灰岩—泥灰岩韵律层的差异成岩作用  

Differential Diagenesis of Limestone—Marl Alternations

作　　者：刘喜停[1] 颜佳新[1] 薛武强[1] 

机构地区：[1]中国地质大学(武汉)生物地质与环境地质国家重点实验室,武汉430074

出　　处：《地质论评》2012年第4期627-635,共9页Geological Review

基　　金：国家自然科学基金项目(编号41072078)资助的成果

摘　　要：灰岩—泥灰岩韵律层包括结核状灰岩到灰岩和泥灰岩互层,广泛分布在陆棚及深海环境中,出现于各地质时期,是研究高分辨率地层学和环境恢复的理想工具。但是成岩作用在灰岩—泥灰岩韵律层形成过程中的作用一直存在分歧,有的学者认为差异化学压实成岩作用加强了原始沉积的差异,有的学者认为成岩作用不仅能够强烈歪曲原始环境特征,还可以通过自身成岩作用形成与原始沉积特征类似的现象。灰岩—泥灰岩韵律层中的差异成岩作用是指泥灰岩中的不稳定碳酸盐矿物在海底成岩环境中经过溶解、迁移和在灰岩中再沉淀,导致灰岩层没有明显被压实,而泥灰岩层受到明显压实。本文重点评述了差异成岩作用发生的环境和过程,并对与之相关的胶结物来源问题和有机质在早期成岩过程中的作用进行了讨论。并以华南中二叠统栖霞组韵律层为例,探讨了差异成岩作用在其形成过程中的作用,最后对以后的研究方向进行了展望。Limestone--marl alternations, including the entire spectrum from nodular alternations to well- bedded sequences, widely distributed from shallow shelf to pelagic realm, are usually interpreted to reflect palaeoenvironmental signals in a high resolution. Despite the long lasting research history on limestone--marl alternations, it is still controversial if these alternations reflect environmental changes or are produced by pure diagenetie process. Some scholar believe that the diagenetic process only enhances the differences of primary signals, while others propose that pure diagenesis can not only alter the original records but also produce the same phenomenon as primary deposits. Differential diagenesis in limestone--marl alternations includes redistribution of calcium carbonate from marl layers to limestone beds by dissolution, migration of ions, and reprecipitation. Aragonite in marl layers was dissolved to cement limestone, which took place in shallow-burial realm. Thenceforth, mechanical compaction and then pressure dissolution were concentrated in the less cemented strata. The dissolution of aragonite in the shallow marine burial realm is thought to have been initiated by modification of the pore-water chemistry by bacterial oxidation of organic matter. This article reviews the environment and the process of differential diagenesis, discusses the related question, including the source of the cements and the role of organic matter during early diagenesis. At last, the Qixia Formation is selected as an example to explain the origin of those alternations.

关 键 词：灰岩 泥灰岩 差异成岩作用 海水埋藏成岩作用 栖霞组 

分 类 号：P581[天文地球—岩石学]