Geology of the Scotian Margin - Margin structural evolution

The margin off Nova Scotia formed during Late Triassic rifting and Middle Jurassic separation of the North American and African plates. Rifting produced a 200 km-wide zone of variably thinned continental crust beneath the present shelf and slope. Seismic data and studies of basin infilling and subsidence show that the continental crust was thinned by up to 50% prior to breakup and initiation of sea floor spreading. The overlying Scotian Basin is a composite of smaller rift basins bounded by long, sinuous faults. Thick salt deposits accumulated in these early rift basins, later deforming younger sequences as the margin evolved. Images of deeper crustal structure were obtained through the acquisition of several lines of deep seismic reflection data in1988-89, and show that faulting style and basin geometry vary along the margin. Thermal subsidence and crustal extension were greater to the northeast, where the thick (up to10 km) post-rift succession and numerous salt structures obscure basement and deeper structure. Magnetic anomaly data and seismic reflection characteristics suggest a transition in rifting type from a typical volcanic margin observed along the U.S. Atlantic coast to an anomalous non-volcanic margin off eastern Nova Scotia. Recent numerical modeling efforts have explained some of the observed margin geometry and subsidence patterns in terms of variations in the rifting history, heat flow and style of extension. These same factors have influenced the occurrence, trapping and maturity levels of hydrocarbons within the basin, and studies of the evolution of the margin should be linked to observations of margin stratigraphy and petroleum systems.