碳酸盐岩中与古暴露面相关的成岩作用

Diagenesis Related to Ancient Exposed Surfaces in Carbonate Rocks

碳酸盐岩沉积物记录了环境演变、古气候变迁以及后期成岩环境等重要的指示信息,同时碳酸盐岩也是重要的油气地质储集体,因而受到人们的普遍关注。碳酸盐岩不整合暴露面通常发育3层结构:风化土壤层带、半风化岩石带、原岩带。相比而言,半风化岩石带碳酸盐岩成岩作用比碎屑岩更为复杂,尤其是沉积物埋藏后的抬升,使之再次暴露,导致碳酸盐岩形成复杂的成岩响应。系统总结了碳酸盐岩埋藏后的抬升暴露所形成的与古暴露面相关的成岩现象,分别从风化带古土壤、半风化带与暴露面相关的成岩结核、古岩溶以及角砾岩化等方面阐述了与古暴露面相关的标志特征及其形成机制,从而为碳酸盐岩中古暴露面的识别提供充足的地质依据。

Plentiful information on the sedimentary environment evolution, palaeoclimate changes and late diagenesis has been recorded in carbonate rocks. Meanwhile, carbonate rocks are widespread and of great significance in hydrocarbon reservoirs. Stratigraphic sections through unconformity surfaces can be divided into three intervals： weathered soil layer, partially-weathering rock layer, and host rocks. The diagenesis in the partially-weathered carbonates is more complex than that in clastic rocks, especially due to the uplift after the sediment burial. Carbonate rocks generally undergo more complicated diagenetic reactions after being re-exposed. In this paper diagenetic phenomenon related to the ancient exposure surface during the uplift and re-exposure periods after the burial of the carbonates is summarized. The features and the formation mechanism associated with the ancient exposure surface, such as the palaeosol, the diagenetic nodules, the palaeokarst and the brecciation, are also discussed in order to provide sufficient geological evidence for identifying ancient exposed surfaces in carbonate rocks.