Brittle deformation in the Afikpo Basin (Southeast Nigeria): Evidence for a terminal Cretaceous extensional regime in the Lower Benue Trough, Nigeria

Abstract

This paper deals with the regional and structural framework of the Cretaceous rocks in the Afikpo Basin located in the southeastern part of the Lower Benue Trough. Results from regional tectonics are presented together with those of the microtectonic analysis of microfaults in the Owutu-Afikpo-Adadama area in the basin.The Owutu-Afikpo-Adadama ridge at the north-central part of the basin marks the boundary between the Late Cenomanian-Turonian-Conianian sediments and the Campanian-Maastrichtian sandstones. This ridge trends N45ºE on average and is faulted in three main directions, namely: (1) N-S normal faults; (2) NE-SW strike-slip faults; and (3) NW-SE strike-slip faults. The faulted rocks along these brittle discontinuities are mainly cataclastics with internal fracture cleavage and sigmoidal quartz mosaics that are reminiscent of extensional deformation. The cataclasites often bear slickenside striations.The NE-SW and NW-SE strike-slip faults are the results of the youngest brittle events on the Owutu-Afikpo-Adadama ridge. These faults were reactivated after deposition of the Campanian-Maastrichtain sediments (post-depositional faults) and, therefore, are post-Maastrichtain. Microfault analysis of these fault trends suggests an extensional regime that prevailed in the Lower Benue Trough. These results are of significance because this event is least poorly understood and less documented in contrast to the Cenomanian and Santonian events that affected the older Cretaceous strata in this region.

Subsurface Structural Investigation for Evaluation of Hydrocarbon Potential Using Aeromagnetic Data over Parts of Southeastern Nigeria

“…The most extensive marine transgressions in the trough occurred during the Turonian-Coniacian times. This led to the deposition of the Eze-Aku Group, comprising of paralic sequences of two marine transgresssive cycles the Late Cenomanian-EarlyTuronian and Late Turonian and Early Coniacian strata unconformably overlying the Middle Albian-Early Cenomanian Asu River Group (Odigi, 2009). The Late Turonian-Coniacian calcareous sandstone ridges of storm origin belong to the Amasiri, while the underlying paralic sequences are predominantly shales which grade into bioclastic limestones and sandstones and are referred to as Ezillo Formation (Ojoh, 1992).…”

Remote sensing signature of geological structures inferred on landsat imagery of Afikpo area Southeastern Nigeria

“…The base of sediments of Asu River Group Late Albian to Early Cenomanian is about 3000 m. The Eze Aku Group overlies the Asu River Group unconformably with a thickness of about 2000m Late Cenomanian to Early Santonian sediments ( Figure 2). The Eze Aku Group is unconformably overlain by post-Santonian sediments of pro-Niger Delta (Odigi and Amajor, 2009;Odigi, 2010).…”

Hydrocarbon-Generating Potential of Eocene Source Rocks in the Abakaliki Fold Belt, Nigeria / Potencial za nastanek oglikovodikov v eocenskih izvornih kamninah nariva Abakaliki

“…Terminal tectonic event during late Maastrichtian had been reported [9,27], where rifting, deformation and high heat flow from magmatic activity played an important role [28]. Thermal heat flow peak for Eocene tectonism was modelled based on intensive erosion [9] during the period.…”