SALT TECTONICS IN A STRIKE-SLIP BASIN: BAY ST. GEORGE SUBBASIN, NEWFOUNDLAND, CANADA (Invited Presentation)

The late Paleozoic Maritimes Basin comprises a series of partially connected and isolated fault-bounded subbasins trending generally northeast across much of Atlantic Canada. One such subbasin, the Bay St. George subbasin in southwest Newfoundland, shows significant folding, faulting, and salt tectonism that is visible along coastal outcrops onland and in geophysical datasets offshore. Most previous structural analyses in the Maritimes Basin predate advances that have revolutionized strike-slip and salt tectonics; data integration is key to unravelling the complex deformation history of the area.

Seismic reflections can be related to bedrock structures visible on the bathymetric surface and linear anomalies on the aeromagnetic maps. Three groups of peaks are picked on seismic profiles, tied to bedrock structures visible on the bathymetric surface and linear anomalies on aeromagnetic maps, and correlated with known evaporite-bearing Mississippian stratigraphy. In the Bay St. George subbasin mapped structures include salt-cored anticlines, salt-expulsion minibasins, salt welds, positive flower structures, and a tectonic wedge. Two large salt-cored anticlines parallel the NE–SW subbasin axis trend. Minibasins adjacent to these salt structures show angular unconformities and drastic sediment thickness variations suggesting that salt was moving early in the subbasin history. In the central offshore, a tectonic wedge inserted to the west cuts across suprasalt structures. Salt movement, however, could have continued during wedge insertion. In the north and south extremities of the subbasin, the locus of salt expulsion migrated southeast; in the central subbasin, where the subbasin was affected by the inversion process, the locus of expulsion migrated northwest. The Maritimes Basin contains significant known and potential resources of evaporites, coal, oil, and natural gas, the distribution of which are strongly influenced by both strike-slip and salt tectonics.