Preservation of meandering river channels in uniformly aggrading channel belts |
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| Authors: | Wietse I van de Lageweg Filip Schuurman Kim M Cohen Wout M van Dijk Yasuyuki Shimizu Maarten G Kleinhans |
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| Affiliation: | 1. Faculty of Geosciences, Universiteit Utrecht, 3508 TC Utrecht, The Netherlands;2. Discipline of Geography and Spatial Sciences, School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia;3. Department of Rivers, Deltas and Coasts, Royal HaskoningDHV, Amersfoort, The Netherlands;4. Department of Applied Geology and Geophysics, Deltares, Utrecht, The Netherlands;5. TNO Geological Survey of the Netherlands, Utrecht, The Netherlands;6. Department of Geography, Durham University, Durham DH1 3LE, UK;7. Division of Environmental and Resource Engineering, University of Hokkaido, Sapporo, Japan |
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| Abstract: | Channel belt deposits from meandering river systems commonly display an internal architecture of stacked depositional features with scoured basal contacts due to channel and bedform migration across a range of scales. Recognition and correct interpretation of these bounding surfaces is essential to reconstruction of palaeochannel dimensions and to flow modelling for hydrocarbon exploration. It is therefore crucial to understand the suite of processes that form and transfer these surfaces into the fluvial sedimentary record. Here, the numerical model ‘NAYS2D’ is used to simulate a highly sinuous meandering river with synthetic stratigraphic architectures that can be compared directly to the sedimentary record. Model results highlight the importance of spatial and temporal variations in channel depth and migration rate to the generation of channel and bar deposits. Addition of net uniform bed aggradation (due to excess sediment input) allows quantification of the preservation of meander morphology for a wide range of depositional conditions. The authors find that the effect of vertical variation in scouring due to channel migration is generally orders of magnitude larger than the effect of bed aggradation, which explains the limited impact bed aggradation has on preservation of meander morphology. Moreover, lateral differences in stratigraphy within the meander belt are much larger than the stratigraphic imprint of bed aggradation. Repeatedly produced alternations of point bar growth followed by cut‐off result in a vertical trend in channel and scour feature stacking. Importantly, this vertical stacking trend differs laterally within the meander belt. In the centre of the meander belt, the high reworking intensity results in many bounding surfaces and disturbed deposits. Closer to the margins, reworking is infrequent and thick deposits with a limited number of bounding surfaces are preserved. These marginal areas therefore have the highest preservation potential for complete channel deposits and are thus best suited for palaeochannel reconstruction. |
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| Keywords: | Aggradation meandering river morphodynamic modelling preservation stratigraphy |
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