• Journal of the Korean earth science society
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• v.41 no.4
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• pp.367-380
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• 2020

LA-MC-ICP-MS zircon U-Pb dating was conducted to constrain the timing of fossil formation and the depositional age of the uppermost Jinju Formation located in Natural Monument No. 534 (Tracksite of Pterosaurs, Birds, and Dinosaurs in Hotandong, Jinju), and 87 Cretaceous, 1 Precambrian, and 2 Jurassic zircons were obtained from 90 valid analytical points. Most Cretaceous zircons were found to have a youngest graphical peak age of ca. 106.5 Ma, suggesting the depositional age of the uppermost Jinju Formation. Based on this study and previous works, the average sedimentation rate of the Jinju Formation was calculated to be approximately 0.17-0.31 mm/year in the Milyang Subbasin, and the Cretaceous zircons of the uppermost Jinju Formation seem to have originated mainly from the western or northwestern parts of the Gyeonggi Massif. Unlike the Nakdong and Hasandong formations of the Sindong Group, most zircons analyzed in the uppermost Jinju Formation were Cretaceous. This suggests that volcanic activity occurred in the area closer to the Gyeongsang Basin due to the roll-back of subducting paleo-Pacific Plates during the Jinju period.

• Economic and Environmental Geology
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• v.8 no.4
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• pp.183-201
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• 1975

The south and southwestern parts of Jeonra-namdo has been known as an alunite province in Korea. The alunite deposits investigated for the present study are Okmaisan, Seongsam, Bugog, Gasado south, Gasado north, Jangsando, Dogcheon and Jungyongri deposits. The main purpose of this study is to depict the genetical origin of the alunite deposits. The rocks distributed in the areas mentioned above consist chiefly of rhyolitic tuff, breccia tuff and andesitic tuff of Cretaceous age which represent different episodes of volcanic activities during Cretaceous epoch. The attitude of bedding of the tuffaceous rocks varies from place to place but generally dips very gently. The alunite deposits are embedded mostly in the rhyolitic tuff so that they appear as layered deposits, this occurrence may be the result of stratigraphic and lithologic controls. The result of this study can be summarized as below. The mineral sequence studied by the mineral paragenesis and the result of the spectrograph anlyses is such that (1) alunite was formed at first and pyrophyllite was nearly contemporaneous with alunite but pyrophyllite formation can be recognized as a secondary mineralization products, (2) kaoline was succeeded to form later and hematite finally deposited, and (3) pyrite was deposited from the begining to the end of the above mineralization period. The compositional change of host rocks is such that CaO, $SiO_2$ and $Na_2O$ were largely removed from the parent rocks and some $Al_2O_3$ and $SO_3$ were transported by the solution so as to enrich the rocks. The sequencial process of such mineralization has resulted in forming those distinguish mineral zones; alunite, kaoline, pyrophyllite, silicifide and sulphide zone which manifest irregular shape. These deposits were formed by hydrothermal solution which was possibly low temperature and contained sulphuric acid originated from $H_2S$ and $SO_2$ gases.

• Economic and Environmental Geology
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• v.28 no.5
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• pp.519-525
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• 1995

Recently, there have been several cases of serious accidents on concrete structure resulting from rapid deterioration of concrete strength. On the view point of long term stability of concrete, deterioration of concrete strength is mostly due to chemical reaction between alkali and reactive aggregates (alkali-aggreagte reaction; AAR) in concrete rather than a problem of execution. For long-term stability of concrete, concrete aggregates must be carefully selected. Some of rocks used for concrete aggregates contain deleterious minerals reactive to alkali components in concrete. Most of AAR result from chemical reaction between alkali components and reactive silica minerals in aggregates (so called alkali-silica reaction; ASR). The silica minerals are as follows; quartz with seriously distorted lattice structure, volcanic glass, chalcedony, opal, cristobalite, tridymite, etc. ASR may cause expansion and cracks, further collapse in concrete structure, in a few years. In case of crushed aggregates, only a part of rock mass without reactive minerals must be produced in aggregates mine after thorough examination of the distribution of rocks with reactive minerals. In case of natural aggregates, the total content of reactive minerals must be calculated, if, the content is more than 20%, the rate should be lower by mixing other non-reactive crushed- or natural aggregates. If it is obliged to use concrete aggregates all containing deleterious minerals in a discrete area, they must be used with low alkali cement Even if it is low quality in the chemical properties, aggregates with suitable range in the physical properties can be utilized as the aggregate of other purposes.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.57-68
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• 2014

This study categorizes the distributed sand around coastal area of Jeju volcanic Island into three groups according to their components, and arranges their characteristics. In the case of basic physical properties, the silicate sand has slightly greater specific gravity than general sand, and the carbonate sand with widespread distribution has a lower specific gravity. In the gross, the carbonate sand has poor particle classifying and low uniformity coefficient because carbonate minerals of relatively large grain size are mixed. The relation between compressive strength and components shows conflicting tendency that silicate and carbonate components have positive correlation and negative correlation with compressive strength, respectively. Based on the components ratio of one to one, the sand having low carbonate component ratio is expected to be able to utilize in construction fine aggregate. To compare between square root (ACI 308) and cube root (KCI 2012) of compressive strength at computation of elastic modulus, it is considered to non-dimensional elastic modulus.

• Journal of Climate Change Research
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• v.8 no.4
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• pp.401-414
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• 2017

Vegetation and landscape characteristics at the three highest summits of Republic of Korea, i.e. Seoraksan, Jirisan and Hallasan, are analyzed on the basis of species composition, physiognomy, vegetation distribution and structure of alpine plants, along with landform, geology, soil and habitat conditions. Dominant high mountain plants at three alpine and subalpine belts contain deciduous broadleaved shrub, Rhododendron mucronulatum var. ciliatum (31.6%), and evergreen coniferous small tree, Pinus pumila (26.3%) at Seoraksan, deciduous broadleaved tree, Betula ermanii (35.3%), evergreen coniferous tree, Picea jezoensis (23.5%) at Jirisan, and evergreen coniferous tree, Abies koreana (22.6%), deciduous broadleaved shrub, Rhododendron mucronulatum var. ciliatum, and Juniperus chinensis var. sargentii (19.4%) at Hallasan, respectively. Presence of diverse landscapes at the peak of Seoraksan, such as shrubland, grassland, dry land along with rocky areas, and open land may be the result of hostile local climate and geology. High proportion of grassland and wetland at the top of Jirisan may related to gneiss-based gentle topography and well developed soil deposits, which are beneficial to keep the moisture content high. Occurrence of grassland, shrubland, dry land, conifer vegetation, and rocky area at the summit of Hallasan may due to higher elevation, unique local climate, as well as volcanic origin geology and soil substrates. Presences of diverse boreal plant species with various physiognomy at alpine and subalpine belts, and wide range of landscapes, including rocky, grassland, shrubland, wetland, and conifer woodland, provide decisive clues to understand the natural history of Korea, and can be employed as an relevant environmental indicator of biodiversity and ecosystem stability.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.361-372
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• 2016

Lahar, one of catastrophic events, has the potential to cause the loss of life and damage to infrastructure over inhabited areas. This study using Laharz_py program, was performed schematic prediction on the impact area of lahar hazards at the Mt. Halla volcano, Jeju island. In order to comprehensively address the impact of lahar for the Mt. Halla, two distinct parameters, H/L ratio and lahar volume, were selected to influence variable for Laharz_py simulation. It was carried out on the basis of numerical simulation by estimating a possible lahar volumes of 30,000, 50,000, 70,000, 100,000, 300,000, $500,000m^3$ according to H/L ratios (0.20, 0.22 and 0.25) was applied. Based on the numerical simulations, the area of the proximal hazard zone boundary is gradually decreased with increasing H/L ratio. The number of streams which affected by lahar tended to decrease with increasing H/L ratio. In the case of H/L ratio 0.20, three streams (Gwangryeong stream, Dogeun stream, Han stream) in the Jeju-si area and six streams (Gungsan stream, Hogeun stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. In the case of H/L ratio 0.22, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and five streams (Gungsan stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. And in the case of H/L ratio 0.25, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and one stream (Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. The results of this study will be used as basic data to create a risk map for the direct damage that can be caused due to volcanic hazards arising from Mt. Halla.

• Journal of the Korean Geographical Society
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• v.30 no.3
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• pp.242-254
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• 1995

The Hadano Basin is located at a distance of about 70kms and 60kms from Tokyo and Yokohama and lies in the south-west part of the Kanto region in Japan. The basin area, which correspoends to the catchment of the Kaname River, is about areal size of 60.7$\textrm{km}^2$ and extends about length of 8kms in E-W direction and about width of 5kms in N-S direction (Fig.1). The Hadano basin is filled with thick pile of the alluvum from deposits composed of volcanic materials, mostly came from the Hakone Volcano and overlain by Fuji Volcanic ashes. Fluvial deposits form the good aquifer, therefore water resources of Handano City has been largely depending upon the eroundwater. Urbanization and industrialization of the basin has been rapid in the last thirty years, after activation of "Factory Attraction Policy of Hadano City" in 1956. Growth in population and number of factory due to urbanization changed the land-use pattern of the basin rapidly and increased the water demands. Therefore, Hadano City exploited a new source of water supply, and have introduced the prefectureal waterworks since 1976. On the other hand, the rapid urbanization has brought about the pollution of streams in the basin by domestic sewage and industrial waste water. Diffusion rate of sewerage systems in Hadano City is 38% in 1993. In ordcr to examine the impact of anthropogenic factors on river environments, the author took up the change of land-use and diffusion area of sewerage as parameters, and performed field surveys on water discharge and quality. The survey has been made at upstream and downstream of the main stream regularly per month, to get informati ons about the variation of discharge and water quality aiong the stream and its diurnal fluctuation. Annual variation has been analyzed based the data from Hadano City Office. The results are summarized as follows. 1. Stream discharge has been increasing by urbanization (Fig.3). Water quality (C $l^{-10}$ , N $H^{+}$$_{ 4}$-N, BOD) has been improving gradually after the application of sewerage service, yet water pollution load at the lower station has increased than that at the upper one because of the larger anthropogenic discharge volumes (Fig.4). 2. Corrclation coefficient of discharges between upper and lower was 0.81-0.92. Pollutant loads of the R. Kamame after the confluence with R. Kuzuha grew up by 2.4-3.7 times as compared with its upper reaches, and it increased to 3.7-6.9 times after the confluence with the R. Muro (Fig.5). 3. The changes of water quality along the stream can be divided into two groups (Fig.6a). First: water quality of the R. Kaname and R. Shijuhachisse is becoming worse towards the lower reaches because the water from branches are polluted. Second: water quality are improved in the lower where spring and small branch streams supply clear water, for example R. Mizunashi, R. Muro and R. Kuzuha. 4. Measured discharge at the upper station in the R. Shijuhachisse is 0.153㎥/sec, and about 55% of this is recharged until it reaches to the lower point. The R. Mizunashi has a discharge of 1.155㎥/sec at the upper point, is recharged 0.24㎥/sec until the midstream and groundwater spring 0.2㎥/sec at the lower reaches. R. Kuzuha recharged all the mountain runoff (0.2㎥/sec) at the upper reaches. The R. Muro is supplied by many springs and the estimated discharge of spring was 0.47㎥/sec (Fig.6b). 5. Diurmal variations in discharge and water quality are influenced clearly by domestic and industrial waste waters (Fig.7, 8).ed clearly by domestic and industrial waste waters (Fig.7, 8).

• Journal of the Korean earth science society
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• v.45 no.2
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• pp.136-146
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• 2024

This paper introduces the seismic facies classification and mapping of igneous bodies found in the sedimentary sequences of the Yellow Sea shelf area of Korea. In the research area, six extrusive and three intrusive types of igneous bodies were found in the Late Cretaceous, Eocene, Early Miocene, and Quaternary sedimentary sequences of the northeastern, southwestern and southeastern sags of the Gunsan Basin. Extrusive igneous bodies include the following six facies: (1) monogenetic volcano (E.mono) showing cone-shape external geometry with height less than 200 m, which may have originated from a single monogenetic eruption; (2) complex volcano (E.comp) marked by clustered monogenetic cones with height less than 500 m; (3) stratovolcano (E.strato) referring to internally stratified lofty volcanic edifices with height greater than 1 km and diameter more than 15 km; (4) fissure volcanics (E.fissure) marked by high-amplitude and discontinuous reflectors in association with normal faults that cut the acoustic basement; (5) maar-diatreme (E.maar) referring to gentle-sloped low-profile volcanic edifices with less than 2 km-wide vent-shape zones inside; and (6) hydrothermal vents (E.vent) marked by upright pipe-shape or funnel-shape structures disturbing sedimentary sequence with diameter less than 2 km. Intrusive igneous bodies include the following three facies: (1) dike and sill (I.dike/sill) showing variable horizontal, step-wise, or saucer-shaped intrusive geometries; (2) stock (I.stock) marked by pillar- or horn-shaped bodies with a kilometer-wide intrusion diameter; and (3) batholith and laccoliths (I.batho/lac) which refer to gigantic intrusive bodies that broadly deformed the overlying sedimentary sequence.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.69-79
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• 2009

Major and trace elements were analyzed in three core sediments to investigate geochemical characteristics of East Sea sediments and provenance changes during late Quaternary in Ulleung Basin. Comparing with Yellow and South Sea sediments, contents of major elements were generally similar while contents of trace elements were significantly different. Furthermore, within this basin, there were some variabilities in trace element compositions. In the western slope sediments (WS), Mo was enriched over 6 times as much as other sites. On the other hand, Zr, Nb, Hf and Ta were enriched in basin sediments (Basin), and Ca and Cs were enriched in southern slope sediments (SS). After excluding elements derived from biogenic, authigenic and diagenetic origins, the lithogenic elements (K, Ti, Cs, Zr, Nb, Hf and Ta) could be classified into three groups from the comparison of element/Al ratios among cores. The first group consisted of elements (K and Ti) that showed the nearly similar element/Al ratios among three cores. The second group contained Cs which showed significant difference between two slope sediments. The third group elements (Zr, Nb, Hf and Ta) showed highly enriched in basin relative to both slope areas. The depth profiles of metal/Al ratios in basin sediments provided the following interpretation for the compositions of sediment and their variation. From 10,000 yr B.P. to 7,000 yr B.P. two lithogenic components (volcanic ashes and western slope sediments) were mixed and deposited in the basin. After 7,000 yr B.P., however, southern slope sediments were mixed with volcanic ashes and deposited in basin area. This event of source change is nearly close to inflow period of the Tsushima Warm Current to Ulleung Basin. Thus, it might be suggested that element geochemistry in Ulleung basin sediment indicate the change of current system in the study area.

• Journal of Soil and Groundwater Environment
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• v.13 no.6
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• pp.72-84
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• 2008

This study was carried out to provide proper management plans for small portable water supply system in the Nonsan area through water quality monitoring, hydrogeochemical investigation and multivariate statistical analyses. Nonsan area is a typical rural area heavily depending on small water supply system for portable usage. Geology of the area is composed of granite dominantly along with metasedimentary rocks, gneiss and volcanic rocks. The monitoring results of small portable water supply system showed that 13-21% of groundwaters have exceeded the groundwater standard for drinking water, which is 5 to 8 times higher than the results from the whole country survey (2.5% in average). The major components exceeding the standard limits are nitrate-nitrogen, turbidity, total coliform, bacteria, fluoride and arsenic. High nitrate contamination observed at southern and northern parts of the study area seems to be caused by cultivation practices such as greenhouses. Although Ca and $HCO_3$ are dominant species in groundwater, concentrations of Na, Cl and $NO_3$ have increased at the granitic area indicating anthropogenic contamination. The groundwaters are divided into 2 groups, granite and metasedimentary rock/gneiss areas, with the second principal component presenting anthropogenic pollution by cultivation and residence from the principal components analysis. The discriminant analysis, with an error of 5.56% between initial classification and prediction on geology, can explain more clearly the geochemical characteristics of groundwaters by geology than the principal components analysis. Based on the obtained results, it is considered that the multivariate statistical analysis can be used as an effective method to analyze the integrated hydrogeochemical characteristics and to clearly discriminate variations of the groundwater quality. The research results of small potable water supply system in the study area showed that the groundwater chemistry is determined by the mixed influence of land use, soil properties, and topography which are controlled by geology. To properly control and manage small water supply systems for central and local governments, it is recommended to construct a total database system for groundwater environment including geology, land use, and topography.