Stratigraphy and periodic variations of grain-size distribution recognized in flood event deposits : a case study of the sediment cores from the Kazusa Group, central eastern part of the Boso Peninsula, Japan

Ito Takuma, Nakazato Hiroomi, Hashimoto Tsutomu, Xue Ziqiu

doi:10.4116/jaqua.59.89

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Other Title

房総半島中東部の上総層群から得られたコア試料の層序と洪水起源堆積物の周期性
ボウソウハントウチュウトウブノカズサソウグンカラエラレタコアシリョウノソウジョトコウズイキゲンタイセキブツノシュウキセイ

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Abstract

<p>Sediment cores (Mobara cores) were obtained from the Kazusa Group in the central eastern part of the Boso Peninsula, central Japan. Identified tephras were attributed to the marker tephra Ch2 and Ch3 in the Middle Pleistocene Chonan Formation, which deposited during oxygen isotope stage 16. Characteristics of flood event deposits have been documented in a shelf-margin delta deposit of the Chonan Formation. Flood event deposits were also recognized in the cores, and grain-size profile of the flood event deposits enables to identify periodic variations. According to the correlation with a detailed age model of the Choshi core, depositional age of the Mobara cores was established. The spectra of the stratigraphic variations of grain size shows about 3300-year, 1000-year and 850-year periodicities above 95% significant level. These periodicities are shorter duration than Milankovitch cycles. The millennial-scale cycles could be attributed to the precipitation changes associated with the East Asian monsoon and the long-term ENSO-like (El Niño-Southern Oscillation) events during the Middle Pleistocene.</p>

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The Quaternary Research (Daiyonki-Kenkyu)

The Quaternary Research (Daiyonki-Kenkyu) 59 (4), 89-102, 2020-08-01

Japan Association for Quaternary Research

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