Aeromagnetic Data Interpretation for Identifying Sedimentary Piles/cover Within Onitsha and Environs, South-East Nigeria Using Half Slope Method

This study presents an interpretation of aeromagnetic data to identify sedimentary cover within Onitsha and its environs, southeastern Nigeria using the half slope method. It lies within latitudes 6⁰00¹N to 6⁰30¹N and longitudes 5⁰30¹E to 6⁰00¹E, with an area of 3025 km². The geology of the study area is predominantly the geology of the Niger Delta Basin. The aeromagnetic data sheet 300 was acquired from the Nigerian geological survey agency (NGSA). The Aeromagnetic data obtained were subjected to various data preprocessing enhancement and geophysical techniques namely; contour mapping, shaded relief imaging, analytic signal, Rose diagram, and Half Slope analysis. Qualitatively, the results showed that the magnetic intensity ranges from 8000nT to 8130nT within the total magnetic intensity (TMI) map whereas, in residual anomaly map, the magnetic intensity ranges from 0nT to 120nT across the area. Also, the result from the analytical map, shaded relief map and Rose diagram reveals a major lineament of northeast to southwest (NE-SW) trend and minor trends of northwest-southeast (NW-SE) and west – east (W-E) across the study area. Quantitatively, the Half Slope method analysis reveal the sedimentary cover to range from 4.32km to 11.2km with an average of 7.476km. The sedimentary thickness map shows that the study area has predominately of high sedimentary cover. The findings underscore the efficacy of aeromagnetic methods in deducing sedimentary cover/pile/thickness, with implications for hydrocarbon accumulation and mineral exploration.