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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 9
Clim. Past, 11, 1181–1195, 2015
https://doi.org/10.5194/cp-11-1181-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Climatic and biotic events of the Paleogene

Clim. Past, 11, 1181–1195, 2015
https://doi.org/10.5194/cp-11-1181-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 23 Sep 2015

Research article | 23 Sep 2015

Astronomical calibration of the geological timescale: closing the middle Eocene gap

T. Westerhold1, U. Röhl1, T. Frederichs2, S. M. Bohaty3, and J. C. Zachos4 T. Westerhold et al.
  • 1MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Straße, 28359 Bremen, Germany
  • 2Department of Geosciences, University of Bremen, 28359 Bremen, Germany
  • 3Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH, UK
  • 4University of California, Santa Cruz, California, USA

Abstract. To explore cause and consequences of past climate change, very accurate age models such as those provided by the astronomical timescale (ATS) are needed. Beyond 40 million years the accuracy of the ATS critically depends on the correctness of orbital models and radioisotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical timescale and confirms the intercalibration of radioisotopic and astronomical dating methods back through the Paleocene–Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous–Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the ATS into the Mesozoic.

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Testing hypotheses for mechanisms and dynamics of past climate change relies on the accuracy of geological dating. Development of a highly accurate geological timescale for the Cenozoic Era has previously been hampered by discrepancies between radioisotopic and astronomical dating methods, as well as a stratigraphic gap in the middle Eocene. We close this gap and provide a fundamental advance in establishing a reliable and highly accurate geological timescale for the last 66 million years.
Testing hypotheses for mechanisms and dynamics of past climate change relies on the accuracy of...
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