A novel approach for prediction of lithological heterogeneity in fluvial point‐bar deposits from analysis of meander morphology and scroll‐bar pattern

Russell, Catherine; Mountney, Nigel P.; Hodgson, David M.; Colombera, Luca

doi:10.1002/9781119424437.ch15

Cited by 21 publications

(29 citation statements)

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“…Eastings ( diagram with different colours in Figure 8b. The accumulated fluvial point-bar elements that comprise the deposits of the channel belts have been modelled as having simple forms developed through expansional and rotational meander transformations (Fustic et al, 2012;Ghinassi & Ielpi, 2015;Ielpi & Ghinassi, 2014;Russell, Mountney, Hodgson, & Colombera, 2019). The model, however, is capable of modelling point-bar elements developed through more complicated meander-bend transformation behaviour (Figure 4).…”

Section: Modelling Resultsmentioning

confidence: 99%

“…The accumulated fluvial point-bar elements that comprise the deposits of the channel belts have been modelled as having simple forms developed through expansional and rotational meander transformations(Fustic et al, 2012;Ghinassi & Ielpi, 2015;Ielpi & Ghinassi, 2014;Russell, Mountney, Hodgson, & Colombera, 2019). The two cross sections A-A′ and B-B′ show linear aggradation, i.e., a constant relationship between basin aggradation rate and river migration rate, but temporal variations in aggradation rate can also be modelled by PB-SAND different colours inFigure 8b.…”

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confidence: 99%

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Three‐dimensional forward stratigraphic modelling of the sedimentary architecture of meandering‐river successions in evolving half‐graben rift basins

2019

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The spatial organisation of meandering-river deposits varies greatly within the sedimentary fills of rift basins, depending on how differential rates of fault propagation and subsidence interplay with autogenic processes to drive changes in fluvial channel-belt position and rate of migration, avulsion frequency and mechanisms of meander-bend cut off. This set of processes fundamentally influences stacking patterns of the accumulated successions. Quantitative predictions of the spatio-temporal evolution and internal architecture of meandering fluvial deposits in such tectonically active settings remain limited. A numerical forward stratigraphic model-the Point-Bar Sedimentary Architecture Numerical Deduction (PB-SAND)-is applied to examine relationships between differential rates of subsidence and resultant fluvial channel-belt migration, reach avulsion and channel-deposit stacking in active, faultbounded half-grabens. The model is used to reconstruct and predict the complex morphodynamics of fluvial meanders, their generated channel belts, and the associated lithofacies distributions that accumulate as heterogeneous fluvial successions in rift settings, constrained by data from seismic images and outcrop successions.The 3D modelling outputs are used to explore sedimentary heterogeneity at various spatio-temporal scales. Results show how the connectivity of sand-prone geobodies can be quantified as a function of subsidence rate, which itself decreases both along and away from the basin-bounding fault. In particular, results highlight the spatial variability in the size and connectedness of sand-prone geobodies that is seen in directions perpendicular and parallel to the basin axis, and that arises as a function of the interaction between spatial and temporal variations in rates of accommodation generation and fault-influenced changes in river morphodynamics. The results have applied significance, for example, to both hydrocarbon exploration and assessment of groundwater aquifers. The expected greatest connectivity of fluvial sandbody in a half-graben is primarily determined by the complex interplay between the frequency and rate of subsidence, the style of basin propagation, the rates of migration of channel belts, the frequency of avulsion and the proportion and spatial distribution of variably sand-prone channel and bar deposits.How to cite this article: Yan N, Colombera L, Mountney NP. Three-dimensional forward stratigraphic modelling of the sedimentary architecture of meandering-river successions in evolving half-graben rift basins. Basin Res.

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Section: Modelling Resultsmentioning

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Three‐dimensional forward stratigraphic modelling of the sedimentary architecture of meandering‐river successions in evolving half‐graben rift basins

2019

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“…formation of point bars on the inner bank of meander bends. As well as the large-scale lithological variations observed in point bar deposits [37], there are smaller-scale variations, whereby mud-prone sediment is interbedded with sand-prone sediment as inclined heterolithic strata [38]. These complex internal heterolithic variations are particularly important when considering circumstances where chute channels may traverse the point bar deposit because the internal architecture of the hyporheic zone could be more complex and its lateral extent altered.…”

Section: Hydrological Characterisationmentioning

confidence: 99%

“…Flow rates fluctuate around a meander bend, whereby stronger currents are observed at the outer bank and weaker flow is observed on the inner bank [46]. In meandering fluvial systems where alluvium is accreted onto point bar deposits, the finer-grade alluvium is deposited on the inner bank of the downstream limb of the bend, whereas the coarser-grade alluvium is deposited at, and upstream of, the meander apex [37,47].…”

Section: Hydrological Characterisationmentioning

confidence: 99%

The Hyporheic Zone

Banks¹,

Palumbo-Roe²,

Russell³

2019

Hydrology - The Science of Water

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This chapter introduces the key concepts of the hyporheic zone. It considers the research context in terms of the Water Framework Directive and the breadth of literature associated with the hyporheic zone. The interplay between hydrological, chemical and biological processes is explained, and a range of different approaches to field sampling and monitoring are described. A framework for considering the factors contributing to the conceptualisation of the hyporheic zone is presented, with an emphasis on the importance of understanding streambed sediments and their architecture to assess hydraulic functioning and modelling of the hyporheic zone. The hyporheic zone in karst catchments is also given specific consideration.Returning to the theme of linked hydrological, biological and chemical processes, the results of two case studies demonstrate the value of integrating hydrological measurements with geochemistry in order to elucidate hyporheic zone functioning.

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“…However, even though the planform transformations of meander bends (i.e. expansion, rotation, translation and combinations thereof) are well-known (Daniel, 1971;Brice, 1974;Jackson, 1976;Nicoll & Hickin, 2010), the relationships between these transformations and resulting sediment-body architecture remains relatively under-explored (Ghinassi et al, 2014;Durkin et al, 2015;Johnston & Holbrook, 2019;Russell et al, 2019). It follows that only a precise understanding of the interplay between planform transformation, spatio-temporal changes in channel hydraulic geometry and vertical shifts of the channel system can reveal the effective three-dimensional geometry of point-bar bodies.…”

Section: Introductionmentioning

confidence: 99%

An integrated approach to determine three‐dimensional accretion geometries of tidal point bars: Examples from the Venice Lagoon (Italy)

et al. 2020

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Low rates of lateral migration (centimetres to decimetres per year) combined with relatively high rates of vertical accretion (millimetres to centimetres per year) recorded in microtidal channels of the Venice Lagoon (Italy) give rise to point-bar geometries and internal facies arrangements that differ substantially from widely accepted models of point-bar sedimentary architecture. In this study, field data from the Venice Lagoon are combined with a three-dimensional forward stratigraphic model, the 'Point-Bar Sedimentary Architecture Numerical Deduction' (PB-SAND), to predict the stratal geometries of point bars formed in aggradational settings. The PB-SAND uses a combined geometric and stochastic modelling approach that can be constrained by field evidence. The model applied determines the geometry of four point bars generated by 9 to 11 m wide channels cutting through salt marshes. An iterative best-fit modelling approach has been used to obtain multiple simulations for each case study, each of which fits the observations derived from the analysis of time-series historical aerial photographs and 44 sedimentary cores. Results demonstrate how the geometry of the bars is determined by the development of two key stratal surfaces: the point-bar brink and channel-thalweg surfaces. These surfaces are defined by the progressive translation and vertical shift of the point-bar brink (i.e. break of slope between bar top and bar slope) and the channel thalweg (i.e. deepest part of the channel) during bar evolution. The approach is used to: (i) reconstruct three-dimensional point-bar geometries; (ii) propose alternative reconstructions; (iii) provide insight to drive the acquisition of additional data to better constrain the proposed models; and (iv) provide insight into the mechanism of bar growth for slowly migrating channels in settings subject to relatively high rates of aggradation. This study highlights how interaction between styles of planform transformation and latero-vertical shifts of meandering channels can determine the geometry of related sedimentary bodies. Keywords Aggradation, channel-thalweg trajectory, point-bar brink trajectory, tidal meander, Venice Lagoon. negligible with respect to lateral migration processes. Hence, point bars are commonly described as purely laterally accreting bodies

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A novel approach for prediction of lithological heterogeneity in fluvial point‐bar deposits from analysis of meander morphology and scroll‐bar pattern

Cited by 21 publications

References 129 publications

Three‐dimensional forward stratigraphic modelling of the sedimentary architecture of meandering‐river successions in evolving half‐graben rift basins

Three‐dimensional forward stratigraphic modelling of the sedimentary architecture of meandering‐river successions in evolving half‐graben rift basins

The Hyporheic Zone

An integrated approach to determine three‐dimensional accretion geometries of tidal point bars: Examples from the Venice Lagoon (Italy)

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