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Ian A. Kane - One of the best experts on this subject based on the ideXlab platform.
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differentiating submarine channel related thin bedded turbidite facies outcrop examples from the rosario formation mexico
Sedimentary Geology, 2017Co-Authors: Larissa Hansen, Ian A. Kane, Richard H T Callow, Ben KnellerAbstract:Abstract Thin-bedded turbidites deposited by sediment gravity flows that spill from submarine channels often contain significant volumes of sand in laterally continuous beds. These can make up over 50% of the channel-belt fill volume, and can thus form commercially important hydrocarbon reservoirs. Thin-bedded turbidites can be deposited in environments that include Levees and depositional terraces, which are distinguished on the basis of their external morphology and internal architecture. Levees have a distinctive wedge shaped morphology, thinning away from the channel, and confine both channels (internal Levees) and channel-belts (external Levees). Terraces are flat-lying features that are elevated above the active channel within a broad channel-belt. Despite the ubiquity of terraces and Levees in modern submarine channel systems, the recognition of these environments in outcrop and in the subsurface is challenging. In this outcrop study of the Upper Cretaceous Rosario Formation (Baja California, Mexico), lateral transects based on multiple logged sections of thin-bedded turbidites reveal systematic differences in sandstone layer thicknesses, sandstone proportion, palaeocurrents, sedimentary structures and ichnology between channel-belt and external Levee thin-bedded turbidites. Depositional terrace deposits have a larger standard deviation in sandstone layer thicknesses than external Levees because they are topographically lower, and experience a wider range of turbidity current sizes overspilling from different parts of the channel-belt. The thickness of sandstone layers within external Levees decreases away from the channel-belt while those in depositional terraces are less laterally variable. Depositional terrace environments of the channel-belt are characterized by high bioturbation intensities, and contain distinctive trace fossil assemblages, often dominated by ichnofabrics of the echinoid trace fossil Scolicia. These assemblages contrast with the lower bioturbation intensities that are recorded from external Levee environments where Scolicia is typically absent. Multiple blocks of external Levee material are observed in the depositional terrace area where the proximal part of the external Levee has collapsed into the channel-belt; their presence characterizes the channel-belt boundary zone. The development of recognition criteria for different types of channel-related thin-bedded turbidites is critical for the interpretation of sedimentary environments both at outcrop and in the subsurface, which can reduce uncertainty during hydrocarbon field appraisal and development.
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sedimentological criteria to differentiate submarine channel Levee subenvironments exhumed examples from the rosario fm upper cretaceous of baja california mexico and the fort brown fm permian karoo basin s africa
Marine and Petroleum Geology, 2011Co-Authors: Ian A. Kane, David M. HodgsonAbstract: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.
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submarine channel Levee shape and sediment waves from physical experiments
Sedimentary Geology, 2010Co-Authors: Ian A. Kane, Jeff Peakall, William D Mccaffrey, Benjamin Charles KnellerAbstract:Abstract Submarine channel Levees aggrade through repeated overspill events from the channel axis. The shape of the Levees may therefore reflect some characteristic(s) of the overspilling flow. It has been noted that basin floor Levees typically have a relatively low-relief and taper exponentially to their termination; in contrast slope channel Levees may be much steeper close to the channel. A simple physical experiment was performed where a surge-like sediment-laden current flowed through a curved channel. Significant overspill occurred and generated a deposit flanking the channel on either side. The experiment was repeated 25 times to build up low-relief channel-Levees. It was found that in proximal areas, Levees were steep and characterised by power-law decays, a transitional zone of logarithmically thinning Levee was found a little further down-channel, followed by exponential decays in medial to distal areas. The style of Levee decay is a function of spatial variation in overbank sedimentation rates. Where flows rapidly lose momentum and deposit across the grain-size spectrum, i.e., in proximal areas, Levees tend to be steep; farther down the channel, the steep Levee slope gives way to a more gradually tapering deposit. In more distal parts of the channel, deposition is directly related to sediment settling velocity (rather than the suspended load exceeding flow transport capacity as is the case in proximal areas), the deposit reflects this with relatively simple exponential thickness decays. Additionally, small-scale sediment waves developed under lee wave conditions on the inner-bend overbank. The waves initially migrated slightly towards the channel, but as the style of overspill evolved due to intra-channel deposition, flows moved out of the lee wave window and sedimentation became out of phase with the wavelength of the features and the topography was healed.
H M S M A Elmilady - One of the best experts on this subject based on the ideXlab platform.
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morphodynamic evolution of a fringing sandy shoal from tidal Levees to sea level rise
Journal of Geophysical Research, 2020Co-Authors: H M S M A Elmilady, M Van Der Wegen, Dano Roelvink, A J F Van Der SpekAbstract:Intertidal shoals are vital components of estuaries. Tides, waves, and sediment supply shape the profile of estuarine shoals. Ensuring their sustainability requires an understanding of how such systems will react to sea level rise (SLR). In contrast to mudflats, sandy shoals have drawn limited attention in research. Inspired by a channel-shoal system in the Western Scheldt Estuary (Netherlands), this research investigates governing processes of the long-term morphodynamic evolution of intertidal estuarine sandy shoals across different timescales. We apply a high-resolution process-based numerical model (Delft3D) to generate a channel-shoal system in equilibrium and expose the equilibrium profile to variations in wave forcing and SLR. Combined tidal action and wave forcing initiate ridge formation at the seaward shoal edge, which slowly propagates landward until a linear equilibrium profile develops within 200 years. Model simulations in which forcing conditions have been varied to reproduce observations show that the bed is most dynamic near the channel-shoal interface. A decrease/increase in wave forcing causes the formation/erosion of small tidal Levees at the shoal edge, which shows good resemblance to observed features. The profile recovers when regular wave forcing applies again. Sandy shoals accrete in response to SLR with a long (decades) bed-level adaptation lag eventually leading to intertidal area loss. This lag depends on the forcing conditions and is lowest near the channel and gradually increases landward. Adding mud makes the shoal more resilient to SLR. Our study suggests that processes near the channel-shoal interface are crucial to understanding the long-term morphodynamic development of sandy shoals.
David M. Hodgson - One of the best experts on this subject based on the ideXlab platform.
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integrating outcrop and subsurface data to assess the temporal evolution of a submarine channel Levee system
AAPG Bulletin, 2016Co-Authors: Emma A Morris, Stephen S Flint, Rufus L Brunt, Stefan M Luthi, David M. Hodgson, Yolanda KolenbergAbstract:The morphological evolution of submarine channel systems can be documented using high-resolution three-dimensional seismic data sets. However, these studies provide limited information on the distribution of sedimentary facies within channel fills, channel-scale stacking patterns, or the detailed stratigraphic relationship with adjacent Levee-overbank deposits. Seismic-scale outcrops of unit C2 in the Permian Fort Brown Formation, Karoo Basin, South Africa, on two subparallel fold limbs comprise thin-bedded successions, interpreted as external Levee deposits, which are adjacent to channel complexes, with constituent channels filled with thick-bedded structureless sandstones, thinner-bedded channel margin facies, and internal Levee deposits. Research boreholes intersect all these deposits, to link sedimentary facies and channel stacking patterns identified in core and on image logs and detailed outcrop correlation panels. Key characteristics, including depth of erosion, stacking patterns, and cross-cutting relationships, have been constrained, allowing paleogeographic reconstruction of six channel complexes in a 36-km2 (14-mi2) area. The system evolved from an early, deeply incised channel complex, through a series of external Levee-confined and laterally stepping channel complexes culminating in an aggradational channel complex confined by both internal and external Levees. Down-dip divergence of six channel complexes from the same location suggests the presence of a unique example of an exhumed deep-water avulsion node. Down-dip, external Levees are supplied by flows that escaped from channel complexes of different ages and spatial positions and are partly confined and share affinities with internal Levee successions. The absence of frontal lobes suggests that the channels remained in sand bypass mode immediately after avulsion.
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origin evolution and anatomy of silt prone submarine external Levees
Sedimentology, 2014Co-Authors: Emma A Morris, Rufus L Brunt, David M. Hodgson, Stephen S FlintAbstract:Submarine external Levees are constructional features that develop outside slope channel systems, and are a volumetrically significant component of continental margins. However, detailed observations of their process sedimentology and depositional architecture are rare. Extensive exposures of external Levees at multiple stratigraphic intervals and well-constrained palaeogeographic positions in the Fort Brown Formation, Karoo Basin, South Africa, have been calibrated with research boreholes. This integrated data set permits their origin, evolution and anatomy to be considered, including high-resolution analysis of sedimentary facies distribution and characterization of depositional sub-environments. An idealized model of the stratigraphic evolution and depositional architecture of external Levees is presented, and variations can be attributed to allogenic (for example, sediment supply) and autogenic (for example, channel migration) factors. Initiation of external Levee construction is commonly marked by deposition of a basal sand-rich facies with sedimentary structures indicating rapid deposition from unconfined flows. These deposits are interpreted as frontal lobes. Propagation of the parent channel, and resultant flow confinement, lead to partial erosion of the frontal lobe and development of constructional relief (Levees) by flow overspill and flow stripping. Overall fining-upwards and thinning-upwards profiles reflect increased flow confinement and/or waning flow magnitude through time. Identification of a hierarchy of Levee elements is not possible due to the absence of internal bounding surfaces or sharp facies changes. The down-slope taper in Levee height and increasing channel sinuosity results in increasing numbers of crevasse lobe deposits, and is reflected by the increased occurrences of channel avulsion events down-dip. External Levees from the Fort Brown Formation are silt-rich; however their stratigraphic evolution and the distribution of many components (such as sediment waves and crevasse lobe) share commonalities with mud-rich external Levees. This unique integrated data set has permitted the first high-resolution characterization of external submarine Levee systems.
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sedimentological criteria to differentiate submarine channel Levee subenvironments exhumed examples from the rosario fm upper cretaceous of baja california mexico and the fort brown fm permian karoo basin s africa
Marine and Petroleum Geology, 2011Co-Authors: Ian A. Kane, David M. HodgsonAbstract: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.
Robert J Twiss - One of the best experts on this subject based on the ideXlab platform.
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subsidence sea level rise and seismicity in the sacramento san joaquin delta
San Francisco Estuary and Watershed Science, 2005Co-Authors: Jeffrey F Mount, Robert J TwissAbstract:Anthropogenic accommodation space, or that space in the Delta that lies below sea level and is filled neither with sediment nor water, serves as a useful measure of the regional consequences of Delta subsidence and sea level rise. Microbial oxidation and compaction of organic-rich soils due to farming activity is the primary cause of Delta subsidence. During the period 1900-2000, subsidence created approximately 2.5 billion cubic meters of anthropogenic accommodation space in the Delta. From 2000-2050, subsidence rates will slow due to depletion of organic material and better land use practices. However, by 2050 the Delta will contain more than 3 billion cubic meters of anthropogenic accommodation space due to continued subsidence and sea level rise. An Accommodation Space Index, which relates subaqueous accommodation space to anthropogenic accommodation space, provides an indicator of past and projected Delta conditions. While subsidence and sea level rise create increasing anthropogenic accommodation space in the Delta, they also lead to a regional increase in the forces that can cause Levee failure. Although these forces take many forms, a Levee Force Index can be calculated that is a proxy for the cumulative forces acting on Levees. The Levee Force Index increases significantly over the next 50 years demonstrating regional increases in the potential for island flooding. Based on continuing increases in the Levee Force Index and the Accommodation Space Index, and limited support for Delta Levee upgrades, there will be a tendency for increases in and impacts of island flooding, with escalating costs for repairs. Additionally, there is a two-in-three chance that 100-year recurrence interval floods or earthquakes will cause catastrophic flooding and significant change in the Delta by 2050. Currently, the California Bay-Delta Authority has no overarching policy that addresses the consequences of, and potential responses to, gradual or abrupt landscape change in the Delta.
Carlos Pirmez - One of the best experts on this subject based on the ideXlab platform.
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architecture and evolution of upper fan channel belts on the niger delta slope and in the arabian sea
Marine and Petroleum Geology, 2003Co-Authors: Mark E Deptuck, Gary S Steffens, Mark D Barton, Carlos PirmezAbstract:Abstract High-resolution multichannel 2-D and 3-D seismic data, primarily from upper fan reaches of near-seafloor channel-Levee systems on the Niger Delta slope and in the Arabian Sea, reveal a high level of detail and architectural complexity. Several architectural elements are common to each system examined in this study. They include inner Levees, outer Levees, erosional fairways, channel-axis deposits, rotational slumps blocks, and mass transport deposits. Although the scale of individual systems varies significantly, similarities in first-order architectural elements and their configurations suggest that common depositional processes are involved regardless of scale differences. Most of the channel-Levee systems examined in this study are characterized by a basal erosional fairway that is bordered by outer Levees of varying thickness. Together these elements define the base and margins of the channel-belt, where channel-axis deposits and inner Levees are the dominant architectural elements. Vertical, sub-vertical, and lateral stacking patterns of sinuous and/or meandering channels create seismic facies that range from narrow to wide zones of high amplitude reflections (HARs) with chaotic to continuous and shingled to horizontal reflections. Some HARs appear as isolated or stacked asymmetric to symmetric u- and v-shaped reflections, referred to here as channel-forms. Channel-belts evolve within the confines of the scalloped erosional fairway walls (flanked by outer Levee), and are similar in morphology to meander-belts in fluvial systems, but commonly have a greater component of vertical aggradation. Detailed study of one particular channel-Levee system on the Niger Delta slope shows a period of incision followed by three distinct phases of channel development during its aggradational history. Each fill phase corresponds to a different channel stacking architecture, planform geometry, and nature of terrace development, with important implications for reservoir architecture. In some cases, multiple phases of inner Levee growth are observed, each intimately linked to the channel migration and aggradation history. Channel sinuosity evolves dynamically, with some meander loops undergoing periods of accelerated meander growth at the same time that others show little lateral migration.
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amazon submarine fan drilling a big step forward for deep sea fan models
Geoscience Canada, 1997Co-Authors: Richard N Hiscott, Carlos Pirmez, Roger D. FloodAbstract:The results of coring on the Amazon sub-marine fan in 1994 challenge previous ideas about facies architecture and genesis of fan deposits. A shingled set of latest Pleistocene, upward-fining channel-Levee units is underlain by, and locally interleaved with, equally voluminous sand-rich deposits. The sands occur as 5-25 nv thick packets, locally rich in semi-consolidated mud clasts. Each sand-rich unit is inferred to have been partly derived from an upfan avulsion site, land-ward of which entrenchment of the pre-existing channel floor occurred. Sands were distributed into the adjacent inter-channel low, where lack of confinement allowed spreading of turbidity currents to form sheet-like sand-rich bodies. Subsequently, the advance of a new Leveed channel over the sheet sands focussed sand transport along the channel axis, with simultaneous accumulation of muddy overbank deposits in the Levees. Ancient channel-Levee systems atop sheet sands, including those in some oilfields, may have similarly formed during single lowstands of sea level and as a result of repeated cycles of Levee progradation and upfan avulsion. Resume Les resultats de sondages realises sur le cone sous-marin de l'Amazone en 1994 remettent en question les conceptions acceptees concernant l'arrangement structurale et la genese des depots des cones sous-marins. Les cordons de galets a granoclassement normal presents dans les derniers depots pleistocenes, d'unites sedimentaires de Levees de rive de chenaux, recouvrent, et s'interstratifient par endroits avec des volumes d'egale importance de depots fortement sableux. Ces unites sableuses se presentent en paquets de strates de 5 m a 25 m d'epaisseur comportant par endroits de nombreux clastes de boues. Des indices permettent de supposer que les materiaux de chacune de ces unites sableuses proviennent en partie de sites d'avulsion situes en amont, juste en aval du lit d'anciens chenaux. Les sables ont ete etales dans les depressions entre les chenaux adjacents ou des courants de turbidite ont pu former des couches sableuses de grande continuite, etant donnee l'absence de structures de confinement. Par suite du developpement d'un nouveau chenal sur la couche sableuse, le transport des sables s'est concentre le long de l'axe du chenal et, des couches de boues ont ete deposees sur les Levees. D'anciens systemes de chenaux a Levees reposant sur des unites tres etendues de sable, entre autres, ceux de certains bassins petroliers, ont pu se former durant un seul et meme episode de basse mer, par repetition du cycle de progradation de Levees suivie d'avulsions d'amont d'un cone sous-marin.
