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S. S. Flint - One of the best experts on this subject based on the ideXlab platform.
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stratigraphic hierarchy and three dimensional evolution of an exhumed Submarine Slope channel system
Sedimentology, 2020Co-Authors: D. M. Hodgson, S. S. Flint, Daniel Bell, Anna Ponten, Larissa Hansen, Ian A KaneAbstract:Submarine Slope channel systems have complicated three‐dimensional geometries and facies distributions, which are challenging to resolve using subsurface data. Outcrop analogues can provide sub‐seismic‐scale detail, although most exhumed systems only afford two‐dimensional constraints on the depositional architecture. A rare example of an accessible fine‐grained Slope channel complex set situated in a tectonically quiescent basin that offers seismic‐scale, down‐dip and across‐strike exposures is the Klein Hangklip area, Tanqua‐Karoo Basin, South Africa. This study investigates the three‐dimensional architecture of this channel complex set to characterise the stratigraphic evolution of a Submarine channel‐fill and the implications this has for both sediment transport to the deep‐oceans and reservoir quality distribution. Correlated sedimentary logs and mapping of key surfaces across a 3 km2 area reveal that: (i) the oldest channel elements in channel complexes infill relatively deep channel cuts and have low aspect‐ratios. Later channel elements are bound by comparatively flat erosion surfaces and have high aspect‐ratios; (ii) facies changes across depositional strike are consistent and predictable; conversely, facies change in successive down depositional dip positions indicating longitudinal variability in depositional processes; (iii) stratigraphic architecture is consistent and predictable at seismic‐scale both down‐dip and across‐strike in three‐dimensions; (iv) channel‐base‐deposits exhibit spatial heterogeneity on one to hundreds of metres length‐scales, which can inhibit accurate recognition and interpretations drawn from one‐dimensional or limited two‐dimensional datasets; and (v) channel‐base‐deposit character is linked to sediment bypass magnitude and longevity, which suggests that time‐partitioning is biased towards conduit excavation and maintenance rather than the fill‐phase. The data provide insights into the stratigraphic evolution and architecture of Slope channel‐fills on fine‐grained continental margins and can be utilised to improve predictions derived from lower resolution and one‐dimensional well data.
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time transgressive confinement on the Slope and the progradation of basin floor fans implications for the sequence stratigraphy of deep water deposits
Journal of Sedimentary Research, 2016Co-Authors: D. M. Hodgson, S. S. Flint, Rufus L Brunt, Ian A Kane, Andrea OrtizkarpfAbstract:Abstract Observations from outcrop and subsurface datasets indicate that key stratigraphic surfaces in ancient Submarine Slope successions are diachronous and form during periods of seascape degradation and sediment bypass. Evidence for time transgressive confinement of Submarine channel–levee systems includes composite basal erosion surfaces, cut-off bends and hanging valleys, and external levees overlying lobe deposits. After the onset of a sediment supply cycle, progressive confinement will develop on the Submarine Slope, through a combination of incision and external levee construction, such that successive sediment gravity flows will maintain their downSlope energy farther into the basin. This way, frontal lobe deposits are incised by channel systems and overlain by external levee deposits as the channel–levee system becomes more entrenched and propagates farther into the basin. The stratigraphic response on the related basin floor is fan growth and net progradation until a maximum basinward extent is reached, which corresponds to the time of maximum through-channel sediment transfer (bypass). At this time a maximum regressive surface forms, although in reality this is challenging to identify in the rock record. Conceptually, this basin-floor process response to progressive Slope confinement at a point could be autocyclic, but would be amplified with an allogenically driven waxing-then-waning sediment supply cycle. The coupled progressive confinement of the Submarine channel–levee system and basin-floor fan growth will result in a diachronous lithological basal surface to the system. This challenges the idea of the deep-water sequence boundary being isochronous and passing into a single correlative conformity at the base of the basin floor fan, or that there is temporal distinction between deposition by high- and low-density turbidity currents.
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Submarine Slope degradation and aggradation and the stratigraphic evolution of channel-levee systems
Journal of the Geological Society, 2011Co-Authors: D. M. Hodgson, C. N. Di Celma, Rufus L Brunt, S. S. FlintAbstract:Two seismic-scale Submarine channellevee systems exposed in the Karoo Basin, South Africa provide insights into Slope conduit evolution. Component channel fills in a levee-confined channel system (Unit C) and an entrenched channel system (Unit D) follow common stacking patterns; initial horizontal stacking (lateral migration) is followed by vertical stacking (aggradation). This architecture is a response to an equilibrium profile shift from low accommodation (Slope degradation, composite erosion surface formation, external levee development, sediment bypass) through at-grade conditions (horizontal stacking and widening) to high accommodation (Slope aggradation, vertical stacking, internal levee development). This architecture is likely common to other channellevee systems.Supplementary material: A detailed correlation panel (presented schematically in Figure 2) is available at www.geolsoc.org.uk/SUP18456.
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Depositional Environments and Sequence Stratigraphy of an Exhumed Permian Mudstone-Dominated Submarine Slope Succession, Karoo Basin, South Africa
Journal of Sedimentary Research, 2010Co-Authors: J. Figueiredo, D. M. Hodgson, S. S. Flint, John P. KavanaghAbstract:Abstract The physical stratigraphy of a 470-m-thick, claystone-dominated exhumed middle to upper Submarine Slope succession was constrained within an area of 400 km2 in which five sand-prone units were characterized (Units D/E, E, F, G, and H). Units D/E to Unit F show an overall pattern of thickening upward and basinward stepping. This stacking pattern is reversed from the top of Unit F to the base of Unit H, above which basinward stepping is again observed. Different architectural styles of sand-prone deposits occupy predictable stratigraphic positions within the basinward-stepping section, starting with intraSlope lobes through channel–levee complexes to entrenched Slope valleys. Sandstone percentage is highest in the intraSlope lobes and lowest in the Slope valley fills, reflecting a change from depositional to bypass processes. The landward-stepping stratigraphy is dominated by claystone units with thin distal fringes of distributive deposits. The upper basinward-stepping succession (Unit H) is a distributive system possibly linked to a shelf edge delta. Across-strike complexity in the distribution of sand-prone units was controlled by cross-Slope topography driven by differential compaction processes. Hemipelagic claystones separating the sand-prone units represent shutdown of the sand delivery to the whole Slope and are interpreted as relative sea-level highstand deposits. Eleven depositional sequences are identified, nine of which are arranged into three composite sequences (Units E, F, and G) that together form a composite sequence set. The highly organized physical stratigraphic stacking suggests that glacioeustasy, during the Late Permian icehouse period, was the main driving process for the analyzed succession.
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Submarine Slope Systems
Geological Society London Special Publications, 2005Co-Authors: D. M. Hodgson, S. S. FlintAbstract:Submarine Slopes provide the critical link between shallow-water and deep-water sedimentary environments. They accumulate a sensitive record of sediment supply, accommodation creation/destruction, and tectonic processes during basin filling. There is a complex stratigraphic response to the interplay between parameters that control the evolution of Submarine Slope systems, e.g. Slope gradient, topographic complexity, sediment flux and calibre, base-level change,tectonic setting, and post-depositional sediment remobilization processes. The increased understanding of Submarine Slope system has been driven partly by the discovery of large hydrocarbon fields in morphologically complex Slope settings, such as the Gulf of Mexico and offshore West Africa, and has led to detailed case studies and improved generic models for their evolution. This volume brings together research papers from modern, outcrop and subsurface settings to highlight these recent advances in understanding of the stratigraphic evolution of Submarine Slope systems.
D. M. Hodgson - One of the best experts on this subject based on the ideXlab platform.
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Repeated degradation and progradation of a Submarine Slope over geological timescales
Journal of Sedimentary Research, 2021Co-Authors: Christopher A L Jackson, D. M. Hodgson, Andrew E. Mcandrew, Tom DreyerAbstract:ABSTRACT Submarine Slopes prograde via accretion of sediment to clinoform foresets and degrade in response to channel or canyon incision or to mass-wasting processes. The timescales over which progradation and degradation occur, and the large-scale stratigraphic record of these processes, remain unclear due to poor age constraints in subsurface-based studies and areally limited exposures of exhumed systems. We here integrate 3D seismic reflection and borehole data to study the geometry and origin of ancient Slope canyons developed in late Mesozoic strata of the Måløy Slope, offshore Norway. Slope degradation and canyon incision commenced during the late Kimmeridgian, coincident with the latter stages of rifting. Later periods of canyon formation occurred during the Aptian to Albian and the Albian to Cenomanian, during early post-rift subsidence. The canyons are straight, up to 700 m deep, and 10 km wide on the upper Slope and die out downdip onto the lower Slope. The canyons trend broadly perpendicular to and crosscut most of the rift-related normal faults, although syn-filling fault growth locally helped to preserve thicker canyon-fill successions. The headwalls of the oldest (late Kimmeridgian) canyons are located at a fault-controlled shelf edge, where younger canyons overstep this fault, which was inactive when they formed, extending across the paleo-shelf. DownSlope, Aptian to Albian canyons either erode into the older, late Kimmeridgian to Barremian canyon fills, forming a complicated set of unconformities, or in the case of the Albian to Cenomanian canyons, die out into correlative conformities. Boreholes indicate that the canyon bases are defined by sharp, erosional surfaces, across which we observe an abrupt upward shift from shallow- to deep-marine facies (i.e., late Kimmeridgian canyons), or deep marine to deep marine facies (Aptian to Albian and Albian to Cenomanian canyons). Missing biostratigraphic zones indicate the canyons record relatively protracted periods (c. 2–17 Myr) of structurally enhanced Slope degradation and sediment bypass, separated by > 10 Myr periods of deposition and Slope accretion. The trigger for Slope degradation is unclear, but it likely reflects basinward tilting of this tectonically active margin, enhanced by incision of the Slope by erosive sediment gravity flows. The results of our study have implications for the timescales over which large-scale Slope progradation and degradation may occur on other tectonically active Slopes, and the complex geophysical and geological record of these processes. We also show that canyon formation can cause large volumes of margin-derived sediment to bypass proximal sub-basins within rifted terranes, an important process not currently captured by marine rift-basin tectono-stratigraphic models.
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stratigraphic hierarchy and three dimensional evolution of an exhumed Submarine Slope channel system
Sedimentology, 2020Co-Authors: D. M. Hodgson, S. S. Flint, Daniel Bell, Anna Ponten, Larissa Hansen, Ian A KaneAbstract:Submarine Slope channel systems have complicated three‐dimensional geometries and facies distributions, which are challenging to resolve using subsurface data. Outcrop analogues can provide sub‐seismic‐scale detail, although most exhumed systems only afford two‐dimensional constraints on the depositional architecture. A rare example of an accessible fine‐grained Slope channel complex set situated in a tectonically quiescent basin that offers seismic‐scale, down‐dip and across‐strike exposures is the Klein Hangklip area, Tanqua‐Karoo Basin, South Africa. This study investigates the three‐dimensional architecture of this channel complex set to characterise the stratigraphic evolution of a Submarine channel‐fill and the implications this has for both sediment transport to the deep‐oceans and reservoir quality distribution. Correlated sedimentary logs and mapping of key surfaces across a 3 km2 area reveal that: (i) the oldest channel elements in channel complexes infill relatively deep channel cuts and have low aspect‐ratios. Later channel elements are bound by comparatively flat erosion surfaces and have high aspect‐ratios; (ii) facies changes across depositional strike are consistent and predictable; conversely, facies change in successive down depositional dip positions indicating longitudinal variability in depositional processes; (iii) stratigraphic architecture is consistent and predictable at seismic‐scale both down‐dip and across‐strike in three‐dimensions; (iv) channel‐base‐deposits exhibit spatial heterogeneity on one to hundreds of metres length‐scales, which can inhibit accurate recognition and interpretations drawn from one‐dimensional or limited two‐dimensional datasets; and (v) channel‐base‐deposit character is linked to sediment bypass magnitude and longevity, which suggests that time‐partitioning is biased towards conduit excavation and maintenance rather than the fill‐phase. The data provide insights into the stratigraphic evolution and architecture of Slope channel‐fills on fine‐grained continental margins and can be utilised to improve predictions derived from lower resolution and one‐dimensional well data.
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time transgressive confinement on the Slope and the progradation of basin floor fans implications for the sequence stratigraphy of deep water deposits
Journal of Sedimentary Research, 2016Co-Authors: D. M. Hodgson, S. S. Flint, Rufus L Brunt, Ian A Kane, Andrea OrtizkarpfAbstract:Abstract Observations from outcrop and subsurface datasets indicate that key stratigraphic surfaces in ancient Submarine Slope successions are diachronous and form during periods of seascape degradation and sediment bypass. Evidence for time transgressive confinement of Submarine channel–levee systems includes composite basal erosion surfaces, cut-off bends and hanging valleys, and external levees overlying lobe deposits. After the onset of a sediment supply cycle, progressive confinement will develop on the Submarine Slope, through a combination of incision and external levee construction, such that successive sediment gravity flows will maintain their downSlope energy farther into the basin. This way, frontal lobe deposits are incised by channel systems and overlain by external levee deposits as the channel–levee system becomes more entrenched and propagates farther into the basin. The stratigraphic response on the related basin floor is fan growth and net progradation until a maximum basinward extent is reached, which corresponds to the time of maximum through-channel sediment transfer (bypass). At this time a maximum regressive surface forms, although in reality this is challenging to identify in the rock record. Conceptually, this basin-floor process response to progressive Slope confinement at a point could be autocyclic, but would be amplified with an allogenically driven waxing-then-waning sediment supply cycle. The coupled progressive confinement of the Submarine channel–levee system and basin-floor fan growth will result in a diachronous lithological basal surface to the system. This challenges the idea of the deep-water sequence boundary being isochronous and passing into a single correlative conformity at the base of the basin floor fan, or that there is temporal distinction between deposition by high- and low-density turbidity currents.
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Submarine Slope degradation and aggradation and the stratigraphic evolution of channel-levee systems
Journal of the Geological Society, 2011Co-Authors: D. M. Hodgson, C. N. Di Celma, Rufus L Brunt, S. S. FlintAbstract:Two seismic-scale Submarine channellevee systems exposed in the Karoo Basin, South Africa provide insights into Slope conduit evolution. Component channel fills in a levee-confined channel system (Unit C) and an entrenched channel system (Unit D) follow common stacking patterns; initial horizontal stacking (lateral migration) is followed by vertical stacking (aggradation). This architecture is a response to an equilibrium profile shift from low accommodation (Slope degradation, composite erosion surface formation, external levee development, sediment bypass) through at-grade conditions (horizontal stacking and widening) to high accommodation (Slope aggradation, vertical stacking, internal levee development). This architecture is likely common to other channellevee systems.Supplementary material: A detailed correlation panel (presented schematically in Figure 2) is available at www.geolsoc.org.uk/SUP18456.
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Depositional Environments and Sequence Stratigraphy of an Exhumed Permian Mudstone-Dominated Submarine Slope Succession, Karoo Basin, South Africa
Journal of Sedimentary Research, 2010Co-Authors: J. Figueiredo, D. M. Hodgson, S. S. Flint, John P. KavanaghAbstract:Abstract The physical stratigraphy of a 470-m-thick, claystone-dominated exhumed middle to upper Submarine Slope succession was constrained within an area of 400 km2 in which five sand-prone units were characterized (Units D/E, E, F, G, and H). Units D/E to Unit F show an overall pattern of thickening upward and basinward stepping. This stacking pattern is reversed from the top of Unit F to the base of Unit H, above which basinward stepping is again observed. Different architectural styles of sand-prone deposits occupy predictable stratigraphic positions within the basinward-stepping section, starting with intraSlope lobes through channel–levee complexes to entrenched Slope valleys. Sandstone percentage is highest in the intraSlope lobes and lowest in the Slope valley fills, reflecting a change from depositional to bypass processes. The landward-stepping stratigraphy is dominated by claystone units with thin distal fringes of distributive deposits. The upper basinward-stepping succession (Unit H) is a distributive system possibly linked to a shelf edge delta. Across-strike complexity in the distribution of sand-prone units was controlled by cross-Slope topography driven by differential compaction processes. Hemipelagic claystones separating the sand-prone units represent shutdown of the sand delivery to the whole Slope and are interpreted as relative sea-level highstand deposits. Eleven depositional sequences are identified, nine of which are arranged into three composite sequences (Units E, F, and G) that together form a composite sequence set. The highly organized physical stratigraphic stacking suggests that glacioeustasy, during the Late Permian icehouse period, was the main driving process for the analyzed succession.
Daniel Bell - One of the best experts on this subject based on the ideXlab platform.
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stratigraphic hierarchy and three dimensional evolution of an exhumed Submarine Slope channel system
Sedimentology, 2020Co-Authors: D. M. Hodgson, S. S. Flint, Daniel Bell, Anna Ponten, Larissa Hansen, Ian A KaneAbstract:Submarine Slope channel systems have complicated three‐dimensional geometries and facies distributions, which are challenging to resolve using subsurface data. Outcrop analogues can provide sub‐seismic‐scale detail, although most exhumed systems only afford two‐dimensional constraints on the depositional architecture. A rare example of an accessible fine‐grained Slope channel complex set situated in a tectonically quiescent basin that offers seismic‐scale, down‐dip and across‐strike exposures is the Klein Hangklip area, Tanqua‐Karoo Basin, South Africa. This study investigates the three‐dimensional architecture of this channel complex set to characterise the stratigraphic evolution of a Submarine channel‐fill and the implications this has for both sediment transport to the deep‐oceans and reservoir quality distribution. Correlated sedimentary logs and mapping of key surfaces across a 3 km2 area reveal that: (i) the oldest channel elements in channel complexes infill relatively deep channel cuts and have low aspect‐ratios. Later channel elements are bound by comparatively flat erosion surfaces and have high aspect‐ratios; (ii) facies changes across depositional strike are consistent and predictable; conversely, facies change in successive down depositional dip positions indicating longitudinal variability in depositional processes; (iii) stratigraphic architecture is consistent and predictable at seismic‐scale both down‐dip and across‐strike in three‐dimensions; (iv) channel‐base‐deposits exhibit spatial heterogeneity on one to hundreds of metres length‐scales, which can inhibit accurate recognition and interpretations drawn from one‐dimensional or limited two‐dimensional datasets; and (v) channel‐base‐deposit character is linked to sediment bypass magnitude and longevity, which suggests that time‐partitioning is biased towards conduit excavation and maintenance rather than the fill‐phase. The data provide insights into the stratigraphic evolution and architecture of Slope channel‐fills on fine‐grained continental margins and can be utilised to improve predictions derived from lower resolution and one‐dimensional well data.
Ian A Kane - One of the best experts on this subject based on the ideXlab platform.
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stratigraphic hierarchy and three dimensional evolution of an exhumed Submarine Slope channel system
Sedimentology, 2020Co-Authors: D. M. Hodgson, S. S. Flint, Daniel Bell, Anna Ponten, Larissa Hansen, Ian A KaneAbstract:Submarine Slope channel systems have complicated three‐dimensional geometries and facies distributions, which are challenging to resolve using subsurface data. Outcrop analogues can provide sub‐seismic‐scale detail, although most exhumed systems only afford two‐dimensional constraints on the depositional architecture. A rare example of an accessible fine‐grained Slope channel complex set situated in a tectonically quiescent basin that offers seismic‐scale, down‐dip and across‐strike exposures is the Klein Hangklip area, Tanqua‐Karoo Basin, South Africa. This study investigates the three‐dimensional architecture of this channel complex set to characterise the stratigraphic evolution of a Submarine channel‐fill and the implications this has for both sediment transport to the deep‐oceans and reservoir quality distribution. Correlated sedimentary logs and mapping of key surfaces across a 3 km2 area reveal that: (i) the oldest channel elements in channel complexes infill relatively deep channel cuts and have low aspect‐ratios. Later channel elements are bound by comparatively flat erosion surfaces and have high aspect‐ratios; (ii) facies changes across depositional strike are consistent and predictable; conversely, facies change in successive down depositional dip positions indicating longitudinal variability in depositional processes; (iii) stratigraphic architecture is consistent and predictable at seismic‐scale both down‐dip and across‐strike in three‐dimensions; (iv) channel‐base‐deposits exhibit spatial heterogeneity on one to hundreds of metres length‐scales, which can inhibit accurate recognition and interpretations drawn from one‐dimensional or limited two‐dimensional datasets; and (v) channel‐base‐deposit character is linked to sediment bypass magnitude and longevity, which suggests that time‐partitioning is biased towards conduit excavation and maintenance rather than the fill‐phase. The data provide insights into the stratigraphic evolution and architecture of Slope channel‐fills on fine‐grained continental margins and can be utilised to improve predictions derived from lower resolution and one‐dimensional well data.
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time transgressive confinement on the Slope and the progradation of basin floor fans implications for the sequence stratigraphy of deep water deposits
Journal of Sedimentary Research, 2016Co-Authors: D. M. Hodgson, S. S. Flint, Rufus L Brunt, Ian A Kane, Andrea OrtizkarpfAbstract:Abstract Observations from outcrop and subsurface datasets indicate that key stratigraphic surfaces in ancient Submarine Slope successions are diachronous and form during periods of seascape degradation and sediment bypass. Evidence for time transgressive confinement of Submarine channel–levee systems includes composite basal erosion surfaces, cut-off bends and hanging valleys, and external levees overlying lobe deposits. After the onset of a sediment supply cycle, progressive confinement will develop on the Submarine Slope, through a combination of incision and external levee construction, such that successive sediment gravity flows will maintain their downSlope energy farther into the basin. This way, frontal lobe deposits are incised by channel systems and overlain by external levee deposits as the channel–levee system becomes more entrenched and propagates farther into the basin. The stratigraphic response on the related basin floor is fan growth and net progradation until a maximum basinward extent is reached, which corresponds to the time of maximum through-channel sediment transfer (bypass). At this time a maximum regressive surface forms, although in reality this is challenging to identify in the rock record. Conceptually, this basin-floor process response to progressive Slope confinement at a point could be autocyclic, but would be amplified with an allogenically driven waxing-then-waning sediment supply cycle. The coupled progressive confinement of the Submarine channel–levee system and basin-floor fan growth will result in a diachronous lithological basal surface to the system. This challenges the idea of the deep-water sequence boundary being isochronous and passing into a single correlative conformity at the base of the basin floor fan, or that there is temporal distinction between deposition by high- and low-density turbidity currents.
Wolfram Geissler - One of the best experts on this subject based on the ideXlab platform.
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Submarine Slope failures due to pipe structure formation.
Nature communications, 2018Co-Authors: Judith Elger, Christian Berndt, Lars Rüpke, Sebastian Krastel, Felix Gross, Wolfram GeisslerAbstract:There is a strong spatial correlation between Submarine Slope failures and the occurrence of gas hydrates. This has been attributed to the dynamic nature of gas hydrate systems and the potential reduction of Slope stability due to bottom water warming or sea level drop. However, 30 years of research into this process found no solid supporting evidence. Here we present new reflection seismic data from the Arctic Ocean and numerical modelling results supporting a different link between hydrates and Slope stability. Hydrates reduce sediment permeability and cause build-up of overpressure at the base of the gas hydrate stability zone. Resulting hydro-fracturing forms pipe structures as pathways for overpressured fluids to migrate upward. Where these pipe structures reach shallow permeable beds, this overpressure transfers laterally and destabilises the Slope. This process reconciles the spatial correlation of Submarine landslides and gas hydrate, and it is independent of environmental change and water depth.
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Pipe structure formation as a trigger for Submarine Slope failures
The EGU General Assembly, 2017Co-Authors: Judith Elger, Christian Berndt, Lars Rüpke, Sebastian Krastel, Felix Gross, Wolfram GeisslerAbstract:Submarine Slope failures are a hazard to coastal and seafloor environment. Many slides overlap spatially with the occurrence of gas hydrates. Previous studies concentrated on the impact of gas hydrate dissociation on Slope stability without finding conclusive proof for an interrelation. Here, we argue that overpressure below the gas hydrate stability zone may initiate retrogressive Submarine Slope failure by creating hydrofractures that transfer overpressure to weak layers in the shallow subsurface. This process is a more likely trigger for Slope failures in gas hydrate provinces than gas hydrate dissociation as it does not require any changes in the gas hydrate stability conditions. It is able to explain hydrate-related Slope failure initiation at all water depths where hydrates sufficiently reduce the sediment permeability for free gas to accumulate below.
