北部湾涠西南凹陷物源方向及古地理景观分析

南海北部湾涠西南凹陷是以下第三系沉积为主体的中、新生代幕式张裂半地堑盆地.由于该区受太平洋、欧亚及印度三大板块的共同作用,构造十分复杂,成为独特的“南中国海型”被动大陆边缘,沉积物源方向具有其特殊性.以重矿物资料为基础,根据不同稳定性重矿物被风化的难易程度及搬运过程中其含量的变化规律,详细研究该区的重矿物组合序列,认为涠西南凹陷下第三系各组段沉积物源主要来自西部,同时伴有西北向的点物源.在此基础上,结合岩石学及盆地构造演化特征,分析其古地理景观,阐明在三期张裂幕的控制下,其沉积体系具有西厚东薄不对称展布的规律.图3表3参4(赵军摘)

Analysis on material sources and palaeogeographic landscapes of Weixinan sag

Weixinan s ag is an episodic tension subgraben basin which developed in Mesozoic and Cenozo ic. The basin, which stands the south ledge of Eurasian plate, was interacted by Pacific-oceanic plate, Eurasian plate and India plate, forming the so called "South China Sea type" passive continental margin with extremely complicated f eatures in tectonics, and an unique source. On the basis of heavy minerals data the combination arrays of heavy minerals are researched carefully according to t he weathering degree and the variations of its content through transport. The re sult is that the main material source of paleogene strata comes from the west an d the secondary material sources come from the northwest in the Weixinan sag. On these bases the palaeogeographic landscapes are analyzed with the specific char acteristics of sedimentology and construction. The expanding direction of the se dimentary system is from west to east and is unsymmetrical. This system is thick in the west and thin in the east under the control of the three periods of epis odic tens ion.