东尼日尔Termit盆地叠置裂谷的演化:来自构造和沉积充填的制约

东尼日尔Termit盆地是中西非裂谷系中典型的中—新生代裂谷盆地。在充分应用钻井和地震解释资料的基础上,根据构造、沉积充填及主要区域性不整合面的特征,分析了该盆地的演化过程。盆地内主要发育两类断层,第一类断层形成于早白垩世,于古近纪发生继承性活动,第二类断层为形成于古近纪的新生断层。全盆地普遍存在4个主要区域性不整合面,分别位于下白垩统、上白垩统、古近系、新近系—第四系底部。下白垩统和古近系沉积特征受断层活动控制明显,上白垩统和新近系沉积中心位于盆地中部,在其沉积时构造活动较弱。构造和沉积充填特征表明,Termit盆地经历了白垩纪和古近纪—第四纪两期裂谷旋回叠置的演化过程。下白垩统和古近系沉积于同裂谷期,沉积充填受断层活动控制;上白垩统和新近系—第四系沉积于后裂谷期,以热沉降拗陷作用为主。

Polyphase Rift Evolution of the Termit Basin, Eastern Niger:Constraints from Structural and Sedimentary Records

The Termit basin is a typical Mesozoic-Cenozoic intracontinental rift basin of the west and central African rift system.Using well and seismic data,this study analyzed the tectonic evolution of the basin based on structural and sedimentary records.The basin is characterized by border fault systems forming in Early Cretaceous and reactivating in Paleogene,and by intrarift ones developed in Paleogene.Four regional unconformities were identified at the base of Lower Cretaceous,Upper Cretaceous,Paleogene and Neogene-Quaternary strata,respectively.The deposition of the Lower Cretaceous and Paleogene were apparently controlled by fault activities,whereas the depocentres of Upper Cretaceous and Neogene were located in the center of the basin,suggesting that the tectonic activities were weak at that time.Structural and sedimentary characteristics indicate that the Termit basin underwent polyphase rift evolution.The Lower Cretaceous and Paleogene which were controlled by active faulting were deposited during syn-rift,while Upper Cretaceous and Neogene-Quaternary which were defined by thermal subsidence were deposited during post-rift.