Cj. Underwood et al., HIGH-RESOLUTION CARBON-ISOTOPE STRATIGRAPHY OF THE BASAL SILURIAN STRATOTYPE (DOBS LINN, SCOTLAND) AND ITS GLOBAL CORRELATION, Journal of the Geological Society, 154, 1997, pp. 709-718
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
.