T325 Earth Deep Time Revolution by Global Chronostratigraphic Correlation
Wednesday, 30 October 2013
8:00 AM - 12:00 PM
Room 401
HIGH-PRECISION U–PB AGE AND DURATION OF THE LATEST DEVONIAN (FAMENNIAN) HANGENBERG EVENT, AND ITS IMPLICATIONS
Paper number: T325-11
Program: Technical Sessions
Time: 10:30 AM – 10:45 AM
Authors
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Jahandar RamezaniMassachusetts Institute of Technology, Cambridge, MA
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Anne HansonColorado College, Colorado Springs, CO
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Samuel A. BowringMassachusetts Institute of Technology, Cambridge, MA
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Grzegorz RackiUniversity of Silesia, Sosnowiec, N/A
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Michal RakocinskiUniversity of Silesia, Sosnowiec, N/A
Abstract
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.