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The Ireland-Newfoundland and Ireland-Southern Greenland Conjugate Margins: An Inverse Deformable Plate Kinematic Model Provides New Insights Into Hyper-extended Basin Development and Prospectivity

Abstract

Unlike their well-studied cousin - the Iberia-Newfoundland margin - the evolution of the magma-poor Ireland-Newfoundland and the magma-rich Ireland-Southern Greenland conjugate pairs has been the focus of relatively few studies. A two-year research project to develop a deformable plate kinematic model for the North Atlantic between Ireland and Canada now provides us with fresh insights into the evolution of these margins and the prospectivity of their hyper-extended offshore basins.

Given the active nature of the research and debate surrounding the evolution of rifted margins, it is clear that in order to construct an accurate plate reconstruction for the North Atlantic between Ireland and Canada, a quantitative method for calculation of the amount and timing of crustal extension that is independent of any one model for rifted margin formation is required. We present an inverse deformable plate kinematic method that has been tested and refined on several conjugate pairs around the North Atlantic and Arctic margins as an independent means to quantify crustal extension and provide a technique to more accurately restore sedimentary basins to their pre-breakup geometry. The method allows for the quantification of Previous HitBetaNext Hit stretching factors for individual tectonic events or time intervals around the margin. Quantification of Previous HitBetaNext Hit by time interval employs techniques to back-strip Previous HitBetaNext Hit stretching factors for these intervals from maps of total Previous HitBetaNext Hit derived from gravity inversion and other sources. By subdividing total Previous HitBetaTop by tectonostratigraphic interval the palaeo-geometry of the offshore basins can be more accurately restored through time.

As a result of the study we have determined that there is strong evidence that very high crustal thinning factors observed in the central parts of the Porcupine, Rockall and Orphan basins are the result of hyper-extension in the latest Jurassic and Early Cretaceous. The study also found that the Hatton-Greenland magma-dominated margin has been hyper-extended due to stretching of the upper crust. Hyper-extension must have resulted in removal and erosion of much of the potential pre-rift source rocks in these basins although preservation should still be possible locally and on the basin flanks.

The new model has helped us not only to determine the amount, direction and timing of extension on the Ireland-Newfoundland and Ireland-Southern Greenland margins prior to breakup, but to identify potential source rock development at several intervals on the margins and to predict the likelihood of source rock preservation. The deformable plate kinematic model allows the pre-breakup palaeo-geometry of basins to be accurately restored and accommodates variations in extension across a margin and asymmetrical extension on either side of the margin. Restored structure maps, palaeogeography maps, reconstructed pre-rift subcrop maps showing Carboniferous and structural trends, sediment source area maps, source rock and reservoir facies maps have been used to evaluate source rock and reservoir potential and provide us with an enhanced understanding of the major controls and mechanisms for basin formation and evolution in offshore Atlantic Ireland and offshore Newfoundland and Southern Greenland. Potential reservoir development has also been correlated with the main tectonic events and their distribution can be mapped and predicted more accurately from basins restored to their palaeo-geometry.