Abstract
The Younger Dryas Impact Hypothesis (YDIH) states that North America was devastated by some sort of extraterrestrial event ~12,800 calendar years before present. Two fundamental questions persist in the debate over the YDIH: Can the results of analyses for purported impact indicators be reproduced? And are the indicators unique to the lower YD boundary (YDB), i.e., ~12.8k cal yrs BP? A test reported here presents the results of analyses that address these questions. Two different labs analyzed identical splits of samples collected at, above, and below the ~12.8ka zone at the Lubbock Lake archaeological site (LL) in northwest Texas. Both labs reported similar variation in levels of magnetic micrograins (>300 mg/kg >12.8ka and <11.5ka, but <150 mg/kg 12.8ka to 11.5ka). Analysis for magnetic microspheres in one split, reported elsewhere, produced very low to nonexistent levels throughout the section. In the other split, reported here, the levels of magnetic microspherules and nanodiamonds are low or nonexistent at, below, and above the YDB with the notable exception of a sample <11,500 cal years old. In that sample the claimed impact proxies were recovered at abundances two to four orders of magnitude above that from the other samples. Reproducibility of at least some analyses are problematic. In particular, no standard criteria exist for identification of magnetic spheres. Moreover, the purported impact proxies are not unique to the YDB.
Highlights
The Younger Dryas Impact Hypothesis (YDIH), first proposed by Firestone et al [1, 2], states that some sort of “major cosmic episode of multiple airbursts/impacts occurred at 12,800 ± 300 calendar years before 1950” [3] and brought on a variety of cataclysms across the Earth’s surface including abrupt climate change, wide spread burning, and extinction of fauna and human groups
The results of analyses of blind samples collected at the Lubbock Lake site to test the YD impact hypothesis produced no evidence of an extraterrestrial impact at the Younger Dryas boundary (YDB)
These results are consistent with a growing body of data that shows that claimed impact indicators are found in deposits both older and younger than the YDB
Summary
The Younger Dryas Impact Hypothesis (YDIH), first proposed by Firestone et al [1, 2], states that some sort of “major cosmic episode of multiple airbursts/impacts occurred at 12,800 ± 300 calendar years before 1950” [3] and brought on a variety of cataclysms across the Earth’s surface including abrupt climate change, wide spread burning, and extinction of fauna and human groups. This proposed event would have occurred at the Younger Dryas boundary (YDB) at the beginning of the Younger Dryas Chronozone (YDC). Instead, purported impact indicators were found at a level well over 1000 years younger that the YDB
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