Structural Delineation of the Anambra Basin, Awgu Section, Southeast Nigeria

Abstract

Tectonism that occurred during the Santonian epoch in the Cretaceous period gave rise to the formation of the Anambra Basin. The deposition of lacustrine, deltaic, transitional marine and marine sediments successively during the upper Cretaceous contributes to the sedimentary fill of the Anambra Basin. The basin fill of the Anambra Basin is characterized as a third-order sedimentary cycle from studies. The study of the deformational structures folds and faults) in the Anambra Basin gives an insight to the understanding of how the formations in the basin were affected by tectonism during sedimentation. Faults and folds were the identified deformational structures examined in the Campanian-Maastrichtian deposits of the basin. Detailed geological mapping was carried out which involves identification and measurements of fault plane, displaced blocks, dips and strikes of overturned beds and fold axis and data interpretation were employed to delineate the structural architecture of the basin in the field. Deformation in the study area is attributed to Post-Santonian compressional and extensional tectonic stress that occurred in the Campanian-Maastrichtian time during sedimentation process and this resulted in the folding, faulting and shearing of deposits seen in the Mamu Formation. Also there were records of overturned shale beds in the Mamu Formation in Obeagu Town in the Awgu axis of the Anambra Basin which will help in the prediction of hydrocarbon accumulation pattern and enhances the potentials for petroleum exploration strategies in the basin.