Formation history of marine terraces in the southeastern coast of Korea during the late Quaternary revealed by quartz OSL dating of marine and colluvial sediments in Nulchado island.

Quaternary marine terraces are valuable archives of past local sea level changes and crustal movements. Thus, understanding the formation history of marine terraces based on reliable chronological framework is essential for reconstructing palaeo-sea level responses to global climate changes and also for evaluating potential seismic hazards. However, in the Korean peninsular, dating marine terraces are often limited because marine terrace sediments, which are the usual targets for dating, are rarely preserved, shallow in depth and dissected into small patches. Further, it is not always possible to trace paleo-coastal sediments as they are covered by topsoil deposits or disturbed by anthropogenic activities. Recently, we found a well-preserved marine terrace at the elevation of ~ 5 m (a.m.s.l) with distinguished lateral extension of ~ 250 m at Nulchado island in the southeastern part of the Korean peninsula. This is covered by colluvial sediments (> ~ 2 m in thickness), and considered to be well-suited for the investigation of the formation history of marine terraces along the southeastern coast of Korea because it is rich in the sedimentological, geological and stratigraphic record, together with clear topographical setting. For OSL dating, we collected fourteen samples (seven samples from marine terrace sediments and another seven from colluvial sediments). From the OSL dating of marine sediments, we obtained the depositional age of ca. 80 ka (MIS 5a; interglacial period), which is in good agreement with previously reported OSL ages from the marine terraces located at ~ 50 km away to the northeast from Nulchado island (e.g., [1]). In this paper, we first examine the suitability of quartz grains of the samples for reliable OSL dating and present multiple and single grain quartz OSL ages of marine and colluvial sediments. Then, we discuss the developmental characteristics of marine terraces in Nulchado island and implications for the formation of marine terraces along the southeastern coast of Korea in comparison with palaeo-sea level changes of this region. [ABSTRACT FROM AUTHOR]