Abstract

To investigate the impact of orogenic inheritance on the characteristics of the North Atlantic rift system we develop new mapping methods that highlight the first-order architecture and timing of rifts, as well as the distribution of heterogeneities inherited from the Palaeozoic Caledonian and Variscan orogenies. These maps demonstrate major differences in the behaviour of the North Atlantic rift system relative to the two orogens, with the Variscan front appearing to be an important boundary: the rift cuts through the Caledonian orogen and is parallel to its structural grain to the north, whereas it circumvents the core of the Variscides to the south. In addition, rifting is protracted and polyphase with break-up being magma-rich north of the Variscan front, as opposed to the south, where a single, apparently continuous extensional event led to magma-poor break-up in less than 50 myr. Also, the North Atlantic rift system reactivates sutures corresponding to large (>2000 km) former oceans, whereas sutures of small (<500–1000 km) oceanic basins are little affected in both the northern and southern North Atlantic. These observations point to a major influence of orogenic inheritance on the characteristics of rift systems.

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