SM-ND ISOTOPIC CHARACTERISTICS OF SEDIMENTARY PROVENANCE - THE WINDERMERE SUPERGROUP OF NW ENGLAND

Nd model ages of Windermere Supergroup sediments increase from the upper Ashgill to the upper Ludlow. Below the lower Llandovery, increasing t(DM) reflects mixing between the underlying Borrowdale Volcanic Group and hemipelagic detritus, possibly sourced from the Laurentian margin. The ongoing rise of t(DM) into the upper Ludlow probably reflects the growing influence of sediment sourced from the Scandian Orogen. A Pridoli drop in t(DM) is interpreted as recording the re-establishment of supply from the local Laurentian margin: north to south sediment dispersal indicating the effective demise of the Iapetus Ocean as a barrier to sediment dispersal.