The outstanding Silurian section of the Valle syncline (Sierra Norte de Sevilla UNESCO Global Geopark, Spain) as an international standard for graptolite biostratigraphy

The Palaeozoic succession of the Sierra Norte de Sevilla UNESCO Global Geopark (Ossa Morena Zone of the Iberian Massif, SW Spain) includes a nearly complete Silurian succession, ca. 150 m in thickness, deposited in outer shelf settings. Among sections explored along the western end of the El Pintado reservoir, in the core part of the Valle syncline, the El Pintado-1 section exhibits graptolite rich Silurian black-shale facies ranging from the base of the Rhuddanian to the upper Ludfordian. Most of the standard graptolite biozones of the Silurian System have been identified in this succession, and high-resolution biostratigraphical studies have led to the unanimous candidacy of this section as replacement GSSP for the base of the Telychian Stage by the International Subcommission on Silurian Stratigraphy. The preliminary record of Llandovery graptolites in the lower part of the succession so far comprises more than 200 species, 19 of them new. Graptolites from the upper Telychian and from the remaining part of the Silurian succession have not yet been studied in detail. The condensed, almost entirely graptolitic black shale Silurian succession of the El Pintado-1 geosite is of enormous value for the world’s palaeontological heritage, reinforced by the future placement here of the GSSP for the base of the Telychian Stage. Due to its fragility and exclusively scientific nature, the section is not open to public visitors of the Geopark, and its difficult accessibility also adds some protection to this internationally important geosite, favouring its conservation beyond the regional legislative framework.