The structure of the Rockall Trough from seismic refraction and wide-angle reflection measurements

Abstract

There are few detailed descriptions of the deep crustal structure of failed cratonic rifts and passive margins, despite their import-ance in constraining the variety of structural models invoked to account for their common structural symmetry, or gross half-graben form^1–3. Such deep crustal-structure profiles also have considerable value in defining the continent/ocean boundary, con-straining plate reconstructions, and determining the overall setting of sedimentary basin development. The Rockall Trough in the North Atlantic Ocean is a sinuous elongate bathymetric depression ~200 km wide and more than 2,000 m deep lying between Rockall Plateau and the British Isles, and the structure, nature and age of its underlying crust are disputed. In the absence of deep crustal-structure profiles, the presence of oceanic crust has been assumed because the trough has to be accommodated in reconstructions of the North Atlantic, although stretched continental crust is equally plausible. The nature of the crust is important for the precise reconstruction of the late Jurassic/early Cretaceous plate history and setting of sedimentary basins of the North Atlantic^4–8. The nature of the crust beneath the trough as well as the structure, thickness and composition of the sedimentary cover is also relevant to oil exploration. Here we report the first observations of deep crustal structure across the Rockall Trough and its margins from seismic refraction and wide-angle reflection profiles. Our results show that the northern Rockall Trough is underlain by highly stretched continental crust, and not by oceanic crust as previously postulated.