Eolian origin of the Miocene loess-soil sequence at Qin’an, China: Evidence of quartz morphology and quartz grain-size

Recent study revealed that the so-called Neogene Gansu System in the western Loess Plateau contains loess-soil sequences of Miocene age. A most complete sequence （QA-I） covers a time interval from ～22 to ～.6.2 Ma BP, consisting of more than 230 visually definable paleosols interbedded with loess layers. A loess-soil sequence of late Miocene-Pliocene age, synchronous with the Hipparian Red Clay in the eastern Loess Plateau, was also recognized, and extends the Miocene sequences into the Pliocene, ～3.5 Ma BP. Recently, Miocene eolian deposits were also reported from the high terraces near Xining.