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Tectpmoc History of the Ryukyu Island Arc, Dcduced from Uranium-Seried Dating of Raised Coral Reefs.

Tectpmoc 琉球岛弧的历史，从凸起珊瑚礁的铀系列测年推导出来。

基本信息

批准号：
04640719
负责人：
OMURA Akio
金额：
$ 1.22万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640719/
关键词：
Ie Island Okinawa Island Hedo-misaki Pleistocene Coral reef terrace Huon Peninsula, PNG Uranium-Series dating Bohole Islands, Philippines αスペクトル^<230>Th ^<234>U法ヒュオン半島コンコーディア琉球石灰岩

项目摘要

Results of this study are summarized as follows :1. Pleistocene coral reef terraces on Ie Island and Hedo-misaki, Okinawa Island, are morpho-stratigraphically subdivided into several steps, by geomorphologic field survey, using 1 : 10,000 aerial photograph. U-series dating vindicated the existence of Holocene coral limestone at the littoral zone around Ie Island, although U-series dates correlative to late Pleistocene were not obtained there, because of diagenetic alteration of fossil corals.2. Results of U-series dating on Pleistocene corals from the Huon Peninsula, Papua New Guinea, and the Bohole Island, Philippines, suggest that age of coral reef terraces younger than 70ka nust be revised. An eustatic sea level change during the last 70,000 years could be proposed, based on those results of U-series dating and the depositional depth inferred from litho- and bio-facies analyzes of terrace deposits.3. The occurrence of raised coral reef formed during the last interglacial maximum was certified at an altitude of 1 to 2 m above the present sea level on the Bohole Island. This fact means that the Bohole Island has not uplifted during the last 130,000 years.4. Two sorts of "concordia", |^<230>Th/^<234>U|-|^<234>U/^<238>U| and |^<230>Th/^<234>U|-|^<231>Pa/^<235>U| curves, were considered to be one of the most valuable tools to verify the reliability of a ^<230>Th/^<234>U coral date.

本研究的主要结果如下：1.通过1：10，000航片的野外地貌调查，将冲绳岛江户岬和伊势岛更新世珊瑚礁阶地的地貌地层划分为若干阶。虽然由于珊瑚化石的成岩作用，在伊岛附近的沿岸的带没有获得与晚更新世相关的铀系年代，但铀系年代测定证实了全新世珊瑚灰岩的存在.对巴布亚新几内亚胡翁半岛和菲律宾Bohole岛更新世珊瑚的铀系测年结果表明，珊瑚礁阶地的年龄小于70 ka，应予以修正。根据U系测年结果和阶地沉积物的岩相和生物相分析推断的沉积深度，可以提出近7万年来海平面的变化.在最后一次间冰期最大期形成的凸起珊瑚礁的出现被证明是在Bohole岛现在海平面以上1至2米的高度。这一事实意味着，在过去的13万年里，Bohole岛没有上升。两种“协和”，|^<230>Th/^<234>U|-|^<234>U/^<238>U|和|^<230>Th/^<234>U|-|^<231>Pa/^<235>U|曲线，被认为是最有价值的工具之一，以验证的可靠性的^<230>Th/^<234>U珊瑚年龄。