New stable isotope data and fossils from Hirnantian stage in Bohemia and Spain: implications for correlation and paleoclimate

Abstract

Rocks in the Late Ordovician paleotropics commonly exhibit the now well-known, positive Hirnantian Isotopic Carbon Excursion (HICE). This event is coincident with both continental scale glaciation in Gondwana and dramatic extinction across the marine realm (Delabroye and Vecoli, 2010). Both the proximate cause of the isotopic excursion and the ultimate drivers of large scale cooling remain the subject of debate. Suggestions range from tectonic effects on weathering or changes in biological productivity, through large basaltic eruptions to gamma ray bombardment. Discussion of these alternative models is beyond the scope of this short paper, however. Our intent is to briefly report the direct association of a new high resolution δ13Corganic record from rocks at a high latitude site that also bears biostratigraphic and sequence stratigraphic data needed to link Hirnantian oceanographic changes (especially those recorded in the paleotropics) with glacial events in the peri-Gondwanan realm (Delabroye and Vecoli, 2010; Young et al., 2010).