• The Journal of the Petrological Society of Korea
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• v.19 no.4
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• pp.269-281
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• 2010

The compiled recent precise age data for the plutonic intrusions of Korean peninsula display that the Jurassic igneous activities occurred on the Yeongnam massif since ca. 200 Ma close to the boundary between Triassic and Jurassic. Since then the igneous activities propagated toward further north through time. The Jurassic igneous activities over the Okcheon belt and its vicinity areas began at about 180 Ma when igneous activities of the Yeongnam massif had been almost over. The igneous activities within the Gyeonggi massif located further north started at somewhat later period ca. 170 Ma. Jurassic igneous activities over the Okcheon belt and its vicinity areas ended a little earlier than the Gyeonggi massif area. Such timing differences upon geographic positions within the Korean peninsula seem to reflect variations in distance to the trench, in the direction of subduction, and/or in subduction angle. Therefore precise understanding of the variations in emplacement ages of Jurassic plutons within Korean peninsula can be a important clue to reconstruct the paleogeography and tectonic environment of the northeast Asia during the Jurassic.

• The Korean Journal of Quaternary Research
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• v.3 no.1
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• pp.17-34
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• 1989

The distribution characteristics of incised meander river are analysed concerning topography, geology, stream order and altitude. Additionally geomorphological development of the Korean peninsular is considered with incised meander. The main findings are as follows: 1. The incised meander is intensively distributed on the west and north slope of T'aebak and Sobaek mountain range, but sparsely distributed on the opposite slopes. 2. Geologically, the occurrence rate of incised meander is high orderly as follows: Joseon supergroup, Pyeongan supergroup, Daedong supergroup metamorphic rock, Gyeongsang supergroup, and granite. The incised meander is developed well on the following conditions: hard rocks against weathering, stratified structure, geologic arrange across the river channel and contacting zone of geological formations. 3. The higher stream orders are, the higher occurrence of incised meander is. 4. Comparing the altitude of present river bed with the summit level of restored map, it is supposed that the incised meander rivers have been dissected about 300-500m down ward. 5. Considering the distribution characteristic of incised meander, it is suggested that not only T'aebak mountain range but Sobaek mountain range is the axis of asymmetrical up-warping in the Korean peninsular. 6. Considering the distribution characteristic of incised meander on the restored map and the stream order, it seems that present incised meander channel was inherited from antecedent meander river that had flowed on High and Middle level erosion surface. But the channel pattern has been modified.

• Korean Journal of Environmental Biology
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• v.38 no.3
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• pp.371-387
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• 2020

This study was conducted to investigate the flora of Mt. Unbongsan in the basalt areas of Korea. From the results of eight field surveys undertaken from March to October 2017, we identified 404 total taxa, representing 364 species, seven subspecies, and 33 varieties, which were placed in 256 genera and 91 families. The plant formation of Mt. Unbongsan is a deciduous broad-leaved and conifer mixed forest, which is common in the middle part of the Korean peninsula. Most of the mountain is covered by a young secondary forest, which is mainly composed of Quercus monglica and Pinus densiflora. Out of these 404 taxa, 193 were the first records for the region, six were endemic to Korea, three were listed on the Korean Red List of threatened species, 34 were floristic target species, and 40 were invasive alien species. The naturalized index(NI) percentage was 9.9%. Mt. Unbongsan has plant diversity, which was associated with the geomorphological landscapes. We considered that the composition and distribution of the species were affected by different environmental factors according to the presence of granite, taluses, block streams, drying ridges, valleys, puddles, wetlands, and streams.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.2
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• pp.101-109
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• 2003

The study area, Kwangneung Experiment Forest (KEF) is located on the west-central portion of Korean peninsula and belongs to a cool-temperate broadleaved forest Bone. At the old-growth deciduous forest near Soribong-peak (533.1 m) in KEF, we have established a 1 ha permanent plot ($100m{\times}100m$) and a flux tower, and the site was registered as a KLTER(Korean long-term ecological research network) and DK site of KoFlux. In this site, we made a stemmap of trees and analyzed forest stand structure and physical and chemical soil characteristics, and estimated carbon budgets by forest components (tree biomass, soils, litter and so on). Dominant tree species were Quercus serrata and Carpinus laxiflora, and accompanied by Q. aliena, Carpinus cordata, and so on. As a result of a field survey of the plot, density of the trees larger than 2 cm in DBH was 1,473 trees per ha, total biomass 261.2 tons/ha, and basal area $28.0m^2$/ha. Parent rock type is granite gneiss. Soil type is brown forest soil (alfisols in USDA system), and the depth is from 38 to 66 cm. Soil texture is loam or sandy loam, and its pH was f개m 4.2 to 5.0 in the surface layer, and from 4.8 to 5.2 in the subsurface layer. Seasonal changes in LAI were measured by hemispherical photography at the 1.2 m height, and the maximum was 3.65. And the spatial distributions of volumetric soil moisture contents and LAIs of the plot were measured. The carbon pool in living tree biomass including below ground biomass was 136 tons C/ha, and 5.6 tons C/ha is stored in the litter layer, and about 92.0 tons C/ha in the soil to the 30 cm in depth. Totally more than about 233.6 tons C/ha was stored in DK site. These ground survey and monitoring data will give some important parameters and validation data for the forest dynamics models or biogeochemical dynamics models to predict or interpolate spatially the changes in forest ecosystem structure and function.

• Economic and Environmental Geology
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• v.36 no.3
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• pp.233-242
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• 2003

The southeasternmost coastal area of the Korean peninsula has been regarded as a seismologically stable area as neither Quaternary faults nor earthquake activity has been reported. To clarify whether the active tectonic movement has occurred or not, a digital marine terrace mapping and fracture mapping have been done in the coastal area. Bed rocks are composed of the Cretaceous volcanic and sedimentary rocks and the Paleogene granite. Wave-cut platform in the area is smaller and narrower relative to that of the northern coastal area. Most of the platforms in the area have little Quaternary sediment. The platforms except the Holocene terrace (1 st terrace) can be divided into three steps. The lowest platform (2nd terrace) has an altitude of 8-11 m. The broad middle one (3rd terrace) is 17 to 22 m high. The highest terrace (4th terrace) is a narrow and sporadic bench with an altitude of about 44 m high. The lowest terrace is correlated to the 2nd terrace of the northern area, which corresponds to the oxygen isotopic stage 5a. The uplift rate calculated from a graphic method is 0.19 m/ky. This low uplift is typical of an intra-plate, suggesting that the area is tectonically stable. The elevation of the platforms tends slightly lower from the north to the south in the survey area. The decreasing altitude of the platforms towards the south is interpreted to result from a local block tilting during the Latest Pleistocene. This also indicates that the eastern coast of the Korean peninsula has been suffering a subsidence to the south.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.3
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• pp.151-159
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• 2012

The potential repository domains for A-KRS (Advanced Korean Reference Disposal System for High Level Wastes) in geological characteristics of KURT (KAERI Underground Research Tunnel) facility site were proposed to develop a repository system design and to perform the safety assessment. The host rock of KURT facility site is one of major Mesozoic plutonic rocks in Korean peninsula, two-mica granite, which was influenced by hydrothermal alteration. The topographical features control the flow lines of surface and groundwater toward south-easterly and all waters discharge to Geum River. Fracture zones distributed in study site are classified into order 2 magnitude and their dominant orientations are N-S and E-W strike. From the geological features and fracture zones, the potential repository domains for A-KRS were determined spatially based on the following conditions: (1) fracture zone must not cross the repository; and (2) the repository must stay away from the fracture zones greater than 50 m. The western region of the fracture zones in the N-S direction with a depth below 200 m from the surface was sufficient for A-KRS repository. Because most of the fracture zones in N-S direction were inclined toward the east, we expected to find a homogeneous rock mass in the western region rather than in the eastern region. The lower left domain of potential domains has more suitable geological and hydrogeological conditions for A-KRS repository.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.6
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• pp.501-517
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• 2011

In general, the tunnel stability during excavation is assessed by comparing measured displacements at roof and sidewall to control criteria. The control criteria were established based on the past experience that considered ground conditions, size of the tunnel cross section, construction method, supports, etc. Therefore, a number of researches on the control criteria using the critical strain have been conducted. However, the critical strain obtained from uniaxial compression tests have drawbacks of not taking damage in rock mass due to increase of stress level and longitudinal arching into account. In this paper, damage-controlled tests simulating stress level and longitudinal arching during tunnel excavation were carried out in addition to uniaxial compression tests to investigate the critical strain characteristics of granite and gneiss that are most abundant rock types in Korean peninsula. Then, the critical strains obtained from damage-controlled tests were compared to those from uniaxial compression tests; the former showed less values than the latter. These results show that the critical strain obtained from uniaxial compression tests has to be reduced a little bit to take stress history during tunnel excavation into account. Moreover, the damage critical strain was proposed to be used for assessment of the brittle failure that usually occurs in deep tunnels.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.1
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• pp.3627-3641
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• 1975

The Government is trying to increase total food grain yield to meet national self sufficiency by means of increasing unit yield as well as extending crop land, and this year he set the target of 321,000 hectare of forest to clear for cropping. This study was carried to investigate the most efficient method of clearing hillock by bulldozer, and successful method to develope yielding potential of newly cleared land in short term. Since the conventional land clearing method is just earth leveling and root removing neglecting top soil treatment, the growth of crop was poor and farmer tends not to care the land. The top-soil-furrowing method is applied through out this study, that is advantageous especially for the land having shallow top soil and low fertility like Korean forest. In this study, various operating method were tried to find out most efficient method separately in connection with the land slope less than 25 percent and over, and several fertilizing methods to develop yielding potential. The results are as follows; 1) For the natural land slope utilization method, applicable to the land having less than 25 percent slope, reverse operating was more efficient than using forward gear of bulldozer. The operating time was 3 hour 32 minutes and 36 seconds using forward gear was 2 hour 32 minutes and 30 seconds for reverse gear operation per 1,000 square meter. 2) Bulldozer having angle blade adjustment needed 7hr 15min. for constructing of terrace per 10a compaire with the one having angle & tilt adjustment needed 6hr 4min for same operations. Specially there is significant difference for operation time of first period (earth cutting) such as bulldozer having angle blade adjustment needed 3hr 56min compaired with the one having angle & tilt adjustment 3hr 59min. In construction of terrace, the bull-dozer having tilting and angle blade adjustment was most suitable and performed efficiently. 3) For the fertilizer application treatment, the grass (Ladino clover) yield in first year was almost same as ordinary field's in the plot applied(N.P.K+lime+manure) while none fertilizer plot showed one tenth of it, and (N.P.K.+lime) applied plot yielded on third. 4) The effect of different land clearing method to yield showed significant difference between each treatment especially in the first year, and the conventional method was the lowest. In the second year, still conventional terracing plot yielded only half of ordinary field while the other plots showed as same as ordinary field's. 5) The downward top soil treatment plot showed most rapid improvement in soil structure during one year physio chemically, it showed increase in pH rate and organic composition, and the soil changed gradually from loam to sand-loam and the moisture content increased against the pF rate, and it gives good condition to grow hay due to the increase of field water capacity with higher available water content. 6) Since the soil of tested area was granite, the rate of soil errosion was increased about 2 to 5 percent influencing in soil structure more sand reducing clay content, and an optimum contour farming method should be prepared as a counter measure of errosion.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.149-164
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• 1988

Electrum-sulfide mineralization of the Samgwang and Sobo mines of the Cheongyang Au-Ag area was deposited in two stages of quartz and calcite veins that fill fault zones in granite gneiss. Radiometric dating indicates that mineralization is Early Cretaceous age (127 Ma). Fluid inclusion and sulfur isotope data show that ore mineralization was deposited at temperatures between $340^{\circ}$ and $180^{\circ}C$ from fluids with salinities of 1 to 8 wt. % equiv. NaCl and a ${\delta}^{34}S_{{\sum}S}$ value of 2 to 5 per mil. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a range of pressures from < 200 to $\approx$ 700 bars, corresponding to depths of ${\approx}1.5{\pm}0.3\;km$ in a hydrothermal system which alternated from lithostatic toward hydrostatic conditions. Au-Ag deposition was likely a result of boiling coupled with cooling. Meaured and calculated hydrogen and oxygen isotope values of ore-forming fluids indicate a significant meteoric water component, approaching unexchanged paleometeoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship among depth, Au/Ag ratio and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved meteoric waters, but only deeper systems (${\geq}1.5\;km$) are exclusively gold-rich.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.153-168
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• 1994

The status of groundwater development in Chungnam was studied with geological characteristics according to the measured data of Korean Rural Development Corporation. The data of 212 survey wells were used for the relation between catchment area and water discharge, and the data of 344 development wells for the relationships between well depth and discharge, between casing depth and discharge, between rock type and discharge, and the relation with lineaments density. The relationship between the catchment area and discharge does not show any special trend, and it is understood that groundwater of hard rock mass is not so much influenced by the surface catchment area. The relationship between well depth and discharge shows two different trends; discharge increasing with depth for alluvial groundwater, but no certain trend between depth and discharge for groundwater of hard rock zone. Discharge increases linearly with the casing depth, and it is reliable because the casing was installed in the weathered zone against well destruction. Generally the rock type does not show any difference of discharge, but the crystalline rocks such as granite and gneiss yield a little more discharge than the more porous rocks such as sedimentary rock or schist. It suggests that the effect of fracture zone is a major governing factor. In Hongsong and Puyo, there are similar in rock type and casing depth, but the big difference in average discharge. The big discharge of Hongsong is concordant with the higher intersection density and longer length of lineament in Hongsong than those of Puyo. Therefore the groundwater development strategy should be focused on the micro topography analysis and geophysical survey for the understanding of the fracture zone rather than catchment area or rock type.