Upper Paleozoic evaporites of southeastern Canada

The Paleozoic fold belt in Atlantic Canada forms the northeastern part of the Appalachian region of North America. During the waning stages of the Middle Paleozoic Acadian orogeny, folding, faulting, uplift and granitic intrusion occurred. The highly fractured basement subsided forming a complex series of northeast-trending horst and graben structures. In this area of regional downwarp, evaporite deposits of two ages were deposited. Minor salt deposits containing glauberite accumulated locally and are preserved as part of continental sequences in Horton Group rocks of late Tournaisian to possibly early Vise'an age. The overlying Windsor Group (middle to late Visdan age) contains thick deposits of salt, and is the only Late Paleozoic marine sequence in southeastern Canada. The Horton Group evaporites are interpreted as local playa lake deposits. Exploratory drilling has con.rmed the occurrence of these evaporites in four diferent areas, but the deposits are not considered to be of economic importance. Temporary tectonic stability, abnormally high temperatures, a nearly land- locked marine setting and semiarid conditions resulted in the rhythmic deposition of Windsor Group evaporites over a wide area. The Windsor Group evaporites, preserved as outliers in New Brunswick and Nova Scotia and in a northeast- trending basin beneath the Gulf of St. Lawrence, are erosional remnants of a much larger evaporite basin. %e salt occurs as bedded deposits or within flow structures that vary in thickness fiom a few centimetres to over 4573 m in structurally thickened sections. The variation in local thickness of these rocks is a function of both environment of deposition and tectonism. In some areas the salt is pure enough to be mined and, locally, contains significant amounts of potash. Some of these mines have the potential for development of underground storage sites for hydrocarbons and industrial waste.