Electrical Resistivity Imaging (ERI) of basin fills in some parts of Eastern Dahomey.


Akinmosin A. A., Omosanya K. O.*, Ikhane P. R., Mosuro G. O. and Adetoso A. O.

Stratigraphic and geophysical analyses of an outcrop at Onikintibi were done with the aim of understanding basin architecture and predicting depositional history. The palynological studies defined the age of the units, and clarified the lithology of the basal component. Three principal lithology types found are conglomeratic sands, compacted ferruginised sandstone, and the weathered basement; these units have resistivity values of >1000 m, >1019 m and <400 m. The basal layer is derived from porphyritic granite protolith. In addition, coarsening-upward stacking pattern of the reddish-brown conglomerate suggests prevalence of continental conditions. High thickness of the Ise units at the western edge suggests greater accommodation space and subsidence during basin development; consequently, the layer tapers to the east in response to waning current. The occurrence of Monoporites annulatus, Laevigatosporites and Acrostichum aureum imply the outcrop is post Paleocene. Longapertites sp. is an extant plant taxa with known ecological preferences assigned to Nypa (a mangrove plant), thus vegetation comparable to Nypa mangrove may have occurred in the region. The lithologic units over the weathered basement are rocks of the Abeokuta group in Eastern Dahomey Basin.

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