Paleomagnetic data are presented for a variety of Ordovician rocks from two regions in Ireland: the South Mayo Trough and some Ordovician inliers of east-central Ireland. Some of these data update previous preliminary results, while others provide new information. In some instances the original remanence direction has been obscured by subsequent remagnetization.Although magnetic inclinations of the Ordovician results are mostly shallower than contemporaneous British results, poor precision precludes any reliable estimate of closure across this sector of the Proto-Atlantic ocean. Declination differences between the South Mayo Trough and British data indicate a 30° clockwise rotation of this tectonic block during the Middle to Upper Devonian.

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