Delineation of Basin Geometry within Parts of Northern Anambra Basin, Nigeria: An Aeromagnetic Approach

Abstract

Total field aeromagnetic anomalies over Ankpa and environs Northern Anambra basin (sheets 269, 270,288 and 289) were acquired, digitized and analyzed with a view of mapping the predominate geologic structures, demarcate the basin geometry, estimation of the basal depth (sedimentary thicknesses) and produce an ideological magnetic potential map of the area. The residual map is noticeable by spirogyra and uneven shaped bodies characterized by different magnetic values ranging from lows, highs and medium magnetic intensities within the range of -91.50nT to 41.60nT. qualitative study of the residual anomalous map shows the presence of basement rocks intrusion around north and south-western portion of the area. Downward continuation map reveals the structures are orienting in NE-SW and NW-SE direction and these conforms with trend of structures in Northern Anambra basin and by extension lower Benue trough. Result from quantitative interpretation shows two basal depth sources, the deeply seated magnetic source which ranges from 1.76 to 4.50km and the near surface seated magnetic sources, ranging from 0.50 to 1.76km. The shallower magnetic basal depth sources are believed to be as a result of basement intrusion or magnetized ore bodies inside the sedimentary infillings. 3-D surface map reveals a depression at the middle part of the study area indicating thicker sediments which trend northwest-southeast direction while the eastern and southern parts have shallower sedimentary thicknesses. The high pass filter map depicts anomalies between the range -16.0nT and 8.7nT.

Keywords:Spectral Analysis, Magnetic Potential, Basin Configuration, High-pass-filter, Downward-Continuation.

DOI: 10.7176/JEES/11-4-04

Publication date: April 30^th 2021