南海北部陆缘东部中生代沉积的地震反射特征

SEISMICREFLECTLVE CHARACTERISTICS OF MESONOIC SEDIMENTS ON THE EASTERN CONTINENTAL MARGIN IN THE NORTH OF THE SOUTH CHINA SEA

本文介绍了中美合作在南海北部陆缘进行的双船地震（合成排列剖面）工作，讨论了新生代沉积之下的中生代沉积之地震反射特征。在今日陆架新生代沉积之下的中生代沉积之地震反射表现杂乱、低振幅和不连续特性，而在今日上陆坡新生代沉积之下的中生代沉积之地震反射呈现连续、较强振幅和可长距离对比的特征。根据地球物理场特征及区域地质资料，我们指出燕山运动时间广东大陆边缘的构造格架：今日东沙群岛—彭湖列岛—带为火山弧，今日陆架区及广东大陆为弧后区，而今日陆坡区则为弧前区。故今日陆架下的中生代沉积为弧背盆地之沉积，表现为陆相沉积；今日陆坡下的中生代沉积为前弧盆地之沉积，表现为海相沉积。

This paper introduces the two-ship seismic work(Synthetic Aperture Profile)on thecontinental margin in the north of the South china Sea by cooperation of Sinica andAmerica,and discusses the seismic reflective characteristics of Mesozoic sediments in thepresent shelf which look chaotic,low-amplitude and discontinuous,while those in thepresent upper slope look continuous,high-amplitude and continuously tracing.Accordingto the characteristics of geophysical field and regional geological data,we consider thattectonical pattern of Gangdong's margin in Yanshan movernent was as follows:the pre-sent Dongsha Islands-penghu Islands were a volcanic arc,the present shelf and continentof Guangdong Province were a back-arc area ,and the present slope was a fore-arc area.So the Mesozoic sediments beneath the Cenozoic sediments on the shelf were in theretroarc basin,and belong to continental facies,and the Mesozoic sediments in the pre-sent slope were in the forearc basin,and belong to a marine facies.