Interpretation of gravity data of Hadejia and its environs using tilt angle derivative method

Abstract

Tilt angle derivative method was applied to satellite gravity data of Hadejia and surrounding for subsurface delineation. The study area falls in the contact region between Chad sedimentary formation and the crystalline basement complex in the Northeastern Jigawa state and Northwestern Yobe state of Nigeria which lies between latitude 8⁰N - 14⁰N and longitude 11⁰E -13⁰E. Satellite gravity data of the area was obtained from Bureau Gravimetrique International (BGI). The Bouguer correction was already applied on the data and the Bouguer graph was plotted using surfer software. Low gravity anomalies are detected in the dominant part of the map with its minimum value appearing in the south-eastern and north-eastern part of the map. The low anomalies are probably due to existence of thick sedimentary sections in these parts of the study area. Edges and Depth of the source of anomaly were also derived from the tilt angle. The tilt angle ranges between -3.5 degrees to 3.5 degrees with edges(boundary) at zero. This describes the edges/boundaries between the two formations. The method also revealed that the area has a depth ranging between 2km to 18km. The sedimentary areas were identified and isolated. Those areas with low anomaly and high depths are sufficient for hydrocarbon accumulation.