Middle-Upper Jurassic stable isotope records and seawater temperature variations: New palaeoclimate data from marine carbonate and belemnite rostra (Pieniny Klippen Belt, Carpathians)

The carbon and oxygen isotope composition of well-preserved belemnite rostra and bulk carbonates from uppermost Aalenian to Lower Tithonian outcrops of the Pieniny Klippen Belt in the Carpathians is under discussion in this paper. New isotope and elemental data from the open marine basin in a rarely studied, northern part of the Tethys Ocean, corroborate the world-wide δ13C variations and global temperature changes of a seawater. The δ13C temporal trends display prominent positive shift in the Upper Callovian-Middle Oxfordian, as well as a declining trend in the Kimmeridgian-Tithonian interval. δ18O values of belemnite rostra suggest a decrease in temperatures during the latest Aalenian-Early Bajocian. The Upper Jurassic temperatures, estimated on the basis of oxygen isotope values and Mg/Ca ratios of belemnite rostra, indicate a warming of the seawater of ca. 5.5 °C in the Late Oxfordian-Early Kimmeridgian. This temperature rise is interpreted to be a result of the global climate warming present during the early Late Jurassic.