东海陆架盆地西部坳陷带构造特征及演化

通过横跨东海陆架盆地西部坳陷带各凹陷的典型地震剖面构造解释,系统总结了西部坳陷带的结构和构造样式特征。采用平衡剖面技术和伸缩率计算方法,恢复了西部坳陷带各时期的地质演化剖面,分析了西部坳陷带不同构造演化阶段的伸缩率变化特征。研究表明,西部坳陷带经历了古新世末的瓯江运动和渐新世末的花港运动,相应地分别在古新统明月峰组(E1m)和始新统温州组(E2w)沉积之后,西部坳陷带处于明显的收缩阶段,伴随发育T80和T20不整合界面。同时,结合区域应力场特征,探讨了西部坳陷带的构造演化过程。东海陆架盆地西部坳陷带伸缩率的时空变化及构造演化过程,是对"中、新生代时期太平洋板块、欧亚板块和印度板块之间汇聚速率和方向的改变"等区域应力场特征的局部响应。

TECTONIC CHARACTERISTICS AND EVOLUTION OF THE WEST DEPRESSION BELT OF THE EAST CHINA SEA SHELF BASIN

Based upon the tectonic interpretation of typical seismic sections of the West Depression Belt in the East China Sea Shelf Basin, this paper systematically summarized the framework and structural styles of the West Depression Belt in different sags. Balanced cross-section technique and the extensional and compressional rates calculation are adopted for reconstruction of tectonic evolution histories in different tectonic evolutionary stages. The results show that the West Depression Belt experienced the Oujiang movement by the end of Paleocene and the Huagang movement by the end of Oligocene. Accordingly, the West Depression Belt was under obvious compression right after the deposition of the Paleocene Mingyuefeng Formation(E1m) and Eocene Wenzhou Formation(E2w) respectively upon the unconformity interfaces of T80 and T20. By quantifying the regional stress field, the paper also discussed the tectonic evolution of the West Depression Belt. The temporal and spatial variations in extensional and compressional rates of the depression belt represent local responses to the regional stress field, such as the change in convergence rate and motion azimuth in Mesozoic and Cenozoic among the Pacific plate, the Eurasian plate and the Indian plate.