The recovery of diagenetic environments of limestone in Early Miocene Zhujiang Formation, Pearl River Mouth Basin

Abstract：Based on core description, thin section observation, SEM and cathodoluminescence analysis, combined with regional?geological?setting, the authors tried to recover the diagenetic environments of limestone in Early Miocene Zhujiang Formation of Pearl River Mouth Basin by identifying?the?diagenetic?fabrics and analyzing the diagenetic characteristics. Some conclusions have been reached: 1) No epigenesis is developed in Zhujiang Formation limestone because of the transgressive background and gradual burial history. However, frequent changes in sea level result in the influence of meteoric water on limestone in the high part of the palaeo-geomorphology. The main diagenetic environments developed in Zhujiang Formation limestone include marine phreatic environment, fresh water phreatic environment, fresh water vadose environment and burial diagenetic environment. 2) Marine phreatic environment is the first and foremost environment that the Zhujiang Formation limestone have experienced during the diagenetic process, in which the main diagenesis includes the encrustation of red algae and mutual crusting effect between red algae and other organisms, the development of organism borings, early lithification of micrite and the formation of micrite envelope, glauconite formation, and the cementation of fringing fibrous calcite, bladed spar calcite and syntaxial calcite. Fresh water phreatic environment is characterized by the cementation of equant and massive calcite and mosaic sparry calcite in optical continuity with enclosed echinoderm fragment, and limited solution, while fresh water vadose environment is lack of cementation but has typical features of non-fabric selective solution and geopetal structure. Chemical compaction, development of stylolite, late leaching and oil emplacement are common in the middle to deep burial diagenetic environment.