[H-CG24] Earth surface processes related to deposition, erosion and sediment transport

[HCG24-P06] Superimposed sequence boundary of the upper Pleistocene Katori Formation observed on marine terrace, Byoubugaura coastal cliff, central Japan

*Hiroko Okazaki¹, Masakazu Nara², Hiroomi Nakazato³, Toru Tamura⁴, Kazumi Ito⁴ (1.Natural History and Institute, Chiba, 2.Kochi Univ., 3.Institute for Rural Engineering, NARO, 4.AIST)

Keywords:marine terrace, MIS 5c, MIS 5a, sequence boundary

Byoubugaura coastal cliff, Chiba prefecture, central Japan, is composed of the Pliocene - Pleistocene Inubo Group of the lower part, and the Pleistocene Katori Formation of the upper part. Wave-cut terrace deposits is observed at the base of Katori Formation, which lies on unconformity between the Inbo Group and Katori Formation. The deposits have erosional surface with boring shell holes under the surface, and contain sub-rounded pebble and shell fragments. The deposits graded into variety of facies, which are inner shelf, mouth bar, and shoreface facies. Based on tepracholonology and OSL dating (Nakazato et al., 2016 etc.), these facies had been deposited in MIS 5e?, 5c and 5a, respectively. Therefore, these facies setting are regarded as high-frequency sea-level fluctuation sequence boundary.

Nakazato, H., Nara^, M., Okazaki, H., Mizuno, K., and Ito, H. (2016) On-Pm1 tephra and marine deposits covering the tephra in the Choshi district, eastern Kanto Plain. JpGU2016, HQR15-P08.