The observed amount of uplift undergone by the deepest marker horizon now exposed in the centre of a complex impact structure (Grieve et al., 1981). Based on observations at 24 impact craters developed in sedimentary rocks on Earth, the structural uplift (SU) in the centre of the crater is generally taken as 0.086D^1.03, where D is the crater diameter (Grieve and Pilkington, 1996).