DETERMINATION OF SEDIMENTARY THICKNESS OF ONITSHA AND ITS ENVIRONS, SOUTHEASTERN NIGERIA USING AEROMAGNETIC DATA

Abstract

Determination of the sedimentary thickness of Onitsha and its environs, southeastern Nigeria using aeromagnetic data was carried out in order to ascertain the sedimentary piles across the area for possible hydrocarbon accumulation. The study area is situated between latitude 6000lN to 6030lN and longitude 6030lE to 7000lE. The aeromagnetic data sheet 300 was acquired from the Nigerian Geological Survey Agency (NGSA) for the study and has an area extent of 3025 km2. The acquired data was processed and analyzed using Geo-softwares (Oasis Montaj, Surfer- 32 and GeoRose) for both qualitative and quantitative interpretation in order to produce maps and models. The anomalies identified were analyzed using the half-slope method. The result from the qualitative interpretation shows high magnetic intensity ranging from 8000 nT – 8135 nT). Th result also shows occurrence of sparse and linear contours indicating high sedimentary thickness cover. The analytical map and Rose diagram show magnetic lineaments trending in the Northeast-Southwest direction. The sedimentary thickness deduced ranged from 3.06 km – 12.41 km with an average 6.63km. The sedimentary thickness map reveals that the area has a high sedimentary thickness around the Northern-Eastern regions of the study area and also indicates the areas of uplift and depression. The study concludes that the area has a high sedimentary cover, which may possibly favour hydrocarbon generation.