The Jurassic-Cretaceous boundary on the northern Tethyan margin: Karpentná and Ropice sections (Outer Western Carpathians, Czech Republic)

Abstract

Microfacies and high-resolution studies at the Silesian Unit (Outer Western Carpathians, Czech Republic) on calpionellids, calcareous and non-calcareous dinoflagellate cysts, foraminifers and calcareous nannofossils, aligned with paleomagnetism, delta C-13(carb) and delta C-18(carb), allow construction of a detailed stratigraphy and palaeoenvironmental interpretations across the Jurassic-Cretaceous (J/K) boundary. Two studied sections consist of allodapic and biomicritic limestones and marlstones. Ropice section spans the stratigraphic range from the upper Tithonian calpionellid Chitinoidella Zone, nannoplankton zone NJT16 to the lower Berriasian calpionellid Alpina Subzone of the Calpionella Zone, nannoplankton NC1 Zone. The J/K boundary is marked by the dominance of small forms of Calpionella alpina, rare occurrence of Nannoconus wintereri, and the first occurrence of organic-walled dinoflagellate cysts Dichadogonyaulax bensonii and Muderongia longicorna. A negative shift in the delta C-13(carb) values corresponds to the Tithonian/ Berriasian boundary, the base of the Calpionella Zone (Alpina Subzone). Karpentna section is represented by upper Tithonian calpionellid Chitinoidella to Crassicollaria zones. Remagnetization was documented in both sections.