Abstract

Abstract: The Devonian Solund Basin in SW Norway is the only Old Red Sandstone basin in the Scandinavian Caledonides from which volcanic rocks have been described. These rhyolitic lavas yield a concordant ID TIMS U–Pb zircon age of 439 ± 1 Ma (Early Silurian) interpreted as dating the crystallization of the rhyolite, and are thus too old to be syndepositional with the Devonian sedimentary rocks. This new age constraint, combined with field observations, suggests that the volcanic rocks form part of a 30 km2 landslide of rhyolite, granite, gabbro and metasedimentary rocks, rather than extension related volcanism as previously suggested. The landslides show an inverted stratigraphy with respect to the nearby Solund–Stavfjord Ophiolite Complex and its overlying volcanic arc, which was formed immediately prior to obduction of Caledonian exotic terranes onto Baltica. The dated rocks thus appear to record the youngest pre-collisional volcanism in the Scandinavian Caledonides. Tectonic models involving Devonian Old Red volcanic rocks in the Scandinavian Caledonides must thus be revised.

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