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Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

Proceedings of the National Academy of Sciences of the United States of America

By:
, , , , ,
DOI: 10.1073/pnas.1200296109

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Abstract

The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various "impact markers" were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis
Series title:
Proceedings of the National Academy of Sciences of the United States of America
DOI:
10.1073/pnas.1200296109
Volume
109
Issue:
19
Year Published:
2012
Language:
English
Publisher:
National Academy of Sciences of the United States of America
Publisher location:
Washington, D.C.
Contributing office(s):
Geology and Environmental Change Science Center
Description:
5 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Proceedings of the National Academy of Sciences of the United States of America
First page:
7208
Last page:
7212