In recent morphodynamic and genetic classifications of dunes, all types of linear dunes are lumped under the heading of longitudinal dunes. This review, however, substantiates three different simple linear dunes : lee dunes, seifs and vegetated
Aeolian features ; Aeolian transport ; Bibliography ; Dune ; Geochronology ; Geomorphogenesis ; Palaeo-environment ; Thermoluminescence ; Wind
Contemporary knowledge on aeolian dune dynamics is reviewed to enable an appraisal of evolutionary mechanisms involved in linear dune stratigraphic sequence development. The degrees of depositional record retention in the dune structures
are evaluated and the corollary applied to methods used in the interpretation of luminescence dating chronologies acquired from such sedimentary accumulations. It is demonstrated that morphogenetic aspects of dune development are an imperative element to invoke
when carrying out palaeoenvironmental reconstruction using luminescence dating ages acquired from linear dune sequences.
Theoretical consideration shows that the steady-state profile of a dune subjected to an unidirectional wind is flat, low and convex with the ratio of dune height to its upwind length = 0,05. Grain size is another factor governing dune profile
. A coarse-grained sand dune has a greater difference in threshold velocity between the crest area and its lower level than a finer-grained sand dune of a similar profile. It will have much longer periods of erosion taking place only at or near the crest
The AA. demonstrate the effect seasonal inter-dune freshwater ponds have on the bleaching of the color of sand dunes by iron reduction in the anaerobic conditions they create. By combining spectral measurements of field samples of dune sand together
with the analysis of satellite images covering 3 dune fields in the NE Brazil, they demonstrate its existence in the field. Interpretations of dunes age based on their color should be handled with care.
The chronology of coastal dune development in the United Kingdom in Dunes of the European Coasts. Geomorphology - Hydrology - Soils.
Datation ; Datation C 14 ; Dune ; Géochronologie ; Géographie de l'Europe ; Géomorphogenèse ; Géomorphologie ; Littoral ; Niveau marin ; Royaume-Uni
Brève présentation des méthodes de datation utilisées pour calculer l'âge des dunes et description du développement des dunes au Royaume-Uni. Comparaison avec les dunes des Pays-Bas. - (CL)
Aquitaine ; Barchan ; C 14 dating ; Classification ; Coastal environment ; Dune ; France ; Geochronology ; Geomorphology ; Holocene ; Palaeosol
The coastal dune field of Aquitaine is one of the most extensive in Europe, which was fixed during the 19th century. This paper proposes a new chronology and a morphological classification for the dune systems found in Médoc.
Results of field work studying the mecanism of movement and advance for longitudinal dunes shows that wind that encounters longitudinal dunes obliquely is deflected on the lee flank and blows along that flank parallel to the crest line.
Monitoring sand dune advance in the Taklimakan Desert
Années 1990 ; Chine ; Domaine aride ; Dune ; Déflation éolienne ; Désert ; Eolien ; Géomorphométrie ; Transport éolien ; Vitesse du vent ; Xinjiang
Aeolian deflation ; Aeolian features ; Aeolian transport ; Arid area ; China ; Desert ; Dune ; Geomorphometry ; Wind speed ; Xinjiang ; Years 1990-99
Sand dune movement was monitored in a sample plot along the desert-crossing highway by means of a topographical survey in late 1991, 1992 and 1993. The results reveal that most of the morphometric parameters of the dunes are not as well correlated
as they are generally supposed to be. The advance rate of the dunes was controlled by the local wind regime and dune morphometry. However, the relationships between advance rate and the morphometric parameters of the dunes are variable for the immature dunes.
Aeolian dune field self-organization - implications for the formation of simple versus complex dune-field patterns
Auto-organisation ; Dune ; Eolien ; Géomorphologie littorale ; Simulation par ordinateur ; Système complexe
Aeolian features ; Coastal geomorphology ; Dune ; Self-organizing behaviour
Les dunes et les champs de dunes comme systèmes complexes. Implications pour les types de champs de dunes simples et complexes. Les variations à l'intérieur de types de dunes simples. Les surfaces géomorphologiques et les archives de roches.
Aeolian features ; Arid area ; Desert ; Dune ; Earth surface processes ; Namibia
Survey data from return visits to a linear dune in the Namib Desert provide information about change in dune form over a decade. The data demonstrate that, although change on these large features is slow, there is none the less considerable movement
over this time-scale. The dunes are therefore confirmed to be currently active and no Pleistocene relics.
Sedimentology and development of parabolic dunes, Grande Prairie dune field, Alberta
Alberta ; Canada ; Dune ; Eolien ; Grande Prairie ; Géographie de l'Amérique ; Structure sédimentaire ; Sédimentologie
Etude des variations de la forme des dunes paraboliques en fonction du régime sédimentaire et des séquences sédimentaires préservées dans les dunes de Grande Prairie, Alberta, Canada.
A recent change in the vegetation cover of linear dunes in the Negev desert forms the basis for the study of the effect of vegetation on linear dune morphology. Destruction of the vegetation brings about abrupt change in the morphology of linear
dunes and turns them into linear braided and seif dunes. This process was analyzed by aerial photography and computer-aided photogrammetric mapping.
A number of examples is given of relationships between the vegetation complex and the morphology of sand dunes, which can be explained on the basis of landscape history and soil processes : foredune complex, parabolisation of former dune ridges
Aeolian features ; Aeolian transport ; Arid area ; Desert ; Dune ; Earth surface processes ; Sand ; Wind
Longitudinal dune fields characteried by nearly uniform interdune spacing are distinguished from longitudinal dune fields characterized by fairly variable interdune spacing and high frequencies of dune coalescence. The empirical and theoretical
evidence indicating that the former may be due to helical air currents aligned with the dunes is reviewed. Hypotheses arguing that the latter may arise indirectly from horizontal pressure gradients or bidirectional wind regimes are dicussed An evolutionary
timescale is estimated for the formation of desert longitudinal dune fields.
Aeolian features ; Dune ; Earth surface processes ; Model ; Simulation ; Wind speed
The AA. analyse Werner's dune-field simulation model for the uni-directional wind regime leading to the evolution of transverse dunes. Following this, they introduce 2 revisions to the Werner model, which lead to dunes that more closely resemble
those in nature. The first revision incorporates wind structure over a dune, and the second considers the wind speedup and the equilibrium dune shape.
Sur la côte baltique de Pologne, les dunes bordières sont bien développées, et, dans les aires de déflation, des dunes paraboliques et des barkhanes actuelles mobiles. Les dunes bordières (Swina, Hal) se sont formées au cours des derniers 5 000 ans
. Pour les dunes mobiles, 4 phases de regain d'activité éolienne ont été reconnues, dans les derniers 4 000 ans, très liés à l'activité humaine. - (CB)
This paper reports a study of surface change on a large, complex linear dune in the Namib Desert. The dune surface responds to a markedly seasonal wind regime. Despite relatively high levels of activity, especially at the dune crest
, there is no evidence of the breakdown of the linear dune form. The conclusion must therefore be that linear dunes can be maintained in bimodal wind regimes and are not necessarily related to unidirectional parallel regimes as others have suggested.
Geological and palynological investigations of two main dune systems west of Nieuwpoort. The Old Dune system is believed to be older than 4300 B.P. The Young Dune area has a complex history: older dunes (2800-900 B.P.) underneath the Young Dune
system: a subphase 11-14 th century A.D.| a subphase starting at the end of the 14th century (large parabolic dunes burying the former landscape).
Biodiversity ; Coastal environment ; Dune ; Ecology ; Georgia (USA) ; Human impact ; Island ; Plant cover ; Taxonomy ; United States of America ; Vegetation
This research investigates how human disturbance has affected foredune vegetation of the Georgia Sea Islands (GSI) in the United States. Both two-factor analysis of variance, ANOVA, and nonmetric multidimensional scaling, NMS, agree that dunes
in human-modified areas have lower dune-grass cover and greater cover of species that are not adapted to building and stabilizing dunes. Therefore, human disturbance may indirectly reduce dune stability by altering the dune vegetation.