Southwestern Korean Peninsula Research Articles

Mesozoic transpressional structural inversion and synkinematic crustal fluid circulation around the northeastern Chungnam basin, southwestern Korean Peninsula: Tectonic implications

This study explores the coupled processes of structural inversion and fluid migration around the northeastern part of the Mesozoic Chungnam Basin in the southwestern Korean Peninsula, focusing on quartz vein systems genetically linked to an orogenic gold deposit. Our results show that the inversion structures reflect the coexistence of strike-slip simple shear and pure shear components caused by NW–SE crustal shortening, leading to a transpressional deformation model. The quartz veins, filling the high-angle faults with a reverse slip component and adjacent hydrofractured wall rocks, represent transient fluid flow related to seismic faulting and fault valving during the inversion. New K–Ar ages of illite polytypes in fault gouges, determined using the Illite-age-analysis (IAA) method, indicate Late Jurassic–Early Cretaceous fault reactivations. Notably, ca. 160 Ma 2M1 illite age from a fault zone filled with an orogenic gold–bearing quartz vein indicates that the inversion and auriferous hydrothermal fluid flow started with a magmatic quiescence in the southern Korean Peninsula likely owing to the flat subduction of the Paleo-Pacific Plate. Our findings suggest that the orogenic gold–bearing vein system was likely sourced from the subcrustal metamorphic fluid in the flat subduction zone of the Mesozoic East Asian Continental margin.

Assessment of Marine Use Zones (MUZs) in the Spatial Planning of Jeonbuk Sea Waters (Southwestern Korean Peninsula)

Assessment of Marine Use Zones (MUZs) in the Spatial Planning of Jeonbuk Sea Waters (Southwestern Korean Peninsula)

Sub-seasonal to seasonal outlook of the 2022–23 southwestern Korea meteorological drought

The southwestern Korean Peninsula had experienced cumulative precipitation deficits from the early spring of 2022, causing a severe meteorological drought in March 2023. As a growing season was forthcoming, the sub-seasonal to seasonal outlook of this ongoing drought came into question. This study aims to investigate a key driver of the ongoing drought and the required precipitation for its termination, and examine the sub-seasonal and seasonal outlooks of the ongoing drought via probabilistic and climate model-based forecasts. Results show a comparable contribution of springtime and summertime precipitation deficits in 2022, indicating that six-month accumulated precipitation deficit of 2022 was a key driver of the ongoing drought. We find that at least 80, 150, and 210 mm (170, 310, and 440 mm) of accumulated precipitation are required for the recovery (full recovery) in March, April, and May 2023, respectively. These required cumulative precipitation are found from 25% and 20% of empirical and dynamic precipitation forecasts, respectively. This study highlights the importance of the collaborative effort of national and local governments and stakeholders on mitigating negative impacts of the ongoing drought.

Revised Geology and Geological Structures of the Northeastern Chungnam Basin in the Southwestern Korean Peninsula

Revised Geology and Geological Structures of the Northeastern Chungnam Basin in the Southwestern Korean Peninsula

Palynological implications for paleoenvironmental changes over the past 81,000 years on the Jeju Strait shelf, off southwestern Korea

Age-controlled palynostratigraphy has revealed changes in the depositional environment, vegetation, and climate of the southwestern Korean Peninsula since marine isotope stage (MIS) 5a. During MIS 5a (ca. 74–81 ka), the Jeju Strait shelf was an inner shelf with deposition influenced by the Jeju Warm Current (JWC), surrounded by land covered by mixed conifer and deciduous broadleaf forests under warm temperate conditions. The paleoenvironment during MIS 4 (57–71 ka) remains unknown due to a lack of palynomorphs from this stage. During mid–late MIS 3 (ca. 29–50 ka), the Jeju Strait shelf was an inner shelf influenced by cold-water masses from the Korean Coastal Current combined with weaker influences by the JWC, and the surrounding land was covered by mixed conifer and deciduous broadleaf forests that were less dense than in MIS 5a under warm and relatively dry conditions. A cold, slightly wet climate during MIS 2 (ca. 12–29 ka) led to the extension of predominantly cold-tolerant conifer forests due to lowstand sea levels, although inland East Asia remained cold and dry. During MIS 1 (ca. 0–12 ka), cold-tolerant conifer forests persisted into the early Holocene, and were subsequently replaced by mixed conifer and deciduous broadleaf forests as a warm climate was restored in the mid–late Holocene, when the depositional environment became an outer shelf due to highstand sea levels, as it remains today.

Physical properties of Quaternary sediments from the western South Korea Plateau, East Sea

Sediment samples were collected with a piston sampler (114 samples) and a box core sampler (266 samples) during research cruises on the R/V Tamhae 2 of the Korea Institute of Geoscience and Mineral Resources (KIGAM) from 2015 to 2019, to examine the characteristics of seafloor sediments from the western South Korea Plateau of East Sea. The in situ velocity was measured at four sites using a seafloor acoustic probe developed by KIGAM (KISAP). The samples were analyzed for their physical properties and the resulting data were examined to gain insights into the distribution patterns of the sediments and how the physical properties varied by burial depth. The actual velocity of the seafloor sediments was investigated by comparing the velocities in the laboratory and in situ velocity measurements at four sites. Overall, the physical properties agree well with the expected characteristics of marine sediments but there is considerable variation in the mean grain sizes. The sediment distributions either increases or decreases gradually with depth, reflecting transport from topographically high areas (e.g., possible source and/or shelf areas). The relationships between the physical properties of samples from two transects, one east-west and the other south-north, are different, and reflect the presence of tephra with a low grain density at the specified depth intervals. The laboratory velocity is higher (approximately 20–40 m/s) than the in situ velocity measured by the KISAP because of differences in the temperature (approximately 22 °C) and pressure (∼100 atmospheric pressure). However, the corrected laboratory velocity agrees well with the in situ velocity. Inconsistencies in the data, such as the measurement frequency and condition of each system, measurement interval, and sediment grain size, are probably responsible for some of the variations in the physical property data.

Geometry and scale property of a gold-silver-bearing vein system associated with an oblique-slip fault zone at Gasado Island, Korea

Gasado Island, on the southwestern Korean Peninsula, comprises c. 50 Ma volcanic rocks that are cut by faults and fractures hosting low-sulfidation epithermal Au-Ag mineralization. In this study, we examined the relationship between the fault-fracture networks and auriferous vein systems to better understand the role of brittle structures in controlling hydrothermal fluid flow. Geometrical and fractal analyses were performed to express and quantitatively compare the vein geometries and thickness population. The results were as follows: (1) The geometrical analysis revealed a strong relationship between Au-Ag-bearing quartz veins and NE-SW-striking, oblique sinistral-normal faults, indicating that these structures are a key control on mineralization. (2) Box-counting fractal analysis applied to veins hosted by fault zone demonstrated that the D-values (fractal dimensions) are directly proportional to vein density – indicating that damage zones control vein density. (3) The linear traverse line analysis yielded cumulative frequency plots of vein thicknesses that showed obvious changes in the slope, which are reflected in the variable D-values. The cause of this slope variability is interpreted to be the presence of hybrid veins that fill secondary fault planes, which disturbs the original linear relationship shown by cumulative thickness distribution data. This study shows that vein density and physical properties are strongly controlled by the types, or existence, of fault damage zones. Understanding fault zone architecture may assist with the prediction of locations that concentrate mineralizing fluids and may benefit the initial stage of mineral exploration.

A new titanopteranMagnatitan jongheonin. gen. n. sp. from southwestern Korean Peninsula

AbstractTitanopterans are spectacular, giant, predatory insects mainly known from the Triassic, but they are known from a few localities in Central Asia (including European Russia) and Australia. The Nampo Group is a nonmarine sequence, located on the southwestern Korean Peninsula, the age of which has remained controversial, due to lack of proper age-constraining fossils. Here, we report a new titanopteranMagnatitan jongheonin. gen. n. sp. from the Amisan Formation, Nampo Group. The division of the radius anterior and radius posterior beyond the distal half of the fossil wing is a characteristic of the family Paratitanidae. This is the first discovery of a titanopteran fossil outside of Central Asia and Australia, suggesting a possible circum-Tethys oceanic distribution. Given the possibly widespread distribution of titanopterans, this group might have played a critical role as giant predatory insects in Triassic terrestrial ecology. Because titanopterans have never been found beyond the Triassic-Jurassic boundary, the occurrence of a titanopteran corroborates the Triassic age of the Nampo Group.UUID:http://zoobank.org/10177029-0044-424f-9816-e3fb057cfe85

Statherian (ca. 1714–1680 Ma) Extension-Related Magmatism and Deformation in the Southwestern Korean Peninsula and Its Geological Significance: Constraints from the Petrological, Structural, Geochemical and Geochronological Studies of Newly Identified Granitoids

In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating revealed that the two granites formed around 1.71 Ga and 1.70–1.68 Ga, respectively. The results of the geochemical analyses showed that both of the granites have a high content of K2O, Nb, Ta, and Y, as well as high FeOt/MgO and Ga/Al ratios. Both granites have alkali-calcic characteristics with a ferroan composition, indicating an A-type affinity. Zircon Lu-Hf isotopic compositions yielded negative εHf(t) values (−3.5 to −10.6), indicating a derivation from ancient crustal materials. Both granite types underwent ductile deformation and exhibited a dextral sense of shear with a minor extension component. Based on field relationships and zircon U-Pb dating, it was considered that the deformation event postdated the emplacement of the alkali feldspar granite and terminated soon after the emplacement of the porphyritic alkali feldspar granite in an extensional setting. These data indicated that there were extension-related magmatic activities accompanying ductile deformation in the southwestern part of the Korean Peninsula during 1.71–1.68 Ga. The Statherian extension-related events are well correlated with those in the midwestern part of the Korean and eastern parts of the North China Craton.

U-Pb Age Dating and Geochemistry of Soft-Sediment Deformation Structure-Bearing Late Cretaceous Volcano-Sedimentary Basins in the SW Korean Peninsula and Their Tectonic Implications

Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- and NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur in the Wido, Buan, and Haenam areas of the southwestern Korean Peninsula. In this study, systematic geological, geochronological, and geochemical investigations of the volcanic-sedimentary successions were conducted to constrain the origin and timing of SSDS-bearing lacustrine strata. The SSDS-bearing strata is conformably underlain and overlain by volcanic rocks, and it contains much volcaniclastic sediment and is interbedded with tuffs. The studied SSDSs were interpreted to have formed by ground shaking during syndepositional earthquakes. U-Pb zircon ages of volcanic and volcaniclastic rocks within the studied volcano-sedimentary successions were ca. 87–84 Ma, indicating that active volcanism was concurrent with lacustrine sedimentation. Geochemical characteristics indicate that these mostly rhyolitic rocks are similar to subduction-related calc-alkaline volcanic rocks from an active continental margin. This suggests that the SSDSs in the study area were formed by earthquakes related to proximal volcanic activity due to the oblique subduction of the Paleo-Pacific Plate during the Late Cretaceous.

The relationships among faults, geology and geophysical data in the southwestern Korean Peninsula, including the Haenam area, and their application for the interpretation of earthquakes

The southwestern Gyeonggi Massif features many faults. The main faults are NE-striking faults, including the Jeonju and Kwangju faults, and they are cut by N-S- and NNE-striking faults. Additionally, E-W-, WNW-, and NW-striking faults occur as minor faults. Historical earthquakes with magnitudes greater than 5.0 have occurred on or near these faults. Earthquakes with focal depths shallower than 12 km have generally occurred on the NE-, NNE-, and N-S-striking faults, while those with hypocenters deeper than 12 km have occurred on the NW-, WNW-, and NE-striking faults or do not show a relationship with any faults. The instrumental earthquakes with magnitudes greater than 5.0 in the Korean Peninsula mainly have hypocenters deeper than 12 km, and their epicenters form a NW-oriented trend. These data effectively reflect two seismogenic layers with a boundary at ca. 12 km, as suggested in a previous study. The recent earthquake in the Haenam area occurred in the lower seismogenic layer. The shallower earthquakes seem to be the result of the reactivation of pre-existing faults. In comparison, the deeper earthquakes tend to occur on recently formed or newly formed faults related to the present regional stress of the Korean Peninsula. The shear-wave velocity tomography of the southwestern Gyeonggi Massif at 1 km corresponds well to the geology. In contrast, the shear-wave velocity variations at 5–9 km generally correspond to the locations of brittle faults. The depth of the ~3.5 km/s isovelocity line is quite irregular and is deeper in areas with active fault movement. In the Gyeongsang basin, the relationship between the shear-wave velocity and faults is somewhat unclear because the thickness of low-density sedimentary rocks is up to 8 km. Shear-wave velocity tomography at 13 km can be used to identify areas with high shear stress. These data indicate that shear-wave velocity tomography may provide different information depending on the depth and that the brittle faults in this region may not extend to a depth of 13 km.

Source and path effects of the ground motions recorded during the 2020 Haenam earthquake swarm in South Korea

On the southwestern Korean Peninsula, a 74-earthquake swarm was recorded between April 26 and May 9, 2020, with a maximum local magnitude (ML) of 3.1. This is the third such event since instrumental seismic recordings began in South Korea in 1978. Because this area is located on a stable continent, this rare swarm event provides an opportunity to analyze earthquake sources and attenuation characteristics in this region. In this study, we first analyzed the intensity measure (IM) and the frequency content of the ground motions recorded during this swarm event. Next, we investigated the effects of earthquake magnitude and source-to-site distance on IMs, compared with those derived from international and local ground-motion models (GMMs). We found that the magnitude scaling slope (i.e., variation of IMs depending on ML) of the earthquake swarm records for ML ≥ 1.8 is similar to the slopes derived from GMMs, while for ML < 1.8, the slope from the records is steeper. For distance scaling (i.e., variation of IMs depending on source-to-site distance), the slopes from records are gentler than those from GMMs. This indicates that ground motion attenuates slowly in this region, compared to other global regions.

Fluid Infiltration and Mass Transfer along a Lamprophyre Dyke–Marble Contact: An Example from the South-Western Korean Peninsula

In this contribution, we report the metasomatic characteristics of a lamprophyre dyke–marble contact zone from the Hongseong–Imjingang belt along the western Gyeonggi Massif, South Korea. The lamprophyre dyke intruded into the dolomitic marble, forming a serpentinized contact zone. The zone consists of olivine, serpentine, calcite, dolomite, biotite, spinel, and hematite. Minor F and Cl contents in the serpentine and biotite indicate the composition of the infiltrating H2O-CO2 fluid. SiO2 (12.42 wt %), FeO (1.83 wt %), K2O (0.03 wt %), Sr (89 ppm), U (0.7 ppm), Th (1.44 ppm), and rare earth elements (REEs) are highly mobile, while Zr, Cr, and Ba are moderately mobile in the fluid. Phase equilibria modelling suggests that the olivine, spinel, biotite, and calcite assemblage might be formed by the dissolution of dolomite at ~700 °C, 130 MPa. Such modelling requires stable diopside in the observed conditions in the presence of silica-saturated fluid. The lack of diopside in the metasomatized region is due to the high K activity of the fluid. Our log activity K2O (aK2O)–temperature pseudosection shows that at aK2O~−40, the olivine, spinel, biotite, and calcite assemblage is stable without diopside. Subsequently, at ~450 °C, 130 MPa, serpentine is formed due to the infiltration of H2O during the cooling of the lamprophyre dyke. This suggests that hot H2O-CO2 fluids with dissolved major and trace elements infiltrated through fractures, grain boundaries, and micron-scale porosity, which dissolved dolomite in the marble and precipitated the observed olivine-bearing peak metasomatic assemblage. During cooling, exsolved CO2 could increase the water activity to stabilize the serpentine. Our example implies that dissolution-reprecipitation is an important process, locally and regionally, that could impart important textural and geochemical variations in metasomatized rocks.

One-off deep crustal earthquake swarm in a stable intracontinental region of the southwestern Korean Peninsula

A deep crustal strike-slip earthquake swarm that occurred in the intracontinental region of the southwestern Korean Peninsula is investigated. The earthquakes are detected using matched filter analysis. The hypocenters are then refined, showing more than 500 micro to small strike-slip earthquakes concentrated on a fault plane with dimensions of 500 m by 300 m at a depth of ~21 km. The low temperature in the source depth facilitates the seismicity. The earthquake swarm was transiently active for 15 days from 25 April 2020 to 12 May 2020, presenting a high seismicity rate with a Gutenberg-Richter b value of 2.01 (±0.05). The earthquake swarm began in the central area and expanded outward with time. The spatiotemporal seismicity distribution reflects bilateral rupture. The focal mechanism solutions suggest a left-lateral strike-slip fault with a strike of 103.6∘ ± 3.2∘ and a dip of 73.3∘ ± 11.7∘. The spatial distribution of seismicity generally agrees with the focal mechanism solutions. The orientation of the inverted stress field agrees with the ambient stress field, suggesting that the earthquake swarm occurred as a consequence of ambient lithostatic stress loading. Coulomb stress changes suggest that the stress increased in the directions of WNW-ESE and NNE-SSW from the fault. The transiently active earthquake swarm began to occur after the 2011 MW9.0 Tohoku-Oki megathrust earthquake, suggesting a rapid release of accumulated stress in response to changes in the properties of the medium caused by the megathrust earthquake.

A new cave amphipod, Pseudocrangonyx wonkimi sp. nov. (Crustacea, Amphipoda, Pseudocrangonyctidae), from the Korean Peninsula.

A new species of pseudocrangonyctid amphipod, Pseudocrangonyx wonkimisp. nov., was found in the groundwater of a cave in the southwestern Korean Peninsula. Pseudocrangonyx wonkimisp. nov. is morphologically most closely related to P. joolaeiLee et al., 2020. However, P. wonkimi is clearly distinguished from P. joolaei by lacking sternal gills, fewer setae on maxilla 1 inner plate, fewer serrate robust setae on the carpus of the gnathopods, lacking bifid setae on the inner ramus of pleopod 3, and fewer articles of rami on pleopod 3. We also determined sequences of mitochondrial cytochrome c oxidase subunit I (COI) of P. wonkimisp. nov. for molecular diagnosis. From the molecular analysis based on COI sequences, P. wonkimi showed the closest relationship with P. joolaei with 15.1% genetic distance.

Rapid Ocean Destratification by Typhoon Soulik over the Highly Stratified Waters of West Jeju Island, Korea

Lim, H.; Miles, T.; Glenn, S.; Kim, D.; Kim, M.; Shim, J.; Chun, I., and Hwang, K., 2020. Rapid ocean destratification by typhoon Soulik over the highly stratified waters of west Jeju Island, Korea. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1480–1484. Coconut Creek (Florida), ISSN 0749-0208.Global warming is affecting ocean disasters by intensifying typhoons, which present a threat to people living in coastal cities. The increase of intensity has been observed in the typhoons approaching the southwestern Korean Peninsula; this increase can be attributed to the increasing water temperature and strong stratification of the Yellow Sea in summer. Typhoon Soulik was formed on August 16, 2018 in the western North Pacific and tracked northwestward toward the Yellow Sea, slowing down as it moved towards the highly stratified coastal waters of western Jeju Island on August 23. However, its intensity rapidly decreased from a typhoon to a tropical storm before it landed on the southwestern Korean Peninsula. Typhoon Soulik was observed by the Korea Institute of Ocean Science and Technology's (KIOST) Ieodo Ocean Research Station (IORS), the Korea Hydrographic and Oceanographic Agency's (KHOA) Moslpo tidal station, and an underwater glider deployed by KIOST and Rutgers University as a part of the Joint Program Agreement (JPA) by the Korean Ministry of Oceans and Fisheries (MOF) and National Oceanic and Atmospheric Administration (NOAA). The glider was deployed over the Yellow Sea Trough, west of Jeju Island near IORS, from August 15 to 25, 2018; during this time, the eye of typhoon Soulik travelled within 26 km of the glider track on August 23 at 04:37 Korea Standard Time (KST). The glider also observed a rapid ocean cooling where the surface temperature dropped from 27.5°C to 16.5°C while the bottom temperature increased from 11°C to 14°C, and the pycnocline deepened from 30 to 60 m. The rapid ocean mixing coincided with a tidal transition followed by several hours of sustained winds and waves with limited mixing and cooling. It is suggested that this rapid ocean destratification might reduce the intensity of typhoon Soulik before landfall.

New Early Cretaceous dinosaurian eggshell Multifissoolithus shimonosekiensis (Dinosauria, Dongyangoolithidae) from the Lower Cretaceous of Shimonoseki, Yamaguchi, Southwestern Japan

ABSTRACT Dinosaur eggshells from Japan provide vital information about the relatively uncommon Early Cretaceous dinosaur eggs in Asia. Here, we describe a new Early Cretaceous dinosaur eggshell, Multifissoolithus shimonosekiensis from Shimonoseki, Yamaguchi, southwestern Japan. The specimen was collected in 1965 from the Aptian-Albian Shimonoseki Subgroup and range in diameter approximately from 1 to 7 cm and in thickness from 3.4 to 4.7 mm. The external surface exhibits roughly parallel clefts diagnostic to the dongyangoolithid Multifissoolithus. Computed tomography images reveal complex internal cavities. Subcircular pore canals extend from the cavities. In radial thin section, the eggshell microstructure resembles prolatocanaliculate pore system with dendrospherulitic morphotype typical of the Dendroolithidae. Similar eggs are reported from Zhejiang, southern China and Gyeonggi, western South Korea, while M. shimonosekiensis differs from them in greater thickness and more extensively developed internal cavities. Microstructural similarity among the Dongyangoolithidae, Dendroolithidae, and Spheroolithidae may indicate their phylogenetically close relationship and deserves further studies. These eggs and M. shimonosekiensis commonly occur in the Aptian-Albian deposits and provide evidence for a shared oofauna in these regions. These eggs were likely laid by closely related dinosaur taxa and future exploration for the skeletal remains of such dinosaurs in the regions is desirable. http://www.zoobank.org/urn:lsid:zoobank.org:pub:910B2029-9B98-4C33-BFC9-FD25AA09FE40

The End of the Korean Paleolithic: The “Light-Brown Layer” Revisited

만 년이 넘는 시간 척도를 다루는 구석기고고학에서 유적형성과정의 이해는 매우 중요하다. 한국후기 구석기시대 유적에서는 흔히 “토양쐐기”라 불리는 땅갈라짐 현상이 나타나는 “암갈색층” 위에 흔히 “명갈색(찰흙)층”이라 불리는 퇴적층이 자리하고 있다. 두께도 얇고 유적의 특정 지점에만 잔존하는 경우가 많지만, 최근 몇 유적에서는 유물이 확인되고 있다. 다만 유물이 암갈색층에서 기원한 것인지, 아니면 명갈색층을 별도의 문화층으로 인정할 수 있는지 더 분명하고도 체계적인 검토가 필요 하다. 이 글에서는 수렵채집민이 유물을 남기고 간 뒤 일어나는 다양한 변형과정을 개괄하고, 익산 서두리, 전주 중동, 진안 진그늘, 임실 하가, 곡성 오지리, 화순 사창, 순천 월평과 죽내리 등 호남지방 유적을 대상으로 문화층으로서 명갈색층을 검토한다. 또한 유물군의 밀집도와 수직 및 수평 분포, 접합석기, 암갈색층과 중복 여부 등을 바탕으로 문화층의 여부를 판단하 고, 절대연대 자료를 비판적으로 해석하여 구석기시대가 끝나가는 시기, 곧 “종말기”의 석기기술의 특징을 살피고자 한다. 그 결과 이 시기 석기군에서는 여전히 돌날과 세석기가 보이지만, 서두리와 오지리 등지에서는 양면을 정교하게 잔손질한 찌르개, 또는 돌화살촉이 알려졌음을 주목한다. 또한 월평과 죽내리, 중동 등지에서 나온 버들잎모양의 창끝찌르개 를 석장리와 대정동 등지에서 수습된 유물과 비교한다. 나아가 기곡과 월소, 화대리, 석장리 등지에서 확인된 돌화살촉을 검토하여 구석기시대 최말기에는 기존의 세석기기술의 토대 위에서 양면찌르개 기술이 발전하고 유행했을 가능성을 논의한다.Understanding site formation processes is crucial in discussions of Paleolithic archaeology dealing with the time scale bigger than 10,000 years. Especially, at many Korean Late Paleolithic sites, the final Pleistocene layer, often called “light brown (clayey) layer,” is deposited on the ”dark brown layer“ containing soil cracks. At several locations, the light brown layer yielded notable Late Paleolithic artifacts including microliths, blades and bifacial points, while it is often difficult to determine whether the layer itself represents a cultural horizon independent from the underlying dark brown layer. The present study deals with a series of Late Paleolithic sites excavated in the Honam region of the southwestern Korean Peninsula. Considering various features, such as vertical and horizontal artifact distributions and number of refitted pieces, the present essay explores the nature of artifact assemblages from Seodu-ri, Jung-dong, Oji-ri, Haga, Wolpyeong, Juknae-ri, and Sachang. A critical evaluation of available radiocarbon dates and OSL dates provides a basis on which we can consider the final Paleolithic assemblages and their characteristics. Importantly, bifacially retouched points were notable as they were unearthed from Seodu-ri and Oji-ri. They are compared with similarbifacial points collected from other sites such as those from Gigok, Wolso and Hwadae-ri. Also, larger leaf-shaped points were collected from Jung-dong, Juknae-ri and Wolpyeong which can be compared with previous collections from Seokjang-ri and Daejeong-dong, which could be dated back to 20,000 cal BC in their appearance. It is emphasized that the bifacially retouched points were the most characteristic artifacts during the final Paleolithic in Korea.

Removal of non-aqueous phase liquids (NAPLs) from TPH-saturated sandy aquifer sediments using in situ air sparging combined with soil vapor extraction

Contamination in coastal aquifer plains is of great concern in many countries given that non-aqueous phase liquids (NAPLs) have polluted numerous sites through accidental oil spills or improper disposal. We have developed a method to remove pollutants such as NAPLs from sandy sediment samples collected from the Mandol area of Gomso Bay in western South Korea. The sediments were collected from around the diffuser in a two-dimensional (2D) acrylic reaction apparatus, and these contained a total petroleum hydrocarbon (TPH) concentration of 89.3 ppm (mg/kg media). The maximum perchloroethylene (PCE) concentration was 398.51 ppm in the unsaturated zone and 0.77 ppm in the saturated zone. Volatile organic compounds (VOCs) were detected between 20 and 44 hour. However, non-volatile contaminants remained in the sediments after treatment. In situ air sparging (IAS) combined with soil vapor extraction (SVE), transformation from sorbed and nonaqueous phases to the vapor phase, is incomplete when treatment is performed using a pervasive air flow for sediments such as the sand of Mandol. During air transformation, the groundwater flow conditions increased the rate of contaminant removal. Although pilot-scale testing in the field site was fluctuated due to the heterogeneous of sediments condition, this 2D study found that the proposed method can alter the measurable geophysical properties of NAPLs. These findings demonstrate that IAS combined with SVE in the saturated zone is an effective technology for aquifer remediation high applicability of sandy coastal sediments contaminated by NAPLs.

백악기 함평분지에서 산출되는 담수 개형충 화석 연구

이 연구에서는 전라남도 함평군 일대에 분포하는 백악기 함평분지에서 산출된 담수 개형충의 분류학적 기재, 생층서 연대 및 고환경을 논의하였다. 연구지역의 개형충 군집은 총 5속 10종으로 이루어져 있으며, 전형적인 호소 환경의 종들로 확인되었다: Cypridea cf. changluensis, C. cf. subprognata, C. sp., Mongolocypris sp. 1, M. sp. 2, Candona cf. arcinaeformis, C. sp. 1, C. sp. 2, Mantelliana sp. 및 Timiriasevia sp. 이 중에서 Mantelliana와 Timiriasevia에 속하는 종들은 남한에서 처음으로 보고되는 분류군들이며, 특히 Timiriasevia의 산출을 통해 함평분지가 주기적인 계절변화의 영향을 받았던 호소환경이었다고 추론하였다. 또한 함평분지의 개형충 군집을 백악기 동아시아의 분류군들과 비교한 결과를 토대로 분지의 형성시기를 Aptian 내지 Albian으로 해석하였다.