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Report No.

Iridium concentration and noble gas composition of Cretaceous-Tertiary boundary clay from Stevns Klint, Denmark

Osawa, Takahito; Hatsukawa, Yuichi; Nagao, Keisuke*; Koizumi, Mitsuo; Oshima, Masumi; Toh, Yosuke  ; Kimura, Atsushi; Furutaka, Kazuyoshi

The Cretaceous-Tertiary (K-T) boundary about 65 million years ago records a mass extinction event caused by a bolide impact. K-T boundary clay collected from Stevns Klint, Denmark was investigated in this work. Iridium concentrations of eight clays across the K-T boundary were determined using a multiple $$gamma$$-ray analysis system after neutron activation. Anomalously high Ir concentrations were detected in five marl samples, with the highest concentration being 29.9 ppb. Four samples were analyzed for all noble gases. No extraterrestrial Ar, Kr, and Xe were discovered in any of the samples, although most of the $$^{3}$$He which was detected was extraterrestrial. Solar-like Ne was observed only in the sample SK4, which had an Ir concentration of 14.3 ppb, indicating the presence of micrometeorites.



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Category:Geochemistry & Geophysics



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