The sequence of biocalcarenites occurred on Shidao Island, the highest one among the Xisha Archipelago, is characterized by the alternation of cross-beddings and parallel beddings, which, owing to the misinterpretation of the sedimentary structures, has caused some controversies.Three kinds of boundary surfaces have been found in the sequence: the first-order boundaries marked with the occurrence of paleosols which is nearly horizontal; the second-order boundaries between dune deposits and interdune deposits, formed by the climbing of the dunes and interdunes under the action of NE-trade wind; and the third-order boundaries of cosets inclining exclusively windward. The dune deposits have well-preserved cross-beddings on a large scale, while the interdune deposits show roughly paralled bedding.In conclusion, the coexistence of the three boundary surfaces and the dune and interdune deposits marks the feature of the eolian biocalcarenites. The eolian deposits started from 3200 yr BP when sea level was low The sequence of biocalcarenites occurred on Shidao Island, the highest one among the Xisha Archipelago, is characterized by the alternation of cross-bedding and parallel beddings, which, due to the misinterpretation of the sedimentary structures, has caused some controversies. Thhree kinds of boundary surfaces have been found in the sequence: the first-order boundaries marked with the occurrence of paleosols which is nearly horizontal; the second-order boundaries between dune deposits and interdune deposits, formed by the climbing of the dunes and interdunes under the action of NE The dune deposits have well-preserved cross-beddings on a large scale, while the interdune deposits show roughly paralled bedding. In conclusion, the coexistence of the three boundary surfaces and the dune and interdune deposits marks the feature of the eolian biocalcarenites. The eolian deposits started from 3200 yr BP when sea ​​level was low