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A new conceptual model for the structural evolution of a regional salt detachment on the northeast Scotian margin, offshore eastern Canada

¹ Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 4J1; steven.ings{at}dal.ca
² Geological Survey of Canada (Atlantic), Natural Resources Canada, Bedford Institute of Oceanography, P.O. Box 1006 Dartmouth, Nova Scotia, Canada, B2Y 4A2

Steve Ings is a Ph.D. candidate in earth sciences at Dalhousie University in Halifax, Nova Scotia, Canada. Steve received a B.Sc. degree in geology from Saint Mary's University in 2002. Steve's research is focused on numerical modeling of margin-scale salt tectonic systems and the application of these models to geological case studies.

In collaborative research projects with industry and university research groups over the past decade, John Shimeld has interpreted a variety of two- and three-dimensional seismic data sets acquired offshore eastern Canada, including the Labrador and Scotian margins. His research interests include polygonal faulting, shallow- and deep-water depositional systems, and salt tectonics. He received a B.A.Sc. degree from the University of Waterloo in 1991 and an M.Sc. degree from Dalhousie University in 1994.

In this study, we examine, using seismic data in conjunction with numerical modeling, a regional-scale salt detachment and associated synkinematic sediments from the Scotian margin, offshore eastern Canada. This part of the Scotian margin is characterized by an up to 4.5-km (2.8-mi)-thick and approximately 175-km (108-mi)-long synkinematic wedge of Jurassic sediments with internal sigmoidal, landward-dipping reflectors. The synkinematic wedge is laterally extensive, encompassing an area of approximately 30,000 km² (11,600 mi²), and soles into an interpreted salt detachment.

The Jurassic synkinematic wedge, which is interpreted to have formed as an open-ended allochthonous salt nappe, was loaded by prograding sediments during the Jurassic. This loading squeezed the salt seaward and caused the overlying sediments to undergo extension and gravity spreading and gliding, detaching on the salt sheet. The open-ended nappe model provides a mechanism for producing a large amount of extension with very little compensating contraction.

Numerical model results indicate that high rates of extension, detaching on even a thin salt layer, can result in similar sigmoidal, landward-dipping strata. Based on the numerical modeling and seismic interpretation results, we propose a new conceptual model for the Jurassic–Paleogene structural evolution of the study area; this model may also have implications for other passive-margin salt basins with regional salt detachments.

This article has been cited by other articles:

				C. Krezsek, J. Adam, and D. Grujic Mechanics of fault and expulsion rollover systems developed on passive margins detached on salt: insights from analogue modelling and optical strain monitoring Geological Society, London, Special Publications, January 1, 2007; 292(1): 103 - 121. [Abstract] [Full Text] [PDF]