Choice of suitable regional and residual gravity maps, the case of the South-West Cameroon zone

Abstract

The quantitative interpretation of gravity anomalies due to shallow structures needs separation between long wavelength anomalies (regional anomalies) and short wavelength anomalies (residual anomalies). The regional-residual field separation can be carried out using the polynomial method. In this case, the so-called regional field of order n is treated as a polynomial of degree n. The present study shows that the degree n must vary between a smallest value nmin and a maximum value nmax. This article presents a method to process gravity data that allows determination of nmin and nmax for a given study area. We apply the method to gravity data of the South-West Cameroon zone. In this chosen study area, we find that regional anomaly maps of orders ranging from 1 to 9 and residual anomaly maps of orders ranging from 1 to 8 can be used for suitable interpretation. The analyses show that one may need residual anomaly maps of several orders to perform satisfactory quantitative interpretation of the different intrusive bodies found in a given area.

Keywords

• gravity
• regional anomaly
• residual anomaly
• upward continuation
• correlation factors
• intrusive body