凝缩段特征及其与烃源岩的关系——以中国南方海相震旦系—中三叠统为例

在层序地层学研究中,可用于确定层序的界面有层序的底界面、初始海泛面和最大海泛面,其中最大海泛面所对应的产物为凝缩段。对凝缩段的识别不仅是认识层序结构的关键,而且对分析地质历史时期全球相对海平面变化至关重要。以中国南方海相震旦系—中三叠统为例,在大量野外剖面详细观测的基础上,识别出凝缩段的物质表现形式有6种类型,分别是硅质岩、黑色页岩、泥质岩、生物化石层、泥晶灰岩和瘤状灰岩。不同类型的凝缩段虽然为不同沉积环境的产物,但均代表了全球性对海平面达到最高位置的产物,其形成时期对应于中国南方烃源岩最佳发育时期。

Features of condensed section and its relationship with source rocks:taking marine Sinian-Middle Triassic in southern China as examples

In sequence stratigraphy, boundaries that can be used to define sequences include bottom boundaries, initial marine flooding surface and maximum flooding surface, of which the sediments corresponding to the maximum flooding surface constitute the condensed section. Identification of condensed section is not only the key to understanding of sequence structure, but also critical to analysis of global relative sea level changes during geologic history. Taking the marine Sinian-Middle Triassic in southern China as examples, 6 rock formations are recognized in condensed section, including silicalite, black shale, argillaceous rock, biogenic fossil bed, micrite and nodular limestone. Although different types of condensed sections have been deposited in different sedimentary environments, they all have been deposited when the global relative sea level reached the highest position. Their formation time, therefore, corresponds to the optimum development stage of source rocks in southern China.