Abstract
Mid-Proterozoic Rb-Sr muscovite ages on metasedimentary boulders within the Highland Border Complex, together with Archean T DM ages on the same clasts, provide constraints on terrane movements in the Scottish Caledonides. An origin for these clasts from cratonic North America is ruled out. Combined radiometric age, T DM , and fauna1 province studies on basement materials provide a potentially productive method of determining the provenance of terranes.