Stratigraphic Division and Correlation of the Nihewan Beds by Multivariate Statistical Analysis

Described in this paper is the principle of optimal partitioning method for stratigraphic divisionand correlation. The Nihewan Beds are taken for example to show how to apply this approach instratigraphic division and correlation. The semiquantitative spectral analysis data on aggregate trace elements in 324 samples taken fromthe nine sections in the Nihewan Basin are treated with multivariate statistical method forstratigraphic division and correlation. First, the data from all the sections are respectively calculatedby the optimal partitioning method to establish the stratigraphic boundaries. The opitmal partitioningmethod has proved itself to be applicable to stratigraphic division and correlation. In our practice the Nihewan Beds are divided into five zones （I-V）. Zone I includes subzonesIa and Ib. Zones Ia, Ib, Ⅱ and Ⅲ are considered to be corresponding to the Pliocene （N;） ,the early Early Pleistocene, the late Early Pleistocene, and the Middle Pleistocene, respectively.Zones IV and V are probably Late Pleistocene in age. This indicates that sediments deposited con-temporaneous in the sections of the same basin are similar in geochemical characteristics, although dif-ferent in geographical location. However, the sediments also show some variations, with atransitional relationship from one section to another. For example, in Zone Ⅱ, the sediments of theXiaodukou section show not only the characteristics of the Nangou-Hongya and Hutouliang sections,but also those of the Xiashagou, Shixiaxi, Shixiadong and Wulitai sections . It can be seen from theabove that the zones can be characteristically correlated with one another. In addition the feasibilityof the optimal partitioning method is also described in the present paper.