Applications of Spectral Analysis and 2D Modeling of Gravity Data for Depth to Basement Estimation in Parts of South Eastern Nigeria.

This study interprets gravity data in parts of southeastern Nigeria using spectral analysis and 2D modeling. The study area is bounded by Latitudes 5°N 30' to 6°N 30' and Longitudes 7°E 0' to 8°E 0'. The Bouguer gravity data was obtained from the Nigerian Geological Survey Agency (NGSA) in Geosoft grid file format. The study uses the spectral analysis method and 2D modeling with GM SYS to estimate the average depth of the sedimentary strata and the basement from the Bouguer anomaly map. The data sets cover the southern part of the Anambra basin and the northern Niger Delta complex. Regional-residual separation was applied to the Bouguer gravity data through the polynomial fitting of the first degree. This gave rise to the residual and regional maps. Further filtering actions accentuated the subtlest anomalies peculiar to the study area. Spectral analysis results reveal two depth models: deep source (D1) and shallow source (D2). The deep source represents depths within the basementrelated sources, while the Shallow source is associated with shallow-related gravity sources. D1 varies from 1.50 km to 4.02 km with an average value of 2.95 km, while D2 varies from 1.91 km to 0.514 km with an average value of 1.50 km. The thickest depth of the Modelled cross-section is at about 6845.62 m, which is within the tertiary recent sediment with clayey sands and shale extending beyond the study area. The average or actual sedimentary thickness of 2.95 km suggests that the area will be plausible for hydrocarbon exploration. The thickest sedimentary cover represents density variation in sedimentary rock of the basin, which occurs at the southern part of block 4 (Okigwe). [ABSTRACT FROM AUTHOR]