High-Resolution carbon isotope stratigraphy of the basal Silurian Stratotype (Dob's Linn, Scotland) and its global correlation

Abstract

Since its designation as the Global Stratotype Section and Point (GSSP) for the base of the Silurian System, the choice of Dob's Linn, Southern Scotland, has received criticism due to the difficulties of relating its well-constrained graptolite biostratigraphy to shallow-water sequences elsewhere. Kerogen samples from across the Ordovician-Silurian boundary interval at Dob's Linn have yielded carbon stable-isotope signatures consistent with those recorded elsewhere, in particular showing a clear positive 13 C excursion in the terminal Ordovician. The architecture of the 13 C curve from Dob's Linn enables very high-resolution stratigraphic subdivision and direct correlation between the deep water Dob's Linn section and time-equivalent carbonate shelf deposits. An integrated stratigraphic scheme using isotope stratigraphy and biostratigraphy of graptolites, conodonts and shelly faunas has been constructed. This direct correlation shows that the shallow water 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 greatly increases the global utility of Dob's Linn as a boundary stratotype.

Carbon isotope chemostratigraphy in Arctic Canada: Sea-level forcing of carbonate platform weathering and implications for Hirnantian global correlation

“…1 in . The flat y 13 C org profile contrasts markedly, however, with our Canadian Arctic y 13 C org profiles, and those from China (Wang et al, 1997) and Scotland (Underwood et al, 1997), which show large positive isotope excursions similar to the large y 13 C carb excursion in Nevada. It would appear, therefore, that the Nevada y 13 C org profile is anomalous, and perhaps only locally significant, and as such the idea that the photosynthetic fractionation factor changed globally across the Hirnantian interval is not supported by the available data.…”

“…At Dob's Linn, Scotland, which is the Global Stratotype Section for the base of the Silurian System, a published y 13 C org curve shows rising values within the upper Dicellograptus anceps biozone (upper P. pacificus biozone of this study) and lower N. extraordinarius biozone, with a peak in the upper part of that zone, and declining values through the P. persculptus biozone (Underwood et al, 1997). However, it has recently been discovered that N. persculptus occurs in what has previously been named the bextraordinarius bandQ (Williams, 1983;Melchin et al, 2003), 1.2 m below the base of the Birkhill shale.…”

“…Both y 13 C carb and y 13 C org data have been previously published from a number of sections around the world, including Estonia and Latvia (Brenchley et al, 2003), Scotland (Underwood et al, 1997), Anticosti Island, Canada (Long, 1993a), Nevada, USA (Finney et al, 1999), and South China (Wang et al, 1997). Brenchley et al (2003) proposed that among the known sections from which C-isotope data had been obtained, the most complete succession is located in Estonia, where the excursion spans the N. extraordinarius and lower N. persculptus biozones.…”

Carbon isotope chemostratigraphy of the Llandovery in Arctic Canada: Implications for global correlation and sea-level change

“…These results, combined with data from Dob's Linn, Scotland (Underwood et al 1997;Heath 1998), Anticosti Island (Azmy et al 1998), and Estonia (Kaljo et al 1998Kaljo & Martma 2000) yield insights into the relative timing of the carbon isotope excursions and their relationship to paleoenvironmental and biotic changes. These results follow from a study of the carbon isotope chemostratigraphy of the Late Ordovician to earliest Silurian in Arctic Canada (Melchin & Holmden in press).…”

Organic geochemical characteristics of black shales across the Ordovician–Silurian boundary in the Holy Cross Mountains, central Poland

“…1 (Berry, 2010;Leggett, 1980;Thickpenny and Leggett, 1987;Trela and Podhalanska, 2010;Wilde, 1987) including Poland (Melchin et al, 2013;Page et al, 2007). During the Ordovician-Silurian transition, there were considerable changes in the atmosphere, ocean, biosphere and, hence, in the general marine depositional conditions (Underwood et al, 1997) inextricably linked with the Late Ordovician (End Hirnantian) glacial event (Melchin et al, 2013;Sheehan, 2001). Glaciation events Mustafa, K.A., Sephton M.A., Spathopoulos, F., Watson, J.S., Krzywiec, P. Organic geochemical characteristics of black shales across the Ordovician-Silurian boundary in the Holy Cross Mountains, Central Poland, Marine andPetroleum Geology, doi:10.1016/j.marpetgeo.2015.08.018. 3 have major influence on the productivity and preservation of organic matter due to the changes in oceanic ventilation and circulation that cause oxygenation of the seawater (Berry and Wilde, 1978;Berry, 2010;Wilde, 1987).…”