Depositional setting of the Upper Triassic siliceous micrite of the Mino-Tamba Belt

• Sano Hiroyoshi

  Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University

• Takano Atsushi

  Luna Incorporation

• Miyamoto Kazuki

  Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University

• Onoue Tetsuji

  Department of Earth and Environmental Sciences, Kumamoto University

Bibliographic Information

Other Title

• 美濃・丹波帯の上部三畳系珪質ミクライトの堆積場
• ミノ ・ タンバタイ ノ ジョウブ サンジョウケイケイシツ ミクライト ノ タイセキジョウ

Abstract

We present the mode of occurrence, microfacies, and age of the Kugo Limestone, which occurs as discrete blocks in the Middle Jurassic to earliest Cretaceous Neo mélange in the Kanayama Unit, western Mino Mountains, central Japan. The Kugo Limestone (~80 m thick) consists exclusively of siliceous micrite with common chert nodules. Siliceous micrite dominantly comprises radiolarian lime–mudstone, with lesser thin-shelled bivalve wackestone and packstone and lacks coarse terrigenous grains. These characteristics indicate its deep-marine sedimentation in a pelagic realm of a mid-oceanic region. The conodont biostratigraphy reveals an age of uppermost Carnian to lower Norian. The Kugo Limestone is coeval with, and similar in lithology to, the previously reported Upper Triassic siliceous micrite in mélange units of the Mino belt and neighboring Tamba belt. These units all contain varying amounts of basaltic volcaniclastic sediments including pebble-sized debris within limestone breccia of debris flow facies. Any dissimilarity lies in the lithologic association with bedded chert. In addition, the Mino–Tamba siliceous micrite shows a heteropic relationship with bedded chert of ocean floor facies in coherent units of the Mino–Tamba Belt. The Mino–Tamba siliceous micrite accumulated above and around the carbonate compensation depth (CCD), with underlying bedded chert. The heteropic relationship enables us to construct a sedimentary profile illustrating deposition of the Mino–Tamba siliceous micrite on a low-lying basaltic mound (presumably of hotspot origin) in a deep ocean floor setting where bedded chert accumulated simultaneously. The top of the basaltic mound was above the CCD and was covered by siliceous micrite lacking bedded chert. Siliceous micrite accompanying bedded chert accumulated on the slope of the mound around the CCD, into which limestone and basaltic debris were transported downslope.

Journal

• The Journal of the Geological Society of Japan

  The Journal of the Geological Society of Japan 123 (3), 163-178, 2017-03-15

  The Geological Society of Japan

Keywords

• Mino-Tamba Belt
• Late Triassic
• deep-marine pelagic limestone

Details

• CRID: 1390001206239674112
• NII Article ID: 130007288197
• NII Book ID: AN00141768
• DOI: 10.5575/geosoc.2016.0061
• ISSN: 13499963
• ISSN: 00167630
• NDL BIB ID: 028130231
• Web Site: http://id.ndl.go.jp/bib/028130231
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I028130231
• Web Site: https://www.jstage.jst.go.jp/article/geosoc/123/3/123_2016.0061/_pdf
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed