Gravity Anomalies Over The Gongola Arm, Upper Benue Trough, Nigeria

Abstract

A regional gravity survey of the Gongola Arm of the Benue trough was carried out with the aim of determining structures of interest. The results of the gravity interpretation showed that the area of study is characterized by negative Bouguer anomalies that trend in the NE-SW direction and range in value from -75 to -15 mGal with an average of -42 mGal. A first order polynomial was used to approximate the regional anomalies in the area. The residual gravity anomaly map shows anomalies that range in value from -32 to +20 mGal. 2.5-D modeling of the residual gravity anomalies suggests that the area has a horst and graben structure, with the grabens being as large as 60 km in width and filled with sediments that are up to 4.5 km thick. Results also suggest the existence of high-density rocks of basic composition at depth. The general indication of the structure of the Gongola arm of the Benue trough is that it is a half graben (width ca 60 km) bounded by normal faults.

Global Journal of Geological Sciences Vol.3(1) 2005: 61-69