西湖凹陷天台斜坡带物源交汇区古近系碎屑锆石形态学与年代学示踪

Morphological and chronological tracing of Paleogene detritalzircons in the provenance intersection area of Tiantai slope in Xihu Sag

西湖凹陷西部斜坡带是东海盆地最为重要的勘探目标区之一,但其南部的天台斜坡区处于海礁隆起与渔山东低隆起物源的交汇区,物源体系不清制约了沉积砂体刻画与储层研究。利用碎屑锆石形态学、锆石U-Pb定年及地震反射特征等研究方法,针对研究区砂体来源进行剖析,明确古近系海礁隆起与渔山东低隆起物源差异及砂体供给特征,进而明确天台斜坡带物源交汇区不同层系母源类型与砂体发育强度关系。结果表明,平湖组沉积时期,天台斜坡区处于渔山东低隆起与海礁隆起联合供砂区,砂体沿断裂转换带向低带展布,平湖组自下而上渔山东低隆起的物源体系逐渐减弱,海礁隆起物源体系逐渐增强;至花港组沉积时期海礁隆起供源作用持续增强。

The western slope of Xihu sag is one of the most important exploration areas in the East China Sea Basin,but the Tiantai slope in the south is located in the intersection area of Haijiao uplift and Yushan low uplift.Unclear provenance system restricts the study of sedimentary reservoirs.Based on the methods of zircon morphology,detrital zircon U-Pb dating and seismic progradation reflection,the difference of the Paleogene provenance supply characteristics between Haijiao uplift and Yushan low uplift was made clear,and then the relationship between material source and strength of different layers in the provenance intersection area of Tiantai slope was determined.The results show that during the Pinghu Formation,the Tiantai slope is located in the arc fault transportation area,the source is jointly supplied by Yushan low uplift and Haijiao uplift,and the sediments are distributed along the fault transition zone to the lower position.During the Huagang Formation,the source supply of Yushan low uplift weakened,and the source supply of Haijiao uplift continued to strengthen.