Earth, Planets and Space (Sep 2024)
OSL dating of marine isotope stage 5e marine terrace deposits on southeastern Kii Peninsula, southwestern Japan
Abstract
Abstract Optically stimulated luminescence (OSL) dating of feldspar is one of the promising solutions towards reliable chronological constraints on the ages of Pleistocene marine terraces. Marine terraces developed along the southeastern coast of the Kii Peninsula, southwestern Japan, face a seismogenic region along the Nankai Trough. In this study, we determined the emergence age of one of these marine terraces by feldspar OSL dating of the marine terrace sediments. The target marine terrace was previously correlated with marine isotope stage (MIS) 5e based on morphostratigraphy. The samples for post-infrared infrared stimulated luminescence (pIRIR) dating were obtained from foreshore deposits of marine terraces. The first infrared stimulation temperature was fixed at 50°C (IRSL50/150 and IRSL50/225), and the pIRIR signals were measured at 150°C (pIRIR150) and 225 °C (pIRIR225). The resulting IRSL50/150, IRSL50/225, pIRIR150, and pIRIR225 ages with standard errors are 105 ± 4, 120 ± 4, 125 ± 5, and 137 ± 4 ka, respectively. The IRSL50/225 age was consistent with the pIRIR150 age, corresponding to MIS 5e. The IRSL50/150 and IRIR225 ages were younger and older than the IRSL50/150 and pIRIR225 ages, respectively. These results show that the Mm1 surface of the marine terrace corresponds to MIS 5e rather than MIS 5c or 7a–c, which is consistent with the chronological framework based on the morphological features of the terraces in the study area. The underestimation/overestimation of IRSL50/150/pIRIR225 ages can be attributed to the underestimation/overestimation of the fading rate. A more robust and comprehensive chronological framework for the marine terraces of the peninsula could be achieved by conducting OSL dating of the marine terraces above and below the MIS 5e terrace. Graphical Abstract
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