下刚果盆地重力滑脱伸展构造生长发育特征

Features of Gravitational Decollement and Extension Structural Development in Lower Congo Basin

下刚果盆地大陆坡上部阿尔布期(Albian)至今主要发育重力滑脱伸展构造。根据构造发育特征和发育位置,将重力滑脱伸展构造区划分为:后缘构造带、中部构造带和前缘构造带。下刚果盆地重力滑脱伸展构造区构造活动最早在后缘构造带发生,其次是中部构造带,最后是前缘构造带。其中中部构造带构造活动最强、主要发育正断裂,及相关的盐构造、地垒和地堑,且生长正断裂至今仍在活动;后缘构造带构造活动强度次之,仍以正断裂为主,盐构造不明显,白垩纪之后该构造带构造活动基本停止;前缘构造带构造活动强度最弱,主要发育盐构造及盐构造相关的褶皱和断裂,该构造带阿尔布期之后构造活动开始减弱,白垩纪之后基本停止。通过对构造演化规律的研究,发现阿尔布期和始新世-中新世是下刚果盆地重力滑脱伸展构造的2个主活动期。

Albian gravitational decollement and extension structures have been mainly developed in the upper continental slope of Lower Congo Basin.According to the structural growing characteristics and position,the gravitational decollement and extension structures were divided into three zones,including posterior margin structural belt,middle structural belt and frontal structural belt.In the tectonic zone,the earliest activity was in the posterior margin structural belt,the nest was in the middle structural belt,the last one was in the frontal structural belt.It was the strongest in the middle structural belt,it mainly developed normal faults and related salt tectonics,horst and graben,and the normal faults have been still developed;the tectonic strength in posterior margin structural belt was followed,the normal faults were dominated,and salt tectonic was not obvious,but the activity almost stopped after the Cretaceous epoch;the frontal structural strength was the weakest,where salt tectonics and their related folds and faults were mainly grown,the tectonic zone was weakened after the Albian,it almost stopped after the Cretaceous.On the research of tectonic evolution,it is found out that the Albian and the Oligocene-Miocene Systems are main active periods of gravitational decollement and extensional structures in Lower Congo Basin.