Palaeomagnetic Studies in the British Caledonides?V Miscellaneous New Data

Abstract

Summary Data are presented for a variety of Palaeozoic rocks from four areas in the British Isles: western Ireland (Arenig pillow lavas at Lough Nafooey, the Cambro–Ordovician Connemara Gabbros, Upper Silurian sediments of the Knocknaveen Group and Salrock Group, and intrusive rocks associated with the latter); the Ordovician of north Pembrokeshire (Trefgarn Andesitic Series, Fishguard Volcanic Series, and some basic intrusions); the Bristol District (Upper Llandovery lavas in the Tort-worth Inlier, uppermost Devonian and basal Carboniferous red sediments); and the Orkney and Shetland Islands (middle Devonian to possibly Carboniferous lavas). These provide palaeomagnetic directions of limited reliability because of restricted sampling, outcrop, or stability evidence. Three extensions of published studies are also reported. In the Hartshill Quartzite (Cambrian) the published result has not been substantiated. The contact aureole of the Arrochar Complex (Siluro-Devonian) provides a variety of stability evidence that its remanence dates from the time of intrusion of the igneous complex. The published results from Mweelrea ignimbrites (Llanvirn) are confirmed with minor modification. Considered with other published data, these new results suggest that the pole relative to Britain remained in the same position from early Silurian to Lower (or even Upper) Devonian time, and comparatively rapid polar shift took place both before and after this interval.