冀中坳陷中北部新生代构造演化特征

Cenozoic tectonic evolution in the north-central Jizhong Depression

在精细地震解释的基础上,采用断层落差法、断层活动强度法、平衡剖面技术和构造物理模拟实验等技术手段,确定了研究区的构造发育特征与构造形成演化过程,并讨论了构造形成机制。结果表明,冀中坳陷中北部在新生代伸展过程中以伸展构造样式为主,兼有走滑构造样式。其中,霸县凹陷以翘倾和滑动断阶构造样式为主,饶阳凹陷背斜构造样式占优,其最北部以走滑构造样式为主。受控于控凹断层的活动性,霸县凹陷和饶阳凹陷不同沉积时期,伸展强度具有较大差异性。饶阳凹陷自南向北受控于留路、河间和马西断层,凹陷的伸展量具有早期(Ek—Es4)"南部大于中北部",向中、晚期(Es3—Ed)逐渐过渡为"中北部大于南部"的特征。霸县凹陷受控于牛东断层沿走向活动性差异,具有南段"早期强-中晚期弱"、中段"早期弱-中期强-晚期较弱"和北段"早期弱-中晚期强"的构造演化过程。利用构造物理模拟实验验证研究区断层发育过程,实验结果与断层发育特征具有很强的相似性,说明构造几何学和运动学特征分析的正确性。基于以上研究,将饶阳凹陷和霸县凹陷的构造演化过程划分为断陷弱早期、断陷强中期和断陷较强晚期3个阶段,并探讨了研究区构造发育演化的形成机制和深部背景。

On the basis of fine seismic interpretation, various methods including fault throw method, tault activity intensity method, balanced cross-section technique and physical simulation are adopted in this paper to analyze the Cenozoic tec- tonic characteristics and evolution process as well as the forming mechanism of structures. The results show that the north- central part of Jizhong Depression was dominated by extensional structures in the Cenozoic, with strike-slip structure style also occurring. In Baxian Sag, tilting and sliding fault terrace structural styles were predominant. While Raoyang Sag was dominated by anticline structural style except for its northernmost part where strike-slip structure style was common. The extensional intensity shows large diversity in different periods in both Baxian Sag and Raoyang Sag, strictly controlled by the activity of boundary faults. Raoyang Sag was controlled by Liulu, Hejian, and Maxi faults from south to north. The ex- tension of sag as characterized by transition from ＂south being larger than central-north＂ in Ek - Es4 to ＂central-north being larger than south＂ in Es3 - Ed. Baxian Sag was controlled by the diversity of Niudong fault activity along strike ,fea- turing in the tectonic evolution of ＂strong early stage but weak middle and late stages＂ in south,＂ weak early stage strong middle stage and weak late stage＂in the central,and ＂weak early stage but strong middle and late stages＂ in north. The physics simulation experiment validates the fault development process of research area. The experiment result has strong similarity with the development characteristics of the faults, demonstrating the correctness of tectonic geometry and kine- matics characteristic analysis. On the basis of above research, the tectonic evolution process of Raoyang Sag and Baxian Sag is divided into three stages, namely weak early stage, strong middle stage, and fair late stage. Finally, the mechanism and deep background of tectonic formation and evolution are discussed.