Evidence for early Tertiary remagnetization of Devonian rocks from the Orcadian Basin, northern Scotland, and associated transcurrent fault motion

Abstract

The moderately inclined, reversed field vectors exhibited by many of the Devonian rocks of the Orcadian Basin are reinterpreted as resulting from a regional, early Tertiary remagnetization event in northern Scotland, relating to the emplacement of the British Tertiary Igneous Province. The nature of the remagnetization appears to be primarily chemical and may relate to the circulation of magma-derived hydrothermal fluids in the porous Old Red Sandstone formations. Fine-grained matrix hematite appears to be an important carrier of this remagnetization component, but other secondary opaque minerals also contribute to the magnetizations of certain sites. Although Orcadian Basin rocks are currently at some distance from the nearest Tertiary igneous center (Skye), geologic and tectonic evidence may allow for southward translation of the Skye igneous center in earliest Tertiary time.