Early Palaeozoic geomagnetism of Gotland

Abstract

The majority of the reef limestones and associated lithologies of Gotland are weakly magnetised and contain a complex natural remanent magnetisation, but it is established that they contain an Early Palaeozoic, probably Late Silurian, magnetisation. The Earth's magnetic field was predominantly of normal polarity, with the north pole situated near 170°E and 20°N, but it has not been possible to distinguish any occurrence of a field reversal. In addition, a few rocks show anomalous directions, which are interpreted - in conjunction with some Ordovician results - as indicating the presence in Wenlockian times of a steeply inclined NNW-SSE axis of magnetisation.