Abstract:

Ghost dune is a kind of aeolian sand landform which is different from the traditional cumulated dune. It belongs to eroded dune and is a negative landform. This paper takes the fluvial ghost dune in the north of Jiayuguan City in Hexi Corridor as the research object. By comparing satellite images and field sedimentary profile data， this paper verifies and discusses its morphological characteristics， formation model， differences from the lava flow ghost dune and its environmental significance. The results show that： （1） The fluvial ghost dunes are mainly distributed near the mountain pass of the river channel， and most of them present a distribution pattern of approximately parallel arcs arranged at different intervals. The arcs have different lengths， and some of them are buried by the dunes and discontinuous， which is similar to the base of the lee slope of the barchan dune. （2） The fluvial ghost dune sedimentary profile can be divided into three layers： the clay layer composed of silty clay （with mud cracks）， the transition layer dominated by fine sand and extremely fine sand， and the eolian layer dominated by fine sand. The form， sedimentary profile and water accumulation on the leeward slope of the dune in the image all indicate that the fluvial ghost dune is formed by the fluvial water carrying sediment and burying the leeward slope of the dune. （3） The reasonable relationship between topography， dune direction and temporary river direction is the key factor for the formation of fluvial ghost dune， which is easier to form when the lee slope of barchan dune faces the direction of water flow. （4） Compared with lava flow ghost dunes， due to the low density， low viscosity and strong fluidity of the fluvial medium， it usually forms an incomplete ghost dune with a curved shape and is easy to be eroded by wind and vice versa. There are also more water flows than lava flows， which can form multi-stage fluvial ghost dunes.

Key words: fluvial ghost dune, Hexi Corridor, morphological characteristics, formation model