11:30 AM - 11:45 AM
[HQR05-04] K-feldspar post-IR IRSL ages suggest the presence of MIS 5a–c marine terraces in the eastern margin of the Kanto Plain, central Japan
Keywords:OSL dating, Quaternary, Kanto Plain
K-feldspar post-IR IRSL (pIRIR) ages are presented here to examine the marine terrace in the Kashima Plateau, eastern Kanto Plain, which has also been exclusively correlated as the MIS 5e. The sediment succession of the Kashima Plateau is characterized by marine to brackish deposits with pIRIR ages of the MIS 7 or 9, overlain by the succession of shallow-marine deposits. The shallow-marine succession is variable; in the landward section it is exclusively fine to medium sands overlain by a several meters thick aeolian unit, while the seaward section is gravelly coarse sands with negligible aeolian capping. This variation is corroborated with pIRIR ages. The landward and seaward sections are dated as 137±14 to 155±12 ka, and 86±9 to 105±8 ka, respectively. pIRIR ages are likely to be overestimated by several thousand to ten thousand years. Therefore, the Kashima Plateau represents a composite marine terrace that is correlated with the MIS 5e and MIS 5a or 5c in the landward and seaward sections, respectively. Along with the Iioka Plateau, this composite marine terrace occurs throughout the eastern margin of the Kanto Plain, which requires the Late Pleistocene tectonic history of the Kanto Plain to be reconsidered.