Limestones as a paleobathymeter for reconstructing past seismic activities: Muroto-misaki, Shikoku, southwestern Japan

Yasufumi Iryu, H. Maemoku, Tsutomu Yamada, Y. Maeda

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Muroto-misaki (Cape Muroto) is located at the southern tip of the eastern half of Shikoku, southwestern Japan and is ~ 100 km north of the Nankai Trough where the Philippine Sea Plate is being subducted beneath the Eurasian Plate. Therefore, the Muroto-misaki area has been seismically uplifted. Sedimentologic analyses were conducted on Holocene limestones that occur along the coast from Muroto-misaki to Meoto-iwa, located ~ 13 km north of the cape. The limestones are limited to less than 9.2 m in elevation. The limestones are up to 4.4 m in mean diameter, up to 0.5 m in thickness, and consist mainly of fossilized sessile organisms, including annelids, corals, bryozoans, encrusting foraminifers, barnacles, nongeniculate coralline algae, and, to a lesser extent, molluscs and peyssonneliacean algae. Acicular and equant cements are minor components. Acicular cements are found in semi-closed spaces between coralline algal crusts and their substrates. The modal composition of limestones was determined by a point-counting technique. Based on the biotic composition, the Holocene limestones can be classified into six types (Types I to VI). A comparison of the vertical distribution of these rock types with that of modern sessile organisms indicates that the top of Type I limestone, which is characterized by the occurrence of hermatypic corals, corresponds approximately to the mean low water springs when the limestones formed. A difference in the highest occurrence of Type I limestone between two sites may represent the variation in the total amount of uplift over the last 1000 to 1500 years, which resulted in an apparent northward decline of paleo-mean low water springs at a rate of ~ 10 cm/km. Therefore, the Holocene limestones are a good paleobathymeter to reconstruct past seismic activities in this area. This study shows that warm temperate carbonate deposits are as excellent recorders of geologic events, such as the timing and scale of repeated coseismic uplifts and elevation of sea levels, as those in the tropics.

Original languageEnglish
Pages (from-to)52-64
Number of pages13
JournalGlobal and Planetary Change
Volume66
Issue number1-2
DOIs
Publication statusPublished - 2009 Mar 1

Keywords

  • Holocene
  • Shikoku
  • annelid
  • coralline algae
  • coseismic uplift
  • limestone

ASJC Scopus subject areas

  • Global and Planetary Change
  • Oceanography

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