Early opening history of the North Atlantic ? I. Structure and origin of the Faeroe?Shetland Escarpment

Abstract

Marine geophysical surveys show that the Escarpment is the buried feather-edge of a thick pile of flood basalts of early Eocene age, overlying a thinner, more widespread layer of basalts of late Palaeocene age. The Escarpment does not, therefore, define the continent-ocean boundary in the southern Norwegian Sea, but instead marks the contemporary shoreline separating terrestrially erupted basalt flows in the north from a restricted shallow-water shelf to the south. The basalts overlie 5-6 km of Mesozoic sediments, which have completely buried a large conical flat-topped seamount of similar dimensions to Anton Dohrn and Rosemary Bank. We call this newly postulated body the Brendan seamount. The Mesozoic sediments are at least as old as early Cretaceous in age, therefore precluding the possibility that the mid-Cretaceous seafloor spreading episode (supposed by some to have created the Rockall Trough) could have also created the thin crust inferred to underlie the Faeroe-Shetland Trough and Mbre Basin.

Evolution of the Vøring Volcanic Margin

“…On the other hand, Hinz et al (1982Hinz et al ( , 1984 place the continent/ocean boundary farther west, near the seaward edge of the lowermost part of the dipping reflectors, and reflector K is interpreted as an upper Mesozoic surface that existed prior to seafloor spreading. Smythe et al (1983) have interpreted the Faeroe-Shetland Escarpment ( Fig. 1) as a buried feather-edge of lower Eocene flood basalts without any relevance to the continent/ocean boundary and inferred that this was also the case for the Wring Plateau Escarpment.…”

“…The Faeroe-Shetland marginal high extends from the Faeroes to the central Jan Mayen Fracture Zone, but has a smaller relief and in general less clear seaward-dipping reflector sequences than at the Wring Plateau. The Faeroe-Shetland Escarpment is also more complex and less prominent than its counterpart to the north (Talwani and Eldholm, 1972;Smythe et al, 1983;Talwani et al, 1983). The Lofoten-VesterSlen Margin north of the Wring Plateau ( Fig.…”

“…Smythe et al (1983) suggested the marginal high is comprised of two basaltic sequences (Fig. 9) overlying pre-rift sediments.…”

Late Paleocene-Eocene Volcanic Events in the Northern North Atlantic Ocean

“…); the upper unit is equivalent to the lower part of the Balder Formation of Deegan and Scull (1977) and to the upper part of the "negative series" and the entire "positive series" of Denmark. To the north and west of the North Sea, the ash sequence has been followed seismically by well log correlation into the West Shetland Basin (Ridd, 1983;Smythe et al, 1983) and along the Norwegian continental margin as far north as Troms (Jakobssen et al, pers. comm.).…”

“…Although less precise, a late Paleocene age is given by study of pollen and spores from the intrabasaltic coal (Lund, 1983). Smythe et al (1983) have proposed that the thin overlying tuff agglomerate sequence is equivalent to the Balder Formation tuffs of the North Sea. The regional significance of this proposal is, however, questionable, since the dissimilarity of the Balder Formation tuffs and Faeroese basalts (Morton and Knox, pers.…”