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Join SEPM in the Exhibition Hall for all-day poster sessions. Channels are conduits through which fluids, sediment (suspended and bed-load) and dissolved loads are transported across the Earth surface. Their general geomorphologic expression is comparable similar in terrestrial, submarine and extraterrestrial environments; however, formative sedimentary processes can be fundamentally different. For example, sinuosity and aspect ratio tend to be similar; however, submarine channels tend to be larger than fluvial channels and the stratigraphic records of fluvial and submarine channel deposits can be different. A key research challenge is the link between the geomorphic expression and stratigraphic record of channels. Rivers are more accessible to direct monitoring compared to submarine channels and the link between fluvial geomorphology and stratigraphy is better understood. In the case of submarine channels, we commonly rely on the stratigraphic record to inform insights about formative processes and evolution.

Join SEPM in the Exhibition Hall for all-day poster sessions. Channels are conduits through which fluids, sediment (suspended and bed-load) and dissolved loads are transported across the Earth surface. Their general geomorphologic expression is comparable similar in terrestrial, submarine and extraterrestrial environments; however, formative sedimentary processes can be fundamentally different. For example, sinuosity and aspect ratio tend to be similar; however, submarine channels tend to be larger than fluvial channels and the stratigraphic records of fluvial and submarine channel deposits can be different. A key research challenge is the link between the geomorphic expression and stratigraphic record of channels. Rivers are more accessible to direct monitoring compared to submarine channels and the link between fluvial geomorphology and stratigraphy is better understood. In the case of submarine channels, we commonly rely on the stratigraphic record to inform insights about formative processes and evolution.

Panel_14419 Panel_14419 8:30 AM 5:00 PM
8:30 a.m.
Dynamic Interplay Between Channel Evolution and Seafloor Topography Linked to Rising Salt Domes, Horn Mountain, Mississippi Canyon, Gulf of Mexico
Exhibition Hall
By simultaneously examining halokinetics and channel evolution of a deepwater area it is possible to unravel the interactions between the two dynamic bodies. The study area is located in the Mississippi Canyon, Gulf of Mexico, and is situated directly off the continental slope in a prominent salt dome region. While there is a plethora of study on submarine channels in the Gulf of Mexico, their interactions with salt domes are poorly documented. Utilizing 3D seismic data and seismic geomorphology techniques, a long-lived Plio-Pleistocene submarine channel system has been investigated to understand the interaction between channel evolution and changing seascape driven by rising salt domes. In the study area, salt diapirism began to affect the seafloor topography during the late Pliocene. This shifting topography has exerted a first order control on the evolution of the meandering submarine channel, as seen in the seismic data. When investigating the channel evolution and halokinetics concurrently, a relationship becomes apparent. The study results reveal a mechanism to determine variable phases of salt movement based on plan-form morphology of preserved channels. For example, highly sinuous channels developed during periods of slow salt movement whereas straighter channels formed when salt moved upward more rapidly. Furthermore, the channels display a feedback mechanism that illustrates how areas of lower topography on the seafloor were created as the salt was reaching its diapiric state, and the channels adjusted by migrating towards these structural lows. As the channels avulsed and migrated, they were subject to an increase in slope. This increase in slope corresponds to and is directly related to a decrease in meander intensity. Thus, this study reveals how salt movement has acted as a structural control on both the location and morphology of the meandering channel complex. By simultaneously examining halokinetics and channel evolution of a deepwater area it is possible to unravel the interactions between the two dynamic bodies. The study area is located in the Mississippi Canyon, Gulf of Mexico, and is situated directly off the continental slope in a prominent salt dome region. While there is a plethora of study on submarine channels in the Gulf of Mexico, their interactions with salt domes are poorly documented. Utilizing 3D seismic data and seismic geomorphology techniques, a long-lived Plio-Pleistocene submarine channel system has been investigated to understand the interaction between channel evolution and changing seascape driven by rising salt domes. In the study area, salt diapirism began to affect the seafloor topography during the late Pliocene. This shifting topography has exerted a first order control on the evolution of the meandering submarine channel, as seen in the seismic data. When investigating the channel evolution and halokinetics concurrently, a relationship becomes apparent. The study results reveal a mechanism to determine variable phases of salt movement based on plan-form morphology of preserved channels. For example, highly sinuous channels developed during periods of slow salt movement whereas straighter channels formed when salt moved upward more rapidly. Furthermore, the channels display a feedback mechanism that illustrates how areas of lower topography on the seafloor were created as the salt was reaching its diapiric state, and the channels adjusted by migrating towards these structural lows. As the channels avulsed and migrated, they were subject to an increase in slope. This increase in slope corresponds to and is directly related to a decrease in meander intensity. Thus, this study reveals how salt movement has acted as a structural control on both the location and morphology of the meandering channel complex. Panel_14838 Panel_14838 8:30 AM 5:00 PM
8:30 a.m.
Characteristics and Evolution of Paleovalley Systems in Settings Where Accommodation Decreases Down Dip
Exhibition Hall
Recent advances in our understanding of the morpholological evolution of paleovalleys, the composite nature of the associated sequence boundary and its expression in down-dip locations have been largely guided by examples from passive margins, where subsidence increases basinward. This study documents a series of incisional fluvio-deltaic sandbodies from the Pennsylvanian Breathitt Group (central Appalachian Basin, USA), which fulfil the traditional definition of paleovalley fills. The Breathitt Group was deposited in an epicontinental foreland basin setting, in which there was no shelf-slope break, and paleovalleys can be tracked from the high accommodation orogenic margin towards the lower accommodation cratonic margin of the basin, over 100 km down-dip. Thus the upper Breathitt Group provides the opportunity to describe changes in up-dip to down-dip characteristics of paleovalleys from setting that contrasts markedly with continental shelf margins. Sandbody architecture has been captured through a combination of centimetre-scale sedimentary logging and annotation of photomosaics from km-long road-cuts to produce correlation panels. Sandbodies are typically 5-20 m thick, 0.5-30 km wide, and dominated by trough cross-bedded medium-to-coarse grained sandstone deposited as longitudinal bars. Heterolithic strata displaying lateral accretion occur, particularly towards the tops of valley fills, as well as rarer heterolith-filled abandonment plugs, slumps and slides. Characteristic changes between the proximal, high accommodation and the distal, low accommodation sectors of the basin include: (1) the number of stratigraphic levels containing major sandbodies decreases, and the sandbodies become increasingly discontinuous, suggesting an overall distributive morphology; (2) the sandbodies erode into increasingly open-marine facies; (3) the sandbodies contain an increasingly diverse, marine ichnofauna, suggesting increasing marine influence down depositional dip. Up-dip, a basinward facies shift at the bases of the paleovalleys is not evident, whereas down-dip an unambiguous basinward facies shift at the bases of the same sand bodies clearly distinguishes them as paleovalley fills. This contrasts with models for paleovalleys derived from passive margins, where the expression of the paleovalley is lost down-depositional dip, and poses the question “where does a channel complex become a palaeovalley-fill?” in settings where accommodation decreases down-dip. Recent advances in our understanding of the morpholological evolution of paleovalleys, the composite nature of the associated sequence boundary and its expression in down-dip locations have been largely guided by examples from passive margins, where subsidence increases basinward. This study documents a series of incisional fluvio-deltaic sandbodies from the Pennsylvanian Breathitt Group (central Appalachian Basin, USA), which fulfil the traditional definition of paleovalley fills. The Breathitt Group was deposited in an epicontinental foreland basin setting, in which there was no shelf-slope break, and paleovalleys can be tracked from the high accommodation orogenic margin towards the lower accommodation cratonic margin of the basin, over 100 km down-dip. Thus the upper Breathitt Group provides the opportunity to describe changes in up-dip to down-dip characteristics of paleovalleys from setting that contrasts markedly with continental shelf margins. Sandbody architecture has been captured through a combination of centimetre-scale sedimentary logging and annotation of photomosaics from km-long road-cuts to produce correlation panels. Sandbodies are typically 5-20 m thick, 0.5-30 km wide, and dominated by trough cross-bedded medium-to-coarse grained sandstone deposited as longitudinal bars. Heterolithic strata displaying lateral accretion occur, particularly towards the tops of valley fills, as well as rarer heterolith-filled abandonment plugs, slumps and slides. Characteristic changes between the proximal, high accommodation and the distal, low accommodation sectors of the basin include: (1) the number of stratigraphic levels containing major sandbodies decreases, and the sandbodies become increasingly discontinuous, suggesting an overall distributive morphology; (2) the sandbodies erode into increasingly open-marine facies; (3) the sandbodies contain an increasingly diverse, marine ichnofauna, suggesting increasing marine influence down depositional dip. Up-dip, a basinward facies shift at the bases of the paleovalleys is not evident, whereas down-dip an unambiguous basinward facies shift at the bases of the same sand bodies clearly distinguishes them as paleovalley fills. This contrasts with models for paleovalleys derived from passive margins, where the expression of the paleovalley is lost down-depositional dip, and poses the question “where does a channel complex become a palaeovalley-fill?” in settings where accommodation decreases down-dip. Panel_14839 Panel_14839 8:30 AM 5:00 PM
8:30 a.m.
Spatial Trends in Stratal Architectures Across the Backwater Transition in Lowland Rivers
Exhibition Hall
A few key questions inevitably arise while mapping seismically-imaged channel bodies from past landscapes. Where was the shoreline? Can the planform of channel bodies help us predict the reservoir characteristics of the preserved deposits? In this talk, we will discuss how the back-water length scale in rivers defines systematic changes in stratal architecture across the transition from normal flow to the back-water influenced zone. A spatial reduction in bed material flux is observed where rivers transition from normal flow to the back-water influenced zone, as the river flow begins to feel the effect of sea-level in the receiving basin. The back-water length, scaled by characteristic flow depth divided by water surface slope, is a characteristic length scale of all rivers entering a receiving basin and is best distinguished in deep lowland rivers with shallow gradient. Measurements along the Holocene Mississippi Channel Belt from Cairo to Head of Passes show a dramatic reduction in the width of the channel belt from roughly 20 times the channel width upstream of the transition zone to nearly equal to the channel width downstream of the transition zone. This variation in width of the channel belt is tied to the decreased lateral mobility of the channel downstream of the back-water transition. The thickness of bank-attached bar deposits, collected from USACE cores in 110 cross-sections, was used as a proxy for channel depth from Cairo to Head of Passes. Thickness trends reveal that bank-attached bars thicken from approximately 20m upstream of the transition to 45m just above Head of Passes, while decreased lateral migration results in less extensive bar deposits. A comparison of 4 different channel belts from the Rhine-Meuse and Mississippi systems is presented. For these two systems, we present a method that uses the backwater length to non-dimensionalize the geometries of channel belts with disparate scales. We apply this scaling to the Mio-Pliocene Mississippi Delta system, imaged in an industry seismic volume over Breton sound, to estimate distance to the shoreline. Our estimates are tested against independent reconstructions of paleo-geography for the area. Results indicate that this method can be a powerful tool for reconstructing paleo-environment of deposition and characterizing reservoir architecture in ancient seismically-imaged channel belts. A few key questions inevitably arise while mapping seismically-imaged channel bodies from past landscapes. Where was the shoreline? Can the planform of channel bodies help us predict the reservoir characteristics of the preserved deposits? In this talk, we will discuss how the back-water length scale in rivers defines systematic changes in stratal architecture across the transition from normal flow to the back-water influenced zone. A spatial reduction in bed material flux is observed where rivers transition from normal flow to the back-water influenced zone, as the river flow begins to feel the effect of sea-level in the receiving basin. The back-water length, scaled by characteristic flow depth divided by water surface slope, is a characteristic length scale of all rivers entering a receiving basin and is best distinguished in deep lowland rivers with shallow gradient. Measurements along the Holocene Mississippi Channel Belt from Cairo to Head of Passes show a dramatic reduction in the width of the channel belt from roughly 20 times the channel width upstream of the transition zone to nearly equal to the channel width downstream of the transition zone. This variation in width of the channel belt is tied to the decreased lateral mobility of the channel downstream of the back-water transition. The thickness of bank-attached bar deposits, collected from USACE cores in 110 cross-sections, was used as a proxy for channel depth from Cairo to Head of Passes. Thickness trends reveal that bank-attached bars thicken from approximately 20m upstream of the transition to 45m just above Head of Passes, while decreased lateral migration results in less extensive bar deposits. A comparison of 4 different channel belts from the Rhine-Meuse and Mississippi systems is presented. For these two systems, we present a method that uses the backwater length to non-dimensionalize the geometries of channel belts with disparate scales. We apply this scaling to the Mio-Pliocene Mississippi Delta system, imaged in an industry seismic volume over Breton sound, to estimate distance to the shoreline. Our estimates are tested against independent reconstructions of paleo-geography for the area. Results indicate that this method can be a powerful tool for reconstructing paleo-environment of deposition and characterizing reservoir architecture in ancient seismically-imaged channel belts. Panel_14834 Panel_14834 8:30 AM 5:00 PM
8:30 a.m.
Evolution of a Large Tidally Influenced Meandering River System in the Cretaceous McMurray Formation, Athabasca Oil Sands, Alberta, Canada
Exhibition Hall
The 3-D reconstruction of meanderbelt deposits from ancient strata can provide significant insight into the long-term (i.e., centuries to millennia) evolution of fluvial systems. A significant challenge to such analyses is limited exposures in outcrop belts and widely spaced or low-resolution perspectives in subsurface datasets. A particularly dense and high quality dataset consisting of 130 km2 of high-quality 3D seismic data and over 350 well penetrations from the Cretaceous McMurray Formation of northeastern Alberta, Canada provides a unique perspective of an immense ancient river system. The high-resolution dataset features large-scale meandering channel elements, associated with paleochannels that were 400-600 m wide and up to 50 m deep. The data reveals evidence for intra-point bar rotation, neck cut-offs, point bar accretion and other morphodynamic processes. The stratigraphic expression of these processes is recognized through creation of a 3-D geocellular model that includes core-calibrated lithologic properties and seismic-constrained surface projections. A specific objective is to characterize the ancient expression of morphodynamic processes that are commonly observed in modern systems, yet rarely described from the rock record. The analysis also provides insight into sandstone and, inherently, reservoir distribution within the ancient meanderbelt. Reconstructed paleochannel migration patterns reveal the evolutionary history of eight individual meanderbelt elements, including point bars, counter point bars, abandoned channel fills, side bars and mid-channel bars, which have been mapped in core, FMI and seismic data and incorporated into the geocellular model. Results of the study show intra-point bar erosion surfaces bound lateral accretion packages characterized by unique accretion directions, internal stratigraphic architecture and lithologic properties. Individual lateral accretion packages fine as they evolve, as do entire point bars. Seismic and FMI characterization also reveals a multi-phase channel abandonment history that includes vertical aggradation, sidebar development and mid-channel bar deposition, which is not typically recognized in ancient meandering river deposits. The 3-D reconstruction of meanderbelt deposits from ancient strata can provide significant insight into the long-term (i.e., centuries to millennia) evolution of fluvial systems. A significant challenge to such analyses is limited exposures in outcrop belts and widely spaced or low-resolution perspectives in subsurface datasets. A particularly dense and high quality dataset consisting of 130 km2 of high-quality 3D seismic data and over 350 well penetrations from the Cretaceous McMurray Formation of northeastern Alberta, Canada provides a unique perspective of an immense ancient river system. The high-resolution dataset features large-scale meandering channel elements, associated with paleochannels that were 400-600 m wide and up to 50 m deep. The data reveals evidence for intra-point bar rotation, neck cut-offs, point bar accretion and other morphodynamic processes. The stratigraphic expression of these processes is recognized through creation of a 3-D geocellular model that includes core-calibrated lithologic properties and seismic-constrained surface projections. A specific objective is to characterize the ancient expression of morphodynamic processes that are commonly observed in modern systems, yet rarely described from the rock record. The analysis also provides insight into sandstone and, inherently, reservoir distribution within the ancient meanderbelt. Reconstructed paleochannel migration patterns reveal the evolutionary history of eight individual meanderbelt elements, including point bars, counter point bars, abandoned channel fills, side bars and mid-channel bars, which have been mapped in core, FMI and seismic data and incorporated into the geocellular model. Results of the study show intra-point bar erosion surfaces bound lateral accretion packages characterized by unique accretion directions, internal stratigraphic architecture and lithologic properties. Individual lateral accretion packages fine as they evolve, as do entire point bars. Seismic and FMI characterization also reveals a multi-phase channel abandonment history that includes vertical aggradation, sidebar development and mid-channel bar deposition, which is not typically recognized in ancient meandering river deposits. Panel_14844 Panel_14844 8:30 AM 5:00 PM
8:30 a.m.
Interpreting Backwater Effects on Fluvial Style and Architecture Within a High-Gradient Compound Incised-Valley Deposit: Example From Cretaceous Ferron Notom Delta, South East Utah
Exhibition Hall
Non-marine sequence stratigraphic models for incised valleys predict systematic changes in fluvial style from lowstand through transgressive to highstand system tracts, assuming a constant rate of marine transgression. Downstream base-level influence on fluvial style however, can be highly variable, and may produce less predictable pattern. The main purpose of this paper is to evaluate the change in plan-view style of rivers from their upstream to downstream versus extent of the effects of backwater length recorded within a Cretaceous compound incised-valley fill in the Ferron Notom Delta, Henry Mountain region, southeast Utah. It was hypothesized that the backwater length, which is proportional to river flow depth and inversely correlated to river slope theoretically controls the effects of base-level change to propagate upstream. Previous studies on modern Mississippi river valley demonstrated that channel, channel-belts in a coastal-plain valley experience predictable morphological and sedimentological changes as they enter their backwater length, and characterized by rivers that are aggradational, avulsive and distributive in nature. This paper, for the first time, attempts to test these hypotheses in an ancient compound valley fill by detailed facies architectural analysis of channel and bar deposits from vertical measured sections and estimation of backwater limits from paleo-flow depth measurements in combination with measured changes in base level, tidal range and fluvial slope along an extensively exposed fluvial long profile. Three major erosional surfaces partitioned the compound valley fill into three sequences that have noticeable morphological and sedimentological differences from the upstream to downstream area. All three incised-valley fills in the downstream area shows a vertical translation from fluvial to tidal facies at the top of the valley. This suggests the rivers entered into their backwater length at the later phase of valley filling causing a systematic vertical decrease in overall grain size as well as an upward increase in preserved dune height and bar thickness. The valley fill deposits at the upstream area, which is roughly 15 km southwest, however, lie beyond the reach of the backwater effect and hence do not show any tidal influence, but consist of much coarser facies within channel bodies of relatively low width-thickness ratio. Non-marine sequence stratigraphic models for incised valleys predict systematic changes in fluvial style from lowstand through transgressive to highstand system tracts, assuming a constant rate of marine transgression. Downstream base-level influence on fluvial style however, can be highly variable, and may produce less predictable pattern. The main purpose of this paper is to evaluate the change in plan-view style of rivers from their upstream to downstream versus extent of the effects of backwater length recorded within a Cretaceous compound incised-valley fill in the Ferron Notom Delta, Henry Mountain region, southeast Utah. It was hypothesized that the backwater length, which is proportional to river flow depth and inversely correlated to river slope theoretically controls the effects of base-level change to propagate upstream. Previous studies on modern Mississippi river valley demonstrated that channel, channel-belts in a coastal-plain valley experience predictable morphological and sedimentological changes as they enter their backwater length, and characterized by rivers that are aggradational, avulsive and distributive in nature. This paper, for the first time, attempts to test these hypotheses in an ancient compound valley fill by detailed facies architectural analysis of channel and bar deposits from vertical measured sections and estimation of backwater limits from paleo-flow depth measurements in combination with measured changes in base level, tidal range and fluvial slope along an extensively exposed fluvial long profile. Three major erosional surfaces partitioned the compound valley fill into three sequences that have noticeable morphological and sedimentological differences from the upstream to downstream area. All three incised-valley fills in the downstream area shows a vertical translation from fluvial to tidal facies at the top of the valley. This suggests the rivers entered into their backwater length at the later phase of valley filling causing a systematic vertical decrease in overall grain size as well as an upward increase in preserved dune height and bar thickness. The valley fill deposits at the upstream area, which is roughly 15 km southwest, however, lie beyond the reach of the backwater effect and hence do not show any tidal influence, but consist of much coarser facies within channel bodies of relatively low width-thickness ratio. Panel_14842 Panel_14842 8:30 AM 5:00 PM
8:30 a.m.
Straight, Asymmetric Channels and Longitudinal Bars Within Channelized Seafloor Areas: Example From The Modern Seafloor
Exhibition Hall
Submarine channels occur in many physiographic domains of the deep-sea environment. They have a large spectrum of planforms, dimensions, internal elements and hierarchic significance. This paper focuses on a type of submarine channel found in different environmental settings of the modern seafloor in the Tyrrhenian Sea. The channels are straight or very gently curving and vary in width from 100 to 500 m, with a maximum relief in the order of 10-15 m. Their main feature is a noticeable asymmetry resulting from a steep, abrupt margin and a gentler, more gradual one. Channels are never isolated, but are rather part of extensive channelized areas. Within the channelized areas, elevated longitudinal areas separate the channels. The elevated areas have sediment waves and scours indicative of flows that from their crests point toward the adjacent channels. Sidescan sonar data show that along the gentle channel margin a clear passage between the channels and the bars cannot be picked up. On the contrary, an abrupt limit is observed in coincidence with the steep channel side. Subbottom profiles indicate that the elevated areas are depositional, with deposits that continue along the gentle channel side and, although often with a different seismic facies, also represent the channel infill. Thus, the elevated areas are not erosional remnants between fully erosional channels. Upslope from the channelized areas the seafloor is flat indicating that it is the site of laterally widespread flows. Therefore, we also infer that the elevated areas are not levees, since they are not formed by flows which overbank the channels. They are rather formed from flows that occupy the whole channelized areas and behave differently in the channels and in the elevated areas. We conclude that the elevated areas are better interpreted as bars. As a whole, we explain the channel as being migrating elements with an erosional cut bank and a depositional one where lateral accretion is occurring from the longitudinal bars. The channels and longitudinal bars are located downslope from slope channel mouths in transient fans, or compose channel belts confined within slope channels. They develop on seafloor with a gradient in excess of 1° and where sampled, they consist of sandy or gravelly sediments. The Tyrrhenian sea data, suggest therefore that laterally migrating channels and longitudinal bars are components of channelized, high-gradient, coarse grained systems connected to deeper base levels. Submarine channels occur in many physiographic domains of the deep-sea environment. They have a large spectrum of planforms, dimensions, internal elements and hierarchic significance. This paper focuses on a type of submarine channel found in different environmental settings of the modern seafloor in the Tyrrhenian Sea. The channels are straight or very gently curving and vary in width from 100 to 500 m, with a maximum relief in the order of 10-15 m. Their main feature is a noticeable asymmetry resulting from a steep, abrupt margin and a gentler, more gradual one. Channels are never isolated, but are rather part of extensive channelized areas. Within the channelized areas, elevated longitudinal areas separate the channels. The elevated areas have sediment waves and scours indicative of flows that from their crests point toward the adjacent channels. Sidescan sonar data show that along the gentle channel margin a clear passage between the channels and the bars cannot be picked up. On the contrary, an abrupt limit is observed in coincidence with the steep channel side. Subbottom profiles indicate that the elevated areas are depositional, with deposits that continue along the gentle channel side and, although often with a different seismic facies, also represent the channel infill. Thus, the elevated areas are not erosional remnants between fully erosional channels. Upslope from the channelized areas the seafloor is flat indicating that it is the site of laterally widespread flows. Therefore, we also infer that the elevated areas are not levees, since they are not formed by flows which overbank the channels. They are rather formed from flows that occupy the whole channelized areas and behave differently in the channels and in the elevated areas. We conclude that the elevated areas are better interpreted as bars. As a whole, we explain the channel as being migrating elements with an erosional cut bank and a depositional one where lateral accretion is occurring from the longitudinal bars. The channels and longitudinal bars are located downslope from slope channel mouths in transient fans, or compose channel belts confined within slope channels. They develop on seafloor with a gradient in excess of 1° and where sampled, they consist of sandy or gravelly sediments. The Tyrrhenian sea data, suggest therefore that laterally migrating channels and longitudinal bars are components of channelized, high-gradient, coarse grained systems connected to deeper base levels. Panel_14837 Panel_14837 8:30 AM 5:00 PM
8:30 a.m.
Channels in Carbonate Environments: 3-D-Seismic Characteristics Extracted From the Sedimentary Record
Exhibition Hall
Submarine channels can form important hydrocarbon reservoirs, and modern and ancient siliciclastic channels have been therefore intensively studied in the past. Significantly less is known of channels in carbonate environments. Particularly in non-tropical carbonate settings, information on channel geometries, morphology, architecture and channel-forming processes is limited. This study presents 3D seismic-reflection data of kilometre-scale submarine channels in non-tropical carbonates from different stratigraphic intervals of the European North Sea and the NW Australian Shelf. Though all systems studied developed under non-tropical deepwater conditions, they show distinctly different geometries interpreted to reflect differences in input variables including sediment flux and size, but also differences in the tectonic environment. 3D-seismic analysis of a kilometre-scale channel in the Upper Cretaceous part of the Chalk Group of the North Sea Central Graben documents a rather isolated, sinuous, leveed system that displays many of the architectural elements known from siliciclastic deepwater turbidites. This channel is interpreted to have formed an important conduit for recurrent turbulent flows transporting failed chalk material into the deeper basin depocentres in response to inversion tectonics. Nearby and at the same stratigraphic level, there are other, less extensive, highly asymmetric channels. These systems lack levees and are interpreted to have been eroded by bottom currents and filled laterally by chalk drifts. The channels preserved in the Paleogene section of the Browse Basin, NW-Australian Shelf, in contrast, are much narrower than the North Sea examples and occur in arrays as vertically and laterally-offset stacked multi-storey systems. The repetitive character and restriction to clinoform fronts suggests their development in response to sedimentation-driven clinoform oversteepening and failure under rather stable tectonic conditions. The significant variability in geometry, morphology and architecture of the deep-water carbonate channels presented documents that generalized predictions of deposit type and the associated reservoir properties are difficult. Controlling factors for this variability include active tectonics, differences in sediment type and size, the type of mass-transport system and the superimposed current regime. An understanding of these parameters will be essential for a successful exploration in deepwater carbonates. Submarine channels can form important hydrocarbon reservoirs, and modern and ancient siliciclastic channels have been therefore intensively studied in the past. Significantly less is known of channels in carbonate environments. Particularly in non-tropical carbonate settings, information on channel geometries, morphology, architecture and channel-forming processes is limited. This study presents 3D seismic-reflection data of kilometre-scale submarine channels in non-tropical carbonates from different stratigraphic intervals of the European North Sea and the NW Australian Shelf. Though all systems studied developed under non-tropical deepwater conditions, they show distinctly different geometries interpreted to reflect differences in input variables including sediment flux and size, but also differences in the tectonic environment. 3D-seismic analysis of a kilometre-scale channel in the Upper Cretaceous part of the Chalk Group of the North Sea Central Graben documents a rather isolated, sinuous, leveed system that displays many of the architectural elements known from siliciclastic deepwater turbidites. This channel is interpreted to have formed an important conduit for recurrent turbulent flows transporting failed chalk material into the deeper basin depocentres in response to inversion tectonics. Nearby and at the same stratigraphic level, there are other, less extensive, highly asymmetric channels. These systems lack levees and are interpreted to have been eroded by bottom currents and filled laterally by chalk drifts. The channels preserved in the Paleogene section of the Browse Basin, NW-Australian Shelf, in contrast, are much narrower than the North Sea examples and occur in arrays as vertically and laterally-offset stacked multi-storey systems. The repetitive character and restriction to clinoform fronts suggests their development in response to sedimentation-driven clinoform oversteepening and failure under rather stable tectonic conditions. The significant variability in geometry, morphology and architecture of the deep-water carbonate channels presented documents that generalized predictions of deposit type and the associated reservoir properties are difficult. Controlling factors for this variability include active tectonics, differences in sediment type and size, the type of mass-transport system and the superimposed current regime. An understanding of these parameters will be essential for a successful exploration in deepwater carbonates. Panel_14841 Panel_14841 8:30 AM 5:00 PM
8:30 a.m.
Sediment Budgets and Depositional Processes Influencing Submarine Canyon Systems, Equatorial Guinea, West Africa
Exhibition Hall
Sediment supply to the Equatorial Guinean continental margin consists predominantly of northbound littoral-drift derived mud and sand from the Ogooue River in Gabon. Locally, sediment is sourced from the Mitemele and Benito rivers, low discharge rivers ending in large estuaries. The sediment flux is low, and delivery of sand to the deep sea is limited to a few locations where canyon heads erode into the shelf edge. These canyons are erosive, sand rich, and terminate in extensive submarine aprons (Type I canyons). The vast majority of submarine canyons along the margin do not indent the shelf edge, are muddy and aggradational, and lack any downslope sediment apron/fan (Type II canyons). Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the Type II canyons. Intra-canyon lateral accretion deposits indicate that canyon concavity is maintained by thick (>150 m), dilute, turbidity currents. This study attempts to reconstruct sediment budgets and routing systems for the Equatorial Guinean continental margin and determine the causal mechanisms for variations in temporal sediment flux. Planktic foraminifera from two cores from the modern seafloor, obtained in water depths of 268 and 497 m, provide radiocarbon ages which indicate an average sedimentation rate of ~30 cm/ky (centimeters per kiloyear) during the last ~40,000 years. This relatively slow accumulation rate does not seem to be influenced by changes in relative sea level, supporting the interpretation that hemipelagic deposition is the dominant process aggrading the Type II canyon system. A long term (8 Ma - Recent) sedimentation rate previously calculated in the study area (3.4 cm/ky) is 10x slower than the short term rate calculated in the present study. This discrepancy in rates may be a manifestation of the Sadler effect, a theory that predicts decreasing sedimentation rate as the measured time interval increases. Although the overall sedimentation rate during the last 40 ka averages ~30 cm/ky, there is an abrupt increase during the 15-10 ka time interval to 80-180 cm/ky. We investigate possible causal mechanisms for this increase using sea surface temperature and salinity proxies derived from foraminiferal trace metal data. Constraining temporal and spatial sediment flux to the study area will aid in understanding the development of low sediment supply continental margins with Type II canyons. Sediment supply to the Equatorial Guinean continental margin consists predominantly of northbound littoral-drift derived mud and sand from the Ogooue River in Gabon. Locally, sediment is sourced from the Mitemele and Benito rivers, low discharge rivers ending in large estuaries. The sediment flux is low, and delivery of sand to the deep sea is limited to a few locations where canyon heads erode into the shelf edge. These canyons are erosive, sand rich, and terminate in extensive submarine aprons (Type I canyons). The vast majority of submarine canyons along the margin do not indent the shelf edge, are muddy and aggradational, and lack any downslope sediment apron/fan (Type II canyons). Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the Type II canyons. Intra-canyon lateral accretion deposits indicate that canyon concavity is maintained by thick (>150 m), dilute, turbidity currents. This study attempts to reconstruct sediment budgets and routing systems for the Equatorial Guinean continental margin and determine the causal mechanisms for variations in temporal sediment flux. Planktic foraminifera from two cores from the modern seafloor, obtained in water depths of 268 and 497 m, provide radiocarbon ages which indicate an average sedimentation rate of ~30 cm/ky (centimeters per kiloyear) during the last ~40,000 years. This relatively slow accumulation rate does not seem to be influenced by changes in relative sea level, supporting the interpretation that hemipelagic deposition is the dominant process aggrading the Type II canyon system. A long term (8 Ma - Recent) sedimentation rate previously calculated in the study area (3.4 cm/ky) is 10x slower than the short term rate calculated in the present study. This discrepancy in rates may be a manifestation of the Sadler effect, a theory that predicts decreasing sedimentation rate as the measured time interval increases. Although the overall sedimentation rate during the last 40 ka averages ~30 cm/ky, there is an abrupt increase during the 15-10 ka time interval to 80-180 cm/ky. We investigate possible causal mechanisms for this increase using sea surface temperature and salinity proxies derived from foraminiferal trace metal data. Constraining temporal and spatial sediment flux to the study area will aid in understanding the development of low sediment supply continental margins with Type II canyons. Panel_14835 Panel_14835 8:30 AM 5:00 PM
8:30 a.m.
Near Bed Flow Process Inferred From Bar Morphology, Sediment Transport and Grain Size Distribution of a Plan-View Exposed Ancient Point Bar Complex
Exhibition Hall
Flow process and sediment transport within a channel bend and associated point bar have been studied in modern streams, theoretical models and physical experiments. However, the accuracy of these models are hard to evaluate for long-term evolution of natural rivers. It is also difficult to compare the resulting plan-form bar morphology and facies architecture of modern and modelled systems with what is preserved in the ancient rock record due to the lack of plan-view exposed outcrops. Moreover, compound point bars and scroll bars that are typically found in meandering rivers show different facies architecture, which is essentially the result of different flow processes that have rarely been distinguished. This study examined a point bar complex based on plan-view exposures of channel belts in outcrop of the Ferron Sandstone, south-central Utah. Flow process, sediment transport and bed shear stress show that compound point bars and scroll bars were formed during falling and rising flood stages respectively. The simulation of sine-generated streams showed that channel dimension parameters, such as radius of curvature and sinuosity, have small ranges of 351-205 m and 1.04-1.22 respectively throughout the evolution of the bend. Variation in flow process was interpreted as the main control on facies architecture and bar morphology. In this case, strong helical flow with a maximum strength of 1.05 was developed during the deposition of scroll bars but not the compound bars. The widely used paleocurrent indicator-dip direction of cross beds-was found to be inconsistent with the mean flow direction or the channel margin orientation. Flow process and sediment transport within a channel bend and associated point bar have been studied in modern streams, theoretical models and physical experiments. However, the accuracy of these models are hard to evaluate for long-term evolution of natural rivers. It is also difficult to compare the resulting plan-form bar morphology and facies architecture of modern and modelled systems with what is preserved in the ancient rock record due to the lack of plan-view exposed outcrops. Moreover, compound point bars and scroll bars that are typically found in meandering rivers show different facies architecture, which is essentially the result of different flow processes that have rarely been distinguished. This study examined a point bar complex based on plan-view exposures of channel belts in outcrop of the Ferron Sandstone, south-central Utah. Flow process, sediment transport and bed shear stress show that compound point bars and scroll bars were formed during falling and rising flood stages respectively. The simulation of sine-generated streams showed that channel dimension parameters, such as radius of curvature and sinuosity, have small ranges of 351-205 m and 1.04-1.22 respectively throughout the evolution of the bend. Variation in flow process was interpreted as the main control on facies architecture and bar morphology. In this case, strong helical flow with a maximum strength of 1.05 was developed during the deposition of scroll bars but not the compound bars. The widely used paleocurrent indicator-dip direction of cross beds-was found to be inconsistent with the mean flow direction or the channel margin orientation. Panel_14847 Panel_14847 8:30 AM 5:00 PM
8:30 a.m.
How Many Turbidity Currents Pass Through a Submarine Channel and What is Their Stratigraphic Expression?
Exhibition Hall
The ability to directly monitor sediment gravity flows that shape submarine channels on the modern seafloor remains largely elusive. As a result, the sedimentary record is perhaps the most accessible and suitable laboratory from which to consider the dynamic history of channelized sediment transfer and deposition within slope channels. Our analysis features the well-preserved fill of an outcropping submarine channel (“Unit -2”) in the Tres Pasos Fm (Cretaceous), Chile. A spectrum of processes results in fill patterns within channelform bodies 15-25 m thick and 200-400 m wide, including an axial sandstone-dominated zone bound by composite erosional surfaces that define lateral contacts with thin-bedded and finer- grained channel margin units. Channel margin deposits drape or lap onto the composite edge of the channel form. Seventy to eighty percent of the cross-sectional channel fill consists of sandstone-dominated (axis) strata and 20-30% mudstone-prone (margin) strata. A series of 17 stratigraphic sections measured at 0.1 cm resolution through the channel fill, from the channel axis through margin transition, document the number and spatial distribution of sedimentation units, or turbidity current events. Our analysis reveals that >500 individual, distinct sedimentation units are present in the single channel fill. However, <5% of the recorded sedimentation units are preserved in channel axis deposits. Insight into prolonged sediment transfer is preserved in cross-sectionally limited channel margin sedimentation units; many of these fine-grained units overlie erosion surfaces, recording deposition from the dilute tails or fringes of highly erosive, mainly bypassing turbidity currents. The total number of distinct sedimentation units represents the minimum number of turbidity currents that passed through the channel over its lifecycle. Stratigraphic correlation reveals that thinner-bedded, finer-grained margin facies track into thicker-bedded axis facies. At least ten discontinuities form the composite surface that defines the contact between channel axis and margin; a nuanced, time transgressive channel evolution interpretation is required to account for the observations made. A simple, two-step cut and fill model for submarine channels does not represent the prolonged and dynamic nature of evolutionary processes. Thick-bedded, sand-rich channel filling is highly episodic and rare against a background of channel maintenance by bypassing turbidity currents. The ability to directly monitor sediment gravity flows that shape submarine channels on the modern seafloor remains largely elusive. As a result, the sedimentary record is perhaps the most accessible and suitable laboratory from which to consider the dynamic history of channelized sediment transfer and deposition within slope channels. Our analysis features the well-preserved fill of an outcropping submarine channel (“Unit -2”) in the Tres Pasos Fm (Cretaceous), Chile. A spectrum of processes results in fill patterns within channelform bodies 15-25 m thick and 200-400 m wide, including an axial sandstone-dominated zone bound by composite erosional surfaces that define lateral contacts with thin-bedded and finer- grained channel margin units. Channel margin deposits drape or lap onto the composite edge of the channel form. Seventy to eighty percent of the cross-sectional channel fill consists of sandstone-dominated (axis) strata and 20-30% mudstone-prone (margin) strata. A series of 17 stratigraphic sections measured at 0.1 cm resolution through the channel fill, from the channel axis through margin transition, document the number and spatial distribution of sedimentation units, or turbidity current events. Our analysis reveals that >500 individual, distinct sedimentation units are present in the single channel fill. However, <5% of the recorded sedimentation units are preserved in channel axis deposits. Insight into prolonged sediment transfer is preserved in cross-sectionally limited channel margin sedimentation units; many of these fine-grained units overlie erosion surfaces, recording deposition from the dilute tails or fringes of highly erosive, mainly bypassing turbidity currents. The total number of distinct sedimentation units represents the minimum number of turbidity currents that passed through the channel over its lifecycle. Stratigraphic correlation reveals that thinner-bedded, finer-grained margin facies track into thicker-bedded axis facies. At least ten discontinuities form the composite surface that defines the contact between channel axis and margin; a nuanced, time transgressive channel evolution interpretation is required to account for the observations made. A simple, two-step cut and fill model for submarine channels does not represent the prolonged and dynamic nature of evolutionary processes. Thick-bedded, sand-rich channel filling is highly episodic and rare against a background of channel maintenance by bypassing turbidity currents. Panel_14846 Panel_14846 8:30 AM 5:00 PM
8:30 a.m.
Use of High-Resolution 3-D Seismic Data to Evaluate Quaternary Valley Evolution History During Transgression, Offshore San Luis Pass, Gulf of Mexico
Exhibition Hall
A novel, shallow-investigation, high-resolution 3D (HR3D) seismic acquisition system has been employed, for the first time in the Gulf of Mexico, to characterize storage potential and de-risk targets for CO2 sequestration. HR3D data can image detailed depositional, architectural, and structural features in the shallow subsurface that have previously been below seismic resolution and/or excluded from industry surveys, which are optimized for deeper targets. One HR3D survey is located just offshore from San Luis Pass, TX and covers an area of 31.5 km2. The dataset images the shallow subsurface with an unprecedented level of detail -- peak frequency of approximately 150Hz (8 25m cables, spaced at 12.5m, 6.25m by 6.25m bin size). Imaged within this dataset at ~100ms, is a mappable erosional unconformity that is interpreted to be associated with the Brazos River system during the last glacial-eustatic lowstand and following Holocene transgression. Through the analysis of stratal slices and the geometries of the valley form and its dendritic features, we explore the evolution history of the valley system during a transgressive episode. Observations indicate that the system evolves from a lowstand meandering channel with clear point-bar deposits to a transgressive estuary characterized by dendritic tidal features that is eventually flooded. This is an exceptional 3D example of a lowstand to transgressive transition and the sedimentary processes that dominate in each instance. A novel, shallow-investigation, high-resolution 3D (HR3D) seismic acquisition system has been employed, for the first time in the Gulf of Mexico, to characterize storage potential and de-risk targets for CO2 sequestration. HR3D data can image detailed depositional, architectural, and structural features in the shallow subsurface that have previously been below seismic resolution and/or excluded from industry surveys, which are optimized for deeper targets. One HR3D survey is located just offshore from San Luis Pass, TX and covers an area of 31.5 km2. The dataset images the shallow subsurface with an unprecedented level of detail -- peak frequency of approximately 150Hz (8 25m cables, spaced at 12.5m, 6.25m by 6.25m bin size). Imaged within this dataset at ~100ms, is a mappable erosional unconformity that is interpreted to be associated with the Brazos River system during the last glacial-eustatic lowstand and following Holocene transgression. Through the analysis of stratal slices and the geometries of the valley form and its dendritic features, we explore the evolution history of the valley system during a transgressive episode. Observations indicate that the system evolves from a lowstand meandering channel with clear point-bar deposits to a transgressive estuary characterized by dendritic tidal features that is eventually flooded. This is an exceptional 3D example of a lowstand to transgressive transition and the sedimentary processes that dominate in each instance. Panel_14843 Panel_14843 8:30 AM 5:00 PM
8:30 a.m.
Regional Stratigraphic Differentiation of Deepwater Fan and Channel Geometries, Offshore Tanzania and Mozambique: Size Matters
Exhibition Hall
The emerging deepwater gas province offshore East Africa presents great opportunities and also dilemmas in high-grading a vast region for petroleum potential. Known hydrocarbon play elements are Cretaceous and Early Tertiary deepwater fan systems, structurally-enhanced stratigraphic traps, and a functioning gas petroleum system with unknown liquids potential. The fan/channel reservoirs contain remarkable reservoir properties and a high degree of connectivity; however, their distribution is more problematic. The ability to map reservoir spatial and temporal distribution is a critical undeveloped play element. We outline a workflow that enables this mapping by generating high-resolution horizon interpretations of a coarse regional 2D seismic grid over a 400,000 square kilometer area. Regional mapping of time-correlative stratal packages outlines the broader depositional and tectonic-stratigraphic framework. Detailed mapping of various architectural elements within these stratal packages reveals systematic variation both within and between stratal intervals. Channel morphology and related geo-body types and dimensions vary both up- and down- depositional gradient, but also according to stratigraphic position. Geo-body dimensions and distribution are dictated by the geomorphic gradient and profile controlling sediment deposition. Steeper profiles have greater potential energy and thus higher incision in up-dip positions, with little levee development and more aggradational frontal splays and lobes occurring down-dip. Sediment partitioning favors down-profile deposition and channel concentration in fewer channels. The resulting stratigraphic record favors single-story channel systems and smaller, multi-storied lobes. Lower-gradient profiles generate more low-energy density flows, resulting in less up-dip incision and significant, symmetric levee development and shingled or progradational frontal splays in down dip positions. The resulting stratigraphic record favors multiple, along-strike channel development creating laterally persistent, single-storied sands and aerially larger, shingled fan lobes. Understanding the distribution and stacking of these different architectural elements through time has significant implications for trapping, reservoir distribution and connectivity. Application of this work provides enhanced predictability to exploration efforts, including distribution of reservoir properties in a regional basin context. The emerging deepwater gas province offshore East Africa presents great opportunities and also dilemmas in high-grading a vast region for petroleum potential. Known hydrocarbon play elements are Cretaceous and Early Tertiary deepwater fan systems, structurally-enhanced stratigraphic traps, and a functioning gas petroleum system with unknown liquids potential. The fan/channel reservoirs contain remarkable reservoir properties and a high degree of connectivity; however, their distribution is more problematic. The ability to map reservoir spatial and temporal distribution is a critical undeveloped play element. We outline a workflow that enables this mapping by generating high-resolution horizon interpretations of a coarse regional 2D seismic grid over a 400,000 square kilometer area. Regional mapping of time-correlative stratal packages outlines the broader depositional and tectonic-stratigraphic framework. Detailed mapping of various architectural elements within these stratal packages reveals systematic variation both within and between stratal intervals. Channel morphology and related geo-body types and dimensions vary both up- and down- depositional gradient, but also according to stratigraphic position. Geo-body dimensions and distribution are dictated by the geomorphic gradient and profile controlling sediment deposition. Steeper profiles have greater potential energy and thus higher incision in up-dip positions, with little levee development and more aggradational frontal splays and lobes occurring down-dip. Sediment partitioning favors down-profile deposition and channel concentration in fewer channels. The resulting stratigraphic record favors single-story channel systems and smaller, multi-storied lobes. Lower-gradient profiles generate more low-energy density flows, resulting in less up-dip incision and significant, symmetric levee development and shingled or progradational frontal splays in down dip positions. The resulting stratigraphic record favors multiple, along-strike channel development creating laterally persistent, single-storied sands and aerially larger, shingled fan lobes. Understanding the distribution and stacking of these different architectural elements through time has significant implications for trapping, reservoir distribution and connectivity. Application of this work provides enhanced predictability to exploration efforts, including distribution of reservoir properties in a regional basin context. Panel_14845 Panel_14845 8:30 AM 5:00 PM
8:30 a.m.
Large Scale Meandering Channel Processes and Product: New Insights From McMurray Formation Type Section
Exhibition Hall
The Lower Cretaceous McMurray Formation Type Section is located 5km downstream from the confluence of the Athabasca and Clearwater rivers and extends 2 km along the east bank of the Athabasca River. This outstanding, up to 80 m thick exposure has been visited by many geologists, but remains poorly documented in literature. The outcrop is comprised of four distinct stratigraphic units. The focus of this report is on heterogeneities observed across the large-scale (35m thick) channel deposit. Since oil-saturated, this outcrop also presents an unparalleled portal for reservoir studies. Data was acquired through detailed two-dimensional outcrop mapping recorded on high resolution photographs and scaled photo-montages, line-drawing of various geological contacts interpreted on both outcrops and images, and integrating detailed (cm-dm) bed-by-bed logging along selected outcrop exposures. Mapping and line drawings were further assisted by the collection of paleo-flow indicators. These data were coupled with core descriptions from drill holes behind the outcrop which allowed for 3D visualization. Point bar evolution is interpreted based on nature (geometry) of contacts, geometric relationship of mapped architectural elements, facies changes between architectural elements, and paleo-current indicators. Detailed mapping revealed numerous enigmatic features commonly not associated with point bar processes and architecture that include: (1) five types of breccia not associated with channel lag deposits; (2) a variety of mud occurrences in high-energy bottom-channel deposits; (3) encased channel shaped features within the mid-to-upper point-bar deposits (interpreted as short lived chute and rill channels); and (4) paleo-current reversals. Observations of detailed reservoir architecture from the Type Section provides a basis for characterizing dynamic interplay of deposition and erosion of channel deposits on various time scales; new insights for point-bar facies models; and more fulsome understanding of the impact of facies heterogeneities on reservoir oil-charge and in-reservoir fluid migration. The Lower Cretaceous McMurray Formation Type Section is located 5km downstream from the confluence of the Athabasca and Clearwater rivers and extends 2 km along the east bank of the Athabasca River. This outstanding, up to 80 m thick exposure has been visited by many geologists, but remains poorly documented in literature. The outcrop is comprised of four distinct stratigraphic units. The focus of this report is on heterogeneities observed across the large-scale (35m thick) channel deposit. Since oil-saturated, this outcrop also presents an unparalleled portal for reservoir studies. Data was acquired through detailed two-dimensional outcrop mapping recorded on high resolution photographs and scaled photo-montages, line-drawing of various geological contacts interpreted on both outcrops and images, and integrating detailed (cm-dm) bed-by-bed logging along selected outcrop exposures. Mapping and line drawings were further assisted by the collection of paleo-flow indicators. These data were coupled with core descriptions from drill holes behind the outcrop which allowed for 3D visualization. Point bar evolution is interpreted based on nature (geometry) of contacts, geometric relationship of mapped architectural elements, facies changes between architectural elements, and paleo-current indicators. Detailed mapping revealed numerous enigmatic features commonly not associated with point bar processes and architecture that include: (1) five types of breccia not associated with channel lag deposits; (2) a variety of mud occurrences in high-energy bottom-channel deposits; (3) encased channel shaped features within the mid-to-upper point-bar deposits (interpreted as short lived chute and rill channels); and (4) paleo-current reversals. Observations of detailed reservoir architecture from the Type Section provides a basis for characterizing dynamic interplay of deposition and erosion of channel deposits on various time scales; new insights for point-bar facies models; and more fulsome understanding of the impact of facies heterogeneities on reservoir oil-charge and in-reservoir fluid migration. Panel_14836 Panel_14836 8:30 AM 5:00 PM
8:30 a.m.
Signal Preservation in Pulsing Turbidity Currents
Exhibition Hall
Recent debate has focused on the potential preservation of the signal of seismic events in the sedimentary record via the initiation of large-scale turbidity current flows. It has been postulated that details of seismic activity may be recorded in turbidites. For example, given the long run out time of turbidity currents, secondary turbidity currents events, initiated by seismic aftershocks, are likely to interact with the primary events creating a “pulsing” flow. Such pulsing flow may also be generated if the failure of a seismic fault lies across an interconnected series of submarine channel systems, where a seismic trigger may generate multiple linked flows. With variation in feeder channel length causing variation in the time taken for individual flows to reach channel confluences, the resultant turbidity current is also expected to be pulsed. Thus, cyclical waxing to waning behavior preserved in graded flow deposits may be a key indicator of secondary seismic activity or a seismic trigger acting over an interconnected channel system. Dependent on the ability for signal preservation in pulsing flows, deposit grading may provide a novel means of assessing proximity to source and/or system architecture. Novel experimental research is presented that explores the dynamics of pulsed turbidity currents. The experimental study is used to quantitatively examine controls on the time and length scale of signal preservation. Parameters investigated include volumes of material released, effective flow density and viscosity (as a proxy of flow mud content). Full flow field visualization was made using an array of interlinked HD cameras. Dyeing separate components of the flow different colors enabled detailed analysis of flow dynamic behavior occurring between head and tail. The secondary pulsing flow was seen to rapidly overtake the first flow. Observations of flow velocity and density suggested that due to stratification the secondary flow was travelling along the density interface between the main body of the primary flow and its turbulent wake. As the pulsing flows created in the laboratory experiments rapidly merged, it suggests that it is difficult to preserve pulsing signals of interacting turbidity currents over long run out distance or times. However, these initial experiments have been carried out with solute currents on flat slopes. Particulate currents travelling over a pronounced gradient may have a significantly different signal preservation behavior. Recent debate has focused on the potential preservation of the signal of seismic events in the sedimentary record via the initiation of large-scale turbidity current flows. It has been postulated that details of seismic activity may be recorded in turbidites. For example, given the long run out time of turbidity currents, secondary turbidity currents events, initiated by seismic aftershocks, are likely to interact with the primary events creating a “pulsing” flow. Such pulsing flow may also be generated if the failure of a seismic fault lies across an interconnected series of submarine channel systems, where a seismic trigger may generate multiple linked flows. With variation in feeder channel length causing variation in the time taken for individual flows to reach channel confluences, the resultant turbidity current is also expected to be pulsed. Thus, cyclical waxing to waning behavior preserved in graded flow deposits may be a key indicator of secondary seismic activity or a seismic trigger acting over an interconnected channel system. Dependent on the ability for signal preservation in pulsing flows, deposit grading may provide a novel means of assessing proximity to source and/or system architecture. Novel experimental research is presented that explores the dynamics of pulsed turbidity currents. The experimental study is used to quantitatively examine controls on the time and length scale of signal preservation. Parameters investigated include volumes of material released, effective flow density and viscosity (as a proxy of flow mud content). Full flow field visualization was made using an array of interlinked HD cameras. Dyeing separate components of the flow different colors enabled detailed analysis of flow dynamic behavior occurring between head and tail. The secondary pulsing flow was seen to rapidly overtake the first flow. Observations of flow velocity and density suggested that due to stratification the secondary flow was travelling along the density interface between the main body of the primary flow and its turbulent wake. As the pulsing flows created in the laboratory experiments rapidly merged, it suggests that it is difficult to preserve pulsing signals of interacting turbidity currents over long run out distance or times. However, these initial experiments have been carried out with solute currents on flat slopes. Particulate currents travelling over a pronounced gradient may have a significantly different signal preservation behavior. Panel_14840 Panel_14840 8:30 AM 5:00 PM
Channels are conduits through which fluids, sediment (suspended and bed-load) and dissolved loads are transported across the Earth surface. Their general geomorphologic expression is comparable similar in terrestrial, submarine and extraterrestrial environments; however, formative sedimentary processes can be fundamentally different. For example, sinuosity and aspect ratio tend to be similar; however, submarine channels tend to be larger than fluvial channels and the stratigraphic records of fluvial and submarine channel deposits can be different. A key research challenge is the link between the geomorphic expression and stratigraphic record of channels. Rivers are more accessible to direct monitoring compared to submarine channels and the link between fluvial geomorphology and stratigraphy is better understood. In the case of submarine channels, we commonly rely on the stratigraphic record to inform insights about formative processes and evolution.

Channels are conduits through which fluids, sediment (suspended and bed-load) and dissolved loads are transported across the Earth surface. Their general geomorphologic expression is comparable similar in terrestrial, submarine and extraterrestrial environments; however, formative sedimentary processes can be fundamentally different. For example, sinuosity and aspect ratio tend to be similar; however, submarine channels tend to be larger than fluvial channels and the stratigraphic records of fluvial and submarine channel deposits can be different. A key research challenge is the link between the geomorphic expression and stratigraphic record of channels. Rivers are more accessible to direct monitoring compared to submarine channels and the link between fluvial geomorphology and stratigraphy is better understood. In the case of submarine channels, we commonly rely on the stratigraphic record to inform insights about formative processes and evolution.

Panel_14420 Panel_14420 8:00 AM 11:50 AM
8:00 a.m.
Introductory Remarks
Four Seasons Ballroom 4
Panel_15759 Panel_15759 8:00 AM 12:00 AM
8:05 a.m.
Fluvial Channel Belt Reservoirs
Four Seasons Ballroom 4
Modern rivers are commonly classified as meandering or braided, but this distinction poorly differentiates the range of interval heterogeneities observed in fluvial channel-belt reservoirs. The problem with this division applied to reservoir type is that class definition is based on unrelated variables (sinuosity in one case, and number of active channel threads in the other), and inferences about a range of other variables that are only weakly related (e.g., mean grain size). Large-scale heterogeneity patterns within channel belts are generally not channel-shaped features, but rather reflect bodies formed as channel segments migrate and then are cut off. These bodies (“storeys”) generally scale to formative river discharge (controlling channel width & depth and the downstream length of adjacent bars). The sinuosity of individual channel segments (before cutoff) defines the width/length ratio of these bodies and internal grain size patterns. Deposits within storeys can be divided into different depositional zones with distinct lateral grain-size trends across the channel bed (which can become vertical trends within the deposits by Walters’ law shifts in bed position): inner-bank (bar), concave bank, and abandonment fill. Inward-fining across the inner-bank zone bed becomes more pronounced with distance downstream along a channel bend and channel sinuosity. Upward-fining deposits are preferentially preserved when a channel bend migrates more downstream relative to rates of expansion. Concave bank zone deposits are highly variable depending on whether deposits form due to eddy aggradation or downstream accretion. Channel-fill-zone grain-size trends depend on rates of channel segment abandonment and vertical aggradation vs. lateral-fill deposition. The width of a channel belt formed by a river of given discharge increases with the sinuosity of individual channel segments and the number of storeys laterally stacked during the sum of channel-bend expansion and cutoff events before river avulsion. Connectivity patterns of subsurface fluid flow along a channel belt depends on storey internal character, lateral stacking pattern, net aggradation, and the width spanned by the final fill formed during belt avulsion. Modern rivers are commonly classified as meandering or braided, but this distinction poorly differentiates the range of interval heterogeneities observed in fluvial channel-belt reservoirs. The problem with this division applied to reservoir type is that class definition is based on unrelated variables (sinuosity in one case, and number of active channel threads in the other), and inferences about a range of other variables that are only weakly related (e.g., mean grain size). Large-scale heterogeneity patterns within channel belts are generally not channel-shaped features, but rather reflect bodies formed as channel segments migrate and then are cut off. These bodies (“storeys”) generally scale to formative river discharge (controlling channel width & depth and the downstream length of adjacent bars). The sinuosity of individual channel segments (before cutoff) defines the width/length ratio of these bodies and internal grain size patterns. Deposits within storeys can be divided into different depositional zones with distinct lateral grain-size trends across the channel bed (which can become vertical trends within the deposits by Walters’ law shifts in bed position): inner-bank (bar), concave bank, and abandonment fill. Inward-fining across the inner-bank zone bed becomes more pronounced with distance downstream along a channel bend and channel sinuosity. Upward-fining deposits are preferentially preserved when a channel bend migrates more downstream relative to rates of expansion. Concave bank zone deposits are highly variable depending on whether deposits form due to eddy aggradation or downstream accretion. Channel-fill-zone grain-size trends depend on rates of channel segment abandonment and vertical aggradation vs. lateral-fill deposition. The width of a channel belt formed by a river of given discharge increases with the sinuosity of individual channel segments and the number of storeys laterally stacked during the sum of channel-bend expansion and cutoff events before river avulsion. Connectivity patterns of subsurface fluid flow along a channel belt depends on storey internal character, lateral stacking pattern, net aggradation, and the width spanned by the final fill formed during belt avulsion. Panel_14855 Panel_14855 8:05 AM 8:25 AM
8:25 a.m.
Preservational Complexity and Completeness in Channel Point Bars and the Heterogeneity of Heterogeneity in Their Reservoir Models
Four Seasons Ballroom 4
Point bars tend to generate sandy lobate reservoir units that fill channels laterally and serve as primary development targets in both conventional and unconventional fluvial plays. Initial models for point bar growth build upon the presumption of periodic shingling of the convex inner channel bend with sheet-form sand layers that cover much of the wetted bend surface. Episodic and repetitive sheet addition causes the channel to migrate in expansional or translational vectors and produces sandy bodies partitioned with regularly spaced, gently dipping, bar-extensive, and sometimes draped accretion surfaces that record the channel form and resemble large cross sets. This results in reasonably predictable and easily modeled reservoir architectures. While field evidence argues that this fundamental modern process and rock product do occur in some approximation, an accumulation of additional field evidence argues that this process is not alone. At least three other processes also produce point-bar forms, and each of these processes preserves contrasting internal reservoir architecture. These processes are fragmentary bar accretion, counter point bar accretion, and mid-channel bar accretion. Fragmentary bar accretion results from high-frequency deposition of small unit bars over only limited areas of the wetted bar surface, commonly followed by dissection and erosional reshaping of the bar surface and local draping. This results in a bar deposit formed of highly fragmented reservoir units lacking through-going accretion sets and prone to unpredictable heterogeneity. Counter-point-bar accretion occurs by forced decoupling of the cut-bank flow shear and accretion along the cut-bank face. This produces concave accretion surfaces in strata typically much muddier and more heterogeneous than classic convex-accretion bars. Lastly, a lobe sandy body mimicking a true point bar may form in otherwise braided systems by preferential accretion of mid-channel bars to the inside bend of a braided river that meanders. These tend to form sets of amalgamated sandy mid-channel bars into point-bar shapes that have mounded accretion surfaces at various orientations. These surfaces may move reservoir fluid flow in erratic direction. Each of these forms are common, and each includes long internal hiatal surfaces that result in total bar accretion rates that are much slower than rates of short-term bar growth. Point bars tend to generate sandy lobate reservoir units that fill channels laterally and serve as primary development targets in both conventional and unconventional fluvial plays. Initial models for point bar growth build upon the presumption of periodic shingling of the convex inner channel bend with sheet-form sand layers that cover much of the wetted bend surface. Episodic and repetitive sheet addition causes the channel to migrate in expansional or translational vectors and produces sandy bodies partitioned with regularly spaced, gently dipping, bar-extensive, and sometimes draped accretion surfaces that record the channel form and resemble large cross sets. This results in reasonably predictable and easily modeled reservoir architectures. While field evidence argues that this fundamental modern process and rock product do occur in some approximation, an accumulation of additional field evidence argues that this process is not alone. At least three other processes also produce point-bar forms, and each of these processes preserves contrasting internal reservoir architecture. These processes are fragmentary bar accretion, counter point bar accretion, and mid-channel bar accretion. Fragmentary bar accretion results from high-frequency deposition of small unit bars over only limited areas of the wetted bar surface, commonly followed by dissection and erosional reshaping of the bar surface and local draping. This results in a bar deposit formed of highly fragmented reservoir units lacking through-going accretion sets and prone to unpredictable heterogeneity. Counter-point-bar accretion occurs by forced decoupling of the cut-bank flow shear and accretion along the cut-bank face. This produces concave accretion surfaces in strata typically much muddier and more heterogeneous than classic convex-accretion bars. Lastly, a lobe sandy body mimicking a true point bar may form in otherwise braided systems by preferential accretion of mid-channel bars to the inside bend of a braided river that meanders. These tend to form sets of amalgamated sandy mid-channel bars into point-bar shapes that have mounded accretion surfaces at various orientations. These surfaces may move reservoir fluid flow in erratic direction. Each of these forms are common, and each includes long internal hiatal surfaces that result in total bar accretion rates that are much slower than rates of short-term bar growth. Panel_14853 Panel_14853 8:25 AM 8:45 AM
8:45 a.m.
Scaling Relationships Between Fluvial Channel Fills, Channel-Belt Sand Bodies and Drainage Basins, With Implications for the Mannville Group, Alberta Foreland Basin
Four Seasons Ballroom 4
Scaling relationships developed from modern fluvial deposits provide useful guidance for interpretation of the stratigraphic record. At the system level, fluvial channel depth and the related thicknesses of channel-belt sand bodies scale to contributing drainage area, whereas, at the local to subregional level, characteristic width-thickness ratios exist for muddy abandoned channel fills (10-30:1) and laterally amalgamated channel-belt sand bodies (70-300:1). Moreover, net deposition as the river goes through its backwater reach, and feels the effects of sea level, results in significantly less lateral migration before avulsion: although muddy channel-fill dimensions may not change, channel-belt width-to-thickness ratios are significantly less (20-50:1), and sand bodies are encased in muddy flood-basin or delta-plain strata. These and other relationships provide insight into the paleogeographic significance and scale of fluvial deposits in the Early Cretaceous Mannville Group, Alberta foreland. At the system level, thicknesses of Mannville point-bar sand bodies commonly exceed 30 m, which suggests a potential drainage area exceeding that of the modern Mississippi. This view is consistent with detrital-zircon signatures of a source terrain that stretched from the Appalachians in the SE US to the Western Cordillera. These two observations converge to indicate that Mannville fluvial-deltaic deposits record the continental-scale river of that time. At the local to subregional level, the well-imaged Lower Mannville McMurray Formation in Athabasca displays channel-fill dimensions consistent with those from modern rivers, and sand body width-to-thickness ratios typical of amalgamated channel belts within the upper limits of, or above, the backwater reach. Backwater lengths in large river systems with deep, low-gradient channels can exceed 500 km, which would suggest contemporaneous McMurray shorelines would have been very far to the north of the type area. It would be rare to see tidal effects all the way through the backwater reach of any river, and very unlikely to see brackish conditions recorded this far upstream. Yet, sedimentological and ichnofacies characteristics in these deposits have historically been, and still are in many cases, interpreted to record brackish and/or tidal influences. Observations of scaling relationships for channel deposits therefore provide alternative interpretations of McMurray strata that are guiding ongoing investigations. Scaling relationships developed from modern fluvial deposits provide useful guidance for interpretation of the stratigraphic record. At the system level, fluvial channel depth and the related thicknesses of channel-belt sand bodies scale to contributing drainage area, whereas, at the local to subregional level, characteristic width-thickness ratios exist for muddy abandoned channel fills (10-30:1) and laterally amalgamated channel-belt sand bodies (70-300:1). Moreover, net deposition as the river goes through its backwater reach, and feels the effects of sea level, results in significantly less lateral migration before avulsion: although muddy channel-fill dimensions may not change, channel-belt width-to-thickness ratios are significantly less (20-50:1), and sand bodies are encased in muddy flood-basin or delta-plain strata. These and other relationships provide insight into the paleogeographic significance and scale of fluvial deposits in the Early Cretaceous Mannville Group, Alberta foreland. At the system level, thicknesses of Mannville point-bar sand bodies commonly exceed 30 m, which suggests a potential drainage area exceeding that of the modern Mississippi. This view is consistent with detrital-zircon signatures of a source terrain that stretched from the Appalachians in the SE US to the Western Cordillera. These two observations converge to indicate that Mannville fluvial-deltaic deposits record the continental-scale river of that time. At the local to subregional level, the well-imaged Lower Mannville McMurray Formation in Athabasca displays channel-fill dimensions consistent with those from modern rivers, and sand body width-to-thickness ratios typical of amalgamated channel belts within the upper limits of, or above, the backwater reach. Backwater lengths in large river systems with deep, low-gradient channels can exceed 500 km, which would suggest contemporaneous McMurray shorelines would have been very far to the north of the type area. It would be rare to see tidal effects all the way through the backwater reach of any river, and very unlikely to see brackish conditions recorded this far upstream. Yet, sedimentological and ichnofacies characteristics in these deposits have historically been, and still are in many cases, interpreted to record brackish and/or tidal influences. Observations of scaling relationships for channel deposits therefore provide alternative interpretations of McMurray strata that are guiding ongoing investigations. Panel_14849 Panel_14849 8:45 AM 9:05 AM
9:05 a.m.
Exploring Deltaic Network Growth and Stratigraphy Through a Rule Based Geometric Model
Four Seasons Ballroom 4
We introduce a unified geometric model in which the short term fluvio-deltaic processes generating discrete sedimentary bodies and long term basin evolution coexist. Geometric aspects of delta channel networks and their long term internal stratigraphic arrangements of deltaic deposits present enormous intricacy in almost every aspect (delta shape and size, number of channels, shoreline shape, etc.). To simulate the planimetric growth of a deltaic network we employ a flexible algorithm based on a set of simple rules some of which are quantitatively anchored in physical processes while others are purely stochastic and connected to the physical process via observed field correlations among various terms (e.g., Syvitski, 2006). The model generates distributary networks in which planform of individual channels emerge from a correlated random walk algorithm through successive addition of short segments (piecewise). Each segment involves a small direction deflection, partly correlated to the previous deflection. Frequent bifurcations result in dense, anabranching channel patterns while more representative deltaic networks are obtained using a small probability bifurcation value (0.01 to 0.05). The proposed network growth model can yield distributary networks of significant morphological variation in terms of shapes, channel planforms, or channel density. The comparison between model outcomes and field analogs will be through a series of metrics such as planform shape of individual channels, delta shape, shoreline shape, or channel density distribution. Long term, a kinematic basin filling mass conservation model is used to render large scale strata arrangements which under constant sediment supply and sea level conditions consists of monotonous parallel topset and foreset packages. Varying the external forcing factors (i.e., sea level, subsidence) yields complex stratal arrangements reflecting the effects of transgression and incision. We argue that this hybrid approach driven by simple rules is suitable for investigating complex systems. By aggregating only few simple rules, due to the random terms built in, this type of model creates complex landscape patterns via randomness built in (e.g. Murray & Paola, 1994). Using simple rules also enables scenario testing and makes it easier to understand the important controls on the stratigraphic outcome. We introduce a unified geometric model in which the short term fluvio-deltaic processes generating discrete sedimentary bodies and long term basin evolution coexist. Geometric aspects of delta channel networks and their long term internal stratigraphic arrangements of deltaic deposits present enormous intricacy in almost every aspect (delta shape and size, number of channels, shoreline shape, etc.). To simulate the planimetric growth of a deltaic network we employ a flexible algorithm based on a set of simple rules some of which are quantitatively anchored in physical processes while others are purely stochastic and connected to the physical process via observed field correlations among various terms (e.g., Syvitski, 2006). The model generates distributary networks in which planform of individual channels emerge from a correlated random walk algorithm through successive addition of short segments (piecewise). Each segment involves a small direction deflection, partly correlated to the previous deflection. Frequent bifurcations result in dense, anabranching channel patterns while more representative deltaic networks are obtained using a small probability bifurcation value (0.01 to 0.05). The proposed network growth model can yield distributary networks of significant morphological variation in terms of shapes, channel planforms, or channel density. The comparison between model outcomes and field analogs will be through a series of metrics such as planform shape of individual channels, delta shape, shoreline shape, or channel density distribution. Long term, a kinematic basin filling mass conservation model is used to render large scale strata arrangements which under constant sediment supply and sea level conditions consists of monotonous parallel topset and foreset packages. Varying the external forcing factors (i.e., sea level, subsidence) yields complex stratal arrangements reflecting the effects of transgression and incision. We argue that this hybrid approach driven by simple rules is suitable for investigating complex systems. By aggregating only few simple rules, due to the random terms built in, this type of model creates complex landscape patterns via randomness built in (e.g. Murray & Paola, 1994). Using simple rules also enables scenario testing and makes it easier to understand the important controls on the stratigraphic outcome. Panel_14850 Panel_14850 9:05 AM 9:25 AM
9:25 a.m.
Break
Four Seasons Ballroom 4
Panel_15760 Panel_15760 9:25 AM 12:00 AM
10:10 a.m.
Channel Scaling and Dynamics in the Fluvial Marine Transition
Four Seasons Ballroom 4
Channels are pervasive features in the modern landscape and stratigraphic record. They occur at various scales in nearly all depositional environments, and represent one of the fundamental reservoir architectures in petroleum systems. This work documents the morphological, kinematic, and architectural changes that channelized systems undergo in the fluvial marine transition (FMT), in terms of physical controls and boundary conditions. In this study, the FMT channels are not considered in isolation. They are compared with other environments (e.g. continental fluvial and deepwater systems) to highlight unique aspects versus commonality in terms of process and product. As the basis of this study, an extensive database of modern systems and shallow analogs has been constructed, sourced from remote sensing, high resolution seismic, and vertical data (core/well). Multiple scales of channelized features are extracted and analyzed including: the geomorphic channel form, oxbow-cutoffs, and channel belts. Geometric statistics measured on these features are used to derive scaling relationships specifically relevant to reservoir characterization. The scaling observations are coupled with known process controls (boundary conditions) to identify and highlight the first order physical controls on channel morphology, kinematics, and resultant architecture. These controls form a process classification that (1) predicts the relative lengthscale of the FMT, ranging from O(< 1 km) to O(1000 km), and (2) polarizes/classifies channelized systems according to process dominance. Process dominance in the FMT is viewed as the significance of episodic fluvial floods in relation to regular tidal flows. The contrasts in morphology that arise from differences in FMT hydrodynamics are mirrored by contrasts in stratigraphy. In particular, the streamwise location of maximum sediment divergence and deposition. As a concrete illustration, we contrast the Mississippi and Amazon systems. Lastly, we examine the interaction of FMT hydrodynamics (the stage-discharge relationship) with relative base level change and avulsion theory, which results in stratigraphic deposits with fundamentally different scaling than their purely fluvial counterparts. Theory coupling hydrodynamic processes, subsidence, and avulsion illustrates the relevance of short-term hydrodynamic processes on the long-term stratigraphic record. Channels are pervasive features in the modern landscape and stratigraphic record. They occur at various scales in nearly all depositional environments, and represent one of the fundamental reservoir architectures in petroleum systems. This work documents the morphological, kinematic, and architectural changes that channelized systems undergo in the fluvial marine transition (FMT), in terms of physical controls and boundary conditions. In this study, the FMT channels are not considered in isolation. They are compared with other environments (e.g. continental fluvial and deepwater systems) to highlight unique aspects versus commonality in terms of process and product. As the basis of this study, an extensive database of modern systems and shallow analogs has been constructed, sourced from remote sensing, high resolution seismic, and vertical data (core/well). Multiple scales of channelized features are extracted and analyzed including: the geomorphic channel form, oxbow-cutoffs, and channel belts. Geometric statistics measured on these features are used to derive scaling relationships specifically relevant to reservoir characterization. The scaling observations are coupled with known process controls (boundary conditions) to identify and highlight the first order physical controls on channel morphology, kinematics, and resultant architecture. These controls form a process classification that (1) predicts the relative lengthscale of the FMT, ranging from O(< 1 km) to O(1000 km), and (2) polarizes/classifies channelized systems according to process dominance. Process dominance in the FMT is viewed as the significance of episodic fluvial floods in relation to regular tidal flows. The contrasts in morphology that arise from differences in FMT hydrodynamics are mirrored by contrasts in stratigraphy. In particular, the streamwise location of maximum sediment divergence and deposition. As a concrete illustration, we contrast the Mississippi and Amazon systems. Lastly, we examine the interaction of FMT hydrodynamics (the stage-discharge relationship) with relative base level change and avulsion theory, which results in stratigraphic deposits with fundamentally different scaling than their purely fluvial counterparts. Theory coupling hydrodynamic processes, subsidence, and avulsion illustrates the relevance of short-term hydrodynamic processes on the long-term stratigraphic record. Panel_14856 Panel_14856 10:10 AM 10:30 AM
10:50 a.m.
Linking Channel Dynamics to Deposits: How Does Process Understanding Change With the Scale of Observation?
Four Seasons Ballroom 4
Linking stratigraphic and sedimentological attributes of depositional landforms to process dynamics is challenging due to the limited spatial and temporal scales over which measurements may be made relative to the scales that the landforms develop. Here we present process-oriented studies of river and submarine channel levee development, and of floodplain evolution conducted using vastly different scales of observation. Levee development studies were conducted in a laboratory basin on experimental channels a few centimeters deep, while the floodplain studies were conducted using globally available satellite imagery spanning decades. In the laboratory, very high spatial and temporal resolution measurements of jet and density current hydrodynamics and sediment transport were made and linked to patterns of deposition. While these process-based experiments are vastly simplified, relative to natural systems, they provided fundamental insights into the conditions necessary for levee formation at the distal ends of rivers and submarine channels. These insights have served to elucidate how balances in lateral sediment transport and jet dynamics govern deltaic channel formation and provided validation datasets for state of the art morphodynamic models. In submarine systems, the dynamics of density, flow spreading, and entrainment of ambient water critically constrain depositional patterns and highlight fundamental difference between submarine and terrestrial systems despite common channel morphologies. Using multi-temporal satellite imagery we measured of river planform change and floodplain development on rivers systems across the globe. These measurements allow us to use natural systems as experimental realizations from a broad range of settings. This large-scale study of floodplain systems does not provide direct measurements of hydrodynamic and morphodynamics controls, but does provide the opportunity to relate variations in the rate of planform change to other measurable attributes of river systems such as: size, discharge, drainage area, slope, sediment supply and character, climate, and vegetation. These coupled measurements help to isolate the dominant watershed-scale controls on floodplain development and motivate hypotheses on the dominant controls on river mobility. This type of study also has the potential to provide empirical parameterizations for system scale modeling of sedimentology and earth system dynamics. Linking stratigraphic and sedimentological attributes of depositional landforms to process dynamics is challenging due to the limited spatial and temporal scales over which measurements may be made relative to the scales that the landforms develop. Here we present process-oriented studies of river and submarine channel levee development, and of floodplain evolution conducted using vastly different scales of observation. Levee development studies were conducted in a laboratory basin on experimental channels a few centimeters deep, while the floodplain studies were conducted using globally available satellite imagery spanning decades. In the laboratory, very high spatial and temporal resolution measurements of jet and density current hydrodynamics and sediment transport were made and linked to patterns of deposition. While these process-based experiments are vastly simplified, relative to natural systems, they provided fundamental insights into the conditions necessary for levee formation at the distal ends of rivers and submarine channels. These insights have served to elucidate how balances in lateral sediment transport and jet dynamics govern deltaic channel formation and provided validation datasets for state of the art morphodynamic models. In submarine systems, the dynamics of density, flow spreading, and entrainment of ambient water critically constrain depositional patterns and highlight fundamental difference between submarine and terrestrial systems despite common channel morphologies. Using multi-temporal satellite imagery we measured of river planform change and floodplain development on rivers systems across the globe. These measurements allow us to use natural systems as experimental realizations from a broad range of settings. This large-scale study of floodplain systems does not provide direct measurements of hydrodynamic and morphodynamics controls, but does provide the opportunity to relate variations in the rate of planform change to other measurable attributes of river systems such as: size, discharge, drainage area, slope, sediment supply and character, climate, and vegetation. These coupled measurements help to isolate the dominant watershed-scale controls on floodplain development and motivate hypotheses on the dominant controls on river mobility. This type of study also has the potential to provide empirical parameterizations for system scale modeling of sedimentology and earth system dynamics. Panel_14851 Panel_14851 10:50 AM 11:10 AM
11:10 a.m.
Deltaic Deposits at Aeolis Dorsa: Sedimentary Evidence for a Standing Body of Water on the Northern Plains of Mars
Four Seasons Ballroom 4
A fundamental and long-standing question regarding Mars history is whether the flat and low-lying northern plains ever hosted an ocean. The best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy. In particular, the topographic expression of channelized deposits provides a window into past depositional environments in areas where detailed field observations at the outcrop scale are not possible. Here, we use high-resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the Aeolis Dorsa region of Mars, just north of the dichotomy boundary. Comparison with terrestrial analogs provides insight to the connection between form and process. At Aeolis Dorsa, Observations of stacked, cross-cutting channel bodies and stratal geometries indicate that these landforms represent exhumed distributary channel deposits. We hypothesize that this distributary system was most likely a delta, rather than an alluvial fan or submarine fan, based on the presence of depositional trunk feeder channel bodies, a lack of evidence for past topographic confinement, channel avulsions at similar elevations, and the presence of a strong break in dip slope between topset and foreset beds. Sediment transport calculations using both measured and derived channel geometries indicate a minimum delta deposition time on the order of 400 years. The location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary, unconfined by any observable craters, suggests a standing body of water potentially 105 km2 in extent or greater and is spatially consistent with hypotheses for a northern ocean. This work highlights the potential for reconstructing paleo-environment from increasingly high-resolution remote sensing data using terrestrial scaling relationships. A fundamental and long-standing question regarding Mars history is whether the flat and low-lying northern plains ever hosted an ocean. The best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy. In particular, the topographic expression of channelized deposits provides a window into past depositional environments in areas where detailed field observations at the outcrop scale are not possible. Here, we use high-resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the Aeolis Dorsa region of Mars, just north of the dichotomy boundary. Comparison with terrestrial analogs provides insight to the connection between form and process. At Aeolis Dorsa, Observations of stacked, cross-cutting channel bodies and stratal geometries indicate that these landforms represent exhumed distributary channel deposits. We hypothesize that this distributary system was most likely a delta, rather than an alluvial fan or submarine fan, based on the presence of depositional trunk feeder channel bodies, a lack of evidence for past topographic confinement, channel avulsions at similar elevations, and the presence of a strong break in dip slope between topset and foreset beds. Sediment transport calculations using both measured and derived channel geometries indicate a minimum delta deposition time on the order of 400 years. The location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary, unconfined by any observable craters, suggests a standing body of water potentially 105 km2 in extent or greater and is spatially consistent with hypotheses for a northern ocean. This work highlights the potential for reconstructing paleo-environment from increasingly high-resolution remote sensing data using terrestrial scaling relationships. Panel_14852 Panel_14852 11:10 AM 11:30 AM
11:30 a.m.
Rivers and Submarine Channels: A Comparison of Their Transport Processes and Resulting Stratigraphic Architecture Over Basin Filling Time Scales
Four Seasons Ballroom 4
Channels act as arteries for the transport of sediment across landscapes and seascapes and help distribute this sediment in basins where thick stratigraphic packages accumulate. Quantitative observations of the planform morphologies of channels in terrestrial and submarine settings indicate strong similarity, suggesting similar transport processes and morphodynamics in the two settings. Observations of these systems in cross-section, however, indicate great differences in their morphologies which likely arise from differences in transport processes and morphodynamics. While significant attention has recently been paid to short time scale differences/similarities of open channel flows and turbidity currents (e.g. direction of helical flow in channel bends) here we focus on a comparison of these flow types and their stratigraphic records over basin filling time scales. In the terrestrial, the ratio for the densities of the channelized flow and the ambient fluid it is moving through is roughly 800. This condition leads to one in which rivers are prone to avulse when they superelevate to a value roughly equal to a channel depth. Coupled with the generation of a backwater regime where terrestrial channels approach the shoreline, the strong difference in flow to ambient fluid densities results in abandoned channels which are topographic lows on landscapes. This condition promotes reoccupation of old channel paths following avulsions and the generation of persistent depositional trends, such as channel clustering. In contrast, the ratio of current to ambient fluid density for turbidity currents in the submarine is only slightly greater than unity. In settings where normal flow dominates, this allows submarine channels to superelevate several multiples of their channel depth. These conditions result in abandoned channels that remain high for a time, leading to avoidance of previous channels and an overall tendency to distribute channel bodies. Further complicating matters though, is the widespread occurrence of non-normal flow in turbidity currents, which in terminal fan settings might lead to stratigraphic architecture similar to terrestrial settings. We explore these processes and products using observations from modern systems and ancient stratigraphic architecture in addition to results from reduced complexity models. Channels act as arteries for the transport of sediment across landscapes and seascapes and help distribute this sediment in basins where thick stratigraphic packages accumulate. Quantitative observations of the planform morphologies of channels in terrestrial and submarine settings indicate strong similarity, suggesting similar transport processes and morphodynamics in the two settings. Observations of these systems in cross-section, however, indicate great differences in their morphologies which likely arise from differences in transport processes and morphodynamics. While significant attention has recently been paid to short time scale differences/similarities of open channel flows and turbidity currents (e.g. direction of helical flow in channel bends) here we focus on a comparison of these flow types and their stratigraphic records over basin filling time scales. In the terrestrial, the ratio for the densities of the channelized flow and the ambient fluid it is moving through is roughly 800. This condition leads to one in which rivers are prone to avulse when they superelevate to a value roughly equal to a channel depth. Coupled with the generation of a backwater regime where terrestrial channels approach the shoreline, the strong difference in flow to ambient fluid densities results in abandoned channels which are topographic lows on landscapes. This condition promotes reoccupation of old channel paths following avulsions and the generation of persistent depositional trends, such as channel clustering. In contrast, the ratio of current to ambient fluid density for turbidity currents in the submarine is only slightly greater than unity. In settings where normal flow dominates, this allows submarine channels to superelevate several multiples of their channel depth. These conditions result in abandoned channels that remain high for a time, leading to avoidance of previous channels and an overall tendency to distribute channel bodies. Further complicating matters though, is the widespread occurrence of non-normal flow in turbidity currents, which in terminal fan settings might lead to stratigraphic architecture similar to terrestrial settings. We explore these processes and products using observations from modern systems and ancient stratigraphic architecture in addition to results from reduced complexity models. Panel_14854 Panel_14854 11:30 AM 11:50 AM
Channels are conduits through which fluids, sediment (suspended and bed-load) and dissolved loads are transported across the Earth surface. Their general geomorphologic expression is comparable similar in terrestrial, submarine and extraterrestrial environments; however, formative sedimentary processes can be fundamentally different. For example, sinuosity and aspect ratio tend to be similar; however, submarine channels tend to be larger than fluvial channels and the stratigraphic records of fluvial and submarine channel deposits can be different. A key research challenge is the link between the geomorphic expression and stratigraphic record of channels. Rivers are more accessible to direct monitoring compared to submarine channels and the link between fluvial geomorphology and stratigraphy is better understood. In the case of submarine channels, we commonly rely on the stratigraphic record to inform insights about formative processes and evolution.

Channels are conduits through which fluids, sediment (suspended and bed-load) and dissolved loads are transported across the Earth surface. Their general geomorphologic expression is comparable similar in terrestrial, submarine and extraterrestrial environments; however, formative sedimentary processes can be fundamentally different. For example, sinuosity and aspect ratio tend to be similar; however, submarine channels tend to be larger than fluvial channels and the stratigraphic records of fluvial and submarine channel deposits can be different. A key research challenge is the link between the geomorphic expression and stratigraphic record of channels. Rivers are more accessible to direct monitoring compared to submarine channels and the link between fluvial geomorphology and stratigraphy is better understood. In the case of submarine channels, we commonly rely on the stratigraphic record to inform insights about formative processes and evolution.

Panel_14421 Panel_14421 1:15 PM 5:05 PM
1:15 p.m.
Introductory Remarks
Four Seasons Ballroom 4
Panel_15817 Panel_15817 1:15 PM 12:00 AM
1:20 p.m.
Turbidity Currents That Co-Evolve With Channels Over Lengths as Much as 1000 km: How Can They Do it?
Four Seasons Ballroom 4
Here we consider the puzzle of long-runout turbidity currents and the channels they create. It is well known, through direct evidence of the flows or from the morphology that they create, that turbidity currents can run out over 1000 km in the ocean. The currents do so without dissipating themselves via the excess entrainment of ambient water. Existing layer-averaged formulations are, however, unable to capture this behavior. Here we use the formalism of a “Turbidity Current with a Roof” to show that the turbidity current partitions itself into two layers. The lower “driving layer” approaches an asymptotic behavior with invariant flow thickness, velocity profile and suspended sediment concentration profile. The upper “rarified layer” continues to entrain ambient water indefinitely, but the concentration in that layer becomes ever more dilute, and the layer ultimately has little interaction with bed morphology. This partition likely allows the driving layer to run out long distances while maintaining coherence, and to follow morphology of its own creation such as leveed subaqueous channels. Here we consider the puzzle of long-runout turbidity currents and the channels they create. It is well known, through direct evidence of the flows or from the morphology that they create, that turbidity currents can run out over 1000 km in the ocean. The currents do so without dissipating themselves via the excess entrainment of ambient water. Existing layer-averaged formulations are, however, unable to capture this behavior. Here we use the formalism of a “Turbidity Current with a Roof” to show that the turbidity current partitions itself into two layers. The lower “driving layer” approaches an asymptotic behavior with invariant flow thickness, velocity profile and suspended sediment concentration profile. The upper “rarified layer” continues to entrain ambient water indefinitely, but the concentration in that layer becomes ever more dilute, and the layer ultimately has little interaction with bed morphology. This partition likely allows the driving layer to run out long distances while maintaining coherence, and to follow morphology of its own creation such as leveed subaqueous channels. Panel_14857 Panel_14857 1:20 PM 1:40 PM
1:40 p.m.
Monitoring the Evolution of Submarine Channels on Fjord Prodeltas and Associated Depositional Basins
Four Seasons Ballroom 4
Submarine channel systems are typically described by their current surface morphology and potentially the buried seismic stratigraphy. The stratigraphy presents the net result of accumulation but does not necessary show the evolution of the surface morphology. Active fjord delta channels change fast enough that repetitive surveying can monitor the evolution of the active geomorphic surface including both accretion and erosional events. Mapping of submarine prodeltas and distal channels in fjords in British Columbia over a decade has revealed their evolution over timescales ranging from years to days and as short as a few minutes. Over the shorter time scales, characteristics of the flow within the proximal channels have been directly monitored in a number of ways. Velocity and suspended sediment profiles and vertical and plan view imaging of surge-type turbidity currents have been obtained. Furthermore, the modification of underlying bedforms on the channel floors has been observed directly associated with those flows. The cumulative impact of episodic upslope migration of bedforms has been seen to be one of the major mechanisms by which the channels evolve over time. At the more distal locations, the dominant channel floor morphology appears to be characterized by knickpoints which, although a much longer length scale than the proximal bedforms, also migrate upslope over time. Over a time scale of years, the knickpoint migration appears to be the single largest influence on the temporal evolution of those channels . At the distal termination of the fjord floor channels, depositional lobes have previously been described by others. Using repetitive surveys over timescales of a few years, the cumulative growth of these lobes has now been monitored. This provides the 3D geometry of the intervening lens. Both the underlying surface and the modern surface can be delineated revealing the spatial variation of the thickness of the accumulation. Again, periodic downstream undulations in the thickness of the lens appear to indicate upcurrent migration of this very long wavelength relief. Taken together, the temporal evolution of channels from the proximal delta front to the distal depositional lobes provides a potential analog for the much slower evolution of deep-sea channel systems. Submarine channel systems are typically described by their current surface morphology and potentially the buried seismic stratigraphy. The stratigraphy presents the net result of accumulation but does not necessary show the evolution of the surface morphology. Active fjord delta channels change fast enough that repetitive surveying can monitor the evolution of the active geomorphic surface including both accretion and erosional events. Mapping of submarine prodeltas and distal channels in fjords in British Columbia over a decade has revealed their evolution over timescales ranging from years to days and as short as a few minutes. Over the shorter time scales, characteristics of the flow within the proximal channels have been directly monitored in a number of ways. Velocity and suspended sediment profiles and vertical and plan view imaging of surge-type turbidity currents have been obtained. Furthermore, the modification of underlying bedforms on the channel floors has been observed directly associated with those flows. The cumulative impact of episodic upslope migration of bedforms has been seen to be one of the major mechanisms by which the channels evolve over time. At the more distal locations, the dominant channel floor morphology appears to be characterized by knickpoints which, although a much longer length scale than the proximal bedforms, also migrate upslope over time. Over a time scale of years, the knickpoint migration appears to be the single largest influence on the temporal evolution of those channels . At the distal termination of the fjord floor channels, depositional lobes have previously been described by others. Using repetitive surveys over timescales of a few years, the cumulative growth of these lobes has now been monitored. This provides the 3D geometry of the intervening lens. Both the underlying surface and the modern surface can be delineated revealing the spatial variation of the thickness of the accumulation. Again, periodic downstream undulations in the thickness of the lens appear to indicate upcurrent migration of this very long wavelength relief. Taken together, the temporal evolution of channels from the proximal delta front to the distal depositional lobes provides a potential analog for the much slower evolution of deep-sea channel systems. Panel_14858 Panel_14858 1:40 PM 2:00 PM
2:00 p.m.
The Size, Velocity, and Suspended Sediment Distribution of Turbidity Currents Traveling Through Channels, and Their Relation with Morphological Evolution and Channel-Related Deposits
Four Seasons Ballroom 4
Many decades of studies of deposits and seascapes formed by turbidity currents have established that patterns are repeated through time and space, a prominent example being the tendency to form and fill channel conduits. Much more recently, the process-modeling community has made progress in the understanding of the distribution of suspended sediment, velocity, and turbulence in turbidity currents, together shaping the “flow structure”. Thus, now is the time to integrate, and investigate in more detail how the process of sediment erosion, transport, and deposition by turbidity currents is related to observed systematics in the physical products preserved in the geological record. Here, we use results from experimental sandy turbidity current studies and insights from published literature to investigate: (1) The morphodynamic co-evolution of the flow structure and the channel morphology during an elementary cycle. This elementary cycle constitutes three phases: channel establishment, channel maintenance, and channel fill. Understanding of the elementary cycle of channelization can help to establish the organization of fundamental building blocks of stratigraphy, and can be applied in modelling of subsurface occurrences of channel deposits. (2) Determinations of the sediment budget of channels from their morphology, which can be applied to make predictions of sediment volumes stored in correlated bodies down-dip. (3) A comparison between experimental channel shapes and channel-fill deposit metrics obtained from literature, which raises a number of important questions; about the relation between morphological conduits and fill-deposit shape; about the controls on transition from channel formation to channel filling; and about the usefulness of choosing system analogues based on simple channel-fill metric concurrence. Some of these questions need to be addressed before truly predictive application claimed under (1) & (2) is feasible. Many decades of studies of deposits and seascapes formed by turbidity currents have established that patterns are repeated through time and space, a prominent example being the tendency to form and fill channel conduits. Much more recently, the process-modeling community has made progress in the understanding of the distribution of suspended sediment, velocity, and turbulence in turbidity currents, together shaping the “flow structure”. Thus, now is the time to integrate, and investigate in more detail how the process of sediment erosion, transport, and deposition by turbidity currents is related to observed systematics in the physical products preserved in the geological record. Here, we use results from experimental sandy turbidity current studies and insights from published literature to investigate: (1) The morphodynamic co-evolution of the flow structure and the channel morphology during an elementary cycle. This elementary cycle constitutes three phases: channel establishment, channel maintenance, and channel fill. Understanding of the elementary cycle of channelization can help to establish the organization of fundamental building blocks of stratigraphy, and can be applied in modelling of subsurface occurrences of channel deposits. (2) Determinations of the sediment budget of channels from their morphology, which can be applied to make predictions of sediment volumes stored in correlated bodies down-dip. (3) A comparison between experimental channel shapes and channel-fill deposit metrics obtained from literature, which raises a number of important questions; about the relation between morphological conduits and fill-deposit shape; about the controls on transition from channel formation to channel filling; and about the usefulness of choosing system analogues based on simple channel-fill metric concurrence. Some of these questions need to be addressed before truly predictive application claimed under (1) & (2) is feasible. Panel_14860 Panel_14860 2:00 PM 2:20 PM
2:20 p.m.
Geomorphic and Stratigraphic Records of the Composite Evolution of Submarine Channels
Four Seasons Ballroom 4
To gain a better understanding of fundamental submarine channel processes and products, we explore geomorphic and stratigraphic records of deep-sea channelized systems through the lenses of modern Earth surface and latest Quaternary continental margins of the west coast of North America, and outcrops of the Cretaceous Magallanes Basin, Chile. Channelized sedimentary systems offshore of the west coast of North America show a breadth of geomorphology and stratigraphic architecture, including channel reaches of varying sinuosity, levees, terraces within channels, and sediment waves in incipient channels and along thalwegs of well-developed channels. Repeat bathymetric surveys of submarine channels in fjords of British Columbia and the Monterey Canyon underscore the transience of fine-scale detail in channelized geomorphology, and sedimentary processes likely active during channel evolution, such as the frequent, multi-phase bed reworking, local deposition, and bypass of turbidity currents. Submarine channel deposits of the Tres Pasos Formation, Chile, include uniquely preserved thin-bedded and fine-grained channel margin units, the deposits of which drape or lap onto the composite edge of the channelform, as well as scours of diverse scales. These characteristics reveal a complex, multi-phase and multi-scale history of incision and bypass of turbidity currents. The stratigraphic evidence for dynamic sedimentary processes of channel evolution in this system is consistent with observations of submarine channels offshore of the west coast of North America. These geomorphic and stratigraphic records provide evidence of the full channel evolutionary cycle, from inception through protracted maintenance by predominantly bypassing sediment gravity flows, to terminal infill with sediment. The primary function of submarine channels is sediment transfer; the stratigraphic record is biased by the sand-rich products of shorter-lived channel filling and abandonment. Our integrated approach of deciphering channelized sedimentary processes, based on modern and ancient analogs, provides a more complete understanding of fundamental submarine sediment-routing processes, as well as insights into channel connectivity and facies heterogeneity. To gain a better understanding of fundamental submarine channel processes and products, we explore geomorphic and stratigraphic records of deep-sea channelized systems through the lenses of modern Earth surface and latest Quaternary continental margins of the west coast of North America, and outcrops of the Cretaceous Magallanes Basin, Chile. Channelized sedimentary systems offshore of the west coast of North America show a breadth of geomorphology and stratigraphic architecture, including channel reaches of varying sinuosity, levees, terraces within channels, and sediment waves in incipient channels and along thalwegs of well-developed channels. Repeat bathymetric surveys of submarine channels in fjords of British Columbia and the Monterey Canyon underscore the transience of fine-scale detail in channelized geomorphology, and sedimentary processes likely active during channel evolution, such as the frequent, multi-phase bed reworking, local deposition, and bypass of turbidity currents. Submarine channel deposits of the Tres Pasos Formation, Chile, include uniquely preserved thin-bedded and fine-grained channel margin units, the deposits of which drape or lap onto the composite edge of the channelform, as well as scours of diverse scales. These characteristics reveal a complex, multi-phase and multi-scale history of incision and bypass of turbidity currents. The stratigraphic evidence for dynamic sedimentary processes of channel evolution in this system is consistent with observations of submarine channels offshore of the west coast of North America. These geomorphic and stratigraphic records provide evidence of the full channel evolutionary cycle, from inception through protracted maintenance by predominantly bypassing sediment gravity flows, to terminal infill with sediment. The primary function of submarine channels is sediment transfer; the stratigraphic record is biased by the sand-rich products of shorter-lived channel filling and abandonment. Our integrated approach of deciphering channelized sedimentary processes, based on modern and ancient analogs, provides a more complete understanding of fundamental submarine sediment-routing processes, as well as insights into channel connectivity and facies heterogeneity. Panel_14863 Panel_14863 2:20 PM 2:40 PM
2:40 p.m.
Break
Four Seasons Ballroom 4
Panel_15818 Panel_15818 2:40 PM 12:00 AM
3:25 p.m.
Comparison of Sedimentary Processes in Twenty-Two Modern Submarine Canyons Along the Northern California Margin
Four Seasons Ballroom 4
Sedimentary processes and resultant facies in submarine canyons are poorly understood because canyons are bathymetrically complex and sedimentologically heterogeneous environments. Thus it has proven difficult to study submarine canyons using traditional wire-line coring techniques. This study uses a novel vibracoring system deployed using a remotely operated vehicle that enables precise core location (latitude, longitude and altitude above thalweg) and can capture coarse-grained sediments. Whilst previous studies have focused on individual canyons, this study makes use of 127 cores from 22 canyons along a 600 km stretch of the California margin enabling recognition of different canyon types and identification of the processes that control them. Canyons can be divided into two types: coarse-grained canyons and fine-grained canyons. Coarse-grained canyons have a sharply defined thalweg-channel filled with chaotic sands and gravels, episodic movement of these coarse sediments maintains and probably actively erodes the thalweg-channel; finer grained sands and silts drape the canyon walls. Fine-grained canyons have a poorly defined thalweg-channel and are filled with fine-grained sands and silts that anneal preexisting channel topography and drape the canyon walls. Coarse-grained canyons are formed where the canyon head intersects the local littoral cell, whereas fine-grained canyons have heads on the continental shelf. Facies type, grain size and composition (% sand) are strongly constrained by altitude above the thalweg and much less by distance down canyon. Whereas the grain size of fine-grained facies comprising sands and silts fines slightly down canyon, the sands and gravels in the canyon axis show no such fining. This lack of fining may reflect episodic remobilization of material during numerous sediment transport events. Infilling of canyons by frequent small events and flushing by occasional large events has been inferred for many decades. Two of the canyons studied have areas devoid of canyon fill, where bedrock is exposed. High-resolution bathymetry within one of these canyons reveals that scouring of the previous canyon fill, presumably by exceptionally high-energy flow events, has exposed the bedrock. This study reveals the spectrum of processes operating in modern canyons are controlled by the type and volume of sediment available and whether the canyon can tap these supplies, which is strongly dependent on the position of the canyon head. Sedimentary processes and resultant facies in submarine canyons are poorly understood because canyons are bathymetrically complex and sedimentologically heterogeneous environments. Thus it has proven difficult to study submarine canyons using traditional wire-line coring techniques. This study uses a novel vibracoring system deployed using a remotely operated vehicle that enables precise core location (latitude, longitude and altitude above thalweg) and can capture coarse-grained sediments. Whilst previous studies have focused on individual canyons, this study makes use of 127 cores from 22 canyons along a 600 km stretch of the California margin enabling recognition of different canyon types and identification of the processes that control them. Canyons can be divided into two types: coarse-grained canyons and fine-grained canyons. Coarse-grained canyons have a sharply defined thalweg-channel filled with chaotic sands and gravels, episodic movement of these coarse sediments maintains and probably actively erodes the thalweg-channel; finer grained sands and silts drape the canyon walls. Fine-grained canyons have a poorly defined thalweg-channel and are filled with fine-grained sands and silts that anneal preexisting channel topography and drape the canyon walls. Coarse-grained canyons are formed where the canyon head intersects the local littoral cell, whereas fine-grained canyons have heads on the continental shelf. Facies type, grain size and composition (% sand) are strongly constrained by altitude above the thalweg and much less by distance down canyon. Whereas the grain size of fine-grained facies comprising sands and silts fines slightly down canyon, the sands and gravels in the canyon axis show no such fining. This lack of fining may reflect episodic remobilization of material during numerous sediment transport events. Infilling of canyons by frequent small events and flushing by occasional large events has been inferred for many decades. Two of the canyons studied have areas devoid of canyon fill, where bedrock is exposed. High-resolution bathymetry within one of these canyons reveals that scouring of the previous canyon fill, presumably by exceptionally high-energy flow events, has exposed the bedrock. This study reveals the spectrum of processes operating in modern canyons are controlled by the type and volume of sediment available and whether the canyon can tap these supplies, which is strongly dependent on the position of the canyon head. Panel_14864 Panel_14864 3:25 PM 3:45 PM
3:45 p.m.
Submarine Channel Morphological Scaling Relationships: A Predictor for Architectural Heterogeneity and a Comparison to Subaerial/River Scaling Relationships
Four Seasons Ballroom 4
Submarine channels are common and persistent features in the modern seascape and stratigraphic record, and represent fundamental reservoir architectures in petroleum systems. Utilizing morphological, kinematic, and architectural (stratigraphic) data, this study documents planform and vertical scaling relationships for submarine channels. We also compare these scaling relationships to subaerial channels (i.e., rivers) to illustrate differences and similarities in morphology and architecture. Using modern bathymetric, high-resolution 3D seismic, core/well, and outcrop data, we have developed an extensive database of planform and vertical channel scales and measurement metrics for submarine channels. Multiple scales of channelized features were extracted and analyzed, including: the geomorphic channel form, oxbow-cutoffs, channel trajectory/mobility, and preserved deposit thickness. Geometric statistics resulting from these features were used to derive scaling relationships relevant to reservoir characterization. These scaling relationships are coupled with additional data (e.g., basin type, slope morphology, net-to-gross) to identify and highlight the first order physical controls on channel morphology, kinematics, and resultant architecture. These controls form the basis for a classification of submarine channels that is objective and quantitative. This classification system is process-based and allows for the prediction of scale, architecture, and heterogeneity of submarine channel deposits of all scales. Subaerial and and submarine channels exhibit qualitatively similar morphology, but their stratigraphic record is known to be quite different. Submarine channel scaling relationships use many of the same metrics as those developed for river systems, allowing for the quantification of differences and similarities. These scaling relationships are highly relevant in both exploration and development settings, where they aid in volumetric analysis as well as heterogeneity prediction and reservoir model construction. Submarine channels are common and persistent features in the modern seascape and stratigraphic record, and represent fundamental reservoir architectures in petroleum systems. Utilizing morphological, kinematic, and architectural (stratigraphic) data, this study documents planform and vertical scaling relationships for submarine channels. We also compare these scaling relationships to subaerial channels (i.e., rivers) to illustrate differences and similarities in morphology and architecture. Using modern bathymetric, high-resolution 3D seismic, core/well, and outcrop data, we have developed an extensive database of planform and vertical channel scales and measurement metrics for submarine channels. Multiple scales of channelized features were extracted and analyzed, including: the geomorphic channel form, oxbow-cutoffs, channel trajectory/mobility, and preserved deposit thickness. Geometric statistics resulting from these features were used to derive scaling relationships relevant to reservoir characterization. These scaling relationships are coupled with additional data (e.g., basin type, slope morphology, net-to-gross) to identify and highlight the first order physical controls on channel morphology, kinematics, and resultant architecture. These controls form the basis for a classification of submarine channels that is objective and quantitative. This classification system is process-based and allows for the prediction of scale, architecture, and heterogeneity of submarine channel deposits of all scales. Subaerial and and submarine channels exhibit qualitatively similar morphology, but their stratigraphic record is known to be quite different. Submarine channel scaling relationships use many of the same metrics as those developed for river systems, allowing for the quantification of differences and similarities. These scaling relationships are highly relevant in both exploration and development settings, where they aid in volumetric analysis as well as heterogeneity prediction and reservoir model construction. Panel_14859 Panel_14859 3:45 PM 4:05 PM
4:05 p.m.
The Importance of Grain Size and Grain Size Distribution on Deep-Marine Channel Evolution
Four Seasons Ballroom 4
In the fluvial sedimentary record sinuous channels and their associated fills are typically manifest as laterally-accreting point bar deposits. In the deep-marine, observations in modern systems and high-resolution seismic time slices indicate that channels there too are commonly sinuous. However, much less frequently reported from the modern or ancient sedimentary records are the associated meter- to several meter-scale laterally-spaced features that typify fluvial lateral accretion surfaces. In the Neoproterozoic Windermere Supergroup (WSG) exceptional exposure and vertically-dipping strata allow the easy recognition of surfaces resembling lateral accretion surfaces in a number of channel fills. These deposits tend to form at the top of much larger, aggradationally-filled (sinuous) channels, or as isolated clusters. Channel fills are 10-15 m thick and consist of amalgamated beds of decimeter-thick, very coarse sandstone/granule conglomerate. These strata, then, are overlain abruptly vertically and obliquely-upward by mudstone interbedded with thin-bedded turbidites. These finer, thinner strata are interpreted to be the inner-bend levee deposits onto which the channel-filling, thicker-bedded, coarser grained strata onlap. Moreover, the successive several-meter-scale lateral-offset stacking of these strata is interpreted to be caused by the continuous lateral migration of a single channel. This, then, begs the question as to why this style of channel filling is common here, but uncommon in much of the deep-marine sedimentary record. Laterally-accreting channels in the WSG are typically filled with very coarse sandstone, granule and even rare pebble conglomerate. These strata are notably coarser than those that fill the many other WSG channels that lack lateral accretion. The coarseness, but also the bimodal grain size distribution of the sediment supply, is interpreted to have had two interrelated consequences: channelized flows were highly density stratified, and accordingly most of the flow’s momentum resided in the basalmost part of the flow. This, then, enhanced erosion along the outer bend, which in turn promoted active lateral migration of the channel. The general lack of well-developed lateral accretion in the deep-marine sedimentary record, therefore, may simply be the general lack of a sufficiently coarse and bimodally distributed sediment supply to alter the structure of the channelized flows and encourage lateral channel migration. In the fluvial sedimentary record sinuous channels and their associated fills are typically manifest as laterally-accreting point bar deposits. In the deep-marine, observations in modern systems and high-resolution seismic time slices indicate that channels there too are commonly sinuous. However, much less frequently reported from the modern or ancient sedimentary records are the associated meter- to several meter-scale laterally-spaced features that typify fluvial lateral accretion surfaces. In the Neoproterozoic Windermere Supergroup (WSG) exceptional exposure and vertically-dipping strata allow the easy recognition of surfaces resembling lateral accretion surfaces in a number of channel fills. These deposits tend to form at the top of much larger, aggradationally-filled (sinuous) channels, or as isolated clusters. Channel fills are 10-15 m thick and consist of amalgamated beds of decimeter-thick, very coarse sandstone/granule conglomerate. These strata, then, are overlain abruptly vertically and obliquely-upward by mudstone interbedded with thin-bedded turbidites. These finer, thinner strata are interpreted to be the inner-bend levee deposits onto which the channel-filling, thicker-bedded, coarser grained strata onlap. Moreover, the successive several-meter-scale lateral-offset stacking of these strata is interpreted to be caused by the continuous lateral migration of a single channel. This, then, begs the question as to why this style of channel filling is common here, but uncommon in much of the deep-marine sedimentary record. Laterally-accreting channels in the WSG are typically filled with very coarse sandstone, granule and even rare pebble conglomerate. These strata are notably coarser than those that fill the many other WSG channels that lack lateral accretion. The coarseness, but also the bimodal grain size distribution of the sediment supply, is interpreted to have had two interrelated consequences: channelized flows were highly density stratified, and accordingly most of the flow’s momentum resided in the basalmost part of the flow. This, then, enhanced erosion along the outer bend, which in turn promoted active lateral migration of the channel. The general lack of well-developed lateral accretion in the deep-marine sedimentary record, therefore, may simply be the general lack of a sufficiently coarse and bimodally distributed sediment supply to alter the structure of the channelized flows and encourage lateral channel migration. Panel_14865 Panel_14865 4:05 PM 4:25 PM
4:25 p.m.
Time Transgressive Submarine Slope Confinement, Increased Flow Efficiency and the Growth of Basin-Floor Fans
Four Seasons Ballroom 4
Observations from outcrop, modern and subsurface datasets indicate that key regressive surfaces formed during phases of submarine slope degradation are time transgressive. These include levee deposits overlying lobes, composite erosion surfaces recording multiple phases of cut and fill, and hanging valleys and cut-off sinuous bends. Progressive confinement on the slope results in sequential sediment gravity flows maintaining their downslope energy farther into the basin during the initial period of slope channel system evolution. In this way, frontal lobes are continuously incised and overlain by external levees as the channel system propagates farther into the basin and becomes more confined at a reference point on the slope by a combination of substrate erosion and levee construction. The stratigraphic response of the linked basin floor fan is growth and net progradation until a maximum basinward extent is reached, corresponding to the time of most efficient slope sediment supply, which marks a maximum regressive surface. Conceptually, this process response could be autocyclic, but would be amplified with an allogenically-driven waxing-then-waning sediment supply cycle. The coupled progressive confinement of the slope channel system and basinward growth of submarine fans will result in a strongly diachronous lithological basal surface to the system and the widespread downstream transition from levee deposits to lobe deposits. This challenges the widely applied lowstand model whereby the deep-water sequence boundary is isochronous and passes into a correlative conformity at the base of the basin floor fan. Observations from outcrop, modern and subsurface datasets indicate that key regressive surfaces formed during phases of submarine slope degradation are time transgressive. These include levee deposits overlying lobes, composite erosion surfaces recording multiple phases of cut and fill, and hanging valleys and cut-off sinuous bends. Progressive confinement on the slope results in sequential sediment gravity flows maintaining their downslope energy farther into the basin during the initial period of slope channel system evolution. In this way, frontal lobes are continuously incised and overlain by external levees as the channel system propagates farther into the basin and becomes more confined at a reference point on the slope by a combination of substrate erosion and levee construction. The stratigraphic response of the linked basin floor fan is growth and net progradation until a maximum basinward extent is reached, corresponding to the time of most efficient slope sediment supply, which marks a maximum regressive surface. Conceptually, this process response could be autocyclic, but would be amplified with an allogenically-driven waxing-then-waning sediment supply cycle. The coupled progressive confinement of the slope channel system and basinward growth of submarine fans will result in a strongly diachronous lithological basal surface to the system and the widespread downstream transition from levee deposits to lobe deposits. This challenges the widely applied lowstand model whereby the deep-water sequence boundary is isochronous and passes into a correlative conformity at the base of the basin floor fan. Panel_14861 Panel_14861 4:25 PM 4:45 PM
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