A fault zone coinciding with a Middle Jurassic, ultramafic dyke exposed in the Picton Quarry in Prince Edward County, Ontario, is marked by steeply dipping, generally east–west-striking fractures. The dyke has been affected by faulting, as evidenced by the presence of subhorizontal slickensides on fractures cutting the dyke rock. This discovery constitutes the first known example of Middle Jurassic or younger faulting having affected Paleozoic strata of southern Ontario and indicates that the structural and tectonic history of the region is more complex than commonly believed.

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