基金supported by the State Key Laboratory of Loess and Quaternary Geology(SKLLQG1316)the Scientific Research Plan Projects of Shaanxi Education Department(15JK1796)+1 种基金the Dominant Discipline Construction Projects of Shaanxi(Historical Geography 0602 SZXKY1302)the Specialized Research Fund Project of Xianyang Normal University(12XSYK0310)