New isotopic age data on rocks from the Long Mynd, Shropshire

New Rb–Sr isotope data on fine-grained sediments from the Long Mynd, west of the Church Stretton Fault in Shropshire, indicate a much younger age for these rocks than has been assumed in recent literature. Well-defined isochrons, one of which corresponds to an age of 529 ± 6 m.y. with an initial 87 Sr/ 86 Sr ratio of 0.7061 ± 0.0001, put the depositional age of the Stretton Series (the stratigraphically lowest part of the sequence) at a maximum of 600 m.y.