Utilizing Gravity Data to Assess Crustal Thickness and Stability in Southern Nigeria

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Abstract:

This research investigates the application of gravity data to determine crustal thickness and the stability of parts of southern Nigeria. Empirical relations, spectral analysis, and 2-D gravity modeling techniques were employed on the bouguer gravity data within the study area. Three empirical relations correlating bouguer gravity with crustal thickness were used to calculate crustal thicknesses. Additionally, the depth ranges to major density interfaces (basement surface, Conrad, and crustal thickness) were determined through spectral analysis of the bouguer anomalies, dividing the bouguer gravity map into thirty sections.

Two-dimensional (2-D) gravity models of the earth’s crust were constructed along three profiles trending in NE, SE, and SW directions. These models, combined with geological and geophysical information, provided correlated crustal thickness values for the study area. The results from the 2-D crustal models revealed that the upper and lower parts of the profiles exhibited a crustal thickness ranging from 28 km to 39 km. The bouguer anomaly of the study area varied from 30 mGal to 0 mGal, 40 mGal to 0 mGal, and 40 mGal to 20 mGal with the three approaches, resulting in average crustal thicknesses of 30 km to 37 km, 30.2 km to 35.6 km, and 28 km to 39 km, respectively. The three different approaches showed a good correlation in the average crustal thickness values obtained.

Based on these findings, the study area is characterized by a high crustal thickness ranging between 28 km to 39 km. Gravity anomaly profiles were modeled along lines drawn in different directions, covering distances between 230 km to 340 km. These profiles helped ascertain crustal thicknesses underlying the study area, with values ranging from 30 km to 38 km. The models identified and delineated boundaries between the Upper Crust, Lower Crust, and Mantle, characterized by densities of 2.7 g/cm3, 2.8 g/cm3, and 3.2 g/cm3, respectively.

The study indicates that the crustal thickness and density have a significant influence on the tectonic stability of the region. As the crustal thicknesses found in the study area are not located in any active plate boundaries (margins), this suggests the tectonic stability of the region. The results contribute to a better understanding of the geological characteristics and tectonic stability of southern Nigeria.

Utilizing Gravity Data to Assess Crustal Thickness and Stability in Southern Nigeria.

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