Redox conditions and marine microbial community changes during the end-Ordovician mass extinction event

The end-Ordovician (Hirnantian) crisis is the first globally distinct extinction during the Phanerozoic, but its causes are still not fully known. Here, we present an integrated geochemical and petrographic analysis to understand the sedimentary conditions taking place before, during and after the Late Ordovician ice age. New data from the Zbrza (Holy Cross Mountains) and Goldap (Baltic Depression) boreholes shows that, like in other worldwide...