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The geomorphology and evolution of aeolian landforms within a river valley in a semi-humid environment: A case study from Mainling Valley, Qinghai–Tibet Plateau

 

Na Zhou^{a, b}, Chun-Lai Zhang^a , Xiao-Xu Wu^{a, c}, Xun-ming Wang^b, Li-qiang Kang^a

 

a State Key Laboratory of Earth Surface Processes and Resource Ecology, MOE Engineering Research Centre of Desertification and Blown-Sand Control, Beijing Normal University, Beijing 100875, China

b Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China

c College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China

 

ABSTRACT

This paper systematically analyzes a valley's aeolian landforms in a semi-humid region and presents a model of its contemporary evolution. Mainling Valley of the Yarlung Zangbo River on the Qinghai–Tibet Plateau was chosen as the case study for the analysis of morphometric characteristics and the evolution sequence of aeolian landforms via field data and remote sensing images. The aeolian landforms were primarily composed of aeolian sand belts on river terraces and dunes (sheets) on hillside slopes. Three types of aeolian sand belts were identified based on their dune types. In type I belts, an erosive air stream combined with relatively high vegetation cover (10%) produced sparsely distributed parabolic dunes with a high variability of dune heights; in type II belts, the continual reworking by the erosive air stream in combination with low vegetation cover (3%) formed more densely distributed barchans and transitional dunes with a moderate variability of dune heights; and in type III belts, the gradual evolution from an erosive sand-laden air stream to a saturated sand-laden air stream in combination with low vegetation cover (2%) produced the densest crescentic dunefields but with the least variability in dune heights. Dune sizes increase, dune shapes become uniform, and dune distribution becomes close from type I to III belts. Lateral linking and merging of the dunes were also observed within the belts. Together this evidence indicates that an evolution sequence may exist. Aeolian dunefields in the belt appear to evolve from embryonic parabolic dunefields to adolescent barchan dunefields and, subsequently, to mature compound crescentic dunefields. As the aeolian sand belt evolves into the mature stage, sand accumulations at the foot of the mountain valley can be steps for sand accumulation on valley-side slopes.

 

KEYWORDS: Aeolian landform; Mainling Valley; Morphometric characteristics; Evolutionary sequence

 

PUBLISHED BY: GEOMORPHOLOGY, 2014, 224: 27-38

 

SOURCE: http://www.sciencedirect.com/science/article/pii/S0169555X14003687