Analysis of the chronological data and observation of a lagoonal sediment core reveal sand washover events between around 2.4 to 2.5 cal. ky BP in the Isumi River lowland. We conducted radiocarbon dating with AMS and constructed an age-depth model using the latest calibration curve and appropriate model routine. In the middle to lower part of the core, dark-gray sand layers are repeatedly deposited. Sand layers may exhibit an erosional surface at the base with fining upward grading. The overwash layers are composed of well-rounded sand with occasional gravel, indicative of transportation. overwash sediment characteristics are consistent with proximal marine deposits, suggesting an ocean origin (though riverine sediment is also similar in character). The age-depth model indicates very high sediment accumulation rates associated with overwash deposits. Based on the amount of accumulated sediment, relatively large-scale redeposition events occurred during this period but more information is needed to constrain the mechanism(s) causing the events. We also present a local reservoir age correction compatible with the Marine20 calibration curve.

中文翻译：

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日本房总半岛东部夷川低地全新世洪水发生年龄

对年代数据的分析和对泻湖沉积物核心的观察揭示了大约 2.4 至 2.5 cal 之间的沙冲事件。ky BP 位于夷隅河低地。我们使用 AMS 进行了放射性碳测年，并使用最新的校准曲线和适当的模型例程构建了年龄深度模型。岩心中下部反复沉积深灰色砂层。沙层可能会在底部呈现出侵蚀表面，并向上细化。溢流层由圆润的沙子组成，偶尔有砾石，表明有运输作用。溢流沉积物特征与近端海洋沉积物一致，表明其起源于海洋（尽管河流沉积物的特征也相似）。年龄深度模型表明与过度冲刷沉积物相关的沉积物堆积率非常高。根据沉积物的累积量，在此期间发生了相对大规模的再沉积事件，但需要更多信息来约束导致事件的机制。我们还提出了与 Marine20 校准曲线兼容的局部储层年龄校正。