Cambrian palaeomagnetic data from Baltica: implications for true polar wander and Cambrian palaeogeography

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Abstract
A reliable Early Cambrian ( c. 535 Ma) and a preliminary Late Cambrian ( c. 500 Ma) palaeomagnetic pole from Baltica (Sweden) overlap within uncertainty, and they are also broadly compatible with Vendian ( c. 583 Ma) palaeomagnetic data. Apparent polar wander for Baltica amounts to less than 25° between 583 and 500 Ma and, therefore, negates recent speculations that the Earth tipped 90° during the Early Cambrian (true polar wander). Throughout Vendian and Cambrian times, Baltica lay at southerly latitudes ( c. 30–60°S). Baltica was geographically inverted, and present-day northern Baltica faced the NW margin of Gondwana which covered the south pole. Laurentia-Eastern Baltica and Laurentia–West Gondwana were separated by the Iapetus Ocean, while the Ægir Sea separated Western Baltica from the Taimyr region of Siberia. During the Cambrian Baltica probably moved eastward along the Gondwana margin, and by c. 515–520 Ma subduction in the Ægir Sea was initiated. A major event is recognized in Late Cambrian or Early Ordovician times ( c. 500–478 Ma) when Baltica must have undergone a 55° counter-clockwise rotation in c. 22 million years (3°/Ma). We relate this to the early Caledonian Finnmarkian Orogeny which involved arc–continent collision following subduction.

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