灰岩成因-结构分类的进展及其相关问题讨论

由Folk在1959，1962年及Dunham在1962年所提出的灰岩因－结构分类体系，具有划时代的意义，至今还得到极为广泛的应用，Embry和Klovan在1971年关于生物礁灰岩的成因－结构分类，即关于骨架灰岩，障积灰岩，粘结灰岩的成因－结构分类的第一次重要的补充，它解决了与生物作用有关的灰岩不符合Folk和Dunham的结构成熟度概念的矛盾，而对成岩作用及其产物的更深入研究，地质学家们发现了许多布成岩作用形成的泥晶化作用和颗粒化作用，由它们所形成的岩石也不符合Folk和Dunbam的结构成熟度概念，导致了Wright在1992年提出了一个更完整的灰岩成因－结构分类体系，把灰岩分为生物作用类，沉积作用类及成岩作用类三大类，即Folk和Dumban描述的分类均属于沉积作用类。要特别指出的是，在从松散沉积物到已石化的竖硬石头的成岩过程中，不但灰岩的结构会发生变化，而且组分也会发生变化，从而使灰岩的成因－结构分类变得更加复杂，关于这方面还存在许多有待进一步研究的问题。在审视Wright在1992年的分类体系时，有必要在沉积作用类中增加“非正常沉积作用亚类灰岩”，针对许多非礁相地层中发育的由生物礁岩石构成的生物层及生物丘，因而有必要对生物作用灰灰岩进行更进一步的分类。

A REVIEW ON GENETIC-TEXTURAL CLASSIFICATION OF LIMESTONES AND THE DISCUSSION OF RELATIVE PROBLEMS

The main genetic textural classifications of limestones were introduced by Folk (1959,1962) and Dunham (1962) and are still,widly used.In the wake of more and more thorough study on sedimentation and diagenesis,particularly about biosedimentation and diagenesis,the gentic textural classification of limestones has become more consummate.The first important replenishing is about the classification of reef limestones introduced by Embry and Klovan (1971),which contain frametone,bafflestone and boundstone.The reason to replenish the classification of reef limestones is that many of their textural forms do not agree with textural maturity proposed by Folk and Dunham.The appreciation of diagenetic process and their products elables geologists to appreciate grainification and micritisation,the rock resulted from which also do not tally with the textural maturity by Folk and Dunham.So,a revised classification of limestones was introduced by Wright in 1992,which divided limestones into three classes:biological textural groups,depositional textural groups and diagenetic textural groups.In terms of this revised classification of limestones,the classification described by Folk and Dunham should belong to depositional texural groups.In the complex diagenetic process of limestones from loose sediments to lithified hard stones,both the components and the fabrics of limestones could be made to change greatly,leading to the complexity of genetic textural classification of limestones.Hence,a lot of problems remain to be solved with regard to the respect of the subdivision of diagenetic textural group of limestones.On the basis of the revised classification proposed by Wright (1992),it is necessary to add two sub categories into the classification.In depostional textural groups,those produced by abnormal deposition such as storm current,grain flow,turbidity current and seismism are different from normal categories of limestones described by Folk and Dunham.Therefore,the sub categories of limestones belonging to abnormal depositional textural limestones should be added.Being directed against the situation that biostromes and bioherms composed by reef rocks are not developed in reef strata,subdivision of biological textural limestones is also necessary.