南海南部北康盆地晚渐新世-中中新世物源变化

Provenance Migration in the Beikang Basin of the Southern South China Sea during the Oligocene to the Mid-Miocene

晚渐新世-中中新世,南海南部经历了重要的构造变革,北康盆地物源发生了重大变化,引起分散体系的变化,从而影响油气资源分布,因此物源研究具有重要意义.利用地震反射资料,开展地震属性分析,通过RMS(均方根振幅)地层切片,分析分散体系,并探讨物源变化及其控制因素.在晚渐新世-中中新世,北康盆地的沉积物源主要来自南侧,分散体系自南向北;不整合面之后海水突然加深,形成以早中新世不整合面(E M U)为界的2个沉积旋回;在每个旋回内,沉积物补给逐渐增多;在中中新世,沉积物源逐渐向北西方向迁移.通过区域分析,认为北康盆地的物源主要来自南部的曾母前陆盆地,物源的变化是曾母前陆盆地逐渐淤浅成陆和向北推进所致.

It is significant to research the provenance of Beikang basin in the southern South China Sea,because oil and gas resources were influenced by the changes of dispersion systems resulted from tectonic-induced migration of provenance.In this paper,seismic reflection data were used in seismic attribute analysis,where stratigraphic slices of RMS(root mean square amplitude)were used to analyze dispersion systems,in order to inquire into provenance migration and its controlling factors.During the Later Oligocene to Middle Miocene,the provenance of the Beikang basin was from the south and the dispersion systems extended from south to north.Two depositional cycles were separated by the Early Miocene Uncomformity(EMU),which formed during seawater deepening.In each cycle,sedimentary supply increased gradually upward.During the Middle Miocene,the depositional provenance migrated northwestward gradually.Regional analysis show that the provenance of the Beikang basin mainly came from Zengmu Foreland basin and the provenance migration is caused by landfill and overthrust northward of the Zengmu Foreland basin.