δ<sup>18</sup>O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material

Longinelli, A.; Sighinolfi, G. P.; Michele, Vincenzo De; Selmo, Enricomaria

doi:10.1111/j.1945-5100.2010.01147.x

Cited by 18 publications

(23 citation statements)

References 21 publications

(33 reference statements)

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“…We also observed distorted layers of hollow vesiculated silica glass tube-like features, similar to some LDG samples (Fig. 12), which are attributed to relic sedimentary bedding structures in the sandstone precursor (39). The Abu Hureyra tubular textures may be relic structures of thin-bedded chert that occurs within the regional chalk deposits.…”

Section: Sem or Eds Analyses To Determine Whether Their Spherules Aresupporting

confidence: 74%

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

Bunch

Hermes

Moore

et al. 2012

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

114

177

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It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica-and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe 3 Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO 2 glass, or lechatelierite, with flow textures (or schlieren) that form at >2,200°C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.tektite | microcraters | oxygen fugacity | trinitite Manuscript TextThe discovery of anomalous materials in a thin sedimentary layer up to a few cm thick and broadly distributed across several continents led Firestone et al. (1) to propose that a cosmic impact (note that "impact" denotes a collision by a cosmic object either with Earth's surface, producing a crater, or with its atmosphere, producing an airburst) occurred at 12.9 kiloannum (ka; all dates are in calendar or calibrated ka, unless otherwise indicated) near the onset of the Younger Dryas (YD) cooling episode. This stratum, called the YD boundary layer, or YDB, often occurs directly beneath an organic-rich layer, referred to as a black mat (2), that is distributed widely over North America and parts of South America, Europe, and Syria. Black mats also occur less frequently in quaternary deposits that are younger and older than 12.9 ka (2). The YDB layer contains elevated abundances of iron-and silica-rich microspherules (collectively called "spherules") that are interpreted to have originated by cosmic impact because of their unique properties, as discussed below. Other markers include sediment and magnetic grains with elevated iridium concentrations and exot...

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Section: Sem or Eds Analyses To Determine Whether Their Spherules Aresupporting

confidence: 74%

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

Bunch

Hermes

Moore

et al. 2012

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

114

177

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“…The rare earth element abundance patterns are indicative of a sedimentary precursor rock, and the trace element abundances and ratios are in agreement with an upper crustal source. In agreement with the strontium and neodymium isotopic data, which suggest a Pan-African age of the parent material for the LDG, Longinelli et al (2011) measured the d 18 O values of bulk rock and quartz from intrusives of Pan-African age and the results obtained were compatible with their values obtained for LDG samples. This was confirmed by Koeberl (2000) in an osmium isotopic study.…”

Section: Libyan Desert Glasssupporting

confidence: 86%

The Geochemistry and Cosmochemistry of Impacts

Koeberl

2014

Treatise on Geochemistry

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“…; Longinelli et al. ). Various field investigations have shown that their strewn field covers a circular area of about 21 km diameter (Barakat et al.…”

Section: Introductionmentioning

confidence: 99%

“…Svetsov and Watson (), Boslough and Crawford (), and Longinelli et al. () proposed that LDG did not originate from a meteorite impact, but from a comet airburst. Finally, using various isotopic compositions, Schaaf and Müller‐Sohnius () and Longinelli et al.…”

Section: Introductionmentioning

confidence: 99%

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Libyan Desert Glass: New field and Fourier transform infrared data

Fröhlich

Poupeau

Badou

et al. 2013

Meteorit & Planetary Scien

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Abstract-Results are presented of new geological observations and laboratory analyses on Libyan Desert Glass (LDG), a unique kind of impact glass found in Egypt, probably 28.5-29.4 million years in age. A new LDG occurrence has been discovered some 50 km southward of the main LDG occurrences in the Great Sand Sea. From Fourier transform infrared (FTIR) analysis, the molecular structure of LDG is refined and significant differences are shown between LDG specimens and other pure silica glasses (fulgurite, industrial fused quartz, and amorphous biogenic silica) that are related to differences in their structures. The slight variations observed here for the mean Si-O-Si angle between the different glasses are attributed to their thermal histories. With regard to the other glasses analyzed, the LDG infrared spectral parameters point to a higher ratio of discontinuities and defects in the tetrahedral (SiO 4 ) network. The quantitative mineralogical constitutions of sandstones and quartzites from the LDG geological setting were analyzed by FTIR. Cretaceous sandstones have a specific composition (about 90 wt% quartz, 10% dickite), clearly different from the Paleozoic ones (about 90 wt% quartz, but ≥7% kaolinite). It is shown that the reddish silts bearing the LDG are constituted mainly of microquartz enriched with dickite, whose particle size distribution is characteristic of fluvio-lacustrine deposits, probably Oligocene to Miocene in age. The target rocks, most probably quartz sand, resulted from the weathering (loss of the cementing microquartz) of the Cretaceous sandstones from the Gilf Khebir Plateau with deposition in a high-energy environment.

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δ¹⁸O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material

Cited by 18 publications

References 21 publications

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

The Geochemistry and Cosmochemistry of Impacts

Libyan Desert Glass: New field and Fourier transform infrared data

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δ18O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material

Cited by 18 publications

References 21 publications

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

The Geochemistry and Cosmochemistry of Impacts

Libyan Desert Glass: New field and Fourier transform infrared data

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δ¹⁸O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material