Framboidal iron oxide: Chondrite-like material from the black mat, Murray Springs, Arizona

Fayek, Mostafa; Anovitz, Lawrence M.; Allard, Lawrence F.; Hull, Sharon

doi:10.1016/j.epsl.2011.11.033

Cited by 22 publications

(16 citation statements)

References 35 publications

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“…The proposed impact deposited the YDB layer, which contains many cosmic-impact proxies, including magnetic and glassy impact spherules, iridium, fullerenes, carbon spherules, glass-like carbon, charcoal, and aciniform carbon, a form of soot (Firestone et al 2007;Wittke et al 2013). In North America and the Middle East, Bunch et al (2012) identified YDB melt-glass that formed at high temperatures (1730Њ to 12200ЊC), as also reported by three independent groups, Mahaney et al (2010) in South America and Fayek et al (2012) and Wu et al (2013) in North America. This study focuses solely on nanodiamonds (NDs), and so, for independent discussions of other proxies, see Haynes et al (2010) and Paquay et al (2009), who found no evidence for the platinum-group elements iridium or osmium.…”

Section: Introductionsupporting

confidence: 79%

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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Section: Introductionsupporting

confidence: 79%

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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“…1) that reported finding significant YDB spherule abundances, as summarized in high-profile previously published papers by Israde et al (7), Bunch et al (8), and LeCompte et al (13). The nine additional sites are located in Arizona (14)(15)(16), Montana † , New Mexico, Maryland, South Carolina (13), Pennsylvania (17); Mexico ‡ , and Venezuela (18)(19)(20)(21). In response to such claims, we here present the results of one of the most comprehensive investigations of spherules ever undertaken to address questions of geochemical and morphological characteristics, distribution, origin, and processes involved in the formation of YDB spherules.…”

Section: Significancementioning

confidence: 84%

“…When fragments of the YDB impactor entered Earth's atmosphere, they fragmented even further, yielding multiple atmospheric airbursts that each produced shock fronts. This multi-impact scenario is supported by two lines of evidence: first, the concentrations of multimillimeter-sized YDB melt-glass and spherules in Syria, Pennsylvania, South Carolina (8,17), Arizona (15), and Venezuela (18)(19)(20)(21) are separated by up to 12,000 km. Such multimillimetersized, aerodynamically shaped objects are probably too large to have traveled 12,000 km during a single airburst/impact (8).…”

Section: Geochemical Andmentioning

confidence: 88%

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago

Wittke

Weaver

Bunch

et al. 2013

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

124

187

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Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world's premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200°C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730°C, indicating that impactrelated incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.Clovis-Folsom | lechatelierite | tektite | wildfires

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“…Magnetic grains at several YDB sites were reported to be enriched in Ir but inferred to show a nugget effect as sometimes Ir enrichment could not be reproduced (10). The concentrations of magnetic spherules reported by Firestone et al (10) have been confirmed by seven independent groups (20,23) from YDB sites in Venezuela (24), Arizona (25), New Mexico, South Carolina, and Maryland (26). Another study by Surovell et al (27) was unable to replicate either the abundances or the chronostratigraphy of the magnetic spherules reported by Firestone et al (10).…”

Section: Significancementioning

confidence: 93%

Origin and provenance of spherules and magnetic grains at the Younger Dryas boundary

Sharma

LeCompte

et al. 2013

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

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Significance This study ties the spherules recovered in Pennsylvania and New Jersey to an impact in Quebec about 12,900 y ago at the onset of Younger Dryas. Our discovery resulted from an exhaustive search that examined the question of whether there is any evidence of extraterrestrial platinum group metals present in the bulk sediments, magnetic grains, and spherules recovered from the Younger Dryas boundary (YDB). We find that the spherules are likely quenched silicate melts produced following the impact at the YDB. The source of spherule osmium, however, is likely terrestrial and not meteorite derived.

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Framboidal iron oxide: Chondrite-like material from the black mat, Murray Springs, Arizona

Cited by 22 publications

References 35 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

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago

Origin and provenance of spherules and magnetic grains at the Younger Dryas boundary

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