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  • 1
    Online Resource
    Online Resource
    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
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1067400
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2002
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    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
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.285.5430.1052
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 1999
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    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
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1080444
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2003
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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