关键词: 东尼日尔, Termit盆地, 叠置裂谷, 构造演化, 沉积充填, 前裂谷期, 同裂谷期, 后裂谷期

Abstract:

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.

Key words: eastern Niger, Termit basin, polyphase rift, structrual evolution, sedimentary record, prerift, synrift, postrift