Bayesian chronological analyses consistent with synchronous age of 12,835–12,735 Cal B.P. for Younger Dryas boundary on four continents

James P. Kennett, Douglas J. Kennett, Brendan J. Culleton, J. Emili Aura Tortosa, James L. Bischoff, Ted E. Bunch, I. Randolph Daniel Jr., Jon M. Erlandson, David Ferraro, Richard B. Firestone, Albert C. Goodyear, Isabel Israde-Alcántara, John R. Johnson, Jesús F. Jordá Pardo, David R. Kimbel, Malcolm A. LeCompte, Neal H. Lopinot, William C. Mahaney, Andrew M. T. Moore, Christopher R. Moore, Jack H. Ray, Thomas W. Stafford Jr., Kenneth Barnett Tankersley, James H. Wittke, Wendy S. Wolbach, and Allen West

PNAS 2015 112 (32) E4344-E4353; published ahead of print July 27, 2015, doi:10.1073/pnas.1507146112


The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835–12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet and of the earliest age of the Younger Dryas climate episode in six proxy records, suggesting a causal connection between the YDB impact event and the Younger Dryas. Two statistical tests indicate that both modeled and unmodeled ages in the 30 records are consistent with synchronous deposition of the YDB layer within the limits of dating uncertainty (∼100 y). The widespread distribution of the YDB layer suggests that it may serve as a datum layer.