U /Pb-zircon datings of Caledonian cover rocks and cover-basement contacts, northern Vestranden, central Norway

Three igneous rocks from the northemmost part of the Western Gneiss Region, west central Norway,
have been dated using the U/Pb-zircon method. Two intrusions which are confined to allochthonous
supracrustal cover units, one of them a trondhjemite dyke and the other a conformable felsic intrusion,
yielded zircon ages in the interval of 450-500 Ma. This defines the maximum age of thrusting for the
concemed cover units. One of a group of pegmatite dykes, which had intruded a basement-cover contact
and were subsequently folded by regional NE-SW trending upright folds, yielded an age of 401 ± 3 Ma.
This age sets a lower age limit for the translation of this cover nappe and an upper age limit for the
folding event. The time of emplacement of the Helgeland Nappe Complex of the Uppermost Allochthon
is also discussed.