Abstract

Three major seismic reflectors were mapped in the Sackville Sub-basin of southeastern New Brunswick. The ‘basal reflectors’ are believed to be derived from an interbedded sequence of Devonian volcanics and sedimentary rocks. The ‘basal Windsor reflector’ and ‘upper Windsor reflector’ represent two thick anhydrite deposits of the Mississippian Windsor Group. A thick and continuous, (hydrocarbon-prone?) Horton sequence of Mississippian age lies between the ‘basal reflectors’ and the overlying ‘basal Windsor reflector’.

The Sackville Sub-basin is believed to have formed as a pull-apart basin during the Late Devonian, and is bounded by the Dorchester, Port Elgin, Memramcook and Hastings faults, which have large normal components of movement. Transtensional forces, which created the sub-basin, are thought to be related to the rise of magma that extruded to form the sequence of interlayered volcanics and sediments represented by the ‘basal reflectors’.

The sub-basin underwent two, or possibly three, periods of transtension, during which it subsided along the boundary faults. This caused the development of free-standing bodies of water throughout the time of Albert and Windsor deposition. The sub-basin also sustained two transpressional events, represented by the basal Hillsborough and the basal Enrage unconformities. During the Pennsylvanian, regional thermal subsidence caused widespread sedimentation and overstepping of the emergent Westmorland, Port Elgin and Hastings blocks.

The Middle Sackville and Tantramar salt ridges may have originated from Windsor brines being concentrated in troughs on both sides of the Sackville Arch.