Sedimentary dynamics and extensional structuring related to early Cretaceous rifting of Neocomian and Barremian deposits of the interior basin of Gabon

摘要

Recent field and subsurface data about the early Neocomian N'dombo series and the Neocomian to mid-Barremian Schistes series of the interior basin of Gabon further our understanding of the initial stages of early Cretaceous N40-60°E extensional rifting. The syn-rift series comprise fluvial-lacustrine claystones-sandstones, rare conglomerates, and carbonates. The syn-rift fill begins with braided-stream feldspathic sandstones. These are overlain first by fluvial-lacustrine deposits and then by predominantly lacustrine-palustrine claystones, which are potential petroleum source rocks. The claystones are eroded in part and are capped by the pre-Aptian angular unconformity marking the end of Cretaceous rifting in the interior basin. This change in syn-rift facies and depositional environments reflects a rise in base level in response to accelerated subsidence after the initial stage of rifting. The syn-rift deposits form two fining-upward sequences several 100-1000 m thick.