Aeromagnetic, gravity, and seismic surveys in the Maritime Provinces of Canada have provided extensive new information bearing on (1) the geometry of the depositional basins, (2) the distribution and shape of the major salt masses, and (3) the sub-salt structure.

The basins and uplifts exhibit a striking geometrical relationship of east- and northeast-trending elements that strongly suggest a shear pattern. This pattern was developed during the Acadian and possibly earlier orogenies. Large crustal blocks, bounded by faults, appear to have tilted and shifted, with rapid erosion and deposition during Mississippian and Pennsylvanian times creating large prisms of sediments which differ greatly in shape, size, and sedimentary facies.

Widespread deposits of rock salt, gypsum, and anhydrite exist in the Windsor Group (Upper Mississippian) in all the Maritime basins. The saline facies is interbedded and interfingered with thin limestones, red and grey shale, and coarse red clastics, and in a few places lies directly on the basement rocks. In the anticlines, notably those of northern Nova Scotia, western Cape Breton, and southern New Brunswick, the rock salt thickened greatly in the axial region of the folds and in places pushed through the overlying rocks to the surface. This sequence of thickening of the salt within the folds followed by diapirism is similar to that of the salt anticlines of the Paradox Basin and South Persia. Little is known about the original depositional thicknesses of the saline facies, but grav ty data indicate wide differences in the amount of rock salt along the axes of the major anticlines. This may indicate the original pattern of salt deposition.

A thick section of sandstone and shale, plentiful oil shows, a basin-wide seal afforded by the evaporite section, and the large structural traps provided by the major anticlines combine to make the sub-salt Horton Group (Lower Mississippian) rocks a prime target for oil and gas exploration in these largely untested basins.

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