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

• Applicant: Dr. Axel Wittmann
• Subject Area: Palaeontology
• Term: from 2008 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 52363829

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.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Dr. John G. Spray, Ph.D.