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Arid Land Geography ›› 2022, Vol. 45 ›› Issue (3): 802-813.doi: 10.12118/j.issn.1000-6060.2021.411

• Earth Surface Process • Previous Articles     Next Articles

Internal sedimentary structure of barchan dune in the southwest of Gurbantunggut Desert

LIU Rui1,2(),LI Zhizhong1,2,3(),JIN Jianhui1,2,3,XIE Xihao1,2,ZOU Xiaojun1,2,MA Yunqiang1,2   

  1. 1. College of Geographical Sciences, Fujian Normal University, Fuzhou 350007, Fujian, China
    2. State Key Laboratory for Subtropical Mountain Ecology of the Ministry of Science and Technology and Fujian Province, Fujian Normal University, Fuzhou 350007, Fujian, China
    3. Institute of Geography, Fujian Normal University, Fuzhou 350007, Fujian, China
  • Received:2021-09-13 Revised:2021-12-07 Online:2022-05-25 Published:2022-05-31
  • Contact: Zhizhong LI E-mail:via0539@outlook.com;lizz@fjnu.edu.cn

Abstract:

The internal sedimentary structure of aeolian dunes preserves important information on the dynamic evolution of dune morphology. In this study, we detected the internal structure of fixed and semi-fixed barchan dunes with various sizes and shapes using ground-penetrating radar in spring and autumn in southwest Gurbantunggut Desert in Xinjiang, China. The depth of the internal structure image information reached 8 m. Through image gain processing, interpretation, and comparative analysis, the following observations are made: (1) This detection revealed five radar facies of the internal structure of dunes: high-angle dipping oblique bedding, wedge cross-bedding, convex cross-bedding, low-angle to sub-horizontal bedding, and massive bedding. The first four bedding types are mainly distributed in shallow layers at 3-5 m, whereas the massive bedding is mainly distributed at depths below 4 m to 5 m. (2) High-angle dipping oblique bedding and wedge cross-bedding are mainly distributed in the upper part of the windward slope and the crest of the high barchan dune (chain). The former is buried in the fore-deposit of the leeward slope, reflecting the frequent sand drift activities on the upper and top of the windward slope of the tall barchan dune, and the buried fore-deposit lamina is exposed because of wind erosion after the dune is “fixed and reduced”. The latter is formed by the filling of wind and sand flow in the windward pit and wind erosion groove of the windward slope or the seasonal variation in the wind direction at the crest. (3) The convex cross-bedding of shrub dunes is widely distributed in the windward slope of barchan dunes, and there are local occurrences in the leeward slope, indicating that the shrub dunes are important in the process of wind and sand on the surface of dunes; the massive stratification may be caused by the disappearance of the original stratification caused by the strong bioturbation of the early aeolian stratification. (4) The sedimentary structural types and combined distribution characteristics reflect the overall stable or declining state of barchan dunes in the study area, which is consistent with the topography characteristics of modern dunes. For example, wind erosion troughs are common in the upper part of the windward slope and the crest, and the development of fore-deposit is slow. Modern sand drift activities are mainly concentrated in the upper part of the sand dune and the crest. Therefore, the internal structural characteristics of barchan dunes differ from mobile barchan dunes and are consistent with the change in the regional physical geography environment of northern Xinjiang characterized by the warming and wetting of the desert climate, the weakening of the average wind speed, and the increase in vegetation coverage.

Key words: ground penetrating radar, Gurbantunggut Desert, fixed and semi-fixed barchan dune, sedimentary structure, environmental significance