The Norway Basin revisited: From continental breakup to spreading ridge extinction

We re-evaluate the structure and spreading evolution of the southeastern Norway Basin (NB) based on a new high resolution aeromagnetic survey (NB-07). The survey covers a complete oceanic spreading segment from the continental-oceanic transition of the Mere margin, off Norway to the aborted Aegir Ridge. The new survey documents a transform margin, an orthogonally rifted segment and an oblique-sheared volcanic margin formed during the onset of breakup, observed from the East Jan Mayen Fracture Zone to the Faroe Platform. The detailed fabric of the NB revealed by the new data indicates that two distinct tectonic phases have reshaped the basin before the cessation of seafloor spreading and abortion of the Aegir Ridge in the Late Oligocene. After continental breakup, Phase I (from C24 to C21r, similar to 52 to 49 Ma) marks the earliest phase of spreading, probably initiated in the central and outer part of the Mere Basin. During this period, competing oceanic segments led to the formation of overlapping systems and pseudo-fault development. We observe a significant change in the NB's oceanic spreading system in the late Early Eocene and, based on observations from surrounding areas, we suggest that this is a record of a major tectonic event in the Norwegian-Greenland Sea around C21r (49-47.9 Ma). During Phase II (from C21r to C10?, 48 to 28 Ma) of NB's development, spreading rates decreased, spreading direction changed, and the number of faulting with large displacement increased leading to the formation of unexpected N-S oriented oceanic fracture zones. The fan-shaped development of the spreading system initiated around C21r (similar to 49-47.9 Ma) instead of C18-C17 (similar to 40-38 Ma) or C24 (53.3-52.3 Ma) as previously proposed. These new observations were used to re-evaluate the tectonic evolution of the Norwegian-Greenland Sea and discuss some implications on the syn- and post-breakup development of the surrounding continental margins and the evolution of the Jan Mayen microcontinent. (C) 2012 Elsevier Ltd. All rights reserved.