Late-Holocene salinity changes in Lake Ogawara, Pacific coast of northeast Japan, related to sea-level fall inferred from sedimentary geochemical signatures

Fumiko Watanabe Nara*, Takahiro Watanabe, Tetsuya Matsunaka, Shin ichi Yamasaki, Noriyoshi Tsuchiya, Koji Seto, Kazuyoshi Yamada, Yoshinori Yasuda

*この研究の対応する著者

研究成果: Article査読

4 被引用数 (Scopus)

抄録

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 (14C) 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 14C 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.

本文言語English
論文番号110907
ジャーナルPalaeogeography, Palaeoclimatology, Palaeoecology
592
DOI
出版ステータスPublished - 2022 4月 15

ASJC Scopus subject areas

  • 海洋学
  • 生態、進化、行動および分類学
  • 地表過程
  • 古生物学

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