Cosmic spherules in the geologic record

Taylor, Susan; Brownlee, D. E.

doi:10.1111/j.1945-5100.1991.tb01040.x

Cited by 97 publications

(96 citation statements)

References 14 publications

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“…Most cosmic Si-rich spherules derive from the most common type of cosmic object, stony meteorites, which are enriched in MgO, so that ∼98% of those spherules have >10 wt% MgO (average: 29%; range: 1-55%; SI Appendix, Fig. S23A) (45,46 We also compared elemental abundances of 90 Fe-rich cosmic spherules having >63 wt% FeO with YDB objects (subset >63 wt % FeO), but found them to be dissimilar ( Fig. 4B; SI Appendix, Table S6).…”

Section: Geochemical Andmentioning

confidence: 99%

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.

122

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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Section: Geochemical Andmentioning

confidence: 99%

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.

122

187

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“…It should be noted that spherules with intermediate textures between the vitreous and barred ones and between the barred and porphyritic textures were also found. This demonstrates possible genetic relationships between the various types of the stony spherules (Taylor and Brownlee 1991) and indicates that the structures and textures of spherules depend on the thermal history and on their primary chemical composition (Brownlee, Bates, and Beauchamp 1983), including the content of volatilesespecially water. A few spherules display a continuous network of dendritic iron oxide crystals in a glass matrix (Fig.…”

Section: Spherulesmentioning

confidence: 99%

“…The straight line on the Mg/Al versus Si/Al plot fits data on bulk carbonaceous chondrites (r = 0.96). The data on the CS are from Kurat et al (1993), Papanastassiou et al (1983), Blanchard et al (1980), Taylor and Brownlee (1991), Maurette et al (1986), and Taylor et al (2000); the data on the UMMs and SMMs are from Kurat et al (1993Kurat et al ( , 1994, Robin et al (1990), andOlinger et al (1990); the data on the chondrites are from Wasson and Kallemeyn (1988), Jarosewich (1990), McSween and Richardson (1977), and Scott et al (1988). (Fig.…”

Section: Comparing Cs With Other Micrometeorites and Carbonaceous Chomentioning

confidence: 99%

“…Micrometeorites can be found where convenient conditions result in their accumulation and preservation (Taylor and Brownlee 1991). Initially, deep-sea deposits (red clay) were the main source for cosmic spherules (Brownlee 1981(Brownlee , 1985, but now micrometeorites are collected mainly from polar ice in the ablation zone of the Greenland ice cap (Maurette et al 1986 and the Antarctic ice sheet (Maurette et al 1991(Maurette et al , 1992Taylor, Lever, and Harvey 2000;Taylor, Lever, and Govoni 2001;Iwata and Imae 2001).…”

Section: Introductionmentioning

confidence: 99%

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Micrometeorites from the northern ice cap of the Novaya Zemlya archipelago, Russia: The first occurrence

Badjukov

Raitala

2003

Meteorit & Planetary Scien

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Abstract-Glacial deposits at the margins of the ice cap of the northern island of the Novaya Zemlya archipelago, Russia, contain numerous spherules and rare scoriaceous particles thought to be extraterrestrial. The 1 Kyr old glacier has decreased in volume and coverage during the last 40 years, leaving the spherules contained in the ice at the margins of the glacier where they can be easily collected.The spherules are similar in their appearance, texture, and mineralogy to cosmic spherules found in deep-sea sediments in Greenland and Antarctica. Silicate spherules have typical bar-like textures (75%) or porphyritic textures (15%), while other spherules are glassy (7%). The spherules from Novaya Zemlya are altered only slightly. There are spherules consisting of iron oxides, metal cores with iron oxide rims, a continuous network of iron oxide dendrites in a glass matrix, and particles rich in chromite (3%). Some spherules contain metal droplets and relict forsterite and low-Ca pyroxene. Silicate spherule compositions match compositions of other cosmic spherules. Both Nova Zemlya and other cosmic spherules are close to carbonaceous chondrite matrices in patterns of variations for Ca, Mg, Si, and Al, which might suggest that their predecessor was similar to carbonaceous chondrite matrices. Unmelted micrometeorites are generally depleted in Ca and Mg and enriched in Al relative to cosmic spherules. The depletion of the micrometeorites in Ca and Mg can be connected with their terrestrial alteration (Kurat et al. 1994), while the Al enrichment seems to be primary.

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“…Wyatt and Whipple, 1950;Burns et al, 1979Burns et al, 1979Gustafson, 1994 11.2 km s 1 Flynn, 1989;Jackson and Zook, 1992 40000 20000 Love and Brownlee, 199380-115 km 10% Taylor et al, 19989 Halliday et al, 1989Bland et al, 1996;Taylor et al, 1998Sandford, 1987Warren andZolensky, 1994 Ganapathy et al, 1978;Murrell et al, 1980;Blanchard et al, 1980;Taylor and Brownlee, 1991Maurette et al, 1987, 1991Taylor et al, 1998;Nakamura et al, 1999Nakamura et al, , 1998, 1998 interplanetary Taylor and Brownlee, 1991;Yada et al, 2005;Genge et al, 2008Maurette et al, 1991Taylor et al, 1998 2% Harvey andTaylor et al, 2000 26-27% Taylor andBrownlee, 1991;Taylor et al, 2000 Taylor andBrownlee, 1991; day et al, 1984Halliday, 20012 Huss, 1990Zolensky et al, 1990;Bland et al, 1996 Kyte et al, 1996;Liu et al, 2009;Schulte et al...…”

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confidence: 99%

Accretion of extraterrestrial matter recorded in the Triassic and Jurassic bedded chert sequence, southwest Japan

Onoue

Sato

2015

Jour. Geol. Soc. Japan

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Triassic and Jurassic bedded chert sequences in Japanese accretionary complexes are recognized as pelagic deep-sea deposits characterized by very low sedimentation rates (less than a few millimeters per thousand years) and the absence of coarse-grained terrigenous clastics. Owing to their low sedimentation rates and long-term continuous deposition, these bedded cherts may record the accretionary history of extraterrestrial material over geologic time. Here, we review studies of extraterrestrial material contained in bedded chert sequences from the Jurassic accretionary complexes, southwest Japan. Cosmic spherules, which are submillimeter-sized extraterrestrial particles that melt during atmospheric entry, have been found in Triassic and Jurassic bedded cherts from the MinoTanba and Chichibu belts. Two major spherule types have been identified, based mainly on their mineral and chemical compositions: iron-type and silicate-type. The extraterrestrial origin is indicated by the presence of metallic iron and nickel in the iron-type spherules, and by the chondritic composition and mineral assemblages of the silicate-type spherules, which contain olivine and low-Ca pyroxene. The detection of platinum group elements (PGE) and data on osmium (Os) isotope ratios ( Os/ Os) in the cherts provide evidence for crater-forming meteorite impact events. Anomalously high PGE concentrations and negative Os isotope-ratio excursions reported from Upper Triassic bedded cherts are also interpreted to indicate a large extraterrestrial impact event. Systematic studies of ancient cosmic spherules and extraterrestrial PGE signatures in bedded cherts could provide evidence for long-term changes in the composition and flux of incoming extraterrestrial matter.

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Cosmic spherules in the geologic record

Cited by 97 publications

References 14 publications

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

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

Micrometeorites from the northern ice cap of the Novaya Zemlya archipelago, Russia: The first occurrence

Accretion of extraterrestrial matter recorded in the Triassic and Jurassic bedded chert sequence, southwest Japan

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