非层状岩的地层分类和研究

Stratigraphic Classification and Intergrated Study of the Non-stratified Rocks

不符合“层序律”的非层状岩多分布在大陆边缘构造带和大陆基底出露区。国际和国家地层规范的实体地层分类 ,都以岩石特征为标准将非层状岩划分为组、群和杂岩等地层单位 ,或与之相当的单位级别系列作为地质填图和描述地方性地层之用。然而 ,非层状岩以地名与习见的岩石名称、加前缀的杂岩或混杂岩构成的名称较为合理和实用 ;单位分级困难 ,不宜强求。作为解释性地层学的分支 ,研究大陆边缘地层通常以构造面分界的岩片、岩块为基本单元 ,推断移置性质和距离 ,恢复不同部位特有地层序列 ,建立构造环境和演变模式 ,因研究对象和范围有别而称为地体地层学、构造地层学、造山带地层学、非史密斯地层学等。实际上 ,这些“学科”的研究对象并不局限于非层状岩 ,研究方法以综合地质构造解释和地层分析为基础 ,其概念系统和研究程序均缺乏稳定的区别 ,无需分别规范化。研究大陆边缘区地层需要引用构造地质学的思路 ,然而提高研究水平所急需的仍是最传统、最基础的东西——提高岩石体的地层控制水平。所以 ,造山带解释性地层研究的灵魂仍是史密斯的基本概念——原始地层有序叠置 ,各地层具有特殊的化石。

A review of classifications of the non stratified rocks shows a general trend to refer them as a special series of lithostratigrapic units, including formation, group and complex. However, the most practical way to field work is using various complex and the lithological name of dominant rock as lithostratigraphic unit, which is not necessary to be further divided. Integrated studies on rocks of continental margins are usually referred to the stratigraphy and reconstructon of tectonic history of terrance and terrance collage. In China, these studies are recently named as tectonostratigraphy, stratigraphy of orogenic belts and “Non Smith stratigraphy”, etc. They are supposed to be differed from conventional stratigraphy by dealing with non stratified rocks. Obviously, they are characterized by their tectonic sittings of working regions, and therefore, are simply a kind of regional stratigraphy, which are not necessarily to be regarded as independent branches of stratigraphy.