Late-Holocene salinity changes in Lake Ogawara, Pacific coast of northeast Japan, related to sea-level fall inferred from sedimentary geochemical signatures
Late-Holocene salinity changes in Lake Ogawara, Pacific coast of northeast Japan, related to sea-level fall inferred from sedimentary geochemical signatures
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DOI：
10.1016/j.palaeo.2022.110907
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发表时间：
2022-03-10
影响因子：
3
通讯作者：
Yasuda, Yoshinori
中科院分区：
文献类型：
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作者：
Nara, Fumiko Watanabe;Watanabe, Takahiro;Yasuda, Yoshinori
本研究旨在通过澄清日本东北部太平洋沿岸小川原湖的盐度变化，为太平洋海平面变化提供重要的见解，该湖在全新世晚期变得微咸。应用放射性碳（C-14）测年，火山灰年代学和地球化学特征，包括溴（Br），碘（I），总硫（TS），总有机碳（TOC），总氮（TN），连续沉积物芯从小川原湖估计盐度变化。核心有两个火山灰层，十和田喷发（To-a;约915 CE）和长白山喷发（B-Tm; 946 CE）。利用植物宏观残体C-14年龄，以B-Tm火山灰为约束条件，建立了岩心年龄模型。在2200-2000 cal BP层中观察到海洋衍生元素（Br，I和TS）的耗尽，表明全新世晚期海平面下降引起的古盐度从咸到半咸的变化。Br，I，TOC和TN浓度的变化显着改变相比，低于B-Tm层。溴和TOC和I和TOC之间的高相关性以上的B-Tm火山灰层的表面表示的有机来源的卤素后长白山喷发，表明改变了湖泊的流域水文系统。后B-Tm沉积物中C/N原子比的变化也支持这种水文变化。两次记录在案的重大火山爆发可能引发了小川原湖水流入系统的这些变化。
This study aimed to provide important insights into Pacific Ocean sea-level changes by clarifying salinity changes in Lake Ogawara on the Pacific coast of northeast Japan, which became brackish in the late Holocene. Radiocarbon (C-14) dating, tephrochronology, and geochemical signatures, including bromine (Br), iodine (I), total sulfur (TS), total organic carbon (TOC), and total nitrogen (TN), were applied to continuous sediment core from Lake Ogawara to estimate salinity changes. The core has two tephra layers, the Towada eruption (To-a; approximately 915 CE) and the Changbaishan eruption (B-Tm; 946 CE). An age model for the core was established using plant macro remain C-14 ages constrained by a B-Tm tephra. The depletion of marine-derived elements (Br, I, and TS) was observed in 2200-2000 cal BP layers, indicating a paleosalinity change from saline to brackish conditions caused by falling sea levels during the late Holocene. Variations in Br, I, TOC, and TN concentrations were significantly changed compared to those below the B-Tm layer. High correlations between Br and TOC and I and TOC above the B-Tm tephra layer to the surface indicated an organic source for the halogens post the Changbaishan eruption, indicating a change to the hydrological system of the lake's watershed. The increasing variation in the C/N atomic ratio in the post-B-Tm sediments also supported this hydrological change. Two recorded significant volcanic eruptions could have triggered these changes to the Lake Ogawara water inflow system.