The Effects of Salt Tectonics in the Evolution of the Jeanne d’Arc Basin, Newfoundland, Canada

Massimo Bonora, Wicaksono Prayitno, Meryl Bonelli, Clara Girona, Thomas P. Buerkert, and Kim Zauderer
Repsol E&P Canada Ltd, The Woodlands, TX.

The Jeanne d’Arc Basin is the largest of a series of Mesozoic rift basin that developed on the Grand Banks of Atlantic Canada as a result of the breakup of Pangea and the opening of the North Atlantic Ocean.

The Grand Banks basins were all affected by three stages of rifting followed by associated thermal subsidence. Initial rifting occurred in the Upper Triassic-Lower Jurassic, prior to spreading of the North Atlantic towards the Grand Banks area. During this initial phase a thick succession of evaporites (Argo Fm) where accumulated in the majority of the early rift basins of the Grand Banks area as well as the neighboring basins along the Nova Scotian Margin.

Different salt tectonic structural styles have long been described in the Scotian Basins and in the adjacent southern Grand Banks basins by various authors. In the Jeanne d’Arc basin although salt diapirs have been recognized and salt movement is believed to be in part responsible for some of the deformation, most of the syn-depositional deformation is still widely attributed to rift-related crustal extension with salt and shale units only playing a passive role in the deformations.

In contrast, we believe that gravity-driven processes (i.e. salt driven tectonics) made possible by mobilization of the thick Argo salt, plays a an significant role in the Jeanne d’Arc sub-basin development, with important effects on sediment transport and deposition, trap development and hydrocarbon maturation.

In this work (using data from the Badger 3D seismic courtesy of WesternGeco) we show that allochthonous salt stock canopies, similar to those observed in the neighboring basins, have developed in the central part of the Jeanne d’Arc basin. These allochthonous salt bodies seem to be generated by the influx of thick Upper Jurassic to Lower Cretaceous sediments; but due to poor seismic imaging, little is known about early post-rift salt mobilization and original salt distribution.

What is clear is that these salt bodies have been emplaced during the Upper Jurassic/Lower Cretaceous time (probably related to the second North Atlantic Rift Stage), forming, in the mapped area at least two large allochthonous canopies fed by deeper feeders. These large salt bodies have subsequently collapsed, and salt in these stock canopies was displaced by Aptian to Upper Cretaceous sediment creating a series of younger mini-basins, most likely triggered by extensional movement related with the Labrador Rift Stage. During sediment loading the evacuated salt moved up and laterally to form secondary salt canopies and diapirs. Some of these diapirs are now found a few hundred meters below the seabed. In some areas, the salt is completely displaced and salt welds are identified.

Our analysis indicates that salt tectonics in the JDA basin has played an active role in the structural evolution of the basin, with significant implications on sediment distribution and hydrocarbon generation, migration and accumulation.

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.