Wind-blown origin of Dongwan late Miocene-Pliocene dust sequence documented by land snail record in western Chinese Loess Plateau

Recently, the first late Miocene-Pliocene eolian deposits from the western Chinese Loess Plateau have been reported. These deposits would complement the eolian record between Quaternary loess-paleosol sequences and Miocene loess sequences, if their wind-blown origin could be documented. However, although several lines of evidence indicate the eolian origin of this sequence, it is still necessary to address this issue through further efforts. Among these, biological approaches are of particular value. Here we analyze the composition and preservation conditions of mollusk assemblages in the Dongwan section. Our results show that all mollusk fossil individuals are preserved in perfect condition without indicating any reworking. All identifiable mollusk species are terrestrial, and are mostly identical to those identified in the Quaternary loess-paleosol sequences of the Chinese Loess Plateau. Generally, the cold-aridiphilous species are dominant in the loess layers, while thermo-humidiphilous species are mostly encountered in the paleosols. The close similarity of the mollusk record in both the Dongwan late Miocene-Pliocene deposits and the Quaternary loess sequence in the Chinese Loess Plateau supports the supposition that the Dongwan section is a typical loess-paleosol sequence, and is, without any doubt, of wind-blown origin.