南黄海盆地东北凹构造特征及伸缩率研究

Tectonic characteristics and extensional-compressional rates of the North-east Sag of South Yellow Sea Basin

  • 摘要: 通过选取南黄海盆地东北凹典型地震剖面,开展精细的构造解释,系统梳理了东北凹构造样式特征。采用平衡剖面恢复技术和伸缩率计算方法,恢复了东北凹各时期的地质演化剖面,分析了东北凹不同构造演化阶段的伸缩率变化特征。研究表明,南黄海盆地东北凹主要发育伸展构造、走滑构造(负花状)和反转构造等多种构造组合样式,经历了晚侏罗世的仪征运动和渐新世末的三垛运动,相应地在中—上侏罗统和渐新统沉积时期,东北凹处于明显的收缩阶段,伴随发育TK40和T20不整合界面。同时,本文结合区域应力场特征,探讨了南黄海盆地东北凹的构造演化历程:以两次构造运动为界,划分为3个构造演化阶段(晚三叠世—侏罗纪的初始断陷阶段、白垩纪—渐新世的裂陷-反转阶段、新近纪—第四纪的区域沉降阶段)。南黄海盆地东北凹伸缩率的时空变化及构造演化过程,是对“晚中生代以来,古太平洋板块相对欧亚板块俯冲汇聚速率和方向的改变”的局部响应。

     

    Abstract: Typical seismic sections are selected for delicate structural interpretation upon the basis of structural features of the North-east Sag of the South Yellow Sea Basin. The balanced cross-section technique and the extensional - compressional rates calculation method are used to reconstruct the tectonic evolution cross-sections for different tectonic evolutionary stages. The characteristics of extensional - compressional rates are analyzed. The results suggest that the North-east Sag of the South Yellow Sea basin is characterized by extensional structures, strike slip structures (negative flower patterns), inversion structures etc. by the Yizheng movement in Late Jurassic and the Sanduo movement by the end of Oligocene. Accordingly, the sag was obviously in compressional status during the deposition of Late Jurassic and Oligocene when the Tk40 and T20 unconformity interfaces were formed. In order to quantify the characteristics of the regional stress field, the paper also reconstructed the tectonic evolution of the north-east sag. Taking the two tectonic movements as the boundaries, the sag is subdivided into three stages of tectonic evolution i.e. the initial faulting- depression stage from Late Triassic to Jurassic, the rifting inversion stage from Cretaceous to Oligocene, and the regional subsidence stage from Neogene to Quaternary. The temporal and spatial variations in the extensional - compressional rates and the tectonic evolution of north-east sag in South Yellow Sea basin represent the local response to the regional stress field, such as the change in convergence rate and motion azimuth between the Pacific plate and the Eurasian plate since Late Mesozoic.

     

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