An optimisation study of gravity data from the Brent crater, Ontario, Canada

The Brent crater is a topographical depression of circular shape located at 46"05' N, 78"29' W (Fig. 1) near the northern boundary of Algonquin Provincial Park in southeastern Ontario. It is approximately 3 km in diameter and 60 m deep. It was excavated in an igneous metamorphic basement within the Grenville Province of the Canadian Shield (Grieve, 1978). Millman et al, (1960) have suggested that if the material forming the lower sections of Brent crater is assumed to be breccia, the total thickness necessary account for the negative gravity anomaly should be about 1.2 km. On the other hand, Innes (1961) has shown that the zone of complete rupture may extend to 1.16 km, a depth equivalent to about one third of the crater's diameter. Taking into consideration previous studies in the area, the purpose of the present study is to compute bounds on the physical properties of the causative body, such as its density contrast, depth of burial and thickness, by applying the linear programming algorithm designed by Huestis & Ander (1983).