Equatorial Baltica in the Vendian: palaeomagnetic data from the Sarek Dyke Swarm, northern Swedish Caledonides

In this paper, we present Vendian palaeomagnetic data for continent Baltica, based on results from the 608 +/- 1 Ma old Sarek Dyke Swarm in northern Sweden. The dykes sit in the Sarektjahkka Nappe of the Seve Nappes, which were thrust eastwards over the Baltic craton during the early Palaeozoic Caledonian Orogeny. In spite of long transport distances as well as deformation and metamorphism in the garnet amphibolite grade along the margins of the nappe, its interior exposes very large volumes of intact diabase dykes and thermally metamorphosed sediments. Both geological and palaeomagnetic data demonstrate that the main component of the NRM is carried by single-domain magnetite in the dykes and was acquired during post-intrusive cooling. The dykes are tilted, but the orientation of the main magnetic component coincides within one degree with the rotation axis for restoring the bedding of the hosting rocks to the palaeohorizontal. This structural correction consequently does not affect the magnetic inclination, and the calculated palaeolatitude of 1degrees is very robust. The Sarek palaeomagnetic data put Baltica, on the Equator during the Varanger glaciations. (C) 2003 Elsevier B.V. All rights reserved