[H-CG23] 堆積・侵食・地形発達プロセスから読み取る地球表層環境変動

[HCG23-P05] Forced regression deposits during MIS 5c and 5a observed in the Iioka marine terrace (the Pleistocene Katori Formation, central Japan)

*岡崎 浩子¹、中里 裕臣²、田村 亨³、伊藤 一充³、奈良 正和⁴ (1.千葉県立中央博物館地学研究科、2.農業・食品産業技術総合研究機構農村工学研究部門、3.産業技術総合研究所地質情報研究部門、4.高知大学教育研究部自然科学系理学部門)

キーワード：強制海退、海成段丘、浅海堆積物

The Kanto Plain, eastern Japan, is known to be the largest Quaternary sedimentary basin characterized by the extensive presence of the raised Last Interglacial marine terrace. The Iioka marine terrace, which exposes a marginal terrace section at the eastern end of the Kanto Plain, consists of the Katori Formation. This report presents that the Katori Formation potentially contains the deposits formed during the MIS 5c and 5a with K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating, tephra correlation, etc. The depositional sequence of the Katori Formation consists of inner shelf, lower shoreface, upper shoreface, beach, and fluvial facies upward above the sequence boundary. The contact between the lower shoreface and the upper shoreface indicates a sharp erosional surface, and the upper shoreface is characterized by tabular-bed sets that may originate from alongshore or oblique shore dunes. The beach and fluvial facies level lower northeastwards (offshore) along with the marine terraces that descend stepwise, which is indicative of a forced regression succession.