The Aeronian/Telychian (Llandovery, Silurian) boundary, with particular reference to sections around the El Pintado reservoir, Seville Province, Spain

Abstract

The upper Aeronian to lower Telychian (Llandovery Series, lower Silurian) strata at the east end of El Pintado reservoir, Seville Province, Spain are documented in terms of their lithologies, graptolite biostratigraphy and δ 13 C org record. This is the first time that a continuously graptolitic section throught the Aeronian/Telychian boundary has been studied in detail. The upper Aeronian part of the section is assigned to the Stimulograptus halli Biozone which is divisible into three, the middle part being referred to the Lituigraptus rastrum Subzone. The Telychian strata are assigned to the Spirograptus guerichi Biozone and lower Sp. turriculatus Biozone. Unusually, two specimens of Sp. turriculatus were found at a level low in the guerichi Biozone. 118 graptolite species are recorded, 18 of which are new and described here together with other species for which the El Pintado material provides new information. Diversity increases considerably in some genera (Glyptograptus, Parapetalolithus, Rastrites, Streptograptus) in the upper halli Biozone and/or lower to middle guerichi Biozone only to decline again (except for Streptograptus) in the upper part of the guerichi Biozone as part of the "utilis Event". This diversity decline coincides with an interval of elevated δ 13 C org values. There are no major δ 13 C org excursions present in the El Pintado sections. The δ 13 C org record through the guerichi Biozone is very similar to that in Arctic Canada. Portsmouth, Burnaby Road, Portsmouth PO1 3QL, UK; david.loydell@port.ac.uk • Jiří Frýda, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21, Praha 6 and Czech Geological Survey, Klárov 3, 118 21 Praha 1, Czech Republic;, Facultad de Ciencias Geológicas, E-28040 Madrid, Spain; jcgrapto@ucm.es Our knowledge of the geological column is remarkably patchy. For some stratigraphical intervals numerous papers exist documenting sections, their contained fossils and chemostratigraphical record. Other intervals -unfortunately these are often around chronostratigraphical boundaries -are remarkably bereft of useful published stratigraphical data. This is usually because of the paucity or even absence of sections without major facies changes that are continuously fossiliferous. One such "unknown" interval has been the uppermost Aeronian to lowermost Telychian (middle to upper Llandovery Series). Recognition that the GSSP for the base of the Telychian Stage is unsatisfactory from a number of viewpoints (Temple 1988;Loydell 1993a;Davies et al. 2011Davies et al. , 2013 has heightened recent interest in the search for more informative sections. The aim of this paper is to document the upper Aeronian and lower Telychian graptolitic strata through sections on the shores of El Pintado reservoir in Seville Province, Spain and to discuss the bio-, chrono-and chemostratigraphy of this part of the Silurian System. The paper commences with a review of published sections, to indicate why the El Pintado sections are so important. It contin...

A record of Late Ordovician to Silurian oceanographic events on the margin of Baltica based on new carbon isotope data, elemental geochemistry, and biostratigraphy from two boreholes in central Poland

“…Although there are studies characterizing δ 13 C org in Ordovician to Silurian strata (e.g. Underwood et al, 1997;Cramer and Saltzman, 2007b;Cramer et al, 2010;Edwards and Saltzman, 2015;Loydell et al 2015) these are mostly confined to the Sheinwoodian or earlier (Kump and Arthur, 1999;Porębska et al 2004;Cramer and Saltzman, 2005;Melchin and Holmden 2006;Cramer et al 2010;Gouldey et al 2010). The organic carbon isotope record for Baltica is particularly limited.…”

Early Silurian δ13Corg excursions in the foreland basin of Baltica, both familiar and surprising

“…Loydell et al, 2017). These biozones are absent (or unfossiliferous) in the nearby Øleå section (Bjerreskov, 1975) correlated to carbon isotope data described from the El Pintado sections in Spain (Loydell et al, 2015), the Ikla core in Estonia (Gouldey et al, 2010;Kaljo and Martma, 2000), and the sections at Cape Manning in Canada (Melchin and Holmden, 2006). Dashed line marks the presumed boundary between the Aeronian and Telychian.…”

“…Walasek et al (2018) discuss the age of the Rumba low, noting that different authors refer to it as either late Aeronian (Kaljo and Martma, 2000), early Telychian (Gouldey et al, 2010), or straddling the Aeronian-Telychian boundary (Cramer et al, 2011). In the Ikla core, Estonia, the lowest values occur in strata containing Metaclimacograptus hughesi which is a common and widespread species that ranges to the very top of the Aeronian (Loydell et al, 2015) but is not known to extend into the Telychian. Hence, the presence of Me.…”

Graptolites from the Rhuddanian-Aeronian boundary interval (Silurian), Prague Synform, Czech Republic

“…Met. hughesi has a very long stratigraphical range having been recorded from the Rhuddanian Cystograptus vesiculosus Biozone (Koren' & Rickards 1996, Loydell 2007 through to the upper Aeronian Stimulograptus halli Biozone (Loydell et al 2015). Slender, ca 0.8 mm wide rhabdosomes of Metaclimacograptus hughesi as discussed by Bulman and Rickards (1968) and figured also by Loydell (1991) a.o.…”