Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

Proceedings of the National Academy of Sciences of the United States of America
By: , and 

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Abstract

It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica-and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe3,/sup>Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO2 glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago
Series title Proceedings of the National Academy of Sciences of the United States of America
DOI 10.1073/pnas.1204453109
Volume 109
Issue 28
Year Published 2012
Language English
Publisher National Academy of Sciences
Publisher location Washington, D.C.
Description 10 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 E1903
Last page E1912
Other Geospatial Asia;Europe;North America