Iridium anomaly associated with the Australasian tektite-producing impact: Masses of the impactor and of the Australasian tektites
Iridium anomaly associated with the Australasian tektite-producing impact: Masses of the impactor and of the Australasian tektites
复制标题
与澳大利亚玻璃陨石产生影响相关的铱异常：撞击体和澳大利亚玻璃陨石的质量
DOI：
10.1016/0016-7037(93)90204-a
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发表时间：
1993
影响因子：
5
通讯作者：
J. Wasson
中科院分区：
文献类型：
--
作者：
G. Schmidt;Lei Zhou;J. Wasson
最近发表的研究大洋钻探计划（ODP）的核心从东南亚附近的揭示微玻璃陨石含量远高于以前研究的核心，这表明铱含量可能会增加玻璃陨石轴承层。我们在东印度洋Ninetyeast海岭ODP 758 B岩芯中确定了一个正的Ir异常，峰值Ir浓度为190 pg/ g，约为连续谱水平的2倍。在10.87 ~ 11.32 m的深度范围内，Ir的净注量为1.8 ± 0.5 ng cm− 2;一个与微玻璃陨石有关的小的额外峰值也贡献了0.5 ng Ir cm−2。769 A岩芯中的Ir浓度显示出更大的分散性，但Ir的小幅增加与微玻璃陨石丰度峰值有关;我们对约束不佳的注量的最佳估计为1.3 ± 0.7 ng cm− 2。深海岩芯数据显示，微玻璃陨石注量福尔斯在远离东南亚的地方呈指数下降，在~400 km处注量下降2倍。在东南亚，这一趋势与泰国东北部熔融片的证据推断的大约1.1 g cm− 2的质量通量合并。综合推断的分布得出澳大拉西亚玻璃陨石的总质量为3.2 ·1016克，远高于先前的估计。假设撞击物的沉降物分布和沉积物成分相似，我们可以计算出其质量为1.5 ·1015 g，比白垩纪末造成沉降的撞击物的最小质量小3个数量级。
Recently published studies of Ocean Drilling Project (ODP) cores from near southeast Asia revealed microtektite contents much higher than those in previously studied cores, suggesting that Ir contents might be enhanced in the tektite-bearing horizons. We determined a positive Ir anomaly in ODP core 758B from the Ninetyeast Ridge, eastern Indian Ocean; the peak Ir concentration of 190 pg/ g was ~2× the continuum level. The net Ir fluence is 1.8 ± 0.5 ng cm−2over the depth interval from 10.87 to 11.32 m; a small additional peak also associated with microtektites contributes another 0.5 ng Ir cm−2. Concentrations of Ir in core 769A show more scatter, but a small Ir enhancement is associated with the peak microtektite abundance; our best estimate of the poorly constrained fluence is 1.3 ± 0.7 ng cm−2.Data on deep-sea cores show that the microtektite fluence falls exponentially away from southeast Asia, the fluence dropping a factor of 2 in ~400 km. In southeast Asia the trend merges with a roughly estimated mass fluence of ~ 1.1 g cm−2inferred from evidence of a melt sheet in northeast Thailand. Integration of the inferred distribution yields a total mass of Australasian tektites of 3.2 · 1016g, much higher than previous estimates. Assuming a similar fallout distribution for the impactor and a chondritic composition allows us to calculate its mass to be 1.5 · 1015g, about 3 orders of magnitude smaller than the minimum mass of the impactor responsible for the extinctions at the end of the Cretaceous.
影响因子：
56.9
作者：
ALVAREZ, LW;ALVAREZ, W;MICHEL, HV
通讯作者：
MICHEL, HV