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Subsidence of the M iyako‐ S one submarine carbonate platform, east of M iyako‐jima I sland, northwestern P acific O cean
Author(s) -
Arai Kohsaku,
Machiyama Hideaki,
Chiyonobu Shun,
Matsuda Hiroki,
Sasaki Keiichi,
Humblet Marc,
Iryu Yasufumi
Publication year - 2014
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/iar.12051
Subject(s) - geology , carbonate platform , siliciclastic , carbonate , reef , bathymetry , seafloor spreading , paleontology , subsidence , geochemistry , sedimentary rock , submarine , bathymetric chart , geomorphology , facies , oceanography , materials science , structural basin , metallurgy
Bathymetric mapping and observations of the seafloor using a remotely operated vehicle ( ROV , Hyper‐Dolphin 3 K ) were carried out on the slopes of the M iyako‐ S one submarine platform, east of M iyako‐jima in the R yukyu I slands, northwestern P acific O cean. The bathymetric map indicates that terraces are present at water depths of approximately 140 m, 330 m, 400 m, and 680 m on the northwestern slope of the platform. A number of NW – SE trending lineaments, probably faults, extend perpendicular to the axis of the R yukyu I sland A rc. Two ROV surveys were conducted at water depths ranging from 519 m (on the slope) to 121 m (shallowest part of the platform). The surveys revealed that well‐indurated carbonate rocks are exposed at terrace margins and on upper slopes, and that the lower slopes are covered with modern sediments consisting of unconsolidated, coarse‐sand‐sized bioclastic carbonates. Calcareous nannofossils from the well‐indurated carbonate rocks indicate a M iddle– L ate P leistocene age, which suggests that the rocks correlate with the Q uaternary reef and fore‐reef deposits of the R yukyu G roup ( R yukyu L imestone) on the R yukyu I slands. No siliciclastic deposits corresponding to the upper M iocene–lower P leistocene S himajiri G roup (as exposed on O kinawa‐jima and M iyako‐jima islands) were recovered during the surveys. Coeval well‐indurated carbonate rocks, all of which formed in a similar sedimentary environment, have been downthrown towards the west due to displacements on the western sides of normal faults. Subsidence of the M iyako‐ S one submarine platform was the result of large vertical displacements on such normal faults. The timing of initial subsidence cannot be tightly constrained, but the presence of the youngest limestone at progressively lower levels towards the west suggests the subsidence continued until after 0.265 M a.