碳酸盐岩中的鸟眼构造及其环境意义

Bird’s-Eye Structures in Carbonate Rocks and Their Environmental Significance

摘要:

鸟眼构造是指碳酸盐岩中毫米级大小的(常为1-5mm)、扁平至球形的、多呈定向排列的孔隙。它们常为亮晶方解石或硬石膏等所充填或半充填。因其形态似鸟眼,故称鸟眼构造;又因它常成群密集出现,故又称窗孔构造。由于它常可作为鉴别沉积环境的标志(这些沉积环境常会有地层圈闭油气藏);同时在未被充填时,又作为储集空间,因而研究鸟眼构造具有重要理论和实际意义。

Abstract:

Up to date, bird’s-eye structures have long been believed to be characteristic facies criteria for recognition of tidal flat environments including intertidal and supratidal environments.
This paper deals in detail with the bird’s-eye structures identified in the Jipao member of the Middle Devonian Dushan Formation, Guizhou Province. In terms of rock textures, sedimentary structures, palaeontology, sedimentary sequences and palaeogeographic settings, the bird’s-eye structures tend to be ascribed to the semi-enclosed lagoonal environments within the platform facies. Therefore the discovery and experimental study of the structures in modern subtidal environments show that the bird’s-eye structures may be recognized not only in tidal flat environments, but also in some subtidal environments.
The paper also discusses the bird’s-eye structures in the intertidal and supratidal environments in the Upper Devonian Yaosuo Formation, Feifengjing and the Upper Devonian Rongjiang Formation, Buzhai, Dushan, Guizhou. By comparison of the bird’s-eye structures in tidal flat environments with those in subtidal environments, it is possible to distinguish the bird’s-eye structures formed in different environments based on the shapes, genesis and associated rocks, and it is emphasized at the same time that comprehensive environmental analysis should be made by combination with the various facies criteria.