3:30 PM - 4:45 PM
[HQR15-P08] On-Pm1 tephra and marine deposits covering the tephra in the Choshi district, eastern Kanto Plain
Keywords:MIS5c, tephra, geomorphic surface
The Zircon U-Pb dating using LA-ICP-MS (Ito, 2014) was applied to the tephra in this study. As a result, the obtained age of 100±60 ka improved the reliability of the correlation between the tephra and On-Pm1.
The outcrop where the tephra was detected shows the following stratigraphy: mud and sand stone of the Kasuga Formation of the Inubo Group, unconformity, shoreface sand, terrestrial mud interbedding the tephra (On-Pm1), shoreface sand with Macaronichnus isp., beach sand, fluvial deposits, Younger Kanto Loam and Holocene dune deposits in ascending order. The age of marine sand overlying the On-Pm1(95.7±5.3ka: Aoki et al., 2008) is more likely to be MIS5a.
Reexamination is necessary about the geomorphic and geotectonic history in this district because it has been assumed that the MIS5a surfaces are distributed in lower altitude area than this point.
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