非洲西海岸里奥-德雷盆地泥底辟平面地质结构特征研究

Study on the planar structure characteristics of mud diapirs in Rio del Rey basin,West Coast of Africa

位于西非尼日尔三角洲盆地东缘的里奥-德雷盆地发育了大规模泥底辟,其活动时间和形成机理存在一定争议。基于对里奥-德雷盆地三维地震剖面的精细解释和平面成图,对其中中新世Nguti构造层顶面的泥底辟平面分布特征进行了重新厘定。结果表明:(1)Nguti构造层顶面的泥底辟可分为北部隐伏区、中部刺穿区和南部刺穿区;(2)北部隐伏区的泥底辟形成于Nguti构造层沉积前,是受早期沉积作用控制的被动泥底辟;中部刺穿区的泥底辟形成于上新世S0构造层沉积前,是受重力构造作用控制的主动泥底辟;南部刺穿区的泥底辟形成于Nguti构造层沉积后,是受重力构造前缘逆冲断层控制的逆冲泥底辟;(3)泥底辟整体上为向南凸出的舌状体,分东、西两段,西段为北北西-北西走向,东段为北北东-北东走向。

The Rio del Rey basin,located in the eastern margin of the Niger Delta Basin in West Africa,develops large-scale mud diapirs.There are some disputes about the activity time and mechanism of the diapirs.Based on the detailed interpretation and mapping of the 3D seismic profile of the Rio del Rey basin,the distribution characteristics of the mud diapir on the top surface of the Miocene Nguti structural layer are redefined.The results show that:(1)mud diapir on the top of the Nguti structural layer can be divided into the northern buried area,the central pierced area,and the southern pierced area;(2)the mud diapir in the northern buried area was formed before the deposition of the Nguti structural layer,and was a passive mud diapir controlled by early sedimentation.The mud diapir in the central pierced area was formed before the deposition of the Pliocene S0 structural layer,and was an active mud diapir developed under the action of gravity sliding structures.The mud diapir in the southern pierced area was formed after the deposition of the Nguti structural layer,and was a thrust mud diapir controlled by thrust structures at the front edge of the gravity structure;(3)the mud diapir as a whole is a tongue shaped body protruding southward,divided into two segments:the west segment along a NNW-NW direction,and the east segment along a NNE-NE direction.