Comparison between the stratigraphy of the eastern and western parts of the Gongola sub-Basin, Northern Benue Trough, Nigeria: The role of tectonics and the Neogene Biu Basalt emplacement on the resultant topography.

Abstract

Detailed field mapping exercise was carried out as well as system logging of the various outcropping lithostratigraphic units in the eastern Gongola sub basin with the aim of establishing any similarity or otherwise with the western sub basin. The study reveals that the pre-Aptian to Coniancian lithostratigraphy succession of both areas of the sub-basins are somewhat similar and comprises of the following units; the Bima Group (lower, middle and upper Bima formations) followed by the Yolde Formation, the Kanawa Formation. The mid Turonian sandy equivalents are directly above the Kanawa Formation and are represented by the Deba-Fulani Member restricted to the southern of the Gongola sub basin, the Dumbulwa Member restricted to the northern part of the sub basin and the Gulani Formation confined to the eastern part of the sub basin. The mid-Santonian tectonic event affected the pre-Santonian succession resulting into the folding, faulting and uplifting of the various lithostratigraphic units. This subsequently led to the formation of synclines and anticlines. The pre Santonian Fika Shale presumed to have been directly above the Gulani Formation is rarely observed in the eastern Gongila sub-basin compare to the western sub basin where it is in found several places. This suggests that the denudational activities spanning from Santonian to Paleocene in the eastern Gongola sub basin was severe before the emplacement of the Neogene Biu Basalt that slowed down the activities. The Campanian-Masatrichtian and the Paleocene successions are restricted to the western Gongola sub-basin.