Integrated stratigraphy of the Llandovery-Wenlock Boundary in the Łopianka–2 outcrop of the Sudeten Mountains, southwest Poland

Stable carbon isotopic composition of organic matter (.13Corg) analyses were carried out along the 7-m-thick section of Lower Graptolitic Shales at the Llandovery/
Wenlock boundary, outcropping on Łopianka Mountain (the Łopianka-2 outcrop) in the Bardo Mountains of the Central Sudetes, Southwest Poland (eastern part of
the European Variscides Belt). This study presents the first attempt to establish integrated biostratigraphical and chemostratigraphical records for Silurian strata in the Bardo Mountains. Graptolite assemblages indicate the presence of centrifugus and murchisoni biozones at the Telychian-Sheinwoodian boundary and mid-Wenlock in the investigated interval, thus continuous graptolitic succession. The succession of graptolite biozones in the upper Wenlock section could not be determined due to the collapsed strata. The isotopic signature of .13Corg showed a positive excursion which is referred to as the Ireviken or early Sheinwoodian Carbon Isotope Excursion (ESCIE). The .13Corg values of the Ireviken interval begin to rise higher than the first occurrence of Cyrt. bohemicus and does not coincide with the base of the murchisoni Biozone. Due to the fact that coupled carbon isotope chemostratigraphy and graptolite biostratigraphy for Silurian strata is a new approach in this region, this may serve as a standard for the Llandovery/Wenlock boundary in the area of the Saxothuringian Zone of the Central European Variscides.