• Journal of The Geomorphological Association of Korea
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• v.26 no.1
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• pp.27-40
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• 2019

This study tries to reveal source areas of fluvial terrace deposits in Danyang and Geum River basins located in the northern and southern parts of the Sobaek Mountains, respectively, through geochemistry. The samples analyzed in this study show different grain size properties and can be grouped into the coarse, medium and fine samples. Grain size properties suggest that the coarse samples are typically fluvial deposits and geochemistry from the coarse samples is also similar to that from the bedrocks within the basins. The fine samples show geochemical properties different from the bedrocks and similar to loess deposits in Korea. However, different geochemical concentrations among the fine samples can be also recognized, indicating mixtures of loess materials with weathering products of the bedrocks. One sample among the medium samples is considered as fluvial deposit due to geochemical similarity to the bedrocks, while geochemistry from another sample among the medium samples indicates that loess materials were mixed with more abundant weathering products of the bedrocks than those in the fine samples.

• Journal of the Korean earth science society
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• v.26 no.8
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• pp.828-835
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• 2005

The purpose of this study is to clarify the landform development of fluvial terrace and the soil characteristics occurring on the terrace deposit. In order to achieve the purpose, the characteristics of soil profiles, the physic-chemical properties of soils that are developed on terrace deposits and X-ray diffraction analysis of clay were investigated. The horizon of Al in the high fluvial surface is silt clay loam of red (2YR 4/6). The soil structure is a developed granular structure. The horizon of B1 is silt clay reddish-brown (2.5YR 4/6). The soil structure is a medium subangular blocky structure. This red soil structure is made on heavy textured and compactly packed parent materials of high terrace sediments and usually has A-B-C profile. In most cases, clay accumulations in B-horizon and clay cutans on ped surfaces are observed, which mean the formation of agrillic horizon. As the result of this study, soils derived from fluvial terrace deposits on high fluvial surfaces are considered paleo-red soil which were developed by pedogenese-strong desilicification and rubefaction and strong leaching of bases- under warmer bio-climatic condition during in the old Pleistocene period.

• Journal of The Geomorphological Association of Korea
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• v.26 no.4
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• pp.21-31
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• 2019

Timing of terrace formation is a key information for understanding the evolution of fluvial systems. In particular, dating strath terrace (i.e. timing of terrace abandonment) is more difficult than depositional terrace that is conventionally constrained by radiocarbon, OSL and other dating methods targeting samples within terrace deposit. Surface exposure dating utilizing cosmogenic ¹⁰Be provides more reliability because it can be applied directly to the surface of a fluvial terrace. Thus, this method has been increasingly used for alluvial deposits. As well as other geomorphic surfaces over the last decades. Some inherent conditions, however, such as post-depositional ¹⁰Be concentration (i.e. inheritance), surface erosion rate, and density change challenge the application of cosmogenic ¹⁰Be to depositional terrace surface against simple bedrock surface. Here we present the first application of ¹⁰Be depth profile dating to a thin-gravel covered strath terrace in Korea. Monte Carlo simulation (MCS) helped us in better constraining the timing of abandonment of the strath terrace, since which its surface stochastically denuded with time, causing unexpected change of ¹⁰Be production with depth. The age of the strath terrace estimated by MCS was 109 ka, ~4% older than the one (104 ka) calculated by simple depth profile dating, which yielded the best-fit surface erosion rate of 2.1 mm/ka. Our study demonstrates that the application of ¹⁰Be depth profile dating of strath terrace using MCS is more robust and reliable because it considers post-depositional change of initial conditions such as erosion rate.

• Journal of the Korean Geographical Society
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• v.40 no.6 s.111
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• pp.716-729
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• 2005

In the Yeongpyeong River, one of the branches of Hantan River, there 4 fluvial terraces are identified. During the Quaternary, lava flow from Hantan River had gone 4.5km into upstream Part of the Yeongpyeong River and damed its entrance, and resultantly its lower basin had become a lava-damed paleolake. This study deals with fluvial terrace surface classification, stratigraphic analysis, deposits analysis, and OSL age dating in from Gungpyeongri to Seongdongri in lower reach of Yeongpyeong River, in order to identify Seomorphological Process of the terrace landforms relating to duration of lava-damed paleolake. Terrace surface T4, named Baekeuiri Formation, has been located under Jeongok lava layer to indicate pre-lava river bed. Terrace surfaces T3 and T2 are supposed to be formed during paleolake time, based on $3{\~}4m$ thick sand deposits including pebble and cobble layers, and clay and silt layers intersected with sand ones in nearly horizontal bedding. Terrace T1 is estimated to be formed as post-lake fluvial terrace after dissection of lava dam, based on the more fresh phase of deposits and very low height from present riverbed. The results of the OSL age dating for the T3 deposit layers indicate approximately $33{\~}40ka$, and still lake phase at that time.

• Journal of The Geomorphological Association of Korea
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• v.23 no.2
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• pp.47-59
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• 2016

The formation age and depositional environment of the marine terrace I of the estimated paleoshoreline altitude of 18m in Sanhari of Ulsan coast, southeastern Korea were investigated on the basis of examination of lithofacies and stratigraphy of terrace deposits. Marine deposits of the terrace is composed of rounded boulders(70cm in diameter) and rounded pebbles(1.0cm in diameter) which overlay them. The above rounded boulders which lie on the paleo-shore platform are considered to have been formed by wave abrasion in the same period that the paleo-shore platform was developed. The rounded pebbles which lie on the rounded boulder layer are considered to have been deposited in gravel beach and berm environment, judging from the laminae developed in this layer. The paleo-shore platform and marine rounded gravel layer of the terrace are assumed to have been formed in the large transgression period of the Last Interglacial culmination stage(MIS 5e), judging from the comparision of the formation age of 125ka B.P. of Juckcheon terrace I in the adjacent Pohang coast which was dated by amino acid dating. The terrestrial deposit of this terrace was largely composed of angular and subangular gravel mixed with marine rounded pebble which has been carried away mainly from the deposit of previous marine terraces and redeposited in this terrace. The lowest peat layer of terrastrial deposit was considered to have been deposited during the period from the late MIS 5e which is the estimated finishing time of deposition of the above marine gravels to the early stage of following regression period(MIS 5d) in which the sea level was still high. The sediments of angular and subangular gravel deposit which lie on this peat layer were assumed to have been deposited during the period from the early stage of the first regression period(MIS 5d) of the Last Interglacial to the Last Glacial. The lower part of the angular gravel layer is composed of the deposits of the fluvial and colluvial sediments, whereas most of the upper and middle part of the layer is mainly composed of angular gravels of colluvial sediments formed in the cold environment.

• Journal of the Korean Geographical Society
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• v.39 no.1
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• pp.27-44
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• 2004

Upper reach of Soyang River at the northernmost area around Taebaek Mountains in South korea is profitable area to understand paleo-environment during the Quaternary such as tectonic process and climate change in the Korean Peninsula. This study explained paleo-environment affect to channel development by geomorphic distribution and characteristics of terrace surfaces, and analysis of deposits at 58 fluvial terraces in upper reach of Soyang River. Fluvial terraces were classified from T1 to T6. Most terraces are distributed on the point bar in meandering channel and one side along river valley. Terraces tend to decrease in number and superficial dissection rate to be higher and channel slope to be steeper if it takes long time from T1 to 6. The paleo-channel of Soyang River is supposed to be stronger meandering in period of T2 than T3. The weathering rind of gravel is generally thicker in older terrace, however, differs by contents of water and air in deposits. Based on the data of stratigraphy, grain size analysis, pollen analysis and rubification index in deposit, formation age of T5 terrace in Soyang River are estimated in MIS(Marine Oxygen Isotope Stage) 10, and T2 terrace are estimated in MIS 6.

• Journal of The Geomorphological Association of Korea
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• v.23 no.1
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• pp.17-33
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• 2016

Samples from newly exposed outcrop of sedimentary layers forming Jeongdongjin coastal terrace in Gangreung area are collected and analyzed to find the sedimentary environment. The site are located at the gentle hillslope of the terrace surface area. The height of the outcrop is about 8m and the altitude of it's highest part is 68~73m MSL. The lowest part of this out crop is the partly consolidated sand layer with gravel veneer within it. It is found that this part is not in-situ weathered sand stone through the OSL method. This sand layer is overlain by the gravel layer with sand matrix. The shapes of the gravels from this part are mainly 'platy', 'elongated', and 'bladed' by the index of Sneed and Folk(1958). In addition, mean roundness is not so high. It is sceptical to regard this part as marine sediments which are continuously exposed to erosional processes. The boundary between the lowest sand layer and gravel layer showing the abrupt change in forming material without any mixture or transitional zone, so gravels are seemed to deposited after some degree of consolidation of the lowest sand layer. In addition, the hight of the boundary between layers are changed by the place, so the surface of the partly consolidated sand layer is not flat and has irregularity on topography when it buried by gravels. Main part of this out crop is the poorly sorted coarse gravel(22.4mm) with sand matrix($1.36{\phi}$) layer with at least 2m thick covering the relatively fine gravels discussed above. Over 20% of particles have 'very platy', 'very elongated' and 'very bladed' shape and only less than 5% of particles have 'compact' shape, So this particles are also very hard to be regard as marine gravels which are abraded by marine processes. It can be concluded that this gravel layer formed by fluvial processes rather than coastal processes base on the form of the clast and sedimentary structure. The gravel layer is covered by fine($3{\sim}4{\phi}$) material layers of psudo-gleization which showing inter-bedding of red and white layers. Chemical composition of matrix and other fine materials should be analyzed in further studies. It is attempted to fine the burial ages of the sediment using OSL method, but failed by the saturation. So it can be assumed that these sediments have be buried over 120ka.