A Blind Test of the Younger Dryas Impact Hypothesis

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.

A multi-proxy study of changing environmental conditions in a Younger Dryas sequence in southwestern Manitoba, Canada, and evidence for an extraterrestrial event

“…These particles cannot be distinguished by limiting observations to a reflected-light microscope. A number of previous studies critical of the YD hypothesis (Surovell et al, 2009; Pinter et al, 2011; Pigati et al, 2012; Holliday et al, 2016) claimed to find “melted YDB spherules” throughout stratigraphic columns they investigated well beyond the YD time frame. However, none of those studies correctly used SEM-EDS, as required, making it unclear whether any YDB high temperature impact spherules were observed at all.…”

The Extraordinary Mediocrity of the Holocene

“…Attempts at replication in identifying geochemical evidence have not always been successful Holliday et al 2016). …”

Radiocarbon simulation fails to support the temporal synchroneity requirement of the Younger Dryas impact hypothesis

“…Supporters of the hypothesis argue that this event is recognizable in the Younger Dryas Boundary (YDB) stratum at sites in North and South America, Europe, and Asia based on the presence of impact proxies such as nanodiamonds, carbon spherules, magnetic spherules, and increased platinum (Firestone et al, 2007; Kennett et al, 2008, 2009a, 2009b, 2015; Firestone, 2009; Israde-Alcantara et al, 2012; Bunch et al, 2012; LeCompte et al, 2012; Petaev et al, 2013; Wittke et al, 2013; Wu et al, 2013; Kinzie et al, 2014; Moore et al, 2017; Kletetschka et al, 2018; Pino et al, 2019). However, independent researchers have failed to identify the proposed impact proxies in YDB aged sediments (Surovell et al, 2009; Daulton et al, 2010, 2017; Haynes et al, 2010; Holliday et al, 2016), questioned whether the markers are necessarily the result of an impact (van der Hammen and van Geel, 2008; A.C. Scott et al, 2010; Pigati et al, 2012; van Hoesel et al, 2012), criticized the methodologies used to date layers containing impact markers (Holliday and Meltzer, 2010; Blaauw et al, 2012; Meltzer et al, 2014; van Hoesel et al, 2014), or disputed the plausibility of an impact or airburst as described by proponents (Boslough et al, 2012). Proponents have also recently proposed that the hypothesized event produced the Hiawatha impact crater located in Greenland (Pino et al, 2019).…”