Research paper Optically stimulated luminescence dating of coastal sediments from southwestern Korea Jin Cheul Kim a, * , Chul Hun Eum b , Sangheon Yi a , Ju Yong Kim a , Sei Sun Hong a , Jin-Young Lee a a Geological Research Division, Korea Institute of Geoscience and Mineral Resources, 92 Gwahang-no, Yuseong-gu, Daejeon 305-350, Republic of Korea b Geochemical Analysis Center, Korea Institute of Geoscience and Mineral Resources, 92 Gwahang-no, Yuseong-gu, Daejeon 305-350, Republic of Korea article info Article history: Received 4 October 2011 Received in revised form 27 January 2012 Accepted 17 March 2012 Available online 27 March 2012 Keywords: Quartz OSL 14 C dating Tidal sediments Korean Peninsula abstract We tested the applicability of optically stimulated luminescence (OSL) dating to fine grained sediments from coastal (coastal lacustrine and tidal) environments. Eight samples were collected from a 16-m-long core taken from the Yeongam tidal flat on the southwestern coast of the Korean Peninsula. A single- aliquot regenerative-dose (SAR) procedure was applied to chemically purified (H 2 SiF 6 ) quartz grains of 4 e11 mm in diameter. OSL dating results were compared with ages obtained from 14 C dating of shells, wood fragments, and bulk sediments. The suitability of the material for OSL dating was confirmed by the luminescence characteristics. The OSL ages of the coastal sediments ranged from 19 to 1.3 ka, fitting well with the available 14 C ages, especially those from wood fragments. Age differences from 500 to 1000 yr were observed between 14 C ages of shells and OSL ages, caused by a constant 14 C reservoir effect in this tidal area. The 14 C ages of the bulk sediments were much older (>2000 yr) than the OSL ages and were not in stratigraphic order. This age discrepancy was most likely caused by incorporation of old and reworked carbon into the bulk sediments. The most reliable materials for 14 C dating are wood fragments. The reproducible OSL signal, the narrow distribution of D e values, and the consistency of the OSL ages with stratigraphic order indicated that fine quartz grains were not affected by incomplete bleaching. The OSL ages coupled with radiocarbon results show that a short period (between approximately 8 and 6 ka) of very rapid sedimentation (5 mm/yr) was followed by a much lower sedimentation rate since 6 ka. This was probably the result of a rapid rise in sea level in the early Holocene followed by a much slower rate in the late-Holocene. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The western part of the Korean Peninsula is one of the predominant tidal flat areas in the world. The evolution of the tidal field has been a response to the sea-level changes since the Last Glacial Maximum (LGM). Coastal sediments, especially tidal sedi- ments, are a marker for defining paleoshorelines. A regional sea level curve has been constructed based on 14 C dates from many tidal flat areas on the western coast of the Korean Peninsula (Kim and Kennett, 1998; Lim, 2001; Lim and Park, 2003; Chough et al., 2004). However, a complete sea level curve has not been recon- structed due to the lack of material suitable for radiocarbon age dating. In addition, several factors may complicate radiocarbon dating of tidal samples, including contamination by old carbon and the marine radiocarbon reservoir effect. Optically stimulated luminescence (OSL) dating is an alternative dating method that is not affected by these problems. Despite uncertainties involving bleaching of the dosimeter and the dose rate estimate, lumines- cence dating has recently been successfully applied to tidal sedi- ments (Hong et al., 2003; Madsen et al., 2005, 2007; Mauz and Bungenstock, 2007; Mauz et al., 2010). Previous optical dating work on tidal sediments in the Korean Peninsula used feldspars (Hong et al., 2003). Feldspar has much brighter luminescence than quartz, and therefore it can provide a better estimate for very young samples. However, this approach is complex for sediments of Holocene age because feldspar dating requires correction for anomalous fading, and the OSL signal of feldspars bleaches at least one order of magnitude slower than the OSL signal of quartz (Godfrey-Smith et al., 1988; Huntley and Lamothe, 2001; Mauz and Bungenstock, 2007). Quartz OSL dating can overcome these problems. However, there have been no successful cases in which quartz OSL dating has been applied to tidal sediments in the Korean Peninsula. In this study, the OSL dating method was applied to fine grained quartz (4e11 mm) of * Corresponding author. Tel.: þ82 10 5099 6150. E-mail addresses: kjc76@kigam.re.kr , aventeee@hanmail.net (J.C. Kim). Contents lists available at SciVerse ScienceDirect Quaternary Geochronology journal homepage: www.elsevier.com/locate/quageo 1871-1014/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.quageo.2012.03.008 Quaternary Geochronology 10 (2012) 218e223