A proposed new global stratotype for Aeronian Stage of the Silurian System: Hlásná Třebaň section, Czech Republic

0490800 - GLÚ 2019 RIV NO eng J - Journal Article
Štorch, Petr - Manda, Š. - Tasáryová, Z. - Frýda, J. - Chadimová, Leona - Melchin, M. J.
A proposed new global stratotype for Aeronian Stage of the Silurian System: Hlásná Třebaň section, Czech Republic.
Lethaia. Roč. 51, č. 3 (2018), s. 357-388. ISSN 0024-1164. E-ISSN 1502-3931
R&D Projects: GA ČR(CZ) GA14-16124S
Institutional support: RVO:67985831
Keywords : Aeronian * geochemistry * graptolites * GSSP proposal * Silurian
OECD category: Paleontology
Impact factor: 1.736, year: 2018

The current Global Stratotype Sectionand Point (GSSP) for the Aeronian Stage (Llandovery Series, Silurian System), on Trefawr track in the Llandovery area of Wales, is an inadequate marker for precise, global, correlation. The International Subcommission on Silurian Stratigraphy has, therefore, undertaken the selection of a new GSSP for this level. The lowest occurrence of the graptolite Demirastrites triangulatus, 1.38m above the base of the black-shale succession of the Zelkovice Formation at the Hlasna Teba section in Central Bohemia, is proposed to mark the base of the Aeronian Stage. The section, which fulfils all formal requirements for stratotype of a chronostratigraphical unit, should be considered as a candidate for the new GSSP. An abundant, well-preserved, diverse graptolite fauna occurs through the section along with common chitinozoans, which indicate that the Spinachitina maennili Biozone spans the boundary interval. The section comprises the lower-middle Aeronian (D.triangulatus-Lituigraptus convolutus graptolite biozones) along with underlying Rhuddanian (Akidograptus ascensus-Coronograptus cyphus biozones) and Hirnantian strata. Several graptolite genera of primary importance in global correlation (Demirastrites, Petalolithus, Rastrites and Campograptus) first appear in the lower part of the triangulatus Biozone. The structurally simple section is somewhat condensed, but there is a uniform succession of black shale without any evidence of disconformity in the broad boundary interval. The C_org isotope record exhibits a minor positive excursion just above the base of the triangulatus Biozone, whereas TOC and N isotope and elemental geochemical records provide evidence for uninterrupted sedimentation under stable, anoxic conditions.
Permanent Link: http://hdl.handle.net/11104/0284939