Responses of coral reefs to increased amplitude of sea-level changes at the Mid-Pleistocene Climate Transition

Kazuyuki Yamamoto, Yasufumi Iryu, Tokiyuki Sato, Shun Chiyonobu, Kenichi Sagae, Eiichi Abe

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29 Citations (Scopus)

Abstract

We show responses of coral reefs to increased amplitude of sea-level changes at the Mid-Pleistocene Climate Transition (MPT) based on lithostratigraphic, sedimentologic and calcareous nannofossil biostratigraphic investigations on Pleistocene reef-complex deposits (Ryukyu Group) on the Motobu Peninsula, Okinawa-jima, Central Ryukyus. Our data show that reef growth started in earliest Quaternary time (1.45-1.65 Ma) and that extensive reef formation dates back to ∼ 0.8 Ma. The mode of Quaternary sedimentation changed at ∼ 0.8 Ma in the study area. Before this time, thick siliciclastics and mixed carbonate-siliciclastics accumulated, which were followed by the deposition of bioclastic sediments (detrital limestone). No indications have been found of episodic subaerial exposures in these deposits and no calcareous nannofossil biozones are lacking. Since the detrital limestone includes biogenic components characterizing fore-reef to shelf environments, the coastal areas of the northern Motobu Peninsula mostly lay in fore-reef to shelf environments for > 0.6 million years (between ∼ 0.8 Ma and 1.45-1.65 Ma), when the sediments had not been subaerially exposed due to sea-level changes characterized by relatively small amplitudes. Coral limestone that formed in the latest Early to Middle Pleistocene between 0.4 Ma and 0.8 Ma extends over the study area, ranging in elevation from 0 to 70 m. This coral limestone grades upward into fore-reef to shelf carbonates (rhodolith, Cycloclypeus-Operculina, and detrital limestones) which is in turn overlain by coral limestone. This succession, combined with configuration of the lithofacies and paleobathymetry inferred from lithology and biogenic components, implies that the reef-complex deposits formed responding to sea-level changes with amplitude of > 60 m. Consequently, we suggest that the change in the mode of sedimentation results from increased amplitude of sea-level fluctuations at ∼ 0.8 Ma. This timing corresponds roughly to the timing of the Mid-Pleistocene Climate Transition (MPT).

Original languageEnglish
Pages (from-to)160-175
Number of pages16
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume241
Issue number1
DOIs
Publication statusPublished - 2006 Nov 1

Keywords

  • Calcareous nannofossils
  • Mid-Pleistocene Climate Transition
  • Quaternary sea-level changes
  • Reef development
  • Ryukyu Group

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

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