Paleoenvironments and relative sea-level changes caused by regional tectonics during the last 4500 years in Kumihama Bay, northern Kyoto Prefecture, central Japan
Paleoenvironments and relative sea-level changes caused by regional tectonics during the last 4500 years in Kumihama Bay, northern Kyoto Prefecture, central Japan
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DOI：
10.1016/j.quaint.2017.11.029
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发表时间：
2017-12
影响因子：
2.2
通讯作者：
K. Yamada;Tetsuro Masuma;K. Seto;M. Uchida;Atsuko Amano;Y. Sampei
中科院分区：
文献类型：
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作者：
K. Yamada;Tetsuro Masuma;K. Seto;M. Uchida;Atsuko Amano;Y. Sampei
介形虫组合进行了检查，粒度和沉积物的化学成分进行了分析，目的是澄清古环境和相对海平面（RSL）的变化与区域构造在日本中部的Kumihama湾。从西北部和东南部的两个岩心中鉴定出介形虫21属38种。通过对沉积相、介形虫组合和沉积物地球化学记录的分析，揭示了以下环境变化。一个封闭的海湾，面积小于今天，存在于4500和4300 cal BP之间。在4300和2000 cal BP之间，RSL上升导致海湾海水影响逐渐增加，最高RSL发生在2000 cal BP。在4000至2500 cal BP之间，Kumihama湾的RSL以1.2 mm/年的速度从-3.8 m移动到-2.0 m。这一速度是不一致的预测RSL的趋势在周边地区，这表明发生在Kumihama湾的沉降在晚全新世。山阴剪切带的构造运动趋势和速率是一致的，这意味着这种沉降可能与菲律宾海板块的俯冲有关。
Ostracode assemblages were examined, and the grain size and chemistry of sediments were analyzed with the aim of clarifying paleoenvironmental and relative sea-level (RSL) changes relating to regional tectonics in Kumihama Bay, central Japan. Overall, 21 genera and 38 species of ostracode were identified from two cores taken in the northwestern and southeastern parts of the bay. The analysis of sedimentary facies, ostracode assemblages and geochemical records of sediments revealed the following environmental changes. A closed bay, with an area smaller than that of today, existed between 4500 and 4300 cal BP. A gradual increase in seawater influence in the bay was caused by an RSL rise between 4300 and 2000 cal BP with highest RSL occurring at 2000 cal BP. Between 4000 and 2500 cal BP, the RSL in Kumihama Bay has shifted from −3.8 m to −2.0 m at a rate of 1.2 mm/yr. This rate is inconsistent with the predicted RSL trend in surrounding regions, suggesting the occurrence of a subsidence in Kumihama Bay during the Late Holocene. The trend in tectonic movement and their rate are common in the San'in shear zone, implying that this subsidence might be related to the subducting of the Philippine Sea Plate.