【摘要】 <正>河北阳原-蔚县盆地的泥河湾层,是我国下更新统的标准地层之一,研究的历史较久,早在1926年巴博尔(Barbour,G.B.,)等人认为泥河湾层(Nihewan Bed)是黄土堆积之前,红土堆积之后的一套河湖相地层,自此之后,驰名中外.到目前为止,有近60篇文章从不同侧面对泥河湾层进行了论述.笔者在1979—1982年期间对泥河湾层进行了调查.本文对泥河湾盆地的大南沟、铺路、红崖南沟、虎头梁、小渡口、下沙沟、石匣西、石匣东、五里台九个地层剖面(图1)采得的324个岩样标本,做了光谱半定量测定,用取得的各元素含量数据,进行了最优分割法(Optimal partitioningmethod)计算,对所计算的结果做了初步的整理分析,进而对泥河湾层的划分与对比进行探讨.更多还原

【Abstract】 The semiquantitative spectrum analysis data of the trace elements taken from 324 samples of 9 sections in the Nihewan Basin are treated with multiva riate statistical method for the stratigraphic division and correlation. At first the data from all sections are respectively calculated by the optimal partitioning method in order to obtain stratigraphic boundaries. Optimal partitioning method applied to dividing strata is efficient. The method is based on the principle that the sum of the diameter of all classes has minimum value, so that the character of samples within a zone have minimum difference and the diffe-rence among various zones is the maximum. In the partitioning process, those, boundaries that appear early and more continuously have more important significance for the stratigraphical division.The results of the analysis indicata that the sediments of the same time in-the sections located in the same basin appear similar geochmical evolutionary characteristics, although their geographical localities are different. However, the sediments also show some variance and the transitional relationship between adjacent sections. For example, in zone II, the sediments in Xiaodukou section show not only characteristics of Hongya and Hu’touliang section, but also similar to those of Xiashagou, Shixiaxi, Shixiadong and Wulitai sections. Based on the facts, the characteristics of zones are reasonably correlated each other. The correlational rationality of the correspondent zones of the sections depend upon the feasibility of division of longitudinal zones, and the result calculated by optimal partitioning method provides the reliable boundaries of the longitudinal zones in sections. At first the average values of each element content in every zone of each section are calculated and aggregate elements which contents have higher average value in a zone than that in a section are selected. Then charac teristic index components are found out by correlating aggregate elements of each zone in the sections, so coresponded correlated zones in different sections can be identified. The principles and methods for the correlation are as follows.1. The principles.1. The approximatly same trend of geochemical evolution occurs in adjacentsections.2. At least one group of characteristic index components should bs presented.3. The reasonable characteristic index components are provided. It means:(a) The characteristic index components within aggregate elements should not be identified at the top and bottom in a section, if it is possible.(b) Judging the correlation-effect, the obtained characteristic index component correlation could not bs altered arbitrarily.II. The methods1. At first, aggregate elements which are obtained by every zone of all sections are ranged based on the order of sections.2. Observing vertically zones, the component nature of characteristic index is traced in each section.3. The correlation should be carried on according to the nature of characteristic index components, in order to obtain the index components zones with correlation characteristis;According to mentioned principles methods, and above, the scheme of the stratigraphical correlation of 9 sections in the basin has been put forward. The Nihewan Formation is subdivided into five geochemical zones from I to V. The zone I includs subzones Ia and Ib. The zones Ia, Ib, II and III are considered to correspond to the Pliocene (N2), the early stage of the Early Pleistocene, the late stage of the Early Pleistocene and the Middle Pleistocene respectively. Zones IV and V probably belong to the Late Pleistocene.更多还原