The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Zhibao Dong - One of the best experts on this subject based on the ideXlab platform.
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qaidam basin as an analog for linear dune formation in chasma boreale mars a comparative analysis
Geomorphology, 2018Co-Authors: Chao Li, Junhuai Yang, Guoxiang Chen, Zhibao Dong, Jiyan LiAbstract:Abstract This paper identifies a terrestrial analog for linear dune fields in the Chasma Boreale, located in the north polar region of Mars, and analyzes it to explain linear dune formation. The straight indurated linear Dunes are elongated downwind of dome Dunes and barchans under a unimodal wind regime, providing a novel research opportunity for geomorphologists to investigate the coexistence of transverse and longitudinal Dunes and the effect of sediment induration on dune morphology. The linear Dunes around the Chaerhan salt lake in the Qaidam Basin are good analogs for the Chasma Boreale linear Dunes because of the similarities in dune morphology and evolution process. Further, the effects of the indurating agents (salt and ice) on the formation of the linear Dunes are similar in both locations. In this paper, we have contrasted and analyzed their dune patterns, the influence of cohesive sediment, and wind regimes in the two areas. The formation process and underlying mechanisms that create the linear Dunes are analyzed through geomorphological evidence and dune flow simulation experiments. The results show that there is a remarkable morphological resemblance between the two areas. Cohesive sediments, especially the interbedded frozen laminae on Mars, increase dune stability, and thus allow the formation of linear Dunes under a small divergence-angle in a bidirectional wind regime. The proto-linear dune facilitates the deposition of sediment along the major axis of the dune, and the lateral wind maintains and promotes the development of linear Dunes. We also discuss how cohesive sediment influences dune morphology and leads to a transition from barchans to linear Dunes, and we examine the feedback between dune form and airflow. The different effects of sediment induration on dune morphology make the determination of aeolian patterns less certain, which has implications for the development of climate models of Mars and Titan.
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Geomorphological hierarchies for complex mega-Dunes and their implications for mega-dune evolution in the Badain Jaran Desert
Geomorphology, 2008Co-Authors: Zhibao Dong, Guangqiang Qian, Wanyin Luo, Zhengcai Zhang, Shengchun Xiao, Aiguo ZhaoAbstract:Abstract The evolution of mega-Dunes is sometimes attributed to factors other than the wind but evidence for this is lacking. It is assumed that the dominance of wind in maintaining the evolution of mega-Dunes should be characterized by regular height–spacing relationships that have been found for simple Dunes or wind ripples which are dominantly formed by the wind. In this context, we studied the height–spacing relationship for the complex reversing mega-Dunes in the Badain Jaran Desert, which features the tallest mega-Dunes in the world. The complex mega-Dunes were divided into three hierarchical orders according to the cumulative probability plots of dune height and spacing measurements, and the coefficients of variability of dune heights and spacings were in accordance with values reported for other deserts. The relationship between dune spacing and height for all the three orders of Dunes could be expressed reasonably well by a uniform linear function that was also applied to the height–wavelength relationship for wind ripples in other deserts. This relationship was found to be similar to those for several other deserts and subaqueous bedforms. This implies that there should be few unique factors in maintaining the evolution of complex mega-Dunes in the Badain Jaran Desert compared with the superimposed simple Dunes and Dunes in other deserts, dune fields and subaqueous bedforms, and that the tallest mega-Dunes on the earth can be maintained by the wind.
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pseudo feathery Dunes in the kumtagh desert
Geomorphology, 2008Co-Authors: Zhibao Dong, Xunming Wang, Guangqiang Qian, Wanyin Luo, Zhenhai WeiAbstract:Abstract The Kumtagh Desert is the last explored desert in China. The unique patterns on aerial photographs and satellite images have led previous researchers to the conclusion that the Kumtagh Desert is the only place over the world where typical feathery Dunes are developed, and that some unique wind regimes are at work. Recent field investigation reveals that the feathery patterns in fact reflect the albedo contrasts between the seif Dunes, bright dune-like drifts and the dark inter-dune lag sediments. The wind regime in the area containing the so-called feathery Dunes is typical of the regime that produces seif Dunes that were considered to be shafts of the feathery Dunes, and the vanes of the feathery Dunes are in fact bright dune-like drifts with indistinct height from the surroundings rather than true transverse Dunes. Further analysis indicates that the sediments of seif Dunes, dune-like drifts and dark inter-dune flats differ in grain size distribution, mineralogy, reflectance spectrum and particle micro-morphology. Sediments that constitute seif Dunes and dune-like drifts are finer and poorly rounded, contain relatively more quartz, and hence have higher albedo, while the sediments that constitute the dark inter-dune flats are coarser and better rounded, contain far less quartz but relatively more andesite and dacite, and hence have lower albedo. As a result, what was originally perceived as unique feathery Dunes are in fact only pseudo-feathery Dunes composed primarily of seif Dunes. This discovery also demonstrates that blowing sand drifts can form dune-like patterns that remain visible for long periods of time. It is important to distinguish between the patterns of true Dunes and those of dune-like drifts (pseudo-Dunes) that cause albedo contrasts in interpreting remote sensing images.
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Formation of the complex linear Dunes in the central Taklimakan Sand Sea, China
Earth Surface Processes and Landforms, 2004Co-Authors: Xunming Wang, Jiawu Zhang, Zhibao Dong, Jianjun QuAbstract:The formation of the complex linear Dunes in the central Taklimakan Sand Sea is discussed based on analyses of wind regimes, sand grain size distributions on the topography of the Dunes, and a combination of geomorphic and geophysical investigations into the morphology of the Dunes. Complex linear dune formation is shown to have five stages. Analysis clearly shows that under the control of wind regime, sand supply and other factors, the simple linear Dunes move sideways while they evolve. This is the main cause for the formation of complex linear Dunes in the central Taklimakan Sand Sea. We have not collected enough evidence to show whether the complexity of the complex linear Dunes is left over from previous wind regimes or whether the previous wind regimes had different dominant wind directions compared to those of modern winds. The evolutionary processes of complex linear Dunes in the region partly support the theory of ‘barchan evolution’ but do not support the ‘roll-vortex’ and ‘bimodal wind regime’ hypotheses. After the complex linear Dunes were developed, the local wind regime and the other controls such as sand supply suggest it is possible for them to maintain their linear shape. The evolutionary process discussed is limited to the region indicated in this paper, and may not be applicable to the whole Taklimakan Sand Sea. There are different evolutionary processes in different dunefields because of variations in the factors that control complex linear dune formation. Copyright © 2004 John Wiley & Sons, Ltd.
Nicholas Lancaster - One of the best experts on this subject based on the ideXlab platform.
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Extraterrestrial Dunes: An introduction to the special issue on planetary dune systems
Geomorphology, 2010Co-Authors: Mary Bourke, James R Zimbelman, Eric J R Parteli, Nicholas Lancaster, Lori K. Fenton, Jani RadebaughAbstract:Abstract Aeolian dune fields have been described on Earth, Mars, Venus and Titan. The plethora of data returned from recent planetary missions has enabled a new era in planetary geomorphic studies. Much of our understanding of planetary dune systems comes from the application of Earth analogs, wind tunnel experiments and modeling studies. Despite the range of atmospheric pressures, composition and gravity, many of the dune forms on extraterrestrial surfaces are similar to those on Earth, although some have notable differences in bedform scale and composition. As an introduction to the special issue on planetary dune systems this paper summarizes the current state of knowledge of planetary dune studies and highlights outstanding questions that require further investigation.
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The sedimentary structure of linear sand Dunes
Nature, 2000Co-Authors: Charlie S. Bristow, S.d. Bailey, Nicholas LancasterAbstract:Linear sand Dunes—Dunes that extend parallel to each other rather than in star-like or crescentic forms—are the most abundant type of desert sand dune1. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record2. Models of linear dune development2,3,4,5,6 have not been able to take into account the sub-surface structure of existing Dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear Dunes can migrate laterally2,7,8. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear Dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear Dunes can support superimposed Dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear Dunes should facilitate their recognition in geological records.
Fahu Chen - One of the best experts on this subject based on the ideXlab platform.
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Pseudo-feathery Dunes in the Kumtagh desert reclassified as linear Dunes and zibars
Aeolian Research, 2009Co-Authors: Zhen-ting Wang, Qingfeng Sun, Xiaozong Ren, Tao Wang, Fahu ChenAbstract:Abstract Dunes with apparent feathery patterns are common in the harsh and inaccessible Kumtagh desert in China. A recent paper by Dong et al. [Dong, Z., Qu, J., Wang, X., Qian, G., Luo, W., Wei, Z., 2008. Pseudo-feathery Dunes in the Kumtagh desert. Geomorphology 100, 328–334] argued that the Dunes are pseudo-feathery Dunes with the different forms (linear versus marginal feather vanes) being related to grain composition differences. Field studies in the region and sedimentological analyses revealed that the dune ‘feathers’ are created by Dunes of different heights, rather than by differences in material composition. The Dunes are, in fact, linear Dunes and zibars corresponding with the rachises and vanes, respectively, and appearing as feathery patterns in aerial photographs and satellite images.
Wanyin Luo - One of the best experts on this subject based on the ideXlab platform.
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Geomorphological hierarchies for complex mega-Dunes and their implications for mega-dune evolution in the Badain Jaran Desert
Geomorphology, 2008Co-Authors: Zhibao Dong, Guangqiang Qian, Wanyin Luo, Zhengcai Zhang, Shengchun Xiao, Aiguo ZhaoAbstract:Abstract The evolution of mega-Dunes is sometimes attributed to factors other than the wind but evidence for this is lacking. It is assumed that the dominance of wind in maintaining the evolution of mega-Dunes should be characterized by regular height–spacing relationships that have been found for simple Dunes or wind ripples which are dominantly formed by the wind. In this context, we studied the height–spacing relationship for the complex reversing mega-Dunes in the Badain Jaran Desert, which features the tallest mega-Dunes in the world. The complex mega-Dunes were divided into three hierarchical orders according to the cumulative probability plots of dune height and spacing measurements, and the coefficients of variability of dune heights and spacings were in accordance with values reported for other deserts. The relationship between dune spacing and height for all the three orders of Dunes could be expressed reasonably well by a uniform linear function that was also applied to the height–wavelength relationship for wind ripples in other deserts. This relationship was found to be similar to those for several other deserts and subaqueous bedforms. This implies that there should be few unique factors in maintaining the evolution of complex mega-Dunes in the Badain Jaran Desert compared with the superimposed simple Dunes and Dunes in other deserts, dune fields and subaqueous bedforms, and that the tallest mega-Dunes on the earth can be maintained by the wind.
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pseudo feathery Dunes in the kumtagh desert
Geomorphology, 2008Co-Authors: Zhibao Dong, Xunming Wang, Guangqiang Qian, Wanyin Luo, Zhenhai WeiAbstract:Abstract The Kumtagh Desert is the last explored desert in China. The unique patterns on aerial photographs and satellite images have led previous researchers to the conclusion that the Kumtagh Desert is the only place over the world where typical feathery Dunes are developed, and that some unique wind regimes are at work. Recent field investigation reveals that the feathery patterns in fact reflect the albedo contrasts between the seif Dunes, bright dune-like drifts and the dark inter-dune lag sediments. The wind regime in the area containing the so-called feathery Dunes is typical of the regime that produces seif Dunes that were considered to be shafts of the feathery Dunes, and the vanes of the feathery Dunes are in fact bright dune-like drifts with indistinct height from the surroundings rather than true transverse Dunes. Further analysis indicates that the sediments of seif Dunes, dune-like drifts and dark inter-dune flats differ in grain size distribution, mineralogy, reflectance spectrum and particle micro-morphology. Sediments that constitute seif Dunes and dune-like drifts are finer and poorly rounded, contain relatively more quartz, and hence have higher albedo, while the sediments that constitute the dark inter-dune flats are coarser and better rounded, contain far less quartz but relatively more andesite and dacite, and hence have lower albedo. As a result, what was originally perceived as unique feathery Dunes are in fact only pseudo-feathery Dunes composed primarily of seif Dunes. This discovery also demonstrates that blowing sand drifts can form dune-like patterns that remain visible for long periods of time. It is important to distinguish between the patterns of true Dunes and those of dune-like drifts (pseudo-Dunes) that cause albedo contrasts in interpreting remote sensing images.
Guangqiang Qian - One of the best experts on this subject based on the ideXlab platform.
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Geomorphological hierarchies for complex mega-Dunes and their implications for mega-dune evolution in the Badain Jaran Desert
Geomorphology, 2008Co-Authors: Zhibao Dong, Guangqiang Qian, Wanyin Luo, Zhengcai Zhang, Shengchun Xiao, Aiguo ZhaoAbstract:Abstract The evolution of mega-Dunes is sometimes attributed to factors other than the wind but evidence for this is lacking. It is assumed that the dominance of wind in maintaining the evolution of mega-Dunes should be characterized by regular height–spacing relationships that have been found for simple Dunes or wind ripples which are dominantly formed by the wind. In this context, we studied the height–spacing relationship for the complex reversing mega-Dunes in the Badain Jaran Desert, which features the tallest mega-Dunes in the world. The complex mega-Dunes were divided into three hierarchical orders according to the cumulative probability plots of dune height and spacing measurements, and the coefficients of variability of dune heights and spacings were in accordance with values reported for other deserts. The relationship between dune spacing and height for all the three orders of Dunes could be expressed reasonably well by a uniform linear function that was also applied to the height–wavelength relationship for wind ripples in other deserts. This relationship was found to be similar to those for several other deserts and subaqueous bedforms. This implies that there should be few unique factors in maintaining the evolution of complex mega-Dunes in the Badain Jaran Desert compared with the superimposed simple Dunes and Dunes in other deserts, dune fields and subaqueous bedforms, and that the tallest mega-Dunes on the earth can be maintained by the wind.
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pseudo feathery Dunes in the kumtagh desert
Geomorphology, 2008Co-Authors: Zhibao Dong, Xunming Wang, Guangqiang Qian, Wanyin Luo, Zhenhai WeiAbstract:Abstract The Kumtagh Desert is the last explored desert in China. The unique patterns on aerial photographs and satellite images have led previous researchers to the conclusion that the Kumtagh Desert is the only place over the world where typical feathery Dunes are developed, and that some unique wind regimes are at work. Recent field investigation reveals that the feathery patterns in fact reflect the albedo contrasts between the seif Dunes, bright dune-like drifts and the dark inter-dune lag sediments. The wind regime in the area containing the so-called feathery Dunes is typical of the regime that produces seif Dunes that were considered to be shafts of the feathery Dunes, and the vanes of the feathery Dunes are in fact bright dune-like drifts with indistinct height from the surroundings rather than true transverse Dunes. Further analysis indicates that the sediments of seif Dunes, dune-like drifts and dark inter-dune flats differ in grain size distribution, mineralogy, reflectance spectrum and particle micro-morphology. Sediments that constitute seif Dunes and dune-like drifts are finer and poorly rounded, contain relatively more quartz, and hence have higher albedo, while the sediments that constitute the dark inter-dune flats are coarser and better rounded, contain far less quartz but relatively more andesite and dacite, and hence have lower albedo. As a result, what was originally perceived as unique feathery Dunes are in fact only pseudo-feathery Dunes composed primarily of seif Dunes. This discovery also demonstrates that blowing sand drifts can form dune-like patterns that remain visible for long periods of time. It is important to distinguish between the patterns of true Dunes and those of dune-like drifts (pseudo-Dunes) that cause albedo contrasts in interpreting remote sensing images.
