• 한국지형학회지
• /
• 제25권3호
• /
• pp.71-87
• /
• 2018

As part of further study on Gwangseungri coastal deposits which occurred at 10 ~ 15m above sea level and was analyzed as palaeo-coastal flood-type sediments, six burial ages of six additional samples from the two cross sections (KST1 and, KST2) near to the points of the past study were estimated and the geochemical analysis was performed. Further investigation on the cross section KST1 revealed a reversal of the burial age at the bottom of the section which was identified as palaeo-flooding sediments and supposed to have been buried about 350 years ago. At the lower part of the KST1, the burial age of the sediment layer was estimated to be 3,800 years. The lower part of KST2 sediments was identified as sediments that was formed about 6,600 years ago and about 20,000 years ago. Considering the inclination of the sediment layers, the coastal flooding sedimentsreported to have formed 700 years ago in the previousstudy are located at the top and the KST1 section analyzed in thisstudy seemed to be connected to the lower part. The chemical analysis showed that the relationship between these layers was not continuous but had a discontinuous characteristic influenced by a specific event, and the chemical composition also showed a rapid change. If we judge these together, the lowest part of Gwangseungrisediment layerseemed to have formed during the last glacial period but it was hard to find its origins clearly. On top of this layer, a fine sediment layer containing gravels was also formed.Itseemed thatsedimentation did not occur continuously, but was affected by temporary events in such a way that after a sediment layer was formed, it stopped. Since then, a coastal flooding event occurred about 700 years ago, and part of flooded sediments accumulated in the rear slope. After that, when a flood layer including additional granular materials about 350 years ago was formed, sedimentation along the slope seemed to have occurred.

• 한국제4기학회지
• /
• 제17권2호
• /
• pp.17-23
• /
• 2003

In Korea terrestrial fluvial sequences can be used as pedological and sedimentological markers indicating a millenium-scale environmental and climatic changes imprinted in fluvial sub-environments, which in turn are represented by the cyclicity of fluvial sands, backswamp organic muds, and flooding muds intercalations of frostcracked or dessicated brown paleosols. Post LGM and Holocene fluvial and alluvial sedimentary sequences of Korea are formed in such landscapes of coastal, floodplain, backswamp and hillslope areas. Among them, the most outstanding depositional sequences are fluvial gravels, sands and organic mud deposits in coastal, fluvial, or alluvial wetlands. The aim of this study is to explain the sedimentary sequences and palynofloral zones since the last 15,000years, on the basis of organic muds layers intercalated in fluvial sand deposits. Jangheung-ri site of Nam river, Soro-ri site of Miho river, Youngsan rivermouth site in Muan, Oksan-ri site of Hampyeong and Sanggap-ri site of Gochang are illustrated to interpret their sedimentary facies, radiocarbon datings, and palynofloral zonation. Up to the Middle to Late Last Glacial(up to 30-35Ka), old river-bed, flooding, and backswamp sequences contain such arboreal pollens as Pinus, Abies, and Picea, and rich in non-arboreal pollens like Cyperaceae, Gramineae, Ranunculaceae, and Compositae. During the LGM and post-LGM periods until Younger Dryas, vegetation has changes from the sub-alpine conifer forest(up to about 17-11Ka), through the conifer and broad-leaved deciduous forest, or mixed forest (formed during 16,680-13,010yrB.P), to the deciduous and broad-leaved forest (older than 9,500yrB.P). In the Earliest Holocene flooding deposits, fragments of plant roots are abundant and subjected to intensive pedogenic processes. During Holocene, three arboreal pollen zones are identified in the ascending order of strata； Pinus-Colyus zone(mixed conifer and deciduous broad-leaved forest, about up to 10Ka), Alnus-Quercus forest (the cool temperate deciduous broad-leaved forest, about 10Ka-2Ka), and Pinus forest (the conifer forest, about after 2Ka), as examplified in Soro-ri site of Cheonwon county. The palynological zonations of Soro-ri, Oksan-ri, Sanggap-ri, Youngsan estuary, and Gimhae fluvial plain have been recognized as a provisional correlation tool, and zonations based on fluvial backswamp and flooding deposits shows a similar result with those of previous researchers.

• 한국지형학회지
• /
• 제24권3호
• /
• pp.83-103
• /
• 2017

Sand deposit with shell units is exposed in Hasa-ri, Yeonggwang-gun, Jeonnam province. We investigated the characteristics of sand sediment topography in the Yeonggwang coastal area to collect evidence of the paleo-environmental change. We performed analysis on particle characteristics, chemical composition, and the age of deposition of sediments. The deposit comprise moderately well sorted medium and fine sand ($1.00{\sim}2.19{\varphi}$). Various sedimentary structures can be observed. Geochemical characteristics change by depth and the degree of variation with depth is small. The results obtained from OSL dating show that sand layers below shell units are deposited 0.32-0.43 ka. As the elevation of the shell unit far mean high water levels or highest high water level, the extensive shell layers could only have been deposited during storm surge conditions. Aeolian processes are discounted due to the size of clasts and the location at which they occur. Results of age dating of the surrounding deposits indicate shell deposits formed after around 300 years age. There is a distinct difference between sedimentary layers including dark brown-black layer. The sedimentary characters such as particle size and geochemistry show difference with depth. It is presumed that depositional environmental in Hasa-ri has changed several times before. This study is expected to contribute to finding an evidence about occurrence of storm surges.

• Geosciences Journal
• /
• 제22권6호
• /
• pp.903-919
• /
• 2018

This paper focuses on the depositional processes and environmental changes during initial marine flooding recorded in the lower Cambrian succession of the North China Platform in Shandong Province, China. In order to understand imbalance of accommodation and sediment supply in the initial stage of basin-fill, a detailed analysis of sedimentary facies was made for the lowermost siliciclastic deposits of the Liguan Formation. It reveals ten siliciclastic lithofacies in three large-scale outcrops (Jinhe, Anqianzhuang, and Zhangjiapo sections). These facies are grouped into four facies associations, representing siliciclastic foreshoreshoreface (S1), siliciclastic offshore (S2), distributary mouth bars (S3), and coastal plain (S4). The siliciclastic components occur in a linear belt, emanating from a major drainage system in the northeastern part of the platform. Deposition of siliciclastic sediments was largely controlled by regional topography of the unconformable surface and shoreline configuration as well as strong effect of waves and currents. With ensued rise in sea level and decrease in siliciclastic sediment supply, carbonate sediments prevailed, filling the accommodation created by epeirogenic subsidence and sediment loading.

• 한국지형학회지
• /
• 제24권1호
• /
• pp.25-38
• /
• 2017

To investigate the characteristics of sand sediment topography in the Yeonggwang coastal area of Chonnam and to collect evidence of the past extreme events causing coastal flooding, three sites were surveyed among the sediments of Baeksoo-eup Hassari. In this study, the changes of particle characteristics, chemical composition, and the age of deposition of sediments were investigated. The sediments near Baeksoonam Elementary School at the elevation of 10m near the paleo-coastline are estimated to have been deposited at about 3,400 years ago and the grain size of the upper part of the sandy layer is in the range of $2.47-2.11{\varphi}$. The burial age of the sediment layer at Sadeung junction(BSN-B) was about 100 years. Considering the distance from the current coastline, the sands forming the dune are estimated to have been moved or deposited from the nearby area or the other dune on the front side. The mean grain size is observed to be fining upward. Especially, the mean of the upper part is about $2.3{\varphi}$, which is similar to other survey points. The averaged grain size of the lower part of the BSNC (Hasari-1 Gu) was $2.196{\varphi}$ and the upper part was $2.16{\varphi}$. The sorting showed that the upper part was slightly poorer than the lower, and it was difficult to specify the change of the environment. The burial age of the lower layer, which contains shells, was about 300 years. Considering previous studies, this shell layer is presumed to have formed by coastal flooding, such as a storm surge.

• 한국지구과학회지
• /
• 제36권3호
• /
• pp.222-235
• /
• 2015

고창군 광승리 지역의 해발고도 5 m 내외의 해안 지점(DH)과 해발고도 10-15 m의 단구 상부 지점(KS)에서 시료를 채취하여 화학 분석과 입도 분석 등을 통하여 퇴적 물질의 특성을 파악하였다. DH는 풍화된 기반암을 피복하는 적색 토양층으로 하부에서 상부로 가면서 물질 조성이 점진적으로 변화하였다. DH 시료 내에 점토광물이 포함되어 있는 것으로 나타났다. 이를 근거로 하여 이 층을 제자리 풍화층으로 판단하였다. KS의 경우 구릉의 말단부에 위치하는 자갈층을 피복하는 층으로 물질 조성이 전반적으로 DH 부분과 상당히 다른 것으로 나타났으며, 일부 구간에서 물질의 교란이 일어나거나 외부 물질의 유입이 있었던 것으로 추정되었다. 한편 입자의 입도에 있어서 KS 시료들은 현재의 해빈 물질과 다른 특성이 나타난다. KS의 하부는 해빈에 비하여 세립 물질로 나타났으며, 중간 부분은 해빈보다 조립 물질이다. KS 시료의 분급은 해빈에 비하여 나쁜 것으로 나타났으며, 이 퇴적층중 일부는 지속적인 파랑과 조류에 의한 것보다는 일시적인 고에너지 환경에서 퇴적된 것으로 추정된다. 한편 KS 부분 시료의 매몰 연대는 광여기루미네센스(OSL) 분석에 의하여 0.65-0.71 ka로 추정되었다. 추가적인 연구를 통해 해당 퇴적층과 형성 과정의 특성에 대해서는 명확히 밝혀져야 할 것이지만, 해당 퇴적층은 폭풍에 의한 연안 범람 퇴적층일 가능성이 높은 것으로 추정된다.