Late Cretaceous basalts from Rosemary Bank, Northern Rockall Trough

Abstract

A borehole drilled on the top of Rosemary Bank (Rockall Trough, NE Atlantic), recovered 16.72m of basalts and volcaniclastic sediments beneath a 1.53m thick limestone with basalt clasts, biostratigraphically dated as late Maastrichtian. Magnetostratigraphic data, constrained by the biostratigraphy, indicate extrusion of Rosemary Bank basalts took place during magnetochron C31R (71–69 Ma), or possibly earlier. This provides definite proof of pre-Tertiary volcanism in the Rockall Trough, and indicates that the onset of activity in the North Atlantic Igneous Province took place at least 7 Ma earlier than the postulated arrival of the Icelandic plume at 62 Ma. Geochemical and isotopic data suggest there was an enriched component to the magmatic source. Present data cannot resolve whether the Rosemary Bank basalts are an early manifestation of the Icelandic plume, whether they were associated with a different plume, or whether they were derived from enriched upper mantle without a significant thermal anomaly.

An overview of the Upper Palaeozoic–Mesozoic stratigraphy of the NE Atlantic region

“…Cretaceous strata are probably widespread throughout the Faroe -Shetland -northern Rockall region, although their full extent in the deep-water basins is obscured by Palaeogene volcanic rocks (Figs 4 & 14). The northern Rockall Basin also includes the Late Cretaceous volcanic seamounts of Rosemary Bank and Anton Dohrn (Jones et al 1974;Morton et al 1995) (Fig. 4).…”

“…The volcanic seamounts of Rosemary Bank and Anton Dohrn have been dated as Late Cretaceous on the basis that upper Maastrichtian limestone with basalt clasts is preserved on the top of Rosemary Bank (Morton et al 1995), whereas unmetamorphosed Maastrichtian chalk is preserved in vesicles in lavas from the Anton Dohrn Seamount (Jones et al 1974).…”

The onset of the North Atlantic Igneous Province in a rifting perspective

“…1). Smaller-scale igneous activity preceded these main periods in, for example, the N Rockall Trough (Morton et al 1995;O'Connor et al 2000), continued subsequently in parts of the NAIP area for tens of millions of years (e.g. Tegner & Duncan, 1999;O'Connor et al 2000;Tegner et al 2008), and is continuing on Iceland and on the island of Jan Mayen (e.g.…”

“…Morton et al 1995 andO'Connor et al (2000) and references in these papers. Bergerat & Angelier, 1996).…”

Geometry and growth of sill complexes: insights using 3D seismic from the North Rockall Trough

“…1) as well as smaller centres throughout the basin (Stoker et al 1993). The Anton Dohrn and Rosemary Bank centres are generally believed to be Late Cretaceous in age with Maastrichian chalks being recovered from their summits (Jones et al 1974;Morton et al 1995), but the Darwin centre has to date only provided Palaeocene ages (Tate et al 1999). Associated with the extrusive igneous material, seismic data suggests an Early Tertiary age for the Rockall Trough sills, with intrusion occurring mainly in the Mesozoic sediments ( Fig.…”