Geochemical evidence for major environmental change at the Devonian-Carboniferous boundary in the Carnic Alps and the Rhenish Massif

摘要

A positive carbon isotope excursion is reported for the global Hangenberg Event near the Devonian-Carboniferous boundary, one of the most significant Phanerozoic mass extinction events. The delta C-13 excursion occurs both in micritic limestones and in sedimentary organic matter of black shales and limestones from different palaeogeographical regions, which were precisely correlated by conodont biostratigraphy. The excursion indicates global change in the isotopic composition of marine dissolved inorganic carbon and atmospheric CO2. This resulted from the increased burial of organic matter by globally widespread deposition of black shales.