...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Re-Os depositional ages and seawater Os estimates for the Frasnian-Famennian boundary: Implications for weathering rates, land plant evolution, and extinction mechanisms
【24h】

Re-Os depositional ages and seawater Os estimates for the Frasnian-Famennian boundary: Implications for weathering rates, land plant evolution, and extinction mechanisms

机译：Frasnian-Famennian边界的Re-Os沉积年龄和海水Os估计：对风化率，陆地植物演化和灭绝机制的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Four TOC-rich shale intervals spanning the Frasnian-Famennian (F-F) boundary were recovered in a drillcore (West Valley NX-1) from western New York (USA) and radiometrically dated using Re-Os. Two of the black shale intervals (WVC785 from similar to 2.9 m below, and WVC754 from similar to 6.4 m above the F-F boundary, respectively) yielded statistically overlapping ages with uncertainties of < 1.1%. An interpolated age and associated graphically determined uncertainty of 372.4 +/- 3.8 Ma provides new absolute age constraints on the F-F boundary. This date is similar to 4.1 Ma younger than the latest proposed F-F boundary age of 376.1 Ma obtained by interpolation of U-Pb dates from volcanic zircon [Kaufmann, B., 2006. Calibrating the Devonian Time Scale: A synthesis of U-Pb ID-TIMS ages and conodont stratigraphy. Earth-Science Reviews 76, 175-190], and within uncertainty of the International Commission on Stratigraphy accepted date of 374.5 +/- 2.6 Ma. A third date (from sample WVC802, similar to 8.2 m beneath the F-F boundary) yielded an imprecise age of 357 23 Ma, owing in part to a limited Re/Os range. The initial Os-187/Os-188 (0.45 to 0.47), reflecting contemporaneous seawater Os values, are low but similar to the value of 0.42 reported for the Exshaw Fm (Canada) at the Devonian-Mississippian boundary (ca. 361 Ma) [Selby D., Creaser R.A., 2005. Direct radiometric dating of the Devonian-Mississippian time-scale boundary using the Re-Os black shale geochronometer. Geology 33, 545-548]. This may suggest fairly constant and low global continental weathering rates during the Late Devonian, although in view of the short residence time of Os in seawater (similar to 1-4 x 10(4) yr), further measurements are needed to assess potential short-term variation in seawater Os ratios. Owing to low Os and Re abundances at the F-F boundary, our data are inconsistent with long-term volcanism and bolide impact as potential Late Devonian mass extinction mechanisms. In addition, the Frasnian-Famennian ocean appears to have been depleted with respect to Re, possibly indicating an exhaustion of the Re seawater reservoir owing to high burial rates of redox-sensitive elements under dysoxic/anoxic conditions leading up to the F-F boundary. (c) 2007 Elsevier B.V. All rights reserved.
机译：在纽约（美国）西部的一个钻芯（西山谷NX-1）中，发现了横跨Frasnian-Famennian（F-F）边界的四个富含TOC的页岩层段，并用Re-Os进行了放射性测年。黑色页岩层段中的两个（分别位于F-F边界上方的WVC785距下方约2.9 m和接近​​6.4m的WVC754）产生的统计重叠年龄具有不确定性<1.1％。插值年龄和372.4 +/- 3.8 Ma的相关图形确定的不确定性在F-F边界上提供了新的绝对年龄约束。该日期比最新提议的376.1 Ma的FF边界年龄年轻4.1 Ma，该年龄是通过对锆石中的U-Pb日期进行插值获得的[Kaufmann，B.，2006。校准泥盆纪时标：U-Pb ID的合成-TIMS年龄和牙形质地层。 [Earth-Science Review 76，175-190]，并且在国际地层委员会的不确定性范围内，接受日期为374.5 +/- 2.6 Ma。第三次约会（来自样本WVC802，类似于F-F边界以下8.2 m）产生了357 23 Ma的不精确年龄，部分原因是Re / Os范围有限。最初的Os-187 / Os-188（0.45至0.47）反映了同期的海水Os值，虽然较低，但与泥盆纪-密西西比边界（大约361 Ma）的Exshaw Fm（加拿大）报道的0.42相似。 [Selby D.，Creaser RA，2005。使用Re-Os黑色页岩测年仪对泥盆纪-密西西比河时标边界进行直接辐射测年。地质33，545-548]。这可能表明泥盆纪晚期全球大陆风化率相当恒定且较低，尽管鉴于Os在海水中的停留时间较短（类似于1-4 x 10（4）年），仍需要进一步测量以评估潜在的短期海水Os比的长期变化。由于F-F边界的Os和Re丰度较低，我们的数据与长期的火山作用和硼化物撞击（潜在的泥盆纪晚期生物灭绝机制）不一致。此外，弗拉斯尼亚－法门尼洋似乎已对稀土资源进行了枯竭，这可能表明由于在缺氧/缺氧条件下导致F-F边界的氧化还原敏感元素的高掩埋率，Re海水库已经枯竭。 （c）2007 Elsevier B.V.保留所有权利。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号