Carbon and oxygen isotope record across Pridoli to Givetian stage boundaries in the Barrandian basin (Czech Republic)

Carbon and oxygen isotope composition and the chemistry of limestones, clayey limestones and shales were studied across stage boundaries from Pridoli to Givetian in the Barrandian basin. No substantial isotopic shifts were found at the Pragian–Emsian and Emsian–Eifelian boundaries. A gradual shift in δ13C values from −2.6 to +3.6‰ was observed in Pridoli and Lochkovian limestones. This shift is inferred to have been related to a combination of higher productivity, increased deposition of organic matter and shallowing of the basin. The global Kačák–otomari event just below the Eifelian–Givetian boundary is marked by an abrupt change in carbon isotopic values from about 1 to 3‰ in pelagic carbonates. No δ13C shift was found in shallow-water carbonates at the Eifelian–Givetian boundary. High δ18O values up to −1.3‰ in Pragian, Emsian and early Eifelian limestones indicate that the Barrandian basin was relatively isolated from the world ocean during those intervals. Lower δ18O values up to −7.5‰ in late Eifelian limestones may indicate the end of isolation.