河漫滩相沉积与风成沉积粒度判别函数的建立及在红土中应用

以长江南通段、婺江金华段的河漫滩沉积物和洛川、新疆昭苏的马兰黄土为训练样本,推导出河漫滩相沉积与风成沉积粒度的Fisher判别函数,并用启东河漫滩沉积物、南京下蜀黄土和伊犁马兰黄土对判别函数进行验证。第四纪红土的判别结果显示：新余、南平等地红土具有典型河漫滩沉积特征;长沙、金华、南昌、九江等地红土即具有风成又具有河漫滩沉积的特征,且风成沉积特征随着纬度减小及地形起伏增加而减小。结合现代降尘的粒度组成推测,中亚热带网纹红土的物质来源有近源也有远源。近源组分为来自附近河漫滩泛滥平原沉积物的风力二次搬运,在沉积后依旧保留了河漫滩沉积的大部分粒度特征;远源组分可能与黄土类似,由冬季风从北方物源区搬运而来。

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.