Quaternary International 144 (2006) 53–60 Holocene paleosols of the Upo wetland, Korea: Their implications for wetland formation Wook-Hyun Nahm a,Ã , Jin-Kwan Kim a , Dong-Yoon Yang a , Ju-Yong Kim a , Sangheon Yi a , Kang-Min Yu b a Korea Institute of Geoscience and Mineral Resources (KIGAM), Gajeong 30, Yusung, Daejeon 305 350, Republic of Korea b Department of Earth System Sciences, Yonsei University, Republic of Korea Available online 19 September 2005 Abstract A 4.490 m long core UP-1 was recovered from the marginal part of the Upo wetland. The wetland is a typical riverine wetland in Korea and has been designated as a Protected Wetland in accordance with the International Ramsar Treaty. We studied the Holocene environmental changes of the Upo wetland and the depositional conditions under which the Upo wetland formed. The core is divided into four units on the basis of grain size distribution, abundance of mottles and vertical color variation. Unit 1 has undergone pedogenic processes, resulting in variably weak to moderate soil profile development. Unit 1 paleosols are regarded as synsedimentary soils of floodplain origin, and the radiocarbon data suggest that the whole paleosol profile spans the last 5790 years. The boundaries between the soil horizons are not clear-cut, probably due to a repeated cycle of accumulation, denudation and soil- forming processes. The recurrence of these processes initiated the development of the Upo wetland. The lower boundary of Unit 2 lies at about 2300 14 C yr BP, the beginning of the Subatlantic age in Korea. The lack of intense soil formation and abundant clay content in Unit 2 indicate that the geomorphologically stable wetland was developed around the coring site at that time. This means that the depositional environment changed from a floodplain to a stable, continuously submerging wetland setting. An abrupt change in sediment textures was detected in Unit 3, which commenced formation around 1000–900 14 C yr BP, indicative of geological events such as inundations or inflows of slope-wash sediments. Anthropogenic deforestation and plowing around the Upo wetland area might have started at that time. r 2005 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction In recent years, increasing concern about global environmental change (e.g. Kerr, 1995; Levitus et al., 2001) has led to increasing interest in the wetlands, which are now widely recognized as paleoenvironmental repositories. The primary interest in the inland wetlands is how they have formed and how they were developed under changes in climatic and depositional conditions. However, the evolution of the inland wetlands and the influence of paleoclimate are still poorly understood (Vardy et al., 1997; Iriondo, 2004). Environmental changes have been studied using many analytical methods such as sediment geochemistry, particle size, palynology and radiometric dating techni- ques (Goff and Chague-Goff, 1999). Some records of paleoenvironmental changes can also be obtained from paleopedologic analysis, which can provide an excellent independent approach to interpret the geologic record of wetlands (Driese et al., 2004). Soil formation within fluvial deposits may obscure sedimentary structures indicative of past hydraulic conditions and may obliterate stratification indicating past flood frequencies (Kraus and Bown, 1988). Pedogenic profile character- istics are, however, very useful in the determination of paleoenvironmental conditions because they represent an integration of geomorphic and pedologic processes (Liu et al., 1985; Bown and Kraus, 1987; Bronger and ARTICLE IN PRESS 1040-6182/$ - see front matter r 2005 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2005.05.012 Ã Corresponding author. Tel.: +82 42 868 3119; fax: +82 42 861 9714; mobile: +82 17 214 3241. E-mail address: nahmwh@empal.com (W.-H. Nahm).