick. A few strong reflectors in a generally transparent seismic facies identify the sand-rich channel floors and levee crests. Numerous continuous acoustic reflectors characterize overbank turbidites and hemipelagites that blanket abandoned channel-levee complexes. The interlobe areas between channel complexes fill with homogeneous mud and sand from mass flow and overbank deposition; these exhibit a transparent seismic character. The steep continental rise and sediment “drainage” of Valencia Trough at the end of the channel-levee complexes prevent the development of distributary channels and midfan lobe deposits. Margin setting represents fan and/or source area  相似文献   

16.
Using seismic and Chirp sonar profiles, this paper tests the hypothesis that hyperpycnal flows are the main factor controlling the formation and maintenance of the meandering Kaoping submarine canyon off SW Taiwan. Cross-section geometries, and erosional as well as depositional features vary along the canyon course. In the proximal, sinuous part of the canyon, down-cutting into the shelf strata has created a relief of 340 m. The cause of this intense erosion of the seafloor is suggested to be the frequent development of hyperpycnal flows. A seismic section across a meander in the distal part of the canyon shows levees formed by overspilled sediments at the outer bend, and a terrace characterized by relatively flat stratified facies at the inner bend. The geological setting and climatic conditions in SW Taiwan (e.g. earthquakes, typhoons, floods), as well as major river–canyon connections (for example, direct input of highly concentrated suspended sediment) would all promote hyperpycnal flow generation. This causes axial incision, canyon wall slumping, and the formation of levees by spill-over deposition in the upper reach of the Kaoping Canyon.  相似文献   

17.
The upper Indus Fan is characterized by an average 1∶500 gradient, chanels with 100 m high levees, several continuous subbottom reflectors on 3.5-kHz records, and generally fine-grained sediments. Multichannel seismics show the levee complexes typified by overlapping wedge-shaped reflection sets and channel axis by high-amplitude discontinuous reflections. The middle fan has 1∶500–1∶1000 gradients and channels with ≈20 m high levees. The lower fan has gradients less than 1∶1000, channels with 8–20 m high levees, few or no subbottom reflectors on 3.5-kHz records, and high sand content. Besides the dominant unchannelized turbidity currents, channelized and overbank flows also played a significant role in the sedimentation of the lower fan.  相似文献   

18.
In this paper a channel levee system and the associated depositional lobe are described. The proposed example derives from a recently acquired 3D survey in the West Africa deep-offshore. It is mainly based on a detailed 3D seismic reconstruction, attribute map interpretation and log data from a single well to calibrate seismic responses and sedimentary facies.The stratigraphic section under consideration, informally named the A 100 Sequence, is about 80 ms TWT thick, and of early Pliocene age. The attribute maps focused on this interval clearly show the presence of two narrow (up to 250 m wide) low-sinuosity slope channels that can be followed for more than 32 km in an E–W direction (down slope to the W) as far as the western border of the 3D acquisition. Over most of their length both channels are characterized by the low amplitude aspect of the axial belt and by brighter responses in the flanks (presence of thin-bedded sands in the levee areas). This character, associated with the common convex-down geometry of the reflections lying just above the channel axis, suggests a predominant fine-grained infilling of the thalwegs.One of these channels, termed the Southern Channel, shows a high amplitude lobe-shaped zone in the middle part of its course. The ‘anomalous’ development of this depositional element has been related to a local reduction of the slope gradient, probably induced by the synsedimentary growth of an adjacent mud-cored anticline.Because of hydrocarbon occurrence, the lobe area and the associated feeder channel have been investigated in detail through careful picking of all the mappable reflections inside the channel-lobe system. The resulting physical-stratigraphic framework and the related attribute maps suggest that channel development occurred through distinct growth stages. The lower stage (Stage 1) is expressed by symmetric levees flanking the main channel to the east and by a depositional lobe/lobe fringe area to the west. Between the levee belt and the lobe' a transitional zone occurs where the presence of isolated bypassing bars has been inferred. The upper stage (Stage 2) seems to record a phase of overall bypassing of flows within the channel conduit, producing the westward propagation of the channel and consequent dissection of the previous stage lobe. A contemporaneous lateral spillover from the channel axis of low-density turbidites constructed prominent gull-wing shaped levees that uniformly covered the stage 1 elements.  相似文献   

19.
To date, facies architecture models of submarine channel–levees have largely been derived from seismic data, isolated core data and limited field studies. We report field observations of an Upper Cretaceous submarine channel–levee complex within the Rosario Formation, Baja California, Mexico, which provide high-resolution data of lithofacies and ichnofacies distribution, and levee depositional thickness decay along transects perpendicular to the channel axis. Within the levee, both sandstone thickness and the overall proportion of sandstone decrease according to a power law away from the channel axis. Spatial variation in sedimentary structures away from the channel axis is predictable and provides an important link to the depositional flow regime. In channel-proximal locations, structureless sands, parallel lamination, overturned ripples, and ripple cross-lamination (including climbing ripple cross-lamination) are common; in channel-distal localities starved ripples are abundant. Sandstone bed thickness generally increases up stratigraphy within the levee succession, which is interpreted to indicate increasing turbidity current magnitude and/or contemporaneous channel floor aggradation reducing relative levee relief. However, in the most channel-proximal location sandstone bed thickness decreases with height; combined with evidence from both facies and palaeocurrent analysis this allows the position of the levee crest to be inferred. The thickest beds occur at higher levels with increasing distance from the channel axis, using this evidence we present a model for levee growth and migration of the crest.Quantitative analysis of ichnofacies distribution reveals that traces typical of the Cruziana and Skolithos ichnofacies are superimposed over the ‘normal’ background Nereites ichnofacies, forming a ‘bioturbation front’ which is indicative of proximity to the channel. By analogy with modern canyons and channels, the association of Cruziana and Skolithos ichnofacies with the channel may be attributed to oxygen and nutrient enrichment and possible turbidity current transport of organisms responsible for these ichnofacies.  相似文献   

20.
The upper Indus Fan is characterized by an average 1∶500 gradient, chanels with 100 m high levees, several continuous subbottom reflectors on 3.5-kHz records, and generally fine-grained sediments. Multichannel seismics show the levee complexes typified by overlapping wedge-shaped reflection sets and channel axis by high-amplitude discontinuous reflections. The middle fan has 1∶500–1∶1000 gradients and channels with ≈20 m high levees. The lower fan has gradients less than 1∶1000, channels with 8–20 m high levees, few or no subbottom reflectors on 3.5-kHz records, and high sand content. Besides the dominant unchannelized turbidity currents, channelized and overbank flows also played a significant role in the sedimentation of the lower fan. Margin setting represents fan and/or source area  相似文献   

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