Reconstruction of late Quaternary sea-level and reef growth history in the Ryukyu Islands

琉球群岛晚第四纪海平面及礁体生长历史重建

• 批准号: 21H01169
• 负责人: HUMBLET Marc
• 金额: $ 11.65万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2021
• 资助国家: 日本
• 起止时间: 2021-04-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-21H01169/
• 关键词: Coral reef; Sea level change; Climate change; Quaternary; Okinawa; Sea-level change

Five boreholes (10-27 m in length) were drilled into late Middle Pleistocene limestone (Minatogawa Formation) along a transect perpendicular to shore in southern Okinawa Island in December 2022 and January 2022. The total cored length is 90 m. After shipping the cores to the Kochi Core Center for safe storage, each core was X-ray CT-scanned. The cores were then split in half, photographed, and their lithology, sedimentary structures, and major fossil biotic components, particularly corals, coralline algae, and foraminifers, were carefully described in September 2022. Seven additional boreholes (8-23 m in length) were drilled in the same geological formation in August and September 2022. The total cored length is 98 m. Five of these boreholes were drilled along a second transect perpendicular to shore situated 800 m to the south-west of the first transect. One borehole was drilled between the first and second transect, and another borehole was drilled along the first transect. The seven new cores were shipped to the Kochi Core Center for storage in January 2023. Sampling of the cores of the first transect was conducted at the Kochi Core Center in February 2023 for sedimentological analysis, radiometric dating, taxonomic identification of corals, crustose coralline algae, and foraminifers, as well as elemental and stable isotope geochemistry. In addition, the corals observed in the cores of the first transect were identified at the lower taxonomic level possible and their status (in situ vs. not in situ) duly noted. The thickness of coralline algal crust was also recorded.

2022年12月和2022年1月，在冲绳岛南部垂直于海岸的样带中更新世晚期灰岩（Minatogawa组）中钻了5口井，井长10 ~ 27 m。堆芯总长度为90米。在将堆芯运送到高知堆芯中心进行安全储存后，每个堆芯都进行了x射线ct扫描。然后将岩心分成两半，拍照，并在2022年9月仔细描述了它们的岩性、沉积结构和主要化石生物成分，特别是珊瑚、珊瑚藻类和有孔虫。2022年8月和9月，在同一地质地层又钻了7个井眼（长度为8-23米）。堆芯总长度为98米。其中五个钻孔沿着垂直于海岸的第二个样带钻，位于第一个样带西南800米处。在第一和第二样带之间钻了一个井眼，沿着第一样带钻了另一个井眼。这七个新核于2023年1月被运往高知核中心储存。2023年2月，在高知岩心中心对第一个样带岩心进行了沉积学分析、放射性测年、珊瑚、甲壳珊瑚藻和有孔虫的分类鉴定以及元素和稳定同位素地球化学研究。此外，在第一个样带的岩心中观察到的珊瑚在分类水平上可能较低，并且适当地记录了它们的状态（原位与非原位）。同时记录了珊瑚藻壳的厚度。