Radiolarian assemblages of the Izumi Group in Shikoku and western Awaji Island, Southwest Japan

Yamasaki, Tetsuji

doi:10.5575/geosoc.93.403

Cited by 29 publications

(21 citation statements)

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“…9), while Hollis and Kimura (2001) reviewed the Campanian and Maastrichtian radiolarian zonations in Japan. The radiolarian zonation of the Izumi Group was discussed based on the occurrence of Amphipyndax pseudoconulus, A. tylotus, Dictyomitra koslovae, D. formosa and Pseudotheocampe abschnitta (Yamasaki, 1987;Ishida and Hashimoto, 1998;Tanaka and Yamasaki, 2000;Hashimoto et al, 2001).…”

Section: Introductionmentioning

confidence: 97%

Revised radiolarian zonation of the Upper Cretaceous Izumi inter-arc basin (SW Japan)

Hashimoto

Ishida

Yamasaki

et al. 2015

Revue de Micropaléontologie

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Section: Introductionmentioning

confidence: 97%

Revised radiolarian zonation of the Upper Cretaceous Izumi inter-arc basin (SW Japan)

Hashimoto

Ishida

Yamasaki

et al. 2015

Revue de Micropaléontologie

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“…Macro-fossils (ammonoids and inoceramids) and micro-fossils (radiolarian assemblages) show that the depositional age of the Izumi Group are Campanian to Maastrichtian, Late Cretaceous (Suyari, 1973;Bando and Hashimoto, 1984;Yamasaki, 1987;Hashimoto et al, 2015). Those paleontological studies indicate that the depositional ages are younging toward the east.…”

Section: Introductionmentioning

confidence: 99%

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

Noda

Danhara²,

Iwano³

et al. 2017

Bull. Geol. Surv. Japan

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LA-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).Keywords: Campanian, Cretaceous, Felsic tuff, Fission-track age, Izumi Group, Shikoku, Takikubo Formation, U-Pb age IntroductionThe Izumi Group is forearc basin deposits of the Late Cretaceous, which is narrowly distributed from western Shikoku to the Kii Peninsula along the northern side of the Median Tectonic Line. Macro-fossils (ammonoids and inoceramids) and micro-fossils (radiolarian assemblages) show that the depositional age of the Izumi Group are Campanian to Maastrichtian, Late Cretaceous (Suyari, 1973;Bando and Hashimoto, 1984;Yamasaki, 1987;Hashimoto et al., 2015). Those paleontological studies indicate that the depositional ages are younging toward the east. On the other hand, the paleocurrent directions in the main facies suggest the sediment derivation was mainly from east-northeast to west-southwest (Suyari, 1973;Miyata, 2004), as opposed to the younging direction of the depositional ages. These facts imply that the sedimentary basin of the Izumi Group had been developed in association with strike-slip fault activities (Ichikawa et al., 1981;Miyata, 1989;Noda and Toshimitsu, 2009). Progressive fault displacements along the pull-apart basins could migrate the basin depocenters (e.g., Noda, 2013).Recently, details of the Late Cretaceous volcanic activities in the Sanyo Belt, which is situated at the north of the Izumi Group, were revealed by using U-Pb ages of igneous zircon grains in the felsic volcanic rocks and welded tuff beds (Sato, 2016; Sato et al., 2016a, b) (Fig. 1A). Therefore, radioisotope geochronological data in the Izumi Group may be useful to compare with the volcanic activities in magmatic fronts and to discuss temporal and spatial evolution of the sedimentary basin during the Late Cretaceous time. Although there are a few fission-track ages reported from the Izumi Group of Shikoku Island and the Kii Peninsula (Fig. 1A), no FT and U-Pb age data have been reported from eastern Shikoku to date. This paper reports LA-ICP-MS U-Pb and FT ages of zircons in two felsic tuff beds of the Takikubo Formation (Yamasaki, 1986;Matsuura et al., 2002), which is the lower most formation of the main facies ...

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“…1 Ogg et al 2004Foreman 19771987Taketani, 1982, 1995;, 1995;Hollis and Kimura, 2001198719871973D. koslovae 1987Foreman 1975, 19771987 …”

Section: Kmmentioning

confidence: 99%

Radiolarians from the Upper Cretaceous Himenoura Group, Nakakoshiki-jima Island, Kagoshima Prefecture, Japan.

Aramaki¹,

Komatsu²,

Miyake³

et al. 2013

Jour. Geol. Soc. Japan

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Upper Cretaceous radiolarians are commonly found in the E lithological unit of the Himenoura Group, Nakakoshiki-jima Island, Kagoshima Prefecture, Kyushu, Japan. This radiolarian assemblage is characterized by Amphipyndax stocki, Dictyomitra koslovae, D. multicostata, Pseudoaulofacus floresensis, and Stichomitra asymbatos, indicative of deposition between the Santonian and middle Campanian. The E lithological unit probably formed during the middle Campanian, as the underlying D lithological unit contains abundant middle Campanian inoceramids.

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Radiolarian assemblages of the Izumi Group in Shikoku and western Awaji Island, Southwest Japan

Cited by 29 publications

References 0 publications

Revised radiolarian zonation of the Upper Cretaceous Izumi inter-arc basin (SW Japan)

Revised radiolarian zonation of the Upper Cretaceous Izumi inter-arc basin (SW Japan)

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

Radiolarians from the Upper Cretaceous Himenoura Group, Nakakoshiki-jima Island, Kagoshima Prefecture, Japan.

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