HIGH-RESOLUTION CARBON-ISOTOPE STRATIGRAPHY OF THE BASAL SILURIAN STRATOTYPE (DOBS LINN, SCOTLAND) AND ITS GLOBAL CORRELATION

Since its designation as the Global Stratotype Section and Point (GSSP ) for the base of the Silurian System, the choice of Dob's Linn, South ern Scotland, has received criticism due to the difficulties of relati ng its well-constrained graptolite biostratigraphy to shallow-water se quences elsewhere. Kerogen samples from across the Ordovician-Silurian boundary interval at Dob's Linn have yielded carbon stable-isotope si gnatures consistent with those recorded elsewhere, in particular showi ng a clear positive delta(13)C excursion in the terminal Ordovician. T he architecture of the delta(13)C curve from Dob's Linn enables very h igh-resolution stratigraphic subdivision and direct correlation betwee n the deep water Dob's Linn section and time-equivalent carbonate shel f deposits. An integrated stratigraphic scheme using isotope stratigra phy and biostratigraphy of graptolites, conodonts and shelly faunas ha s been constructed. This direct correlation shows that the shallow wat er successions, including the former stratotype candidate at Anticosti Island, are generally incomplete, with hiatuses related to the rapid sea-level changes during the Hirnantian stage. This confirms and great ly increases the global utility of Dob's Linn as a boundary stratotype .