A low amplitude negative gravity anomaly occurring close to the centre of the Willippa anticline, and previously surveyed in some detail by MESA, has been modelled and interpreted by a geophysical consultant to Frontier Exploration Ltd in order to estimate the shape of and depth to the top of the causative low density body. To assist the interpretation, a comparison was also made of the local Bouguer gravity contour map and a pseudo-structural section derived from a corresponding newly prepared surface geological map.