Geophysical signature of geological units inferred from the analysis of geoid maps in Cameroon and its surroundings

The geoid is the equipotential surface of the earth's gravity field approximated by mean sea level. The use of the geoid in geophysics is illustrated in Cameroon and its surroundings, by the analysis of geoid maps obtained from the local geoid model, CGM05. The medium and short wavelength geoid components, signatures of near-surface geological units, are revealed by removing the long wavelength geoid features. These regional wavelengths are predominant on a geoid contour map. They are due to deep-seated or to near-surface large-extent structures. The regional trends are removed here by filtering, using a hybrid global geopotential model. The geophysical signatures of near-surface small-extent geological structures are therefore revealed. The results help constrain the limiting depths of some geological features of the Cameroon subsurface. These quantities are very useful for the gravity and magnetic subsurface modeling. The analysis also enables the precise mapping of the positions of some structural units and the completion of their geological and geophysical studies. An unknown geologically dense unit, never identified by any previous study, was detected near the Mamfe basin. (C) 2008 Elsevier Ltd. All rights reserved.