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Abstract: Age-controlled pollen stratigraphy from the Paju (UJ-10), Cheonggye (Gwangtong Trench-A), and Hanam (UD-2) sites records the response of vegetation to climate changes and human activity over the past 7000 years in the Han River drainage basin, west-central Korea. The pollen profiles show a transition from natural vegetation to human-disturbed vegetation around 4800 cal BP. During the natural vegetation stage (ca. 7000–4800 cal BP; early Neolithic Age), dense woodlands of mixed deciduous and evergreen broadleaved hardwoods flourished in the surrounding hills and mountains owing to the enhanced East Asian summer monsoon. The human-disturbed vegetation stage (ca. 4800 cal BP–modern; late Neolithic Age to modern) was characterized by transitional forests and open grasslands and can be subdivided into several agricultural stages. During the dry-field cultivation stage (ca. 4800–3000 cal BP; late Neolithic to Bronze ages), humans engaged in dry-field agriculture under cool, dry climatic conditions. The ensuing paddy-field cultivation stage (ca. 3000–800 cal BP; since the Bronze Age) initially developed during an interval of stable, warm, wet conditions from ca. 3000 to ca. 1400 cal BP, during which time people of Bronze and Iron Age cultures engaged in widespread paddy farming. Subsequently, a brief climatic fluctuation (ca. 1400–800 cal BP) caused changes in the agricultural practices of the Unified Silla and Koryo people. During the combined dry-field and paddy-field cultivation stage (ca. 800 cal BP–modern; since the Joseon Dynasty), climatic deterioration affected agricultural practices of the Joseon people and resulted in open forests with wide grasslands during the interval equivalent to the Little Ice Age (1550–1859 AD). Since then, humans in the area have strategically managed pine forests to supply wood for house-building and fuel. [Copyright &y& Elsevier]

Abstract: Organic and inorganic geochemical and mineralogical analyses from core CL4 drilled in the Cheollipo wetland were carried out to investigate the Holocene Climatic Optimum, the formation of pyrite, and the humidity of the Korean western coast during the Holocene time. Lithostratigraphy, mineralogy, major element concentrations and organic contents of the sediments of the CL4 borehole core indicate that the Holocene Climatic Optimum occurred from about 7400 to 4500BP, and that pyrite formed in brackish water tidal flat or salt marsh at least during 7400–6400BP. In addition, sediments coarser in mean grain size and larger in standard deviation corresponded with periods of 8500, 5400, 5000 and 1700BP. During the periods, the coarse sediments seem to have been delivered by high energy storm events. The periods partially overlap with those of high ratios of Si/Al, Na/Al and Na/Ti. These phenomena indicate that the weakly weathered terrigenous sediments were delivered to the Cheollipo borehole core site by storm events. [Copyright &y& Elsevier]

Abstract: Terrace stratigraphy of the southeastern coastal areas of Korea has been studied with the help of terrace mapping and geochronology. Coastal terraces include 90–130m upper High Terrace (uHT), 63–86m High Terrace (HT), 36–55m Middle Terrace (MT) and 8–25m Low Terrace (LT) divisions, each of which has been subdivided. Amongst these, LT 2 formed during the late Pleistocene, based on Tephras Aso-4 (MIS 5c), Ata (MIS 5d or 5e) and OSL ages. The age of LT 1–3 ranges from MIS 5e to 5a, based on tephra ages from Aso-4 (ca. 90ka) and Ata (100–125ka). The uplift rate in the SE part of Korea ranges between 0.14 and 0.22mm/a and it is quite small in comparison to the Japanese island arc, or many other tectonically active East and Southeastern Asian regions. [Copyright &y& Elsevier]

Abstract: Mid- and Late-Holocene changes in vegetation, climate and depositional environment have been deduced from pollen records taken from the Gwangtong Trench-A in Cheonggye-cheon, the tributary of the Han River, with time control provided from three radiocarbon ages. A mid-Holocene hypsithermal occurred between ?7000 and 5000BP, when evergreen and deciduous broadleaved trees flourished at mountainous slope surrounding the lowland riverine area. Afterward climate became cooler until 1700BP. During this period, evergreen and deciduous broadleaved trees were replaced by conifers and cool-loving deciduous broadleaved trees of Picea, Pinus (Diploxylon), Larix/Pseudotsuga and Betula. Since 1700BP, the local vegetation change from alder woodlands to sedges caused by human impact has been identified. The depositional environmental change from lowland riverine to fluvial at 1700BP may allow the people to cultivate crops on dryland fields. Human activities are recognized by the first occurrence of buckwheat (Fagopyrum) associated with a sudden increase in maize (Zea) pollen and pioneer tree, P. (Diploxylon) with arboreal pollen concentration decreasing at 1700BP. [Copyright &y& Elsevier]

To trace the environmental change that occurred at a coastal area during the Holocene, we performed radiocarbon dating and geochemical analyses using sedimentary cores recovered from the Beolgyo tidal flats on the south coast of Korea. The δ 13 C values of total organic carbon (TOC), which represent relative inputs of terrestrial (or freshwater) and marine organic sources, revealed a long-term increasing trend from −27.5 to −21.7‰ during the period between 10,000 and 3000 cal BP, suggesting an evolutionary series of fluvial-dominant to marine-dominant environments, coupled with weakened summer monsoon intensity. From 3000 cal BP to the present, the δ 13 C TOC decreased gradually from −21.7 to −24‰, indicating enhancement of freshwater input during this time. The observed long-term environmental change was divided into six stages based on the averages of the total sulfur content (TS%) and the organic carbon to sulfur ratio (C/S), proxies for paleosalinity. On multi-centennial to millennial timescales, higher C/S ratios and lower TS% were linked to higher δ 13 C TOC values, indicating strong freshwater input at Stage 2 (∼8300–7400 cal BP), Stage 4 (∼4500–3300 cal BP), and Stage 6 (∼1100 cal BP to present). Strong freshwater discharge events synchronously occurred at 4300 cal BP and 3600 cal BP along the south coast of Korea. Further testing should be carried out in other East Asian coastal areas. This study suggests that sedimentary δ 13 C TOC values and C/S ratios can be used in Asian coastal regions to trace past freshwater input events and summer monsoon intensity during relatively stable sea level periods (e.g., the middle to late Holocene). [ABSTRACT FROM AUTHOR]

Abstract: The 18.820m long sediment core MW-1 from the Yeongsan Estuary consists of five primary unconsolidated to semi-consolidated units, ranging in age from late Pleistocene to Holocene, overlying a Cretaceous-aged basement. From oldest to youngest, these units include units-1, 2, 3 (fluvial units), unit-4 (paleosol unit), and unit-5 (Holocene estuarine deposits). Units-1, 2, and 3 are interpreted as in-channel or overbank deposits. Plant materials included within the units and the TOC/TN (total organic carbon/total nitrogen) ratios (11–14) are also indicative of terrestrial origin. Unit-2 yields radiocarbon date of 37,700 14C yrBP. Unit-4, the paleosol unit, is estimated to be originally deposited in fluvial setting such as the area of floodplain or backswamp away from the main channel, based on the sporadic distribution of the stagnant freshwater acritarch Pseudoschizaea and algae Spirogyra. The timing of deposition of the original sediments of the paleosol unit is constrained by radiocarbon age of underlying fluvial sediments (unit-2). The timing of pedogenesis is around the Last Glacial Maximum when sea level of the Yellow Sea was lowered, temperature was lowered, rainfall was reduced, and the inland was sparsely vegetated. Estuarine deposits (unit-5) are interpreted to be deposited during the Holocene marine transgression. [Copyright &y& Elsevier]