Imaging the structure and reconstructing the development of a barchan dune using ground-penetrating radar

Abstract

The formation mechanism and development processes of aeolian landforms are significant research topics of aeolian environment. The analysis of the sedimentary structure and stratigraphic sequence of sand dunes is the key content of this study. Ground penetrating radar (GPR) has been widely used in investigations of aeolian landforms to help detect underground sediment structures. Early studies using GPR to investigate dune sands were aimed at studying sedimentary structures and establishing the cause of GPR reflections, but seldom displayed the complete dune structures. In this study, GPR techniques were used to reveal sedimentary structures and reconstruct the development process of a barchan sand dune in the Mu Us Sandy Land from the perspective of three-dimensional space through reasonable arrangement of GPR survey lines in grids. Based on the analysis of 41 GPR profiles, this study identified five major dune radar facies and three radar surfaces. The results showed the following: 1) the dune structures were mainly sets of low- to high-angle crossbedding with and low-angle superposition surfaces, which could be divided into modern and old deposition. 2) The modern deposition was dominated by trough cross-bedding distributed in the centre of the barchan dune, and the old deposition was dominated by tabular cross-bedding and lateral accretion bedding in dune wings. The leeward slope form was a significant factor impacting the formation of the dune structure. 3) The sedimentary structure showed the barchan dune experienced two major episodes. In the early stage, parabolic dunes migrated over fixed sand dunes and were subsequently covered by the upwind barchan dune. Due to the impacts of wind erosion, the oldest age preserved in modern and old deposition can be approximately 1997 and 1970s respectively. The sedimentary structures imaged by GPR can reveal these geomorphologic processes, which can help better understand the formation mechanisms and development processes of sand dunes.