Pleistocene Reef Complex Deposits in the Central Ryukyus, South-Western Japan

  1. G. F. Camoin2 and
  2. P. J. Davies3
  1. Y. Iryu,
  2. T. Nakamori and
  3. T. Yamada

Published Online: 27 MAY 2009

DOI: 10.1002/9781444304879.ch10

Reefs and Carbonate Platforms in the Pacific and Indian Oceans

Reefs and Carbonate Platforms in the Pacific and Indian Oceans

How to Cite

Iryu, Y., Nakamori, T. and Yamada, T. (2009) Pleistocene Reef Complex Deposits in the Central Ryukyus, South-Western Japan, in Reefs and Carbonate Platforms in the Pacific and Indian Oceans (eds G. F. Camoin and P. J. Davies), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304879.ch10

Editor Information

  1. 2

    CEREGE, Aix-en-Provence, France

  2. 3

    University of Sydney, Australia

Author Information

  1. Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Aobayama, Sendai 980-77, Japan

Publication History

  1. Published Online: 27 MAY 2009
  2. Published Print: 23 MAR 1998

ISBN Information

Print ISBN: 9780632047789

Online ISBN: 9781444304879

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Keywords:

  • Pleistocene reef complex deposits;
  • Ryukyu Group - carbonate and siliciclastic rocks;
  • Cycloclypeus-Operculina limestone;
  • poorly sorted detrital limestone;
  • siliciclastic sediments

Summary

The Ryukyu Group, composed of Pleistocene reef complex deposits that locally pass laterally into terrestrial sediments, is extensively distributed over the Ryukyu Islands. The carbonate rocks are divided into four facies: coral, rhodolith, Cycloclypeus–Operculina, and poorly sorted detrital limestones. Their depositional environments are specified based on the distribution and depth range of the present-day reef biota and associated sediments around the Ryukyu Islands. The stratigraphical succession of the Ryukyu Group is investigated at Toku-no-shima, Okierabu-jima and Yoron-jima, Central Ryukyus. Here reef complex deposits are associated with terrestrial sediments formed at relatively high and low sea-level stands. The highstand deposits are thick, occur extensively, and consist of terrestrial and marine conglomerates, and coral, rhodolith and poorly sorted detrital limestones that are arranged from inland proximal to coastal distal parts. Lowstand deposits are thin, composed mainly of coral limestone, and distributed in very limited areas at elevations less than the highstand deposits. Abundant rhodoliths occur in the deep fore-reef to insular shelf areas in the Pleistocene to present-day Ryukyus, which perhaps indicates that nutrient-rich marine environments observed in Halimeda banks have never prevailed over the shelves on the Ryukyus.