An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis

Surovell, Todd A.; Holliday, Vance T.; Gingerich, Joseph A. M.; Ketron, Caroline; Haynes, C. Vance; Hilman, Ilene; Wagner, Daniel; Johnson, Eileen; Claeys, Philippe

doi:10.1073/pnas.0907857106

Cited by 90 publications

(83 citation statements)

References 14 publications

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“…Still others raised concerns over issues of replicability and laboratory protocols used in the original study (15). Here, we provide evidence that supports an alternative hypothesis for the accumulation of some of the markers in late Quaternary sediments.…”

supporting

confidence: 71%

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

Pigati

Latorre

Rech

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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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.

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supporting

confidence: 71%

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

Pigati

Latorre

Rech

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Also, in a Greenland ice core, Petaev et al (2013) found a large YDB abundance peak in the platinumgroup element platinum. Surovell et al (2009) found no YDB peaks in magnetic spherules, whereas LeCompte et al (2012) found large, welldefined YDB spherule peaks at sites common to the study by Surovell et al Also, critical overviews of the YDB hypothesis are presented in Pinter et al (2011) and Boslough et al (2012).…”

Section: Introductionmentioning

confidence: 86%

Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP

Kinzie¹,

Hee

Stich

et al. 2014

The Journal of Geology

170

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. A B S T R A C TA major cosmic-impact event has been proposed at the onset of the Younger Dryas (YD) cooling episode at ≈12,800 ‫ע‬ 150 years before present, forming the YD Boundary (YDB) layer, distributed over 150 million km 2 on four continents. In 24 dated stratigraphic sections in 10 countries of the Northern Hemisphere, the YDB layer contains a clearly defined abundance peak in nanodiamonds (NDs), a major cosmic-impact proxy. Observed ND polytypes include cubic diamonds, lonsdaleite-like crystals, and diamond-like carbon nanoparticles, called n-diamond and i-carbon. The ND abundances in bulk YDB sediments ranged up to ≈500 ppb (mean: 200 ppb) and that in carbon spherules up to ≈3700 ppb (mean: ≈750 ppb); 138 of 205 sediment samples (67%) contained no detectable NDs. Isotopic evidence indicates that YDB NDs were produced from terrestrial carbon, as with other impact diamonds, and were not derived from the impactor itself. The YDB layer is also marked by abundance peaks in other impact-related proxies, including cosmic-impact spherules, carbon spherules (some containing NDs), iridium, osmium, platinum, charcoal, aciniform carbon (soot), and high-temperature melt-glass. This contribution reviews the debate about the presence, abundance, and origin of the concentration peak in YDB NDs. We describe an updated protocol for the extraction and concentration of NDs from sediment, carbon spherules, and ice, and we describe the basis for identification and classification of YDB ND polytypes, using nine analytical approaches. The large body of evidence now obtained about YDB NDs is strongly consistent with an origin by cosmic impact at ≈12,800 cal BP and is inconsistent with formation of YDB NDs by natural terrestrial processes, including wildfires, anthropogenesis, and/or influx of cosmic dust.

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“…Consequently, determining the nature and origin of observed spherules is essential. Attempts to replicate the spherule abundances and peaks observed by (17) confirmed the presence of YDB spherules, while studies by Surovell et al (18) and Pinter et al (19) did not. Surovell et al examined sediment sequences across the YDB at seven archeological sites in North America, using radiocarbon dates and/or diagnostic cultural artifacts to identify the stratum likely to be the YDB.…”

mentioning

confidence: 91%

“…A number of independent groups have confirmed the presence of YDB spherules, but two have not. One of them [Surovell TA, et al (2009) Proc Natl Acad Sci USA 104:18155-18158] collected and analyzed samples from seven YDB sites, purportedly using the same protocol as Firestone et al, but did not find a single spherule in YDB sediments at two previously reported sites. To examine this discrepancy, we conducted an independent blind investigation of two sites common to both studies, and a third site investigated only by Surovell Firestone et al) proposed that a cosmic impact event occurred at the onset of the Younger Dryas (YD) cooling episode at about 12,900 calendar years Before Present (12.9 ka B.P.).…”

mentioning

confidence: 99%

Independent evaluation of conflicting microspherule results from different investigations of the Younger Dryas impact hypothesis

LeCompte

Goodyear

Demitroff

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Firestone et al. sampled sedimentary sequences at many sites across North America, Europe, and Asia [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 106:16016–16021]. In sediments dated to the Younger Dryas onset or Boundary (YDB) approximately 12,900 calendar years ago, Firestone et al. reported discovery of markers, including nanodiamonds, aciniform soot, high-temperature melt-glass, and magnetic microspherules attributed to cosmic impacts/airbursts. The microspherules were explained as either cosmic material ablation or terrestrial ejecta from a hypothesized North American impact that initiated the abrupt Younger Dryas cooling, contributed to megafaunal extinctions, and triggered human cultural shifts and population declines. A number of independent groups have confirmed the presence of YDB spherules, but two have not. One of them [Surovell TA, et al. (2009) Proc Natl Acad Sci USA 104:18155–18158] collected and analyzed samples from seven YDB sites, purportedly using the same protocol as Firestone et al., but did not find a single spherule in YDB sediments at two previously reported sites. To examine this discrepancy, we conducted an independent blind investigation of two sites common to both studies, and a third site investigated only by Surovell et al. We found abundant YDB microspherules at all three widely separated sites consistent with the results of Firestone et al. and conclude that the analytical protocol employed by Surovell et al. deviated significantly from that of Firestone et al. Morphological and geochemical analyses of YDB spherules suggest they are not cosmic, volcanic, authigenic, or anthropogenic in origin. Instead, they appear to have formed from abrupt melting and quenching of terrestrial materials.

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An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis

Cited by 90 publications

References 14 publications

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

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

Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP

Independent evaluation of conflicting microspherule results from different investigations of the Younger Dryas impact hypothesis

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