Geochemical analyses of the Late Devonian “Kellwasser Event” stratigraphic horizon at Steinbruch Schmidt (F.R.G.)

Abstract

We report here the absence of an Ir anomaly in an exceptionally complete stratigraphic sequence across the Frasnian-Famennian boundary in the Rhenish Slate Mountains of the Federal Republic of Germany. There exists no anomaly either at the “Kellwasser Event” mass extinction horizon (Uppermost gigas-Lower triangularis Subzonal interval), or at the subzonal horizon where an Ir anomaly was reported in the Canning Basin strata in Australia.

No sharp negative Carbon-13 shift is seen at the biological crisis horizon, which could be indicative of the collapse of phytoplanktion productivity. On the contrary, a sudden increase of Carbon-13 ratios is seen at the critical horizon, suggesting that either a “bloom” in phytoplankton activity or upwelling occurred in this interval of time. Such events might have been local phenomena, however, as a comparable Carbon-13 signature has not yet been found outside of Europe.

No sharp increase in Oxygen-18 is seen, which might have been expected if the latest Frasnian-Famennian period of time were one of global oceanic cooling, or if upwelling of colder water had occurred.