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  • Biodiversitätsforschung  (3)
  • Biologie  (3)
  • 1
    Online-Ressource
    Online-Ressource
    Climate and the Collapse of Maya Civilization
    American Association for the Advancement of Science (AAAS) ; 2003
    In:  Science Vol. 299, No. 5613 ( 2003-03-14), p. 1731-1735
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 299, No. 5613 ( 2003-03-14), p. 1731-1735
    Kurzfassung: In the anoxic Cariaco Basin of the southern Caribbean, the bulk titanium content of undisturbed sediment reflects variations in riverine input and the hydrological cycle over northern tropical South America. A seasonally resolved record of titanium shows that the collapse of Maya civilization in the Terminal Classic Period occurred during an extended regional dry period, punctuated by more intense multiyear droughts centered at approximately 810, 860, and 910 A.D. These new data suggest that a century-scale decline in rainfall put a general strain on resources in the region, which was then exacerbated by abrupt drought events, contributing to the social stresses that led to the Maya demise.
    Materialart: Online-Ressource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1080444
    RVK:
    TA 1000
    RVK:
    WA 15000
    Sprache: Englisch
    Verlag: American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2003
    ZDB Id: 128410-1
    ZDB Id: 2066996-3
    ZDB Id: 2060783-0
    SSG: 11
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Online-Ressource
  • 2
    Online-Ressource
    Online-Ressource
    Hafnium Isotope Stratigraphy of Ferromanganese Crusts
    American Association for the Advancement of Science (AAAS) ; 1999
    In:  Science Vol. 285, No. 5430 ( 1999-08-13), p. 1052-1054
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 285, No. 5430 ( 1999-08-13), p. 1052-1054
    Kurzfassung: A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in 87 Sr/ 86 Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.
    Materialart: Online-Ressource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.285.5430.1052
    RVK:
    TA 1000
    RVK:
    WA 15000
    Sprache: Englisch
    Verlag: American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999
    ZDB Id: 128410-1
    ZDB Id: 2066996-3
    ZDB Id: 2060783-0
    SSG: 11
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Online-Ressource
  • 3
    Online-Ressource
    Online-Ressource
    Niobium-Zirconium Chronometry and Early Solar System Development
    American Association for the Advancement of Science (AAAS) ; 2002
    In:  Science Vol. 295, No. 5560 ( 2002-03), p. 1705-1708
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 295, No. 5560 ( 2002-03), p. 1705-1708
    Kurzfassung: Niobium-92 ( 92 Nb) decays to zirconium-92 ( 92 Zr) with a half-life of 36 million years and can be used to place constraints on the site of p -process nucleosynthesis and the timing of early solar system processes. Recent results have suggested that the initial 92 Nb/ 93 Nb of the solar system was high ( 〉 10 −3 ). We report Nb-Zr internal isochrons for the ordinary chondrite Estacado (H6) and a clast of the mesosiderite Vaca Muerta, both of which define an initial 92 Nb/ 93 Nb ratio of ∼10 −5 . Therefore, the solar system appears to have started with a ratio of 〈 3 × 10 −5 , which implies that Earth's initial differentiation need not have been as protracted as recently suggested.
    Materialart: Online-Ressource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1067400
    RVK:
    TA 1000
    RVK:
    WA 15000
    Sprache: Englisch
    Verlag: American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2002
    ZDB Id: 128410-1
    ZDB Id: 2066996-3
    ZDB Id: 2060783-0
    SSG: 11
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Online-Ressource
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