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Nahm, Wook-Hyun,Hong, Sei-Sun E. Arnold Distributed in North America by Cambridg 2014 The Holocene Vol.24 No.12
<P>Multidisciplinary paleoproxy data from three sedimentary cores (9.05-m-long MW-2, 16.50-m-long IL-3, and 11.88-m-long JD-1) recovered from the Yeongsan River Estuary of Korea are presented. A marine influence can be observed at 10,400 yr BP (−21 m) and 8600 yr BP (−14 to −12 m) around the Yeongsan River Estuary. However, if we take the macro-tidal setting of the Yeongsan River Estuary into consideration, actual sea level could differ from the depositional surfaces, and might be higher or lower than the sediment elevation. Precipitation at around 6300–5000 yr BP is estimated to have been higher or stronger than in earlier and later periods. The core sites received increased terrigenous sediment input during this period because of intensified rainfall and consequent river activity. Although sea level was estimated to be high enough to have a strong influence on the study area during the mid-Holocene, the sedimentary features suggest that riverine activity was the dominant factor controlling the sedimentation patterns. This implies that even during the Holocene Climate Optimum in Korea, roughly 7000–5000 yr BP, the wetter condition has occurred within the interval of 6300–5000 yr BP. After the Holocene Climate Optimum, sea level decreased to 0 to −1 m around 5000 yr BP and increased again starting around 4000 yr BP. The time-series results presented in this study are coincident with global trends, and show the potential for developing geomorphological and climate histories for this region.</P>
Holocene paleosols of the Upo wetland, Korea: Their implications for wetland formation
Nahm, Wook-Hyun,Kim, Jin-Kwan,Yang, Dong-Yoon,Kim, Ju-Yong,Yi, Sangheon,Yu, Kang-Min Elsevier 2006 QUATERNARY INTERNATIONAL Vol.144 No.1
<P><B>Abstract</B></P><P>A 4.490m 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 5790years. 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<SUP>14</SUP>CyrBP, 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<SUP>14</SUP>CyrBP, 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.</P>
Responses of the upriver valley sediment to Holocene environmental changes in the Paju area of Korea
Nahm, Wook-Hyun,Kim, Ju-Yong,Lim, Jaesoo,Yu, Kang-Min Elsevier 2011 Geomorphology Vol.133 No.1
<P><B>Abstract</B></P><P>Multidisciplinary paleoproxy data from five sedimentary cores (UJ-03, 06, 07, 10, and 12) recovered from the broad, flat upriver valley in the Paju area of Korea are presented. Twelve AMS radiocarbon dates from cores UJ-03 and 12 provided a high-resolution Holocene record for the sedimentary sequence, ranging from about 8000YBP to the present. From 6400 to 4400<SUP>14</SUP>CYBP (7100–5000cal. YBP), the sediments were dominantly poorly sorted, medium to coarse sands containing angular to subangular pebbles, suggesting that the materials were locally derived. The increased abundance of coarse-grained sediment was attributed to intensified rainfall during the mid-Holocene, despite the dense regional vegetational cover. This period probably corresponded to the Holocene Climate Optimum in the Korean Peninsula. Total organic carbon (TOC) values showed a marked increase from 4400 to 2100<SUP>14</SUP>CYBP (5000–2200cal. YBP), which coincided with an observed decrease in particle size (i.e., a decrease in sand content). These changes indicated the onset of paludification on the silty or sandy valley bottom. Contemporaneously, relative abundances of <I>Pinus</I> and herbaceous pollen increased, and the East Asian summer monsoon became weakened. Several intermittent depositional layers were observed, ranging from 2100<SUP>14</SUP>CYBP (2200cal. YBP) to the present, which contained a high concentration of rootlets, sand, or clay particles. These types of recurring sedimentation events are attributable to climatic shifts and/or human impacts, such as timber harvest and land clearing. The upriver valley catchment was probably sensitive to flash floods due to poorly vegetated slopes, accelerating rates of erosion as a consequence of land use change. This research indicates that the response of a valley system such as that in Paju to climate- or human-induced environmental changes can vary greatly on local and regional scales.</P> <P><B>Highlights</B></P><P>► Response of a valley system to climate- or human-induced changes was traced. ► The increased abundance of coarse grains was attributed to intensified rainfall. ► This period may correspond to the Holocene Climate Optimum in Korea. ► A marked increase in TOC from 4400<SUP>14</SUP>CYBP may indicate the onset of paludification. ► Several depositional layers were observed from 2100<SUP>14</SUP>CYBP to the present.</P>
Holocene Paleosols of the Upo Wetland, Korea
Nahm, Wook-Hyun,Kim, Ju-Yong,Yang, Dong-Yoon,Hong, Sei-Sun,Lee, Jin-Young,Kim, Jin-Kwan Korea Association For Quaternary Research 2003 제사기학회지 Vol.17 No.2
The Upo wetland, the largest natural wetland in Korea, is located in Changnyeong-gun, Gyeongsannam Province ($35^{\circ}33'$ N, $128^{\circ}25'$ E), and 70 km upstream from the Nakdong River estuary. Unlike most other Korean wetlands that have been destroyed under the name of economic development, the Upo wetland has been able to preserve its precious ecosystem throughout the years. Thanks to increased public awareness about natural wetlands and environmental conservation, the Korean Ministry of Environment designated the Upo wetland an 'Ecological Conservation Area' on July 26th, 1997. On March 2nd of the following year, the Upo wetland (8.54 $\textrm{km}^2$) was designated a 'Protected Wetland' in accordance with the international Ramsar Treaty. A 4.49m long (from 9.73 to 5.24 m in altitude) UP-1 core ($35^{\circ}33'05"N$, $128^{\circ}25'17"E$), recovered in the marginal part of the Upo wetland, is divided into eight buried paleosol units of different ages on the basis of the abundance of color mottles and vertical color variations (Aslan et al., 1998). Radiocarbon datings suggested that the paleosol profile represent the last 5700 years. The entire section of the core was more or less subjected to pedogenetic processes, and shows very weak to moderate soil profile development. These Holocene paleosols are therefore regarded as synsedimentary soils of deluvium (deposits formed by floods) origin (Sycheva et al., 2003). Unit 1 to 5 paleosols are generally silt-rich and exhibit moderate profile development. The boundaries between the units are somewhat distinguishable, but not so clear cut. This is due to variable repeated combination of accumulation, denudation and soil forming processes within various periods. Mottle textures gradually decrease in abundance with increasing clay content in Unit 6, which results in weak profile development. The lower boundary of Unit 6 lies around about 2000 yrBP, the beginning of Subatlantic in Korea (Kim et al., 2001). Abrupt sediment textural change is detected in Unit 7, which is interpreted to indicate the human activities on the Upo wetland. Unit 8 represents the recent soil forming processes. The preliminary results of this ongoing study imply the primary factor for pedogenetic processes is the water table fluctuations related to the sedimentary textures like grain size distributions, and the geomorphological stability of the Upo wetland.o wetland.