The replacement Global Stratotype Section and Point (GSSP) of the Telychian Stage of the Llandovery Series, Silurian System, at El Pintado (Spain)

Abstract

The El Pintado 1 Silurian section in Seville Province, Spain, described by Loydell et al. (2015), has been ratified by the IUGS as the replacement GSSP for the base of the Telychian Stage, to replace the Cefn Cerig quarry section in the Llandovery area of Wales, which was found to be within a sedimentary mélange and therefore not a continuous section. No section other than El Pintado 1 has been found to be continuously fossiliferous across the Aeronian/Telychian boundary. In the absence of useful chitinozoan and conodont markers, the base of the Telychian is recognised biostratigraphically solely by major changes in graptolite assemblages and is at the base of the Spirograptus guerichi graptolite Biozone, marked by the first appearances of the cosmopolitan graptolite species Spirograptus guerichi (the stratigraphically lowest Spirograptus to have an entirely helically spiralled rhabdosome with torsion of its proximal end), Monograptus sensu stricto and Paradiversograptus runcinatus, and by diversification within Streptograptus. Chemostratigraphically, the base of the Telychian is straddled by the “Rumba low”negative δ13C excursions. The upper Aeronian and lower Telychian of the El Pintado 1 section have been thoroughly documented by Loydell et al. (2015), based on examination of tens of thousands of graptolites collected from more than 12 m of strata representing the Stimulograptus halli and Spirograptus guerichi graptolite biozones which form part of a largely continuous section through much of the Silurian. The upper Aeronian–lower Telychian part of the section represents apparently continuous sedimentation of graptolitic muds, silts and sands in an outer shelf location. Lithologically, the GSSP is within graptolitic mudstones, 0.6 m above the top of a nodule and 0.25 m below a conspicuously rusty weathering layer. At the GSSP (at 37°59'7.0''N 5°55'42.8''W), helically coiled Spirograptus makes its first appearance as does the first new Telychian Streptograptus species, Streptograptus picarrai. A negative δ13Corg excursion, culminating 1.4–1.6 m above the GSSP, represents the Rumba low in the El Pintado 1 section.