中新世礁相碳酸盐岩沉积构成及成礁模式——以西沙海域为例

 结合最新钻井、地震资料，剖析了中新世生物礁体沉积构成以及成礁演化模式。揭示了研究区造礁生物主要为钙藻，其次为六射珊瑚，附礁生物以有孔虫和介形虫为主。根据是否发育造礁生物将岩石分为礁格架-骨架岩和非礁格架-骨架岩2类，前者包括珊瑚藻格架和珊瑚骨架焦白云岩及红藻-仙掌藻白云岩2种，非礁骨架岩分为生物碎屑灰岩、粒泥灰岩和泥粒灰岩3种。沉积相包括礁格架相、礁坪相、礁后滩相、泻湖相和生物碎屑滩相5种。中新世生物礁是在相对海平面不断上升的背景下沉积演化的，属于加积-退积型生物礁沉积旋回，礁体发育期可分为奠基、初始繁盛、顶峰、暴露衰退4个阶段，暴露衰退末期发生强烈的白云化作用，淡水淋滤溶蚀作用形成较好的储集层。

Sedimentary composition and forming models of Miocene reef carbonate: A case study of Xisha waters

The characteristics of sedimentary composition and evolution models of the Miocene reef are studied by combining the latest drilling data and seismic data. The reef-building organisms in the studied area are mainly calcareous alga, followed by hexacorallia; and accessory reef organisms mainly consist of the foraminifera and ostracod. According to the development of reef-building organism rocks which can be divided into reef skeleton-framestone and non-reef skeleton-framestone, the former includes red coral and reef framework dolomite and red algal-halimedadolomite, and the non-reef skeleton-framestone mainly consists of bioclastic limestone, grain of marl and packstone. The sedimentary facies include reef framework, reef flat, lagoon, backreef bank and bioclastic facies. The sedimentary evolution of Miocene organic reef follows the rising of the relative sea level, then a set of aggradation-retrogradation reef sedimentary cycles. The reef development can be mainly divided into four stages:the foundation, initial prosperity, peak and expose recession. During the fourth stage for reef and development, the favorable reservoir in studied area was formed by extensive dolomitization of exposure shoals.