Podrobnosti záznamu

Název
    Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago
Autor
    Bischoff, J. L.
    Bunch, T. E.
    Daniel Jr., I. R.
    DeCarli, P. S.
    Ferraro, D.
    Firestone, R. B.
    Goodyear, A. C.
    Hermes, R. E.
    Hillman, G. C.
    Howard, G. A.
    Israde-Alcántara, I.
    Kennett, D. J.
    Kennett, J. P.
    Kimbel, D. R.
    Kletetschka, G.
    Kloosterman, J. B.
    Lipo, C. P.
    Lopinot, N. H.
    Moore, A. M. T.
    Moore, Ch. R.
    Nábělek, Ladislav
    Ray, J. H.
    Revay, Z.
    Sakai, S.
    Tankersley, K. B.
    Weaver, J. C.
    West, A.
    Wittke, J. H.
Jazyk
    anglicky
Typ dokumentu
    článek v odborném periodiku
Zdrojový dokument - seriál
    Proceedings of the National Academy of Sciences of the United States of America
Svazek/č.
    Roč. 110, č. 23
Rok
    2013
Poznámky
    Rozsah: 10 s. : E
Předmětová kategorie
    Clovis-Folsom
    lechatelierite
    tektite
    wildfires
Klíčové slovo
    10
    12,800
    Across
    Ago
    Continents
    Deposition
    Evidence
    Four
    Impact
    Million
    Spherules
    Tonnes
Abstrakt (anglicky)
   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 degrees 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 degrees C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across similar to 50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.
Přispěvatel
    AV ČR Brno, Geologický ústav
Kód přispěvatele
    AV ČR, GLÚ
Zdrojový formát
    U
Datum importu
    23. 10. 2014