High-precision U-Pb age and duration of the latest Devonian (Famennian) Hangenberg event, and its implications

Precise U-Pb zircon dates from three volcanic ash beds that bracket the Hangenberg Shale in the Holy Cross Mountains, Poland, constrain the age and duration of one of the most significant palaeobiological events of the Palaeozoic Era, the Hangenberg Event. It is linked to a terminal Devonian global shift from greenhouse to icehouse climate conditions, a global transgression, and widespread black shale deposition. Our results constrain the Hangenberg Event to between 358.97 +/- 0.11Ma and 358.89 +/- 0.20Ma, with a calculated duration of 0.05 +0.14/-0.05Ma. A third, underlying ash bed yielded a distinctly older age of 359.97 +/- 0.46Ma. The duration of ~50-100ka. for the event is comparable to those of Quaternary glaciations, and is consistent with both a glacio-eustatic origin for the eustatic fluctuations and changes in ocean chemistry that led to this major reorganization of the biosphere.