Upper Wenlock δ13C chemostratigraphy, conodont biostratigraphy and palaeoecological dynamics in the Ledai-179 drill core (Eastern Lithuania)

Abstract

Based on the integrated chemostratigraphic and lithostratigraphic studies, as well as biostratigraphic and palaeo­ecological analyses of conodonts in the Ledai-179 core, we present a combined model of change in the upper Wenlock and lowermost Ludlow strata of the inner shelf settings in the eastern part of the Baltic Basin. The comparison of the δ13C trend, and conodont and lithological successions confirms previous suggestions that the Birštonas and Nevėžis formations correspond to the Homerian. This is quite unexpected, however, that the chronostratigraphic position of the Širvinta Formation changed from the Gorstian to the upper part of the Homerian. The numerical biostratigraphic changepoint analyses of local conodont richness, per capita immigration and also per capita extirpation rates revealed several episodes of permanent change. These episodes of dynamic states either preceded or postdated the Mulde extinction interval at the beginning of the late Homerian δ13C excursion, which points to possible transient effects of this extinction event on conodonts.

Keywords

• δ13C chemostratigraphy
• conodonts
• biostratigraphy
• palaeoecology
• Mulde Event
• Eastern Baltic
• Lithuania.