Abstract

The Cumberland basin is part of the large and deep Maritimes Basin of Atlantic Canada, interpreted to have developed at tropical latitudes in a tectonic environment of dextral strike slip. The predominantly Mississippian–Pennsylvanian basin fill includes a thick succession of Viséan evaporites of the Windsor Group. An overlying clastic succession includes, in the coal-bearing Cumberland Group, fossil forests with upright trees, preserved at the Joggins Fossil Cliffs United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site. Analysis of two-dimensional seismic profiles demonstrates that accommodation for the successions overlying the evaporites was provided by salt expulsion, which led to the development of broad open synclines separated by narrow isoclinal anticlines cored by salt. In the western part of the basin (Athol syncline), evaporites remained largely undisturbed until the Pennsylvanian, when their rapid expulsion accommodated accumulation of the thick Joggins succession. In the eastern part of the basin (Tatamagouche syncline), evaporite withdrawal began in the Viséan and continued during Serpukhovian time, providing accommodation for symmetric and wedge-shaped minibasins filled by Windsor and overlying Mabou Group strata. Only a small volume of evaporites remained to be expelled during Pennsylvanian thrusting along the southern basin margin; as a result, the Cumberland Group is relatively thin. To the north, the Black River, Wallace, and Pugwash synclines developed as minibasins having a character intermediate between the Athol and Tatamagouche synclines. Many of the halokinetic structures in the Cumberland basin are similar to those on salt-bearing passive continental margins. However, the tectonic environment in narrow fault-bounded basins encouraged vertical, rather than horizontal movement of salt and overlying sediments, and has produced characteristic inequant, oval minibasin geometries. These features may be characteristic of salt tectonics in strike-slip basins. Salt expulsion has strongly influenced the distribution of hydrocarbons and other resources in the basin.

You do not currently have access to this article.