Elongation and Stability of a Linear Dune

Rozier, Olivier; Narteau, C.; Gadal, Cyril; Claudin, Philippe; Pont, Sylvain Courrech du

doi:10.1029/2019gl085147

Cited by 32 publications

(49 citation statements)

References 38 publications

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“…The linear dunes modelled here are thus more comparable with those that migrate sideways. This model limitation is shared with other CA and LBM simulation studies that exclude secondary‐flow dynamics, where dune flanks are typically at the angle of repose (Rozier et al ., 2019; Gadal et al ., 2020). The internal sedimentary structure of the linear dunes is jointly shaped by bedform interactions and the wind regime.…”

Section: Resultsmentioning

confidence: 99%

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Internal sedimentary structure of linear dunes modelled with a cellular automaton

Liu

Baas

2020

Sedimentology

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Linear dunes are the most common type of dune found on Earth and exist on several extra-terrestrial bodies, but despite this abundance their internal stratigraphy has not been commonly agreed. A cellular automaton is deployed to simulate the development of linear dunes, starting from a flat bed, under bi-modal oblique wind regimes of varying degrees of asymmetry. The internal stratigraphy of the linear dunes is monitored by keeping track of (buried) erosion surfaces, avalanche deposits and vertical accumulation, as well as the age of last subaerial exposure of the sediments. The simulations show the initial pattern-coarsening of a network of small dunes into fewer larger longitudinal ridges via bedform interactions and Y-junction dynamics. Three newly recognized types of bedform interaction are identified that relate to initial Yjunction dynamics: longitudinal crest-splitting, which creates free dune tips that can interact with adjacent dunes, and laterally oscillating interactions that lead to ephemeral Y-junctions (normal or reverse). The results show that these three bedform interactions leave no persistent signatures in the stratigraphic record. However, a further three bedform interactions involving the superposition of one dune onto anothermerging, cannibalizing and repulsion (known from transverse dune field dynamics)do leave specific evidence in the internal stratigraphy of the remaining dune, a buried interaction surface at a specific inclination. The preservation potential of this interaction surface varies between the three types. After the initial pattern-coarsening phase, the linear dunes become larger and more independent and their crest orientation follows the net resultant transport direction. The stratigraphies of mature dunes under wind regimes of differing asymmetry show that under (nearly) symmetrical winds the dune accumulates mainly vertically, with strata dipping parallel to the flanks, while under more asymmetrical wind regimes the internal stratigraphy resembles that of transverse dunes.

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Section: Resultsmentioning

confidence: 99%

“…The morphological development of linear dunes has been simulated with three‐dimensional (3D) numerical computer models since the work of Werner (1995), particularly with reduced‐complexity approaches such as Cellular Automata (CA) and Lattice‐Boltzmann Methods (LBM) (Gao et al ., 2015a,b; Rozier et al ., 2019; Gadal et al ., 2020).…”

Section: Introductionmentioning

confidence: 99%

Internal sedimentary structure of linear dunes modelled with a cellular automaton

Liu

Baas

2020

Sedimentology

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“…The second is proportional to √ QT w , where Q is the characteristic sand flux and T w is the duration of the wind cycle. As shown by Rozier et al (2020), these two length scales control the minimal size and the morphology of isolated elongating dunes. Nevertheless, our numerical simulations suggest that the periodicity in fields of elongating dunes comes from boundary and initial conditions rather than from length scales inherent to the elongation mechanism.…”

Section: Discussionmentioning

confidence: 97%

Periodicity in fields of elongating dunes

Gadal

Narteau

Pont

et al. 2020

Geology

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Dune fields are commonly associated with periodic patterns that are among the most recognizable landscapes on Earth and other planetary bodies. However, in zones of limited sediment supply, where periodic dunes elongate and align in the direction of the resultant sand flux, there has been no attempt to explain the emergence of such a regular pattern. Here, we show, by means of numerical simulations, that the elongation growth mechanism does not produce a pattern with a specific wavelength. Periodic elongating dunes appear to be a juxtaposition of individual structures, the arrangement of which is due to regular landforms at the border of the field acting as boundary conditions. This includes, among others, dune patterns resulting from bed instability, or the crestline reorganization induced by dune migration. The wavelength selection in fields of elongating dunes therefore reflects the interdependence of dune patterns over the course of their evolution.

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“…(2) the orientation of the ripple crests (suggesting migration along the dune); (3) and the fixed sand source of the dunes (Courrech du Pont et al, 2014;Lucas et al, 2015;Reffet et al, 2010;Rozier et al, 2019).…”

Section: Development Of Elongating Linear Dunes At Hellespontus Montesmentioning

confidence: 99%

“…This growth mechanism is supported by recent investigations of the Ténéré desert, Niger, where linear dunes develop on the lee of mesas, in an otherwise sand‐starved region, and migrate by elongation only, with no lateral migration component (Figure 1a; Lucas et al, 2015). Furthermore, numerical simulations suggest that linear dunes elongating from a fixed sediment source take on distinct morphometric characteristics when approaching a steady state, whereby the dunes no longer elongate as the sediment input balances the output (Rozier et al, 2019). Testing these predictions and comparing terrestrial linear dunes to those on other planetary surfaces is critical for understanding dune dynamics, yet there are few studies on planetary linear dunes (other than Titan; e.g., Lucas et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Morphology, Development, and Sediment Dynamics of Elongating Linear Dunes on Mars

Davis

Banham

Grindrod

et al. 2020

Geophysical Research Letters

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Linear dunes occur on planetary surfaces, including Earth, Mars, and Titan, yet their dynamics are poorly understood. Recent studies of terrestrial linear dunes suggest they migrate by elongation only in supply-limited environments. Here, we investigate elongating linear dunes in the Hellespontus Montes region of Mars which are morphologically similar to terrestrial systems. Multitemporal, high-resolution orbital images show these linear dunes migrate by elongation only and that the fixed sediment source of the dunes probably restricts any lateral migration. Some linear dunes maintain their along-length volume and elongate at rates comparable to adjacent barchans, whereas those which decrease in volume show no elongation, suggesting they are near steady state, matching morphometric predictions. Limited sediment supply may restrict Martian linear dunes to several kilometers, significantly shorter than many terrestrial linear dunes. Our results demonstrate the close similarities in dune dynamics across the two planetary surfaces. Plain Language Summary Linear dunes are elongated sand ridges found on Earth, Mars, and Titan and form in areas with at least two wind directions. The way in which linear dunes move is poorly understood, in particular whether they migrate parallel or perpendicular to their ridge crests. Recent investigations have suggested that linear dunes on Earth migrate parallel to their ridge crests in areas with a fixed source of limited sand. The surface of Mars is a natural laboratory for investigating linear dunes. We use time series, high-resolution orbital images to investigate the migration of Martian linear dunes. Like those on Earth, the Martian linear dunes also originate from a fixed sand source and grow parallel to their crests only. Furthermore, we also show that the linear dunes no longer grow as they approach a steady state. Our results demonstrate strong similarities in the behavior of dunes on Mars and Earth.

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Elongation and Stability of a Linear Dune

Cited by 32 publications

References 38 publications

Internal sedimentary structure of linear dunes modelled with a cellular automaton

Internal sedimentary structure of linear dunes modelled with a cellular automaton

Periodicity in fields of elongating dunes

Morphology, Development, and Sediment Dynamics of Elongating Linear Dunes on Mars

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