Age spectra of zircon and related phases from impactites of late Triassic meteorite impact structures and their ejecta deposits

该建议旨在研究晚三叠世（Norian）陨石撞击结构。将用灵敏高分辨率离子微探针技术分析三个撞击结构的撞击岩中的锆石：Manicouagan（100公里厚）、Saint Martin（40公里厚）和罗什舒阿尔特（23公里厚）。根据来自不同陨石坑的撞击岩和靶岩的锆石特征年龄谱进行的物源分析将用于调查它们对远地喷出物沉积物的贡献。将在不列颠哥伦比亚省、加拿大新斯科舍省的芬迪盆地和英国西南部的Norian剖面测试是否存在与Manicouagan撞击坑的形成相对应的全球喷出物层。利用透射电子显微镜和显微拉曼光谱学对冲击变质锆石和相关多晶型物进行详细研究，将补充这项研究，以改进用于撞击事件的U-Pb测年技术。这项研究的主要目标是建立一种方法，用于识别远距离撞击喷出物沉积物和完善这些事件的定年。确定和分析这些关键标志层将完善陨石撞击地球的地层记录，并揭示其潜在的环境影响。

This proposal aims to investigate late Triassic (Norian) meteorite impact structures. Zircons from impactites of three impact structures will be analyzed by the Sensitive High-Resolution Ion Micro-Probe (SHRIMP) technique: Manicouagan (100 km Ø), Saint Martin (40 km Ø) and Rochechouart (23 km Ø). Provenance analyses based on characteristic age spectra of zircons from the different craters’ impactites and target rocks will be used to investigate their contribution to distal ejecta deposits. A test for the existence of a global ejecta layer that corresponds to the formation of the Manicouagan impact crater will be undertaken at Norian sections in British Columbia, in the Fundy basin of Nova Scotia, Canada, and in Southwest Britain. A detailed study of shock-metamorphosed zircons and related polymorphs, using transmission electron microscopy and micro-Raman spectroscopy, will complement the study in order to refine the U-Pb dating technique as applied to impact events. Primary goals of this study are the establishment of a method for the identification of distal impact-ejecta deposits and the refinement of the dating of these events. The identification and analysis of such critical marker horizons will refine the stratigraphic record of meteorite impacts on Earth and unravel their potential environmental effects.