Oxygen Isotopes from Apatite of Middle and Late Ordovician Conodonts in Peri-Baltica (The Holy Cross Mountains, Poland) and Their Climatic Implications

This report provides oxygen isotopes from apatite of late Middle and Late Ordovician conodonts the southern Holy Cross Mountains in south-eastern Poland. It was a unique time interval characterised by significant change climate, tectonic, ocean chemistry. In early Ordovician, were located mid-latitude climatic zone at southwestern periphery Baltica; therefore, δ18Oapatite values this region provide new data on 18O/16O budget seawater reconstructed mainly tropical subtropical realms. Oxygen mixed conodont samples measured using SHRIMP IIe/MC ion microprobe Polish Geological Institute Warsaw. The range 16.75‰VSMOW to 20.66‰VSMOW with an average 18.48‰VSMOW. bioapatite studied section display increasing trend, suggesting progressive decrease sea-surface temperature roughly consistent overall cooling climate. Two distinctive positive excursions have been reported upper Sandbian middle Katian correlated events recognised Baltica. They are interpreted as isotope proxy climate changes triggered growing continental polar ice cap, but increased contradicts recently postulated warming during that Laurentia.