海滩岩在南海北部中晚全新世海平面重建中的应用和不确定性分析

    Application and uncertainty analysis of beachrock to Mid-late Holocene sea-level reconstruction in the northern South China Sea

    • 摘要: 过去海平面变化特征对认识现代海平面变化过程和预估未来情景具有重要科学和现实意义。海滩岩作为热带和亚热带地区海岸潮间带特有的沉积岩,是海岸变迁和古海平面高程的重要标志物。然而,由于存在海滩岩形成后动力条件发生变化、采用的测年方法不同以及海平面高程估算和分析误差等问题,基于海滩岩的过去海平面重建结果依然存在较大争议和不确定性。我们分析和总结了南海北部中晚全新世海滩岩重建海平面的进展,以及在海平面研究中存在的问题和潜在机遇,从海滩岩的形成年代与海滩岩形成后高程产生变化等方面进一步量化研究海滩岩重建海平面变化的不确定性。同时,通过对南海北部海南岛东部沿岸的3块原生珊瑚礁(1块大型块状滨珊瑚和2块滨珊瑚微环礁)进行高精度高程测量和铀系测年,共获得6个海平面数据,结合冰川均衡调整模型(Glacial Isostatic Adjustment,GIA)和ICE-5G模型结果,对基于海滩岩重建的南海北部中晚全新世海平面的可靠性进行比较和评估。以上不确定性分析和研究结果表明,通过年代与高程校正后,海平面重建结果准确性进一步提高。研究结果可为以其他海平面标志物重建的过去海平面的不确定性分析和可靠性分析提供参考和借鉴。

       

      Abstract: The characteristics of the past sea-level change have important scientific and practical significance for understanding the process of the modern sea-level change, and predicting future scenarios. Beachrock, as a unique sedimentary rock in coastal intertidal zones in tropical and subtropical regions, is an important indicator of coastal change and the past sea-level elevation. However, due to the change of dynamic conditions after the formation of beachrock, the different dating methods, the estimation of indicative range represented by beachrock and error analysis, the results of past sea-level reconstruction based on beachrock are still controversial and uncertain. Therefore, we analyze and summarize the progress of sea-level reconstruction of Mid-late Holocene based on beachrocks in the northern South China Sea, as well as the existing problems and potential opportunities in sea-level research. The uncertainty of sea-level reconstruction based on beachrock is further quantitatively studied from the aspects of the formation age of beachrock and the elevation change after the formation of beachrock . At the same time, the high-precision elevation measurement and U-Th dating of three in-situ coral reefs (one large massive Porites and two Porites microatolls) along the east coast of Hainan Island in the northern South China Sea were conducted, and six new sea-level data are obtained. In conjunction with Glacial Isostatic Adjustment (GIA) and ICE-5G model results, they were applied to the reliability analysis and comparison of the reconstructed Mid-late Holocene sea level in the north of the South China Sea based on beachrocks. The uncertainty analysis and results indicate that the accuracy of sea-level reconstruction result is further improved after the correction of age and elevation, which can provide reference for the uncertainty and reliability analysis of the reconstructed sea-level based on other sea-level indicators.

       

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