Division of Pridoli Series in Central Bohemia: graptolite and conodont biostratigraphy, faunal changes, and geochemical record

Pridoli, the fourth series of the Silurian System, represents an interval of faunal changes, which heralded the middle Palaeozoic transformation of marine ecosystem. Understanding of the faunal changes has been limited by lack of widely applicable correlation markers. Consequently, the Pridoli Series remained undivided formally into stages. Herein, the subdivision of the Series is proposed into a lower Jarovian Stage and an upper Radotinian Stage. The base of the Jarovian Stage would correspond to the base of the Pridoli in its defined GSSP. Correlation markers applicable for subdivision of the Series are discussed based on data from sections of the type area of Central Bohemia. The graptolite Wolynograptus bouceki is suggested as the most promising marker to define the base of the Radotinian Stage. The conodont Oulodus detortus enters close to the base of the bouceki Biozone as did also the cephalopod Kopaninoceras fluminese, which is abundant in the Pridoli strata across peri-Gondwana. The bouceki Biozone witnessed successive appearance of faunas previously reported from the upper Pridoli transgrediens graptolite Biozone. Benthic faunas complement graptolite-conodont biozonation on the regional scale, bivalves and the brachiopod Dayia bohemica allow for tentative interregional correlation. The appearance and proliferation of scyphocrinid crinoids represent a time specific biofacies in the upper stage. A shift from slightly negative to slightly positive delta C-13(carb) values coincides with the base of the bouceki Biozone in Bohemian sections. Most of the relevant biohorizons occur in the lower Pridoli. The base of regionally limited graptolite perneri Biozone and conodont eosteinhornensis s. s. and klonkensis biozones in the Radotinian Stage are the youngest markers, preceding the Transgrediens Event and carbon isotope excursions of the uppermost Pridoli. The Hvizdalka section with uninterrupted sedimentation and integrated graptolite and conodont biostratigraphy and geochemical records may be considered a potential stratotype of the proposed Radotinian Stage.

Automated summary

The Pridoli Series, representing the fourth series of the Silurian System, is a crucial period for understanding the marine ecosystem transformation in the middle Palaeozoic era. However, the lack of widely applicable correlation markers has limited the understanding of faunal changes during this period. This study proposes the subdivision of the Pridoli series into two stages and discusses correlation markers based on data from sections in Central Bohemia.