The Creighton granitic pluton, which is located along the southern margin of the Sudbury Basin within the Southern Province, was affected by a local deformation event prior to the widespread brecciation which accompanied the formation of the Sudbury Basin ('Sudbury brecciation event'). Detailed mapping has shown that foliation trends within the eastern portion of the Creighton pluton form a complete elliptical loop parallel to the contact of the pluton. Within the foliation loop is a large deformed inclusion. The deformation within the inclusion is very in homogeneous, and two sets of deformation structures, both of which predate the Sudbury brecciation event, can be recognized. The structures within the inclusion are totally absent from lithologically similar rocks only a few kilometres away, outside the pluton. The structure of the pluton and the inclusion indicate that the pluton was forcefully emplaced and that the inclusion was deformed by constriction during the emplacement of the pluton. The granitic rocks of the pluton must have been rigid enough to transmit stresses which were capable of deforming the rocks of the inclusion, and therefore it appears likely that the Creighton pluton was emplaced as a diapir.