摘要
在南海北部大陆架陆源碎屑沉积占优势的背景上 ,珊瑚岸礁和堡礁周围广泛发育着礁源碳酸盐和陆源碎屑组成的混合沉积。它们以砂屑、砂砾屑结构为主并含有生物格架结构。形成混合沉积的条件是具备碳酸盐和硅质碎屑两类物源、活跃的水动力和干湿交替的气候 ,此外 ,海平面的相对波动也会造成积极的影响。混合沉积方式有随机式、相变式和随机—相变式 3种。混合沉积体通常是多种混合方式交替、叠加而成的沉积复合体。礁源与陆源混合沉积相模式是从岸礁—堡礁相模式基础上发展而来 ,根据其沉积相和沉积结构特征可以分为 5种混合沉积 :①礁基混积岩和礁格架混积岩 ;②礁坪砂砾屑混积岩 ;③礁后海滩—沙堤砾砂屑混合沉积 ;④礁后湖砂屑混合沉积 ;⑤礁前 (礁翼 )浅海砂屑混合沉积。礁源与陆源混合沉积的鉴别标志是珊瑚骨屑和岩屑各占 10 %～ 50 % ,其它生物碎屑不计。南海大陆架是一个典型的现代混合沉积实例 ,该研究结果可为全面研究现代南海沉积学和比较沉积学提供依据。
In the north continental shelf of the South China Sea,which is dominated by terrigenous clastic sediments, around fringing and barrier coral reefs, there widely developed recent mixed sediments, which consist of reefoid carbonates and terrigenous clastics. These mixed sediments are mainly arenaceous and arenaceous rudaceous, and include some biogenic frameworks. Occurrence of both carbonate and siliciclastic sources, active hydrodynamic regimes, alternate dry and wet climates, and the fluctuation of sea level are main factors for forming mixed sediments.There are three patterns of mixed sedimentation,including stochastic, facies change and stochastic-facies change. Mixed sediments are commonly sedimentary complexes generated by diverse patterns of mixed sedimentation. Sedimentary facies model for mixed sediments of recent reefoid carbonates and siliciclastics is developed from the facies model of fringing and barrier reefs. Based on the sedimentary facies and textures,mixed sediments may be subdivided into 5 types as follows:1) reef base mixed sedimentary rocks and reef framework mixed sedimentary rocks;2) reef flat sand gravel mixed sedimentary rocks;3) backreef beach dune gravel sand mixed sediments;4) backreef lagoonal sand mixed sediments;and 5) reef front (flank) littoral sand mixed sediments. Reefoid carbonate and siliciclasstic mixed sediments can be identified through components, in which both coral debris and terrigenous clastics account for 10%～50% respectively and other biogenic fragments are not counted. Recent mixed sediments in the continental shelf of the South China Sea is a typical recent mixed sediment, which may provide scientific basis for the sedimentological research in the South China Sea and for the comparative sedimentological research.
出处
《古地理学报》
CAS
CSCD
2001年第2期47-54,共8页
Journal of Palaeogeography：Chinese Edition
基金
同济大学海洋地质教育部重点实验室"南海珊瑚礁区沉积学研究"课题成果之一
关键词
南海
北部大陆架
混合沉积作用
混合沉积
沉积相模式
South China Sea, north continental shelf, mixed sedimentation, mixed sediments, sedimentary facies model
