Pdaeomagnetic survey of the (Palaeozoic) Shelve inlier and Berwyn Hills, Welsh Borderlands

summary . This study completes palaeomagnetic coverage of Lower Palaeozoic igneous rocks within the Welsh Borderlands, and includes data from Ordovician (Llanvirn and Caradoc) volcanics yielding positive fold tests and palaeomagnetic poles in agreement with other British Ordovician studies. A wide range of Late Ordovician-Lower Silurian (Llandovery) intrusions yield directions of magnetization unlike any previously identified from Lower Palaeozoic rocks of Britain, but highly stable to thermal and af demagnetization, and include a reversal of magnetization. The collective results define a large movement relative to the dipole axis over a period of less than 10 Ma between c .445 and 425 Ma; part of this movement can be explained in terms of complex rotations of the British region during late Ordovician and early Silurian tectonism within the paratectonic Caledonides.