Deep structures and breakup along volcanic rifted margins: insights from integrated studies along the outer Voring Basin (Norway)

Three-dimensional multichannel seismic survey and well data allows a deeper insight into rifting mechanisms and crustal structure of the Norwegian volcanic rifted margin. A surprising high-velocity lower crustal dome marked by a strong amplitude reflection (T Reflection) is described below the north Gjallar Ridge (NGR) near the volcanic plateau formed during the late Paleocene-Early Eocene breakup. Faulting along the NGR occurs during Early Campanian-Paleocene and is controlled by the crustal dome. The T Reflection was previously related to either the top of mafic underplated crust or soft lower crust updomed during the continental breakup. The influence and timing of the crustal dome on the basin structure shows clearly that the dome predates the continental breakup. Based on the structural relationship and the results of the modelling, it is therefore concluded that the T Reflection does not necessarily originate from an anomalous Tertiary magmatic event related to the breakup (underplated material), but could be also partly attributed to pre-breakup mafic material or/and inherited, high pressure granulite/eclogite rocks in the continental domain. (C) 2004 Elsevier Ltd. All rights reserved.