The famous Cretaceous-Paleogene boundary older than we thought
Publiée le 2011-04-22

A very accurate timescale is needed to understand the geological events accompanying the Cretaceous and the disappearance of numerous species, such as dinosaurs. Cyclostratigraphic analysis and astronomical calibration, based on the identification in the sedimentary records of cycles controlled by the variations of the Earth's orbital parameters, provides precise estimates of duration and ages. This method have been used for the first time on the entire stage ending the Cretaceous, by a team of French (CNRS, IMCCE/Observatoire de Paris, Paris 6 University) and American researchers (Johns Hopkins University). The analysis of Upper Cretaceous deep sea marine sedimentary records from Indian and Atlantic Ocean, recovered during Ocean Drilling Program and Deep Sea Drilling Project oceanographic campaigns, associated to the new astronomical solution La2010, allowed the proposal of two ages for the Cretaceous-Paleogene boundary, at 65.59±0.07 Ma or 66±0.07 Ma. The second proposal is in better accordance with the last radio-isotopic dating, moving this boundary 405 000 years back in time from the current estimate.

References :

D. Husson, B. Galbrun, J. Laskar, L. A. Hinnov, N. Thibault, S. Gardin and R. E. Locklair, 2011, Astronomical calibration of the Maastrichtian (late Cretaceous) (EPSL , sous presse)

J. Laskar, A. Fienga, M. Gastineau, H. Manche, 2011, La2010: A new orbital solution for the long term motion of the Earth, soumis à A&A (arXiv:1103.1084v1)

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