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

LeCompte, Malcolm A.; Goodyear, Albert C.; Demitroff, Mark; Batchelor, Dale; Vogel, Edward K.; Mooney, Charles; Rock, B. N.; Seidel, Alfred W.

doi:10.1073/pnas.1208603109

Cited by 67 publications

(108 citation statements)

References 42 publications

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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: 99%

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

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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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Section: Introductionmentioning

confidence: 99%

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

Self Cite

170

View full text Add to dashboard Cite

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“…2, p. 16021), the earliest archaeologically well-documented group occupying the continent. First introduced in a popular book in 2006 (1) and soon thereafter to the scientific community (2), YDIH proponents have offered geological and geochemical evidence of an extraterrestrial impact from localities in and outside of North America (3)(4)(5)(6)(7)(8)(9)(10)(11). Independent investigators have provided support as well (12,13).…”

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confidence: 99%

“…We systematically examined the chronologies of the supposed YDB layer at the 29 sites asserted in multiple sources (2,3,(5)(6)(7)(8)(9)(10)(11) to have evidence of a cosmic impact; our efforts included crosschecking original sources used by YDIH proponents. We find that the supposed YDB layer dates to the onset of the Younger Dryas at only 3 of those 29 sites.…”

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confidence: 99%

Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago

Meltzer

Holliday

Cannon³

et al. 2014

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

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Significance A key element underpinning the controversial hypothesis of a widely destructive extraterrestrial impact at the onset of the Younger Dryas is the claim that 29 sites across four continents yield impact indicators all dated to 12,800 ± 150 years ago. This claim can be rejected: only three of those sites are dated to this window of time. At the remainder, the supposed impact markers are undated or significantly older or younger than 12,800 years ago. Either there were many more impacts than supposed, including one as recently as 5 centuries ago, or, far more likely, these are not extraterrestrial impact markers.

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“…However, other research questions the evidence of an impact, focussing on perceived errors in the dating of the YD boundary layer (Holliday, 2015;Meltzer et al, 2014), the misidentification of terrestrially derived carbon spherules, shocked quartz, and nanodiamonds as extraterrestrial (Pinter et al, 2011;van Hoesel et al, 2015;Tian et al, 2011), the non-uniqueness of YD nanodiamond evidence , and inconsistencies regarding the physics of bolide trajectories and impacts (Boslough et al, 2013). Despite these criticisms, independent researchers have linked spherules found within the YD boundary layer to an impact (LeCompte et al, 2012) and have identified the source of the spherules as northeastern North America (Wu et al, 2013), not only supporting the hypothesis but also suggesting an impact site proximal to the southern margin of the Laurentide Ice Sheet (Wu et al, 2013). Most recently, Wolbach et al (2018a, b) catalogue extensive evidence of global wildfires they argue were ignited by the impact of fragments of a > 100 km diameter comet.…”

Section: Compatibility With Other Hypothesesmentioning

confidence: 99%

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

2018

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Abstract. The Younger Dryas is considered the archetypal millennial-scale climate change event, and identifying its cause is fundamental for thoroughly understanding climate systematics during deglaciations. However, the mechanisms responsible for its initiation remain elusive, and both of the most researched triggers (a meltwater pulse or a bolide impact) are controversial. Here, we consider the problem from a different perspective and explore a hypothesis that Younger Dryas climate shifts were catalysed by the unusually sulfurrich 12.880 ± 0.040 ka BP eruption of the Laacher See volcano (Germany). We use the most recent chronology for the GISP2 ice core ion dataset from the Greenland ice sheet to identify a large volcanic sulfur spike coincident with both the Laacher See eruption and the onset of Younger Dryasrelated cooling in Greenland (i.e. the most recent abrupt Greenland millennial-scale cooling event, the Greenland Stadial 1, GS-1). Previously published lake sediment and stalagmite records confirm that the eruption's timing was indistinguishable from the onset of cooling across the North Atlantic but that it preceded westerly wind repositioning over central Europe by ∼ 200 years. We suggest that the initial short-lived volcanic sulfate aerosol cooling was amplified by ocean circulation shifts and/or sea ice expansion, gradually cooling the North Atlantic region and incrementally shifting the midlatitude westerlies to the south. The aerosol-related cooling probably only lasted 1-3 years, and the majority of Younger Dryas-related cooling may have been due to the seaice-ocean circulation positive feedback, which was particularly effective during the intermediate ice volume conditions characteristic of ∼ 13 ka BP. We conclude that the large and sulfur-rich Laacher See eruption should be considered a viable trigger for the Younger Dryas. However, future studies should prioritise climate modelling of high-latitude volcanism during deglacial boundary conditions in order to test the hypothesis proposed here.

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

Cited by 67 publications

References 42 publications

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

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

Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

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