TREND SURFACE ANALYSIS AND INTERPRETATION OF GRAVITY DATA FROM THE MIDDLE NIGER BASIN, NIGERIA
TREND SURFACE ANALYSIS AND INTERPRETATION OF GRAVITY DATA FROM THE MIDDLE NIGER BASIN, NIGERIA
No Thumbnail Available
Date
1991-03
Authors
LIKKASON, OTHNIEL KAMFANI
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
A set of Bouguer gravity values from the Middle Niger (Nupe) Basin is fitted with polynomial surfaces of various degrees
and these and the associated residuals are contoured. On the basis of close correlation of residuals from the fourth degree surface with geologic structures of the area, and the fact that the fourth degree corresponds with the point which is closest to
the discontinuity on the plot of variances against degrees of polynomial surfaces, giving the optimum degree that fits the data (Zeng, 1989), it is concluded that this surface best represents the regional field
of this area. A prominent long wavelength anomaly on this surface is interpreted to be an upper mantle plume 2-4km above an average Moho depth of 35km. The associated residuals from this surface show prominent positive anomalies of the order of 15mGals. A 3-dimensional computer interpretation attributes these anomalies to shallow sources as well as a high density metamorphic
basement of schist or amphibolite composition. Basic and ultrabasic rocks are considered possible sources of the prominent residual Bouguer anomalies. The negative anomalies are attributed to Older Granite suites that predominate the area and to the thick Cretaceous sediments where such are considered significant. The contour patterns at the boundaries of the basin do not
indicate faulting. This does not, however, rule out faulting at
the contacts of the basin in view of the available evidence of
major and minor faults indicated from Landsat imageries, drilling
Description
A THESIS SUBMITTED TO THE AHMADU BELLO UNIVERSITY I PARTIAL FULFILMENT FOR THE AWARD OF MASTER OF SCIENCE DEGREE IN APPLIED GEOPHYSICS
Keywords
TREND, SURFACE, ANALYSIS, INTERPRETATION, GRAVITY, DATA, MIDDLE, NIGER BASIN, NIGERIA