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It has been found that there existed quite a large quantity of dune rocks in the red sandstone of the Zhidan Group of Ordos Cretaceous strata. Their sedimentary structure, grain size and micro-shape of sand grains show an obvious aeolian features. Both the temporal and spatial distribution and sedimentary characteristics of these dune rocks suggest that probably a large sand sea once existed in the Ordos region. It belonged to a subtropical inland trade-wind desert with persistent hot climate and was also an important part of the Cretaceous red desert in China.