陸前高田平野完新統の堆積相・堆積速度および推定される地殻変動傾向  [in Japanese] Holocene sedimentary facies, sediment accumulation rate and coastal subsidence estimated from a sediment core in the Rikuzentakata Plain, northeast Japan  [in Japanese]

Access this Article

Search this Article

Author(s)

Abstract

三陸海岸の隆起・沈降史復元に向けた手始めとして,陸前高田平野においてコア堆積物の解析を行った.堆積物は,下位から陸上河川堆積物,潮汐の影響する河川および浅海堆積物,プロデルタ〜デルタフロント堆積物,および陸上泥湿地堆積物からなる.合計25試料の<sup>14</sup>C年代測定値に基づいた堆積曲線から推定した堆積速度は,コア下部(9,500〜9,300calBP)で20mm/yr以上,中部(9,300〜3,300calBP)で2〜10mm/yr,上部(1,200calBP以降)で5〜10mm/yrであり,コア中部の堆積速度は日本列島のデルタとしては大きい.これは調査地域がリアスの湾奥に位置しているため,河口低地から内湾環境への移行後も上流からの土砂供給の影響を受け続けていた可能性を示す.また,潮汐の影響する河川および浅海堆積物の堆積環境の特徴から推定される完新世初期の古海面高度と地殻変動を考慮しない同時期の理論的な海面高度との対応から,本地域の完新世を通じた地殻変動は最近100年間と同様に沈降傾向である可能性が示唆される.

To begin the clarification of uplift/subsidence history along the southern Sanriku coast, a 40-m-long core sample (RT1 core) was extracted from the lower reaches of Rikuzentakata Plain, northeast Japan. On the basis of features of the core sediment, sedimentary facies was divided into braided river, tidal influenced environment, delta, and terrestrial marsh, in ascending order. Age-depth curve was described based on twenty-five <sup>14</sup>C ages. For the estimation of Holocene vertical movement, observed relative sea-level (RSL) was compared with theoretical RSL. RSL at 9.5 to 8.6ka was estimated at −30 to −24m by using the altitude of depositional surface of tidal deposits shown by both age-depth curve and molluscan shells in intertidal zone. Estimated RSL is lower than theoretical RSL without tectonic effect. Probable cause of this discrepancy is Holocene tectonic subsidence of the studied area.

Journal

  • The Quaternary Research (Daiyonki-Kenkyu)

    The Quaternary Research (Daiyonki-Kenkyu) 53(6), 311-322, 2014

    Japan Association for Quaternary Research

Codes

  • NII Article ID (NAID)
    130005088896
  • NII NACSIS-CAT ID (NCID)
    AN0034136X
  • Text Lang
    JPN
  • ISSN
    0418-2642
  • NDL Article ID
    025950510
  • NDL Call No.
    Z15-67
  • Data Source
    NDL  J-STAGE 
Page Top