HIGH-PRECISION U–PB AGE AND DURATION OF THE LATEST DEVONIAN (FAMENNIAN) HANGENBERG EVENT, AND ITS IMPLICATIONS

Precise U–Pb zircon geochronological 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 paleobiological events of the Paleozoic Era, and the last major biological turnover event of the Devonian. The multifaceted Hangenberg event is linked to a terminal Devonian global shift from greenhouse to icehouse climate conditions, a global regression, subsequent transgression, and widespread black shale deposition. Widespread marine extinctions associated with the event included several major groups of ammonoids, phacopid trilobites, and various reef-building organisms. In addition, the Hangenberg event records stressed terrestrial flora and a major extinction of marine and terrestrial vertebrate fauna that fundamentally reset vertebrate ecosystems. Our results constrain the Hangenberg Event to a duration of 0.05 +0.14/ -0.05 m.y. The ~50 – 100 k.y. duration of the event is typical of Quaternary glaciations, and is consistent with time scales of both Milankovitch-driven, glacio-eustatic climatic cycles, and changes in ocean chemistry that led to this major reorganization of the biosphere.