Abstract:

Although large-scale ripples (LSRs) are widely distributed in various desert regions of the globe, there are few studies on LSR in China. Through field investigations and observation, remote sensing imagery analysis by Google Earth, and a laser particle size analyzer, spatial distribution patterns and fundamental morphometric and grain size features of both individual and collective forms of LSRs in the Korqin Sandy Land of China are explored. Furthermore, coarse grain sources, differences in granulometric distribution, morphometric features, interior sedimentary structures between LSRs and common ripples, and differences between sands from LSR and common wind ripple are discussed in this study. The results are as follows: (1) LSRs are primarily concentrated on the central and northern parts of Ongniud Bannar, the western extreme of Korqin Sandy Land, and close to or surrounding nearby rocky mountains; they are also primarily distributed in the southern zone of the middle Xilamulun River, on the eastern banks of the Xiangshui River, in the area of the Songshu Mountain, and on the fluvial plain of the lower Chaganmulun River. (2) In line with the dimension, shape, and location of LSRs, plot-, patch-, and stripe-shaped LSR spatial units can be recognized, which are mainly generated on such geomorphic positions as broad interdune, central and upper stoss of a dune, and trough-like lowland, respectively. (3) The average length of LSR is 6.32 m, with an obvious spatial difference; the average strike is NE-SW, significantly perpendicular to the local predominant wind direction and with an insignificant spatial difference; the average spacing is 1.68 m, with a spatial difference; individual LSR has a dissymmetric cross-section. (4) The grains of LSR are comparatively coarser, belonging to the class of middle-coarse sand, which are, however, thinner than those in northwestern China, West Asia, and North Africa; coarse grains are mainly derived from fluvial sediments on ancient river channels, underlying fluvial-lacustrine sediments of late Quaternary, and weathering crusts and alluvial deposits on foothills of nearby denuded mountains. (5) There are considerable differences in appearance, grain composition, geometric morphology, and internal sedimentary structure between LSRs and common sand ripples, which are the small-scale perpendicular bedforms among aeolian depositional landforms and can superimpose on the surfaces of various dunes. The research will, to some extent, advance the principle theories of aeolian geomorphology and effective sand-control practice.

Key words: the Korqin Sandy Land, large-scale ripple (LSR), morphometric features, granulometric characteristics, coarse grain sources