Provenance of the pre-Devonian sediments of England and Wales: Sm-Nd isotopic evidence

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Abstract
ɛ Nd values and clast petrography of the Longmyndian sediments of Shropshire indicate a provenance dominated by juvenile (high ɛ Nd ( t )) Uriconian volcanic sources, but with an increasing detrital contribution from older (low ɛ Nd ( t )) metamorphic sources up-section. By contrast, most Lower Palaeozoic strata of England and Wales have low ɛ Nd ( t )) values, typical of sediments derived from long established continental crust. The Sm–Nd isotopic evidence suggests that Avalonia received sediment from an adjacent large continent in the Cambrian to Lower Ordovician and in the Silurian. Ordovician and Silurian volcanicity supplied juvenile detritus only during and shortly after active volcanism.