| Summary: | International audience The northern North Atlantic ocean and its adjacent continental margins have specific and unusual features: association of the ridge with a major mantle plume, a history of ridge jump and extinction, and intraplate deformation on the margins (inverted basins and compressional domes). Reconstructions of the opening of the North Atlantic ocean, on the basis of two rigid plates (Eurasia and Europe), lead to unacceptable misfits. Furthermore, plate velocities vary significantly across the Jan Mayen Fracture Zone. However, a subdivision of the North Atlantic ocean into micro-plates leads to better fits. We have developed a method for palinspastic reconstruction of the opening of the northern North Atlantic ocean, using magnetic anomalies. Instead of traditional Euler poles, we have used an iterative least-squares method, which minimizes the gaps and overlaps between conjugate anomalies. For this purpose, we have subdivided the northern North Atlantic region into a finite number of oceanic blocks, lying between magnetic anomalies and fracture zones. Minimization of the gaps and overlaps involves rigid translations and rotations of the blocks.We have tested various restoration models, (1) either on a plane that is tangent to the Earth's surface or on a sphere, and (2) assuming that either the European side of the ridge or Greenland is stationary. We thereby obtain a full pattern of displacement for all material points, allowing us to calculate mean spreading rates and strike-slip displacements along the main fracture zones. Our reconstructions show that the spreading history of the Aegir ridge was different from those of the nearby Mohns and Reykjanes ridges. The curvature of the Aegir ridge results from variations in the direction and rate of spreading. The spreading rate increased significantly between anomalies 13 and 15 (late Eocene to early Oligocene), for all ridges and particularly for the Aegir ridge (up to 52 mm/y). Furthermore, the rates were greater in the northern part of the Aegir ...
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