2-1/2 Dimensional Modeling of the Major Structures Underlying Dong and Shelleng of the Upper Benue Valley, Using GM-SYS Computer Modeling

Abstract

Airborne magnetic data over part of Dong and Shelleng area of the upper Benue Valley, N-E basement complex of Nigeria's was carried out to investigate the deep and thick structures of the underlying geology and their relationship with granitic intrusion. These features are interpreted in terms of deep geologic structures, and/or susceptibility variations within basement rocks. The residual separation exercise revealed  the area is underlain by a NE-SW regional trends, which shows it is in agreement with Benue trough, presumed  they have the same structure control. Furthermore, the 3-D residual magnetic anomaly map suggests Dong is likely to be the sedimentary basin. It shows that the magnetic field there is smoother, which is masked off by the effects of the stronger magnetic basement. High amplitude of the anomalies which outcrop at eastern part of Dong where the profile cut across 6 could be the presence of Ngurore basalts. The thickness revealed by the model (D-D¹), Northwestern part Numan has a maximum thickness of 1.4km and minimum of 0.2km. In D-D¹ modeling, it revealed a porphyritic granite with non- uniform thickness of about 1.1Km and minimum of 0.17Km with a width approximately 2.9Km. The first sedimentary layer reveals has a thickness of about 1.0Km and the second varies from 1.0 to 1.6km thick. The width is about 4km.The Alluvium thickness increases progressively between 0.2Km to 0.7Km and the width of about 18km, reveals by the model. The thickness of the basin varies between  0.9km to 2.9Km. The model reveals the width of the basin to about 136Km.

Key Word: Geologic Map, Total Field Map, Regional Field, Residual field and 3-D Residual Field, Model D-D