High-precision TIMS U-series and AMS C-14 dating of a coral reef lagoon sediment core from southern South China Sea
High-precision TIMS U-series and AMS C-14 dating of a coral reef lagoon sediment core from southern South China Sea
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DOI：
10.1016/j.quascirev.2006.01.027
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发表时间：
2006-09
影响因子：
4
通讯作者：
Kefu Yu;Jian-xin Zhao;Pinxian Wang;Q. Shi;Meng Qingshan;K. Collerson;Tung-sheng Liu
中科院分区：
文献类型：
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作者：
Kefu Yu;Jian-xin Zhao;Pinxian Wang;Q. Shi;Meng Qingshan;K. Collerson;Tung-sheng Liu
泻湖沉积物的精确定年一直是一个困难的问题，虽然泻湖剖面，通常与高沉积速率，具有很大的潜力，高分辨率的气候重建。本文报道了南沙永暑礁礁泻湖岩芯的26个高精度TIMS U系列年龄（25个珊瑚分支）和5个AMS 14 C年龄（有孔虫）。所有的日期都是在正确的地层序列，提供了最好的年代迄今为止报告的泻湖存款。研究结果显示，该地区有一个4000年的连续沉积历史，沉积速率从0.8到24.6mma− 1不等，平均值为3.85mma−1，相当于平均净碳酸盐累积速率为2700 gCaCO 3 m −2a−1，显著高于以往全球碳酸盐收支研究中泻湖的平均值（800± 400 gCaCO 3 m −2a−1）。在过去的1000年中，加速沉积的发生与该地区风暴运输珊瑚块的U系列日期确定的强风暴事件密切相关。然而，从长远来看，在过去1000年的沉积速率比以前高得多，可能是由于更激烈的波浪-礁相互作用的结果，自公元500年以来相对海平面下降和礁坪面积扩大，提供更多的沉积物。珊瑚TIMS U系列年龄和有孔虫AMS 14 C年龄显示了572 - 1052年的“放射性碳储层年龄”（R），远高于全球平均值10400年。
Accurate dating of lagoon sediments has been a difficult problem, although lagoon profiles, usually with high deposition rates, have a great potential for high-resolution climate reconstruction. We report 26 high-precision TIMS U-series dates (on 25 coral branches) and five AMS14C dates (on foraminifera) for a 15.4-m long lagoon core from Yongshu Reef, Nansha area, southern South China Sea. All the dates are in the correct stratigraphical sequence, providing the best chronology so far reported for lagoon deposits. The results reveal a ∼4000-a continuous depositional history, with sedimentation rates varying from 0.8 to 24.6mma−1, with an average of 3.85mma−1, which corresponds to an average net carbonate accumulation rate of ∼2700gCaCO3m−2a−1, significantly higher than the mean value (800±400gCaCO3m−2a−1) used for lagoons in general in previous studies of global carbonate budget. Episodes of accelerated depositions within the last 1000 years correlate well with strong storm events identified by U-series dates of storm-transported coral blocks in the area. However, in the longer term, the sedimentation rates during the past 1000 years were much higher than earlier on, probably due to more vigorous wave–reef interaction as a result of relative sea-level fall since 500 AD and expansion of reef flat area, supplying more sediments. The coral TIMS U-series ages and foraminifera AMS14C dates reveal intriguing apparent “radiocarbon reservoir ages” (R) from 572 to 1052 years, which are much higher than global mean values of ∼400 years.