南沙海域新生代地层划分与对比

DIVISION AND CORRELATION OF CENOZOIC IN NANSHA OFFSHOREAREA OF SOUTH CHINA SEA

南沙海域新生代沉积厚逾万米，目前已在第三系发现了近百个油气田，但在重要的基础工作－地层划分对比方面尚缺乏全区统一性研究，因此地域间对比可信度低，实用性差。文中综合应用岩性、古生物、地震资料，追踪对比标志特征明显、具有年代地层意义的诸多界面，建立了全区年代地层系统框架，从总体上看，所建立的纵向地层系统积叠关系在大区域上的对比可信。按地震反射波特征划分了以T7为界面的上、下两大波系和To－Tg的10个主要反射界面。通过连层对比，并应用古生物断带资料，赋予了各层序的时代内涵。研究表明，除早期断块高部位和继承性发育的隆起区外，南沙海域新生界发育完整，上古新统－第四系皆有分布，并可进行大区域追踪对比。

The Cenozoic sedimentary thickness is over 10,000m in the Nansha Offshore Area,and almost one hundred oil and gas fields have been discovered in the Tertiary. But in aspect of the stratigraphic division and correlation,which is a very important basic work,the regional systematic study is insufficient. Therefore,the correlations between different regions are less reliable and poorly practicable.By using synthetic data, including lithology, palaeontology and seismic, the authors trace and correlate the boundaries with distinct features and chronostratigraphic meaning and then reconstruct the chronos-tratigraphic frame work. Two major reflection wave sets are divided by the T7 boundary and ten main reflection boundaries are recognized as To to Tg. These sequences are endowed with the chronologic meanings by correlating based on the palaeontologic data. Hence,the fairly reliable vertical stratigraphie relations are established. From this study,it is suggested that there develops a complete Cenozoic from late Paleocene to Quaternary in the Nansha Area, excluding on the fault block highs formed in the early rifting period and the inherited uplift areas