Crude quantitative estimates of the original northwest–southeast dimension of the Sudbury Structure, south-central Canadian Shield

The Sudbury Structure, central Ontario, is the remnant of a large cryptoexplosion structure whose oval map pattern (diameter ratio 2.2) differs markedly from the circular outline of many meteorite impact craters. Finite-element modelling shows that (i) the original northwest–southeast dimension could have been 2–3 times larger than at present and (ii) the vertical dimension of the Sudbury Structure was > 10 km before tectonic deformation. Although our structural analyses furnish data that govern the geometric modelling, large uncertainties remain where the state of tectonic deformation is poorly constrained. A series of two-dimensional models was made to cope with kinematic uncertainties and to assess their effect on the estimates of the geometry of the original Sudbury Structure.