Conodont biostratigraphy and carbon isotope stratigraphy of the Middle Ordovician (Darriwilian) Komstad Limestone, southern Sweden

Abstract

The Komstad Limestone forms a distal part of the widespread ‘orthoceratite limestone’ of the Baltoscandian continent. In this paper, we present an integrated conodont biostratigraphy and carbon isotope stratigraphy for a major part of this formation and address its significance for evaluating Middle Ordovician correlation and overall stratigraphy. Four conodont zones are distinguished, including the Lenodus antivariabilis Zone, Lenodus variabilis Zone, the Yangtzeplacognathus crassus Zone, and the Eoplacognathus pseudoplanus Zone. Carbon isotopes have previously not been published from the Komstad Limestone. The data herein show that carbonate strata may retain a comprehensive pristine δ13C signal despite relatively strong thermal influence during diagenesis (Conodont Color Alteration Index 4–5).