略论碳酸盐岩岩相古地理研究中的一些问题

碳酸盐岩的岩相古地理研究是碳酸盐岩石学的核心内容,它与石油、天然气以及其它沉积矿产的勘探和开发有极为密切的关系。 把碳酸盐岩的主要沉积环境浅海,划分为两种性质大不相同的陆表海和陆缘海的是伊迪^[1]和肖^[2]。古代碳酸盐岩大都是在陆表海中形成的,而现代我们所看到的浅海却大都是陆缘海,因此,在用现代碳酸盐沉积物的沉积环境去推论古代碳酸盐岩的古沉积环境时,就应格外谨慎。

SOME PROBLEMS CONCERNING LITHOFACIES AND PALEOGEOGRAPHY OF CARBONATES

Study on carbonate lithofacies is rapidly developed during last 20 years and great achievrments have been made.However,the method used for graphic compilation is out-of-date,and does not fit the progress made in studying lithofacies.The author holds that the following problems should be duly considered in work of lithofacies study:1)avoidance of schematic illustrations;2)Strength ening the study on the of rocks,especially of dolomites ;3)correct interpretation of isopach map,for instance.zero isoline might not mean old land;what is more important is the existence of marginal sediments;4)petrofabrie method which is liable to mix up rocks of different origin not suitable for elucidating sedimentary fecies and paleoseomrphology. All these factors and variables,such as structure and texture of rocks,biological assemblages and ecology,etc.which could independently reflect certain aspect of sedimentary environment,should be counted up according to mapping units so as to make regional isogram.Thus,a paleogeographic map in.numericalquantities can be conpiled after overall considering regularities of variation of individual While making the Huabei and Ordos paleogeorraphic maps of Yehli stage (Early Ordovician),the author has used single factors such as thickness,gtsins,colour and penecontemporaneous dolomite,etc,as well as terrigenous detritus,intrabasin detritus,open sea biota,calcareous algae and gypsum,and obtained a good result.