Absence of geochemical evidence for an impact event at the Bølling-Allerød/Younger Dryas transition

High concentrations of iridium have been reported in terrestrial sediments dated at 12.9 ka and are interpreted to support an extraterrestrial impact event as the cause of the observed extinction in the Rancholabrean fauna, changes in the Paleoindian cultures, and the onset of the Younger Dryas cool...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences
Main Authors: Paquay, François S, Goderis, Steven, Ravizza, Greg, Vanhaecke, Frank, Boyd, Matthew, Surovell, Todd A, Holliday, Vance T, Haynes, C Vance, Jr, Claeys, Philippe
Format: Article in Journal/Newspaper
Language:English
Published: 2009
Subjects:
Earth and Environmental Sciences
CHONDRITIC IMPACTOR
ISOTOPIC COMPOSITION
GREENLAND ICE
MASS-SPECTROMETRY
meteorite
Pleistocene extinction
Clovis
platinum group elements
Os isotopes
K-T BOUNDARY
YOUNGER DRYAS
METEORITIC NANODIAMONDS
PLATINUM-GROUP ELEMENTS
ABRUPT CLIMATE-CHANGE
CRETACEOUS-TERTIARY BOUNDARY
Greenland
Online Access:https://biblio.ugent.be/publication/917168
http://hdl.handle.net/1854/LU-917168
https://doi.org/10.1073/pnas.0908874106
https://biblio.ugent.be/publication/917168/file/2054072
Description
Summary:High concentrations of iridium have been reported in terrestrial sediments dated at 12.9 ka and are interpreted to support an extraterrestrial impact event as the cause of the observed extinction in the Rancholabrean fauna, changes in the Paleoindian cultures, and the onset of the Younger Dryas cooling [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 104:16016-16021]. Here, we report platinum group element (PGE: Os, Ir, Ru, Rh, Pt, Pd), gold (Au) concentrations, and Os-187/Os-188 ratios in time-equivalent terrestrial, lacustrine, and marine sections to seek robust evidence of an extraterrestrial contribution. First, our results do not reproduce the previously reported elevated Ir concentrations. Second, Os-187/Os-188 isotopic ratios in the sediment layers investigated are similar to average crustal values, indicating the absence of a significant meteoritic Os contribution to these sediments. Third, no PGE anomalies distinct from crustal signatures are present in the marine record in either the Gulf of California (DSDP 480, Guaymas Basin) or the Cariaco Basin (ODP 1002C). Our data show no evidence of an extraterrestrial (ET)-PGE enrichment anomaly in any of the investigated depositional settings investigated across North America and in one section in Belgium. The lack of a clear ET-PGE signature in this sample suite is inconsistent with the impact of a large chondritic projectile at the Bolling-Allerod/Younger Dryas transition.

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