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The Kumtagh Desert, the last desert in China to be explored, contains a distribution of feathery dunes, a type of complex linear dune composited by linear dunes and lingoid zibars. A debate about the existence, underlying relief and formation process of these dunes has been ongoing since 1974. The authors use ground-penetrating radar (GPR) images across dunes and interdune areas to better understand the shallow underlying relief and sedimentary structure of the dunes in the Kumtagh Desert. The results are compared with adjacent outcrops and exposures in an excavated trench. No evidence was found for underlying relief, such as yardangs, consistent with the trend and distribution of linear dune ridges that might have controlled the orientation of the dune. However, outcrop observation and remote sensing investigation indicate little gravel bar topography across or along the dunes. Lingoid zibars are common in interdune corridors. Sedimentary structures imaged by GPR in the zibar dunes indicate low-angle strata dipping towards the SW, indicative of sand accumulation on the leeside of the lingoid zibar with dune migration towards the SW. Strata within the linear dunes are less well-resolved but are interpreted to indicate a bimodal dip that has been recognized in previous studies of linear dunes.