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| Titel |
A global cyclostratigraphic framework constrains the timing and pacing of environmental changes over the Late Devonian (Frasnian – Famennian) mass extinction |
| VerfasserIn |
David De Vleeschouwer, Anne-Christine Da Silva, James E. Day, Michael Whalen, Philippe Claeys |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128225
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| Publikation (Nr.) |
 EGU/EGU2016-8193.pdf |
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| Zusammenfassung |
| Milankovitch cycles (obliquity, eccentricity and precession) result in changes in the
distribution of solar energy over seasons, as well as over latitudes, on time scales of ten
thousands of years to millions of years. These changing patterns in insolation have induced
significant variations in Earth’s past climate over the last 4.5 billion years. Cyclostratigraphy
and astrochronology utilize the geologic imprint of such quasi-cyclic climatic variations to
measure geologic time. In recent years, major improvements of the Geologic Time Scale have
been proposed through the application of cyclostratigraphy, mostly for the Mesozoic and
Cenozoic (Gradstein et al., 2012). However, the field of Paleozoic cyclostratigraphy
and astrochronology is still in its infancy and the application of cyclostratigraphic
techniques in the Paleozoic allows for a whole new range of research questions. For
example, unraveling the timing and pacing of environmental changes over the Late
Devonian mass extinction on a 105-year time-scale concerns such a novel research
question.
Here, we present a global cyclostratigraphic framework for late Frasnian to early Famennian
climatic and environmental change, through the integration of globally distributed
sections. The backbone of this relative time scale consists of previously published
cyclostratigraphies for western Canada and Poland (De Vleeschouwer et al., 2012; De
Vleeschouwer et al., 2013). We elaborate this Euramerican base by integrating new
proxy data –interpreted in terms of astronomical climate forcing- from the Iowa
basin (USA, magnetic susceptibility and carbon isotope data) and Belgium (XRF
and carbon isotope data). Next, we expand this well-established cyclostratigraphic
framework towards the Paleo-Tethys Ocean, using magnetic susceptibility and carbon
isotope records from the Fuhe section in South China (Whalen et al., 2015). The
resulting global cyclostratigraphic framework implies an important refinement of the
late Frasnian to early Famennian stratigraphy, but also allows for an evaluation of
the role of astronomical forcing in perturbing the global carbon cycle and pacing
anoxic conditions throughout the Late Devonian mass extinction event. The late
Frasnian anoxic Kellwasser events, for example, each represent only a portion of a
405-kyr eccentricity cycle, with the onset of both events separated by 500-600
kyr.
References:
De Vleeschouwer, D., Whalen, M. T., Day, J. E., and Claeys, P., 2012, Cyclostratigraphic
calibration of the Frasnian (Late Devonian) time scale (western Alberta, Canada): Geological
Society of America Bulletin, v. 124, no. 5-6, p. 928-942.
De Vleeschouwer, D., Rakociński, M., Racki, G., Bond, D. P., Sobień, K., and Claeys, P.,
2013, The astronomical rhythm of Late-Devonian climate change (Kowala section,
Holy Cross Mountains, Poland): Earth and Planetary Science Letters, v. 365, p.
25-37.
Gradstein, F. M., Ogg, J. G., Schmitz, M., and Ogg, G., 2012, The Geologic Time Scale 2012
2-Volume Set, Elsevier.
Whalen, M. T., Śliwiński, M. G., Payne, J. H., Day, J. E., Chen, D., and da Silva, A.-C., 2015,
Chemostratigraphy and magnetic susceptibility of the Late Devonian Frasnian–Famennian
transition in western Canada and southern China: implications for carbon and nutrient
cycling and mass extinction: Geological Society, London, Special Publications, v.
414. |
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