Microfossils from Siliceous Rock Pebbles Contained in the Lower Cretaceous Ishido Formation of the Sanchu Group, Central Japan

DOI Web Site Web Site 1 Citations 35 References
  • OZEKI Masanori
    Graduate School of Life and Environmental Sciences, University of Tsukuba
  • SHIMIZU Norikazu
    Graduate School of Life and Environmental Sciences, University of Tsukuba
  • AGEMATSU Sachiko
    Department of Geoscience, Faculty of Life and Environmental Sciences, University of Tsukuba
  • SASHIDA Katsuo
    Department of Geoscience, Faculty of Life and Environmental Sciences, University of Tsukuba

Bibliographic Information

Other Title
  • 山中層群石堂層（下部白亜系）の珪質岩礫より産する微化石
  • ヤマナカソウグンセキドウソウ(カブ ハクアケイ)ノ ケイシツガンレキ ヨリ サンスル ビカセキ

Search this article

Abstract

<p> Zircons in Cretaceous sandstones have recently been the focus of a new provenance analysis technique. Microfossil-bearing clasts in conglomerate are also used in this analysis; however, there are few reports on clasts, including microfossils, which are mainly found in the vicinity of Shikoku and Hokuriku districts. Although the Ishido Formation, Sanchu Group, in the Kanto Mountains, is considered to be Barremian in age based on the occurrences of ammonoids, interbedded with conglomeratic beds, there have been no reports of microfossil-bearing clasts from this bed. To confirm whether each fore-arc basin in the whole of southwest Japan had a common hinterland during the Late Mesozoic, microfossils are extracted from gravels in the Ishido Formation to examine their ages. As a result of acidic treatment, Permian and Triassic radiolarians and Triassic conodonts are obtained from eight chert and siliceous mudstone pebbles of the Ishido Formation. On the basis of their lithofacies and ages, these pebbles of this formation are likely to derive from the Chichibu Belt, which constitutes a large part of the Kanto Mountains. These results indicate that, in the Early Cretaceous period, not only granitic rocks but also Jurassic accretionary complexes were exposed as hinterlands of each fore-arc basin in the Shikoku and Kanto districts. Moreover, based on previous reports on the zircon spectra in Cretaceous sandstones and microfossil-bearing clasts in the conglomerates, hinterlands, such as granitic rocks and Jurassic accretionary complexes, of each fore-arc basin in the whole of southwest Japan including the Kanto district, as well as Kyushu and Shikoku districts, indicate common exposure and denudation histories.</p>

Journal

Citations (1)*help

See more

References(35)*help

See more

Related Projects

See more

Keywords

Details 詳細情報について

Report a problem

Back to top