Bulletin des Centres de Recherches Exploration-Production Elf Aquitaine, Vol.17, No.2, 371-383, 1993
LATE JURASSIC RIFTING - EARLY CRETACEOUS RIFTING AND LATE CRETACEOUS TRANSPRESSIONAL INVERSION IN THE UPPER BENUE BASIN (NE NIGERIA)
This paper examines the regional and structural framework of the Cretaceous Upper Benue basin (NE Nigeria). Results from regional tectonics combined with those of the microtectonic analysis of pre-lithification and brittle microfaults detail the tectonic evolution of the basin. A three phased tectonic history is characterized. Rifting movements started during the Late Jurassic period during which Pre-Bima fanglomerates and microconglomerates locally deposited. A second phase of rifting prevailed from the Neocomian to Early Albian when the Upper Benue basin developed under a N60-degrees-E extensional regime. On a regional scale, extensional normal and transtensional fault blocks prevailed resulting in the deposition of the thick clastic continental Bima series in the half-grabens which were controlled by the Benue N50-degrees-E and Chad N140-degrees-E structural trends. The Upper Benue basin evolved as a late rift to sag basin during the Late Albian to the Early Cenomanian in response to NE-SW extensional and transtensional regimes. Primitive half-grabens and wrench-induced troughs became inverted during the Late Cretaceous N-S to N140-degrees-E transpressional inversion,The structural style related to this event is expressed by transpressional anticlines, drag folds, positive flower structures and inverted fault blocks. As the Late Cretaceous inversion terminates, the Paleocene sedimentation truncates the positive structures and covers them in the northwestern area.