The discriminant function with grain size of floodplain and aeolian sediments and its application in the quaternary red clay

In recent years, increasing interest has been focused on the Quaternary Red Clay(QRC) in the middle and lower reaches of the Yangtze River. The QRC profiles generally contain two parts, the Xiashu Loess(XSL) or Homogeneous Red Clay(HRC) on the topside and the Vermicular Red Clay(VRC) below. The provenance of the QRC was discussed furiously.Some scholars believed that Xuancheng, Jiujiang, and Jinhua etc. share the similar characteristics with the XSL, which may originate from aeolian dust deposit. But the others believed that the QRC in Jinhua and Changsha etc. was deposited by flood. Because of these arguments, this paper collected the QRC samples from Jiujiang(JJ), Jiangxi province; Jinhua(TX), Zhejiang province; Changsha(CS), Hunan province; Nanchang(NC), Jiangxi province; Xinyu(XY) Jiangxi province; Nanping(NP), Fujiang province.Discriminant analysis is a usual method in statistical analysis; it can be used to identify the objects in two groups, and have been widely applied. In this paper, the two groups of training samples were floodplain deposits(FPD) from Nantong(NT) and Jinhua(TG), aeolian dust deposits(ADD) of Malan Loess from Luochuan(LC) and Yili(ZS); the testing samples contained the QRC, FPD in Qidong(QD), Xiashu Leoss from Nanjing(XG) and Malan Loess from Zeketai(ZKT).The discriminate results of QRC were complicated. The samples from NP were all identified as ADD; the samples from JJ, NC, TX and CS were identified as both FPD and ADD. On the topside of the QRC profile, the XSL and HRC were always identified as ADD, and the VRC at the bottom of the profile were not only FPD but also ADD.The identification result of QRC suggests that the provenances of QRC from the middle and lower reaches of the Yangtze River are not only floodplains but also aeolian dust deposits.The north plains of Yangtze River are the dominant dust sources for the QRC which are identified as FPD. The QRC which is identified as ADD is deposited by the winter monsoon, and the aeolian characteristics decreased with latitude reduction and terrain fluctuation.