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

• Published in: Terra nova (Oxford, England) Vol. 26; no. 3; pp. 222 - 229
• Main Authors: Myrow, Paul M., Ramezani, Jahandar, Hanson, Anne E., Bowring, Samuel A., Racki, Grzegorz, Rakociński, Michał
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01-06-2014
• Subjects: Geological time; Glaciers; Mountains; Paleobiology; Paleoclimate science; Poland, Holy Cross Mts
• ISSN: 0954-4879; 1365-3121
• DOI: 10.1111/ter.12090

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 ± 0.11 Ma and 358.89 ± 0.20 Ma, with a calculated duration of 0.05 +0.14/−0.05 Ma. A third, underlying ash bed yielded a distinctly older age of 359.97 ± 0.46 Ma. The duration of ~50–100 ka. 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.