Neogene eolian deposits within the West Qinling Mountains: Climatic and tectonic implications

The Qinling Mountains constitute a key climate barrier between southern and northern China. Our recent investigations revealed widely spread eolian deposits of Neogene age mantling the piedmont highlands of the intermountain basins within West Qinling. Micro-mammalian fossils dated a 150.2 m section (NL-VI) near Xihe for the late Miocene to Pliocene (similar to 10-4 Ma). Soil micromorphology, grain-size and geochemical analysis consistently define typical loess-soil alternations for the upper (0-66 m) and lower (98-150.2 m) parts of the section, with the middle section (66-98 m) having been affected by episodic slope erosions. These results add important insights to the earlier studies about the widespread eolian deposition in northern China during the Miocene, prior to 8 Ma. They also suggest that the basic configuration of the ridges and inter-ridge basins of West Qinling has already formed by similar to 10 Ma. The well-preserved eolian deposits are unlikely to support intense substratum deformation and rapid uplift of West Qinling since the late Miocene.