• The Journal of the Petrological Society of Korea
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• v.26 no.3
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• pp.255-269
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• 2017

Five year term monitoring investigating variation of allochthonous originated gravels are has been conducted in the beach gravel deposit of the Island Dokdo natural reserve which takes purity and uniqueness with enormous attention though a number of areas. The beach gravel deposits near the dock of the Dongdo and near the accommodation facility of the Seodo comprise various types of gravels including basalt, trachyte, and tuff from the Dokdo itself, and granite, rhyolite, gneiss, quartzite, marble, and concrete from elsewhere. The types of the allochthonous gravels on the basis of the study in 2011 and in 2016 shows no difference, so is the ranking of abundance of the allochthonous gravels; granite-concrete-gneiss in turn on the Dongdo, concrete-gneiss-granite in turn on the Seodo. Nevertheless, the relative ratio of the allochthonous gravel area against the total area is decreased. While it is suspected that the disintegrated facility and the influx of material for construction are the main 2 reasons for the contamination by allochthonous gravel, diminished total contamination ratio indicate that supervising allochthonous material has been improved; at least not worse during the 5 years. On the other hand, it is inferred that gradual influence of rockfall also has been made the gravel beach changed. Therefore, consistent rockfall investigation must be inquired.

• The Journal of the Petrological Society of Korea
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• v.27 no.1
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• pp.25-36
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• 2018

The volcanic rocks around Mieukdo Island, Tongyeong, are classified as lower andesitic rocks (Jusasan Subgroup) and rhyolitic rocks (Unmunsa Subgroup), and upper andesitic rocks (Yokji Subgroup) and rhyolitic rocks (Saryang Subgroup). We confirmed their eruption timings and stratigraphic relationships, based on SHRIMP U-Pb zircon dating for zircons from major stratigraphic units of the subgroups. By the SHRIMP U-Pb dating, the samples yield the concordia ages of $88.95{\pm}0.44Ma$(n=11) in Punghwari Tuff and $82.56{\pm}0.95Ma$(n=10) in Chudo Tuff of the lower andesitic rocks, and $73.01{\pm}0.75Ma$(n=11) in Dara Andesite of the upper andesitic rocks. And then samples show a concordia age of $71.74{\pm}0.47Ma$(n=14) in Namsan rhyolite dyke of the upper rhyolitic rocks and an apparent age of $70.7{\pm}3.5Ma$ in granodiorite dyke, These data confirm the eruption or injection timings of the units and allow them to distinguish chronostratigraphy of Jusasan, Unmunsa, Yokji and Saryang Subgroups around the Mireukdo Island. In addition, the subgroups give a clue that can make a chronostratigraphical correlation with different volcanic units of the Late Cretaceous Yucheon Group in the Gyeongsang basin.

• Journal of the Korean association of regional geographers
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• v.7 no.1
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• pp.97-106
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• 2001

There are a few interesting areas which show freezing during summer season in Korea, three of them are especially important. They are located at Milyang(Gyungnam province), Uisung and Chungsong(Gyungbook province). They are named Eoleumgol(ice-valley) or Binghyul(ice-cave). The purpose of this study is to clarify geomorphological and geological characteristics about the distribution areas of freezing during summer season in Korea in relation to previous works, which have been studied in hydrological or micro-climatological viewpoints. The main results are summarized as follows. 1) The main geomorphological and geological characteristics in the distribution areas of freezing during summer season (1) Thick debris accumulated slope within deep valley (2) North facing slope (3) The component debris of volcanic rock such as andesite or rhyolite 2) The ice-cave as a system that give rise to freezing phenomenon in summer season is closely related to talus slope. The ice-cave has thick accumulated debris and lots of vacant spaces within the rock deposits, some of vacant spaces are very big and connected with underground water system. 3) A partly freezing within underground water system is required freezing phenomenon in summer season. Judging from this point of view, two ideas are suggested; one is the evaporation theory, another is that the frozen condition in winter remains untill late summer.

• Journal of Korean Society of Forest Science
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• v.104 no.4
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• pp.588-597
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• 2015

This study was carried out to identify the reasons of the landslide by land creeping in South Korea in order to provide basic information for establishing the management plan for prevention. Total 29 sites of landslide areas caused by land creeping were observed in South Korea. Among them, the soil-composition of most frequent landslide areas occurred by land creeping was colluvium landslide as 75.9% (22 sites), followed by clay soil landslide as 10.3% (3 sites), bedrock landslide as 6.9% (2 sites), and weathered rock landslide as 6.9% (2 sites). According to the types of parental rocks, the investigated landslide areas were divided into 3 types: 1) metamorphic rocks including schist, phylite, migmatitic gneiss, quartz schist, pophyroblastic gneiss, leucocratic granite, mica schst, banded gneiss and granitic gneiss, 2) sedimentary rocks including limestone, sandstone or shale and mudstone, 3) igneous rocks such as granite, andesite, rhyolite and masanite. As a result, it was noticed that the landslides occurred mostly at the metamorphic rocks areas (13 sites; 44.8%), followed by sedimentary rock areas (12 sites; 41.4%), and igneous rock areas (4 sites; 13.8%). Looking at the direct causes of the landslide, the anthropological activities (71%) such as cut slopes for quarrying, construction of country house, plant, and road, farming of mountain top, and reservoir construction were the biggest causes of the landslides, followed by the land creeping landslides (22%) caused by geological or naturally occurred (22%), and cliff erosions (7%) by caving of rivers and valleys.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.332-344
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• 2007

Various geophysical well logs have been made along the four deep wells in Pohang, Gyeongbuk. The primary focus of geophysical well loggings was to improve understanding the subsurface geologic structure, to evaluate in situ physical properties, and to estimate aquifer production zones using fluid temperature and conductivity gradient logs. Especially natural gamma logs interpreted with core logs of borehole BH-1 were useful to discriminate the lithology and to determine the lithologic sequences and boundaries consisting of semi-consolidated Tertiary sediments and intrusive rocks such as basic dyke and Cretaceous sediments. Cross-plot of physical properties inferred from geophysical well logs were used to identify rock types such as Cretaceous sandstone and mudstone, Tertiary sediments, rhyolite, and basic dyke. The temperature log indicated $82.51^{\circ}C$ at the depth of 1,981.3 meters in borehole BH-4. However, considering the temperature of borehole BH-2 measured under stable condition, we expect the temperature at the depth in borehole BH-4, if it is measured in stable condition, to be about 5 or $6^{\circ}C$ higher. Several permeable fractures also have been identified from temperature and conductivity gradient logs, and cutting logs.

• The Journal of the Petrological Society of Korea
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• v.7 no.1
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• pp.27-36
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• 1998

The volcanic piles in the northern Yucheon Minor Basin area are the Hagbong basaltic rocks, the Chaeyaksan basaltic rocks, the Jusasan andesitic rocks, the Unmunsa rhyolitic rocks, and the Tertiary voicanics. Stratigraphically, from the lowermost, (1) the Hagbong basaltic rocks are composed mainly of basaltic tuff with two olivine basalt flows intercalated, (2) the Chaeyagsan basaltic rocks are predominantly in tuffs and agglomerate with 3 basaltic flow interlayers, (3) the Jusasan andesitic rocks consist of thick piles of alternated sequences of 4 andesite flows and 5 andesitic tuffs and tuffaceous sediments and (4) the Unmunsa rhyolitic rocks which embed some rhyolite and obsidian are dominant in tuffs such as ash flow and crystal welded tuff. These volcanics reveal distinguishable characteristics in petrochemistry. In discriminating by major elements, the Hagbong and the Chaeyagsan basaltic rocks are alkaline, whereas the latter is also spilitic. In comparison, the volcanic rocks of the Jusasan andesitic rocks and the Tertiary sequences are characteristically calc-alkaline although their distribution is spatially separated. On the other hand, the variations in immobile trace elements indicate that the Hagbong basaltic rocks range from alkaline to calc-alkaline and from WPB/VAB transition to VAB, whereas the Chaeyagsan basaltic rocks are calc-alkaline WPB/VAB transition type and the two others calc-alkaline VAB. In order to show such a variety in their rock series of the volcanic rocks, the environment during their magma generation, magma rising, and post-eruption alteration could be positively considered.

• The Journal of the Petrological Society of Korea
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• v.16 no.2 s.48
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• pp.47-58
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• 2007

This study examines the distribution of basement rocks in Gyochon-ri, Muan-eup, Muan-gun, Jeonnam where ground subsidence occurred in June 2005, and traces corrosion of limestone. Mica schist and rhyolite are distributed in the surface of the study area, but thick limestone layer with large and small caverns are distributed underground. A horizon of limestone with maximum width of 300 m and 4 km of length was found along the detour which is in the north of pound subsidence. Such identification of limestone presence would be very useful to predict potential ground subsidence. Limestone in this area was disturbed by fold and fault due to severe shearing deformation. Small caverns were frequently found in anticline part of folds formed in limestone layer. Schists with different thicknesses were intercalated in the limestone with shearing deformation and consist of sheet silicate minerals (chlorite and mica) and quartz. In sections of weathered specimen, it is shown that biotite of schist part was altered into chlorite and corrosion of calcite around the schist followed. This suggest that ground water permeated between intercalated sheet silicate minerals and corrosion of limestone began. And small caverns were generated where active corrosion occurred. This study suggests that because of many reasons (for instance, reclamation of the Bulmu reservior and excess pumping), cavern water level was lowered and cave sediments were removed, and it caused ground subsidence to occur.

• Journal of the Korean Society of Earth Science Education
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• v.9 no.2
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• pp.163-172
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• 2016

The aim of this study is to investigate the geological features distributed in the northwest coast, Goheung Gun as a geological field course of all levels. The study area is about 1.6km coast in direction of northwest from Sumundong ferry to Jangsun beach. The learning contents of the geology units in science textbooks from elementary school to high school was analyzed and, geomorphology and geology of study area was investigated for this study. In this study area, lots of geomorphology and geology elements related to the learning contents of the geology units in science textbooks were founded such as gravel beach, sea cliff, granite, rhyolite, andesite, gneiss, sedimentary rocks, fault, unconformity, stratification, cross bedding, graded bedding, intrusion structure, vein, dyke, plant fossil and spheroidal weathering. Characteristically, strata, stratification, granite, sedimentary rocks(conglomerate, sandstone, mudstone and shale), fault, plant fossil and weathering phenomenon were commonly involved with the learning contents of the geology units in elementary school science, middle school science and high school earth science I, II. This area is to be recommended as a site of geological field course for all students from elementary school to high school, as various field work materials for geological learning were distributed and, geological observation trail of about 400m in length for observation of strata and so on was installed along the coast in direction of the northwest from Sumundong ferry.

• Economic and Environmental Geology
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• v.31 no.3
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• pp.249-264
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• 1998

The Creataceous volcanic rocks distributed in the southeastern part (Kyeongsang basin) of Korea peninsula are composed of basalt, basaltic andesite, andesite, dacite and rhyolite. The variation of major elements show that contents of MgO, CaO, $FeO^T$, $Al_2O_3$, $TiO_2$ and $P_2O_5$ decrease with increasing of $SiO_2$, but $K_2O$ contents are increased slightly, $Na_2O$ widely dispersed. We can show slightly inflection point and low frequency of dacites in range between 63-65 wt.% $SiO_2$, while continuous trend exit in variation diagram. Variation trends in Harker diagrams for the major, minor, trace and REEs suggest that the BAV (basaltic to andesitic volcanics) and DRV (dacitic to rhyolitic volcanics) are not related to a simple crystal fractionation process. In the regime of under 65 wt. % in silica content, fractionation of olivine and clinopyroxene is predominant, while that of plagioclase happens strongly higher than 65 wt.% (e.g., $SiO_2$, vs. Eu and Sr, MgO vs. $Al_2O_3$ and CaO). The latter means low-pressure fractional crystallization for DRV. On the discriminant diagram, DRV are located in more mature environment than BAV. The $(Ce/Sm)_N$ vs. CeN digram shows that these two classes cannot be related to crystal fractionation. If they had been produced by fractionation, although they plotted in a slightly elongate cluster along the same horizontal trend, DRV should lie to the right of these primitive compositions. These diagrams clearly rule out a simple fractionation throughout from BAV to DRV. BAV had been influenced greatly subductiong slab as shown by K/Yb vs. Ta/Yb. We suggest that BAV primitive magma generated higher degree of partial melting than DRV primitive magma. LILE (K, Ba, $Rb{\pm}Th$) enriched characteristics as shown in BAV are inherited from subducting slab fluids and/or higher degree of partial melting of mantle material. However, lower degree of partial melting of mantle relative to BA V and contamination at high-level magma reservoir caused LILE enrichment to DRV.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.5
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• pp.245-252
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• 2006

This experiment was conducted to investigate the distribution and compositions of clay mineral and to replenish the soil classification system in Korea. Soil layer samples were collected from 26 residuum and colluvium soil series out of 390 soil series in Korea, and then analyzed for soil physical and chemical characteristics, mineral and chemical compositions of clay in B horizon soils. Major clay minerals of residuum and colluvium were illite and chlorite in soils originated from the sedimentary rock such as limestone, shale, sandstone and conglomerate; quartz and kaolin in soils originated from rhyolite, neogene deposits, porphyry and tuff; and kaolin and quartz in the soils originated from granite, granite gneiss and anorthosite. Clay minerals in Korean soils were divided into 4 groups: mixed mineral group(MIX) mainly contained with illite, kaolin and vemiculite; kaolin group(KA) with kaolin and illite; chlorite group(CH) with chlorite and illite; and smectite group(SM) with kaolin, illite and smectite. The most predominant clay mineral group was kaolin group(KA) with kaolin and illite; an mixed mineral group(MIX) with illite, kaolin and vemiculite. Cation exchange capacity (CEC) of clay was low in the soils mainly composed with MIX and KA groups and silica-alumina molar ratio of clay was high in the soils composed with SM group