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首页> 外文期刊>Journal of Asian earth sciences >The Deccan Trap - Cretaceous-Paleogene boundary connection; new ~(40)Ar/~(39)Ar ages and critical assessment of existing argon data pertinent to this hypothesis
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The Deccan Trap - Cretaceous-Paleogene boundary connection; new ~(40)Ar/~(39)Ar ages and critical assessment of existing argon data pertinent to this hypothesis

机译：Deccan陷井-白垩纪-古宙边界连接；新的〜（40）Ar /〜（39）Ar年龄和与该假设相关的现有氩气数据的临界评估

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摘要

The Cretaceous-Paleogene boundary (KPgB) was dated by the ~(40)Ar/~(39)Ar method herein from the western interior of North America at 65.48 ± 0.12 Ma (1σ), in good agreement with other recent published estimates. For the Deccan Traps, India, new argon ages as well as others available in the literature, are assessed for reliability based on (a) statistical reliability of plateau/isochron sections and (b) freshness of material dated utilizing the alteration index method. From tholeiitic lavas from the Composite Western Ghats Section (CWGS), only six ages are found to be reliable estimates of the time of crystallization. These ages along with the magnetic polarity of the lavas agree with the geomagnetic polarity time scale (GPTS) at ～67-64 Ma. Alkaline rocks from the Anjar area of Kutch, provide three reliable ages that suggest a hiatus in lava extrusion around KPgB. For the Rajahmundry basalts, the upper flow's age defines its formation during chron 29n; a single age from the lower reversed polarity flow appears somewhat dichotomous when plotted against the GPTS. The reliable lava ages indicate the most voluminous (reversed polarity) sections of the CWGS were extruded at a time statistically indistinguishable from that of the KPgB. The Deccan Trap - KPgB faunal extinction hypothesis remains plausible, but must compete with the latest report, favoring a very close temporal connection (～0.03 m.y.) between the Chixculub (Impact) Crater and the KPgB.
机译：白垩纪-古近界（KPgB）是通过〜（40）Ar /〜（39）Ar方法从北美西部内陆测得的，年代为65.48±0.12 Ma（1σ），与其他近期发表的估计吻合良好。对于印度的Deccan捕集阱，根据（a）平稳/等时截面的统计可靠性和（b）使用变化指数法确定日期的材料新鲜度，评估了新的氩气年龄以及文献中其他可用的氩气的可靠性。从复合西高止山脉部分（CWGS）的熔融熔岩中，仅发现了六个年龄是结晶时间的可靠估计。这些年龄和熔岩的磁极性与〜67-64 Ma的地磁极性时标（GPTS）一致。来自库奇（Kutch）安贾尔（Anjar）地区的碱性岩石提供了三个可靠的年龄，表明在KPgB周围的熔岩挤出中存在裂隙。对于拉贾蒙德里玄武岩，上部流的年龄确定了其在时间29n的形成。相对于GPTS绘制时，来自较低极性反流动的单个年龄显得有些二分法。可靠的熔岩年龄表明，CWGS的最大体积（反极性）部分在挤出时与KPgB在统计上没有区别。 Deccan陷阱-KPgB动物灭绝假说仍然是合理的，但必须与最新报告相抗衡，这有利于Chixculub（Impact）陨石坑与KPgB之间的时间联系非常紧密（约0.03 m.y.）。

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