LA-ICP-MS U–Pb and fission-track ages of felsic tuff beds of the Takikubo Formation, Izumi Group in the Kan-onji district, eastern Shikoku, southwestern Japan
2017; Volume: 68; Issue: 3 Linguagem: Inglês
10.9795/bullgsj.68.119
ISSN2186-490X
AutoresAtsushi Noda, Tohru Danhara, Hideki Iwano, Takafumi Hirata,
Tópico(s)earthquake and tectonic studies
ResumoLA-ICP-MS U–Pb and fission-track (FT) dating were performed for detrital zircons in two felsic tuff samples (KT01 and KT02) in order to estimate the depositional age of the Takikubo Formation (Izumi Group) in the Kan-onji district, eastern Shikoku, southwestern Japan. Total 30 grains analyzed for each sample indicated that the U–Pb ages composed of multiple populations chiefly of younger (75–85 Ma) and older (85–95 Ma) clusters. The concordia ages calculated by grains in the younger clusters were 78.3±0.5 Ma (2σ) for KT01 (number of accepted grains n = 23) and 80.8±0.7 Ma (2σ) for KT02 (n = 9). The U–Pb ages of KT01 are comparable with 79±7 Ma (2σ) of the FT age from the same sample. The U–Pb ages of KT01 could constrain the maximum depositional age near the basal part of the Takikubo Formation, which was middle of the Middle Campanian (polarity chron C33n in the magnetostratigraphy).
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