A new high-precision 40 Ar/ 39 Ar age for the Rochechouart impact structure: At least 5 Ma older than the Triassic-Jurassic boundary
A new high-precision 40 Ar/ 39 Ar age for the Rochechouart impact structure: At least 5 Ma older than the Triassic-Jurassic boundary
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Rochechouart 撞击构造的新高精度 40 Ar/ 39 Ar 年龄：比三叠纪-侏罗纪边界至少早 5 Ma
DOI：
10.1111/maps.12880
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发表时间：
2017
影响因子：
2.2
通讯作者：
Cohen B
中科院分区：
文献类型：
--
作者：
Cohen B
位于法国中南部的Rochechourt撞击结构，最大直径为40-50公里，以前被确定为三叠纪-侏罗纪边界的1%不确定性，当时全球约30%的属灭绝。为了高精度地评估撞击与三叠纪-侏罗纪边界之间的时间关系，我们使用多收集器ARGUS‐ V40 Ar/39 Ar质谱重新检查了该结构的年龄。四份冲击熔体的结果具有高度的可重复性，得出的年龄为206.92 ± 0.20/0.32 Ma（2σ，完全分析/外部不确定度）。因此，罗什舒阿尔特撞击构造比三叠纪-侏罗纪界线早5.6 ± 0.4 Ma，因此与大灭绝在时间上没有联系。罗什舒阿尔特以前被认为是一个多次撞击事件的一部分，但当与其他所谓的“成对”结构的新年龄相比，结果没有提供晚三叠世同步撞击的证据。广泛分布的中大西洋岩浆区的泛滥玄武岩仍然是三叠纪-侏罗纪大规模灭绝的最可能原因。
The Rochechourt impact structure in south‐central France, with maximum diameter of 40–50 km, has previously been dated to within 1% uncertainty of the Triassic–Jurassic boundary, at which time ~30% of global genera became extinct. To evaluate the temporal relationship between the impact and the Triassic–Jurassic boundary at high precision, we have re‐examined the structure's age using multicollector ARGUS‐V40Ar/39Ar mass spectrometry. Results from four aliquots of impact melt are highly reproducible, and yield an age of 206.92 ± 0.20/0.32 Ma (2σ, full analytical/external uncertainties). Thus, the Rochechouart impact structure predates the Triassic–Jurassic boundary by 5.6 ± 0.4 Ma and so is not temporally linked to the mass extinction. Rochechouart has formerly been proposed to be part of a multiple impact event, but when compared with new ages from the other purported “paired” structures, the results provide no evidence for synchronous impacts in the Late Triassic. The widespread Central Atlantic Magmatic Province flood basalts remain the most likely cause of the Triassic–Jurassic mass extinction.