Development of extension over time during rifting of the Jeanne d’Arc Basin, offshore Newfoundland

McIlroy, Caroline (2014) Development of extension over time during rifting of the Jeanne d’Arc Basin, offshore Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Jeanne d’Arc Basin formed during multiple rift events and passive subsidence associated with the opening of the North Atlantic Ocean through the Mesozoic and Cenozoic. It is typically reported that crustal thinning is greater than extension due to brittle faulting. Although there have been measurements of total extension from fault analysis along single transects across the basin or from change in crustal thickness, quantifying the extension using detailed fault analysis for the different rift phases and how it changes throughout the basin has not previously been attempted. 2D and 3D seismic data and well data were used to create time structure maps at the start of each rift phase. These maps were restored to their position before each rift phase using beta values derived from fault heave extension estimates. The restored maps were compared with restorations produced using change in crustal thinning to measure beta. It was established that fault heave measurements from the 2D data underestimate extension by approximately 50% when compared with measurements from the 3D data. This observation was incorporated into the extension estimates. Extension was most significant during the Late Triassic to Early Jurassic rift phase in the Jeanne d’Arc Basin. The total amount of extension measured using fault heaves in this study corresponds closely with the total amount of extension measured using change in crustal thickness in the regional North Atlantic deformable plate model, for total extension with beta values generally around 2. This indicates that stretching is uniform with depth in this area. This detailed study can be used to refine the regional North Atlantic deformable plate model. Time structure maps of the syn-rift and post-rift thickness were created for a larger area extending into the northern Jeanne d’Arc Basin and the southern Orphan Basin. The post-rift thickens dramatically northwards to overlie thin syn-rift in the north of the area. It is suggested that depth dependent extension caused by ductile flow of continental mantle lithosphere towards the rift axis led to large scale thermal subsidence in this area.

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