Valley-marginal sand dunes in the south-west Kalahari: their nature, classification and possible origins

Bullard, Joanna E.; Nash, David J.

doi:10.1006/jare.2000.0646

Cited by 37 publications

(13 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dune lies adjacent to the eastern trough wall and its alignment closely mirrors that of the trough. Planimetrically, it is very similar to valley‐marginal dunes in southern Africa [ Bullard and Nash , 2000] but in the Arnus example, the main body of sediment is contained within the trough rather than on the surrounding surface, as is found in the African examples. The falling dunes described above provide a sediment pathway linking the lateral dune to a sediment source on the Planitia surface to the east.…”

Section: Resultsmentioning

confidence: 93%

Aeolian sediment transport pathways and aerodynamics at troughs on Mars

2004

View full text Add to dashboard Cite

[1] Interaction between wind regimes and topography can give rise to complex suites of aeolian landforms. This paper considers aeolian sediment associated with troughs on Mars and identifies a wider range of deposit types than has previously been documented. These include wind streaks, falling dunes, ''lateral'' dunes, barchan dunes, linear dunes, transverse ridges, sand ramps, climbing dunes, sand streamers, and sand patches. The sediment incorporated into these deposits is supplied by wind streaks and ambient Planitia sources as well as originating within the trough itself, notably from the trough walls and floor. There is also transmission of sediment between dunes. The flow dynamics which account for the distribution of aeolian sediment have been modeled using two-dimensional computational fluid dynamics. The model predicts flow separation on the upwind side of the trough followed by reattachment and acceleration at the downwind margin. The inferred patterns of sediment transport compare well with the distribution of aeolian forms. Model data indicate an increase of wind velocity by $30% at the downwind trough margin. This suggests that the threshold wind speed necessary for sand mobilization on Mars will be more frequently met in these inclined locations.INDEX TERMS: 1815 Hydrology: Erosion and sedimentation; 1824 Hydrology: Geomorphology (1625); KEYWORDS: Trough, aeolian, dune, MOC, MOLA, computational fluid dynamic modeling Citation:

show abstract

Section: Resultsmentioning

confidence: 93%

Aeolian sediment transport pathways and aerodynamics at troughs on Mars

2004

View full text Add to dashboard Cite

show abstract

“…Classification of sand is important as it can be used to categorise the wide variety of desert dune types and provide useful terms of reference for comparing dune forms in different environments and regions (see e.g. [2]). Sand dunes represent an important habitat in Egypt because they cover a considerable area.…”

Section: Introductionmentioning

confidence: 99%

Radioactivity of sand, groundwater and wild plants in northeast Sinai, Egypt

Ramadan

Seddeek

Nijim

et al. 2011

Isotopes in Environmental and Health Studies

View full text Add to dashboard Cite

The radioactivity levels are poorly studied in non-coastal arid regions. For this reason, 38 locations covering an area of about 350 km 2 in northeast Sinai, Egypt, were investigated by γ -ray spectroscopy. Moderately significant correlations among 238 U, 234 Th, and 226 Ra isotopes and low significant correlations between the concentrations of 238 U-series and 232 Th in sand were obtained. No evidence of correlation was found between the concentrations of radioisotopes and pH, grain size, total organic matter content, bicarbonate or calcium carbonate concentrations of the sand samples. The mean values of soil-to-plant transfer factor were 0.15, 0.18, 1.52 and 0.74 for 226 Ra, 232 Th, 40 K, and 137 Cs, respectively. The range of concentrations of 226 Ra, 232 Th, and 40 K in water samples collected from five wells were <0. 4-0.16, <0.4-0.13, and <0.15-1.62 Bq l −1 , respectively. The mean absorbed dose rate in outdoor air at a height of 1 m above the ground surface for the sand samples was 19.4 nGy h −1 . The Ra eq activities of the sands are lower than the recommended maximum value of 370 Bq kg −1 criterion limit for building materials.

show abstract

“…Despite the fact that the migration of the straightened parabolic dune ceased after reaching the wet riverbed, it still received abundant sand supply resulting in a growth in height. The original parabolic dune form metamorphosed into a large [A very similar dune type was described by Bullard and Nash (2000).] Beside the earlier-mentioned prime forms, other members of the parabolic dune type can also be identified in the study area.…”

Section: Study Areamentioning

confidence: 69%

“…(e.g. Lancaster, 1995;Bullard and Nash, 2000). However, the process of classification is mostly descriptive, and distinctive parameters between different desert dune types are rarely determined (Wang et al, 2002;Valle et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Human impact on fixed sand dunes revealed by morphometric analysis

Kiss

Sípos

Kovács

2009

Earth Surf Processes Landf

View full text Add to dashboard Cite

The Nyírség is the second largest alluvial fan in Hungary covered by fixed sand dunes. The primary aim of the paper is to describe the morphology of dunes in the region and classify them based on their morphometric characteristics. The other major aim is to select those dunes which were exposed to significant anthropogenic impact, and to determine the spatial and temporal differences in the intensity of human activity. The following dune types were separated: valley-marginal, transitional valley-marginal, transitional parabolic, filled, partially and unfilled parabolic dunes. After defining different dune types and their parameters, certain dunes were selected based on exposure to significant anthropogenic impact. Definite connection was demonstrated between the intensity of human environmental impact and the rate of erosion on fixed sand dunes. The erosion of sand dunes was most intensive in Medieval times, most likely due to concentration of agricultural land use. Figure 7. Present-day relative height plotted against calculated original height. (1) Dunes far from villages; (2) dunes within 1 km vicinity of villages.

show abstract

Valley-marginal sand dunes in the south-west Kalahari: their nature, classification and possible origins

Cited by 37 publications

References 43 publications

Aeolian sediment transport pathways and aerodynamics at troughs on Mars

Aeolian sediment transport pathways and aerodynamics at troughs on Mars

Radioactivity of sand, groundwater and wild plants in northeast Sinai, Egypt

Human impact on fixed sand dunes revealed by morphometric analysis

Contact Info

Product

Resources

About