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2659843 
Journal Article 
The Younger Dryas impact hypothesis: a cosmic catastrophe 
Holliday, VT; Surovell, T; Meltzer, DJ; Grayson, DK; Boslough, M 
2014 
Yes 
Journal of Quaternary Science
ISSN: 0267-8179
EISSN: 1099-1417 
29 
6 
515-530 
WOS:000344003200002 
In this paper we review the evidence for the Younger Dryas impact hypothesis (YDIH), which proposes that at similar to 12.9k cal a BP North America, South America, Europe and the Middle East were subjected to some sort of extraterrestrial event. This purported event is proposed as a catastrophic process responsible for: terminal Pleistocene environmental changes (onset of YD cooling, continent-scale wildfires); extinction of late Pleistocene mammals; and demise of the Clovis 'culture' in North America, the earliest well-documented, continent-scale settlement of the region. The basic physics in the YDIH is not in accord with the physics of impacts nor the basic laws of physics. No YD boundary (YDB) crater, craters or other direct indicators of an impact are known. Age control is weak to nonexistent at 26 of the 29 localities claimed to have evidence for the YDIH. Attempts to reproduce the results of physical and geochemical analyses used to support the YDIH have failed or show that many indicators are not unique to an impact nor to similar to 12.9k cal a BP. The depositional environments of purported indicators at most sites tend to concentrate particulate matter and probably created many 'YDB zones'. Geomorphic, stratigraphic and fire records show no evidence of any sort of catastrophic changes in the environment at or immediately following the YDB. Late Pleistocene extinctions varied in time and across space. Archeological data provide no indication of population decline, demographic collapse or major adaptive shifts at or just after similar to 12.9 ka. The data and the hypotheses generated by YDIH proponents are contradictory, inconsistent and incoherent. Copyright (C) 2014 John Wiley & Sons, Ltd. 
Clovis; extinction; extraterrestrial impact; Younger Dryas; Younger Dryas impact hypothesis