南大西洋东岸尼日尔三角洲大型重力滑动构造东南缘的断裂和泥构造

The faults and shale tectonics in the southeastern flank of the Niger Delta large scale gravity gliding tectonics

尼日尔三角洲位于南大西洋东岸被动大陆边缘之上,以大型重力滑动构造为主要构造特征。该大型重力滑动构造的东南缘位于喀麦隆境内,断裂和泥构造都很发育。这里的断裂包括重力滑动构造后缘伸展形成的正断层、侧翼剪切形成的撕裂断层和泥底辟成因的断层。泥柱和泥墙是研究区的两种类型的泥构造。泥柱代表主动泥底辟;泥墙是撕裂断层控制下被动泥底辟的结果。研究区重力滑动构造相关的断裂活动起始于中新世中期,随后,在上新世和第四纪各有一个断裂活动的加速期。每个断裂活动的加速期都伴随有泥底辟。中新世中期有一次泥底辟,上新世和第四纪各有两次泥底辟。

The Niger Delta is located on the eastern passive continental margin of the South Atlantic Ocean.The delta body consists a large gravity-gliding tectonics.The SinoPec´s Cameroon block is a petroleum exploration block on the southeastern side of the gravity-gliding tectonics.Both fault and shale tectonics are well developed in this block.The faults in this block include the normal faults induced by the trail extension of the gravity gliding tectonics,the tear faults induced by the shear between the gravity gliding tectonics and the original rocks and the faults induced by the shale diapir.Stock and wall are the two types of the shale tectonics in this block.The shale-stocks in the western part of the block were formed by the active shale diapir.The shale-walls in the middle-eastern part of the block were formed by the passive shale diapir controled by the tear faults.The gravity tectonics related faulting initiated in the Middle Miocene,and accelerated in Pliocene and Quaternary respectively.Each faulting accelerating stage accompanied with shale diapir activities.One shale diapir activity accompanied with the middle Miocene faulting,two with the Pliocene and Quaternary faulting respectively.