The Windermere Supergroup of NW England was deposited in a foreland basin on the northern margin of Eastern Avalonia and preserves an almost complete Ashgill to Pøídolí sequence. It was ideally positioned to record provenance changes associated with the closure of the Iapetus Ocean. Petrographic, geochemical and Nd isotopic parameters show distinct and concordant temporal trends. The late Ashgill to early Llandovery is characterized by progressive hemipelagic dilution of material derived from the underlying Borrowdale Volcanic Group. From the Llandovery onward, petrographic and geochemical data indicate supply from a recycled orogen source: input from the Scandian orogen may be inferred. No conclusive evidence is recorded of Laurentian input into the basin. By the late Wenlock a unified sedimentary system probably spanned the Iapetus ocean. An abrupt reversal in provenance trends towards the end of the Ludlow records basin inversion, the occlusion of the Iapetus seaway and concomitant cannibalization of older foreland basin sediments. Provenance data derived from upper Wenlock to Pøídolí sediments aid the characterization of marine foreland basins.