• Journal of Korean Society of Forest Science
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• v.109 no.1
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• pp.62-71
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• 2020

With the aim of restoring slow-moving landslide areas, this study collected fundamental data from tree-ring analysis of curved trees in these areas. We collected both upper and lower stem disks to measure the azimuth angles of six trees with growth curvature caused by tension cracks. Additionally, we analyzed various factors in the slow moving landslide area. The geological strata and main constitutive rocks in the study area were anorthosite-formed in the Precambrian period; moreover, there were no intrusive rocks, other geological strata, geological folds, or faults. The talus with weathered rocks was distributed in the upper zone of the slow-moving landslide area. According to annual-ring analysis of curved trees and terrain analysis by satellite imagery, slow-moving landslide occurred from the top to the bottom end of the slope between 1999 and 2011. There was a significant relationship (P < 0.01) between the azimuth angle of cracks caused by the slow-moving landslide and the angle of the curved trees. These results suggest that the occurrence of slow-moving landslides could be confirmed through analysis of annual-rings of curved trees, underground water levels, and terrain (by satellite imagery).

• Economic and Environmental Geology
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• v.22 no.2
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• pp.129-139
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• 1989

The anthracite coalfields of Korea are confined to the areas where sedimentary rocks of Permian and Jurassic are preserved. The Chungnam coalfield lies in the sedimentary rocks of Jurassic which belongs to the Daedong Supergroup (the Nampo group). For the property analysis of each coal seam interbeded in Daedong Supergroup, Seongju area is chosen and twelve coalseams are taken. Many standard tests have been established for optical analysis (maceral analysis, coalification degree measurement), chemical analysis (proximate, ultimate analysis) and physical analysis (ignition temperature, ash fusion temperature, hardgrove grindability index and X-ray diffraction). The Jurassic anthracite mainly consist of vitrinite and macrinite and the range of the reflectance is $R_{max}$ 5.0-6.5 which means metaanthracite rank. By the chemical composition analysis, it shows low H/C and high O/C value compare with international average value. By the physical analysis, it has very high ignition temperature ($531-584^{\circ}C$) and ash fusion temperature ($1510-1700^{\circ}C$) and very low combustion velocity (0.2-1.9 mg/min). The very wide range of the hardgrove grindability index (46-132) means that the grindability controlled mainly by the structural conditions of coal bearing strata.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.4
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• pp.429-453
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• 2022

Numerical modeling and scenario composition are needed to characterize the geological environment of the disposal site and analyze the long-term evolution of natural barriers. In this study, processes and features of the hydro-mechanical behavior of natural barriers were categorized and represented using the interrelation matrix proposed by SKB and Posiva. A hydro-mechanical coupled model was evaluated for analyzing stress field changes and fracture zone re-activation. The processes corresponding to long-term evolution and the hydro-mechanical mechanisms that may accompany critical processes were identified. Consequently, practical numerical methods could be considered for these geological engineering issues. A case study using a numerical method for the stability analysis of an underground disposal system was performed. Critical stress distribution regime problems were analyzed numerically by considering the strata's movement. Another case focused on the equivalent continuum domain composition under the upscaling process in fractured rocks. Numerical methods and case studies were reviewed, confirming that an appropriate and optimized modeling technique is essential for studying the stress state and geological history of the Korean Peninsula. Considering the environments of potential disposal sites in Korea, selecting the optimal application method that effectively simulates fractured rocks should be prioritized.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.455-468
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• 1999

Carbonated mineral waters fo $Ca(Mg)-HCO_3$ type spring out fissure of Jurassic granite in the valley floor of the Chungsong area. The water has been long as a Dalki medicinal water because of its unique therapeutic effect against clacium deficit, stomach and skin troubles, ect. The water has a high $CO_2$ concentration ($P_{CO_2}$=0.51~1.12atm) and exhibits strong pH buffering (5.9~6.26) by $H_2CO_3/HCO_3$ couple. Electrical conductivity ranges from 1,900 to 3100 $\mu$S/cm. Environmental isotopic data $(^{2}H/^{1}H, ^{18}O/^{16}O \;and \;^3H)$ indicates that the water is of meteoric origin recharged in the Cretaceous sedimetary strata distributed in upper part of the catchment area at least before 1950s, The high $P_{co_2}$ and carbon isotope data (${\delta}^{13}C=-3\sim-0.2\textperthousand$) suggest that the potential source of carbonated mineral water was originated in deep-seated $CO_2$ as wel as aboundant carbonate minerals of sedimentary desimetary rocks. The major source minerals of the dissoved species in the carbonated mineral water appear to be carbonate minerals, albite and K-feld-spar in sedimentrary rocks.

• The Journal of the Petrological Society of Korea
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• v.13 no.1
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• pp.1-15
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• 2004

In this study we propose that the ‘enclaves’ which occur in the granites should be translated into ‘Po-yu-am’in Korean. Also we suggest some criteria to discriminate the mafic microgranular enclaves (MME) of igneous origin from the xenoliths, which possibly come from the plutonic, volcanic and sedimentary country rocks. The color of the MME is gray green∼dark gray and the mineral grains are fine and equigranular. The MME are generally of ellipsoidal shape and can be easily found within the granites. They do not show any evidence of contact metamorphism by granite host. On the other hand. the xenoliths are generally of angular shape and are of the same mineral assemblage and texture as the country rocks around the granites. The distribution of the xenoliths is mostly concentrated along the intruding plane of the granites near the country rocks. The xenoliths were partly metamorphosed by the granite intrusion. The xenoliths from the plutonic rocks are easily distinguished from the MME in terms of their angular shape and coarser grain size, but they do not have any metamorphic mineral assemblage and texture. The xenoliths from the tuffaceous rocks show angular shape and porphyritic and pyroclastic textures. Large size xenoliths from the sedimentary rocks specifically preserve bedding structure which are indicative of the sedimentary strata. However, the sedimentary xenoliths of small size are often difficult to distinguish from the MME. Metamorphic minerals and texture are a useful key to discriminate the small-sized sedimentary xenoliths from the MME. In summary the xenoliths in the granites can be megascopic ally distinguished from the MME by comparing their color, shape, grain size and remnant original structure like bedding. Additionally the metamorphic mineral assemblage and texture are microscopic discriminators between the xenoliths and the MME in the granites.

• Journal of the Korean earth science society
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• v.33 no.4
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• pp.329-336
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• 2012

In September 2009, a perfectly preserved fossil of a dinosaur egg nest was discovered in the Cretaceous formations of the Aphaedo area in Shinan, Jeollanam-do, South Korea. In order to estimate the age of dinosaur eggshells and the depositional age of the Cretaceous sediments in Aphaedo area, a whole-rock K-Ar dating was carried out on volcanic pebbles showing a sedimentary structure contemporaneous with the Aphaedo strata, acidic tuffs overlaying the strata conformably, and acidic dike rocks intrude to both of them. Volcanic rocks observed in the strata are 3-20 cm in diameter as pebbles found in lenticular conglomerate and pebble bearing mudstone strata. K-Ar whole-rock dating was performed on six different volcanic pebbles which show a sedimentary structure contemporaneous with the dinosaur egg nest contained in the strata, and all samples show Late Cretaceous ages: Cenomanian ($97.6{\pm}1.9$Ma), Coniacian ($87.6{\pm}1.7$ Ma), Santonian ($84.5{\pm}1.7$Ma) or Campanian ($82.5{\pm}1.6$, $77.3{\pm}1.5$, $75.7{\pm}1.5$ Ma). The K-Ar whole-rock age of acidic tuffs overlaying the Cretaceous formation conformably was estimated to be Campanian ($79.2{\pm}1.6$ or $77.3{\pm}1.5$Ma), when the dating was carried out under the same conditions. The acidic dike intruding both Cretaceous formation and acidic tuff showed a K-Ar whole-rock age of $70.9{\pm}1.4$Ma (Campanian). Therefore, the depositional age of the Cretaceous formation in the Aphaedo area and the time when dinosaurs lived in the study area are considered to be 77-83 Ma. Such results indicate that the ages of dinosaur eggshells from Aphaedo area can be correlated with the ages of the Seonso Formation (81Ma) with dinosaur egg nest fossils and the Uhangri Formation (79-81Ma) with dinosaur, pterosaur and web-footed bird tracks.

• Journal of the Korean Geographical Society
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• v.50 no.5
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• pp.459-472
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• 2015

Weathering hollows which develop on various rocks are the terrain whose lithological characteristics and formation of the bed rock is under active discussion. The shore in Dapyeong-ri, Sacheon-si has alternation of strata of pelite and sandstone, and the weathering hollows develop on the shore platform and the sea cliff where sandstone is exposed. To analyze the development characteristics of weathering hollows by development of joints, interpenetration of veins and physical and chemical features of the stone, the study conducted a topographic investigation, XRD analysis and an observation using a polarizing microscope. As the result of the investigation and analysis, tafoni and gnamma are spread in the same area and new tafoni is being formed as the existing weathering hollows are destroyed by the expansion and growth of the joint. The vein, which was found to be a quartz vein, may accelerate the development of weathering hollows combining with the joint but may also hamper their growth if the veins are penetrating perpendicularly. It is generally known that weathering hollows develop regardless of the type of rocks, however, the analysis on the lithological features show that the development is limited on the fractured and broken rocks.

• The Journal of the Petrological Society of Korea
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• v.19 no.1
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• pp.67-87
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• 2010

This article deal with petrotectonic setting and petrogenesis from petrography and chemical analyses of the Cretaceous volcanic and intrusive rocks in the Cheolwon basin. The volcanic rocks are composed of basalts in Gungpyeong Formation, Geumhaksan Andesite, and rhyolitic rocks (Dongmakgol Tuff, Rhyolite and Jijangbong Tuff), and intrusive rocks, Bojangsan Andesite, granite porphyry and dikes. According to petrochemistry, these rocks represent medium-K to high-K basalt, andesite and rhyolite series that belong to calc-alkaline series, and generally show linear compositional variations of major and trace elements with increase in $SiO_2$ contents, on many Harker diagrams. The incompatible and rare earth elements are characterized by high enrichments than MORB, and gradually high LREE/HREE fractionation and sharp Eu negative anomaly with late strata, on spider diagram and REE pattern. Some trace elements exhibit a continental arc of various volcanic arcs or orogenic suites among destructive plate margins on tectonic discriminant diagrams. These petrochemical data suggest that the basalts may have originated from basaltic calc-alkaline magma of continental arc that produced from a partial melt of upper mantle by supplying some aqueous fluids from a oceanic crust slab under the subduction environment. The andesites and rhyolites may have been evolved from the basaltic magma with fractional crystallization with contamination of some crustal materials. Each volcanic rock may have been respectively erupted from the chamber that differentiated magmas rose sequentially into shallower levels equivalenced at their densities.

• Economic and Environmental Geology
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• v.26 no.3
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• pp.403-420
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• 1993

The Cretaceous Kyongsang Basin is known to be composed of several tectonic blocks (or subbasins) with each distinct stratigraphic succession. The study area represents a major part of one of these blocks, i. e. the $\check{U}is\check{o}ng$ block. The area is charaterized by a suite of WNW-trending sinistral strike-slip faults as well as a number of ring faults. A total of 292 independently oriented core samples were drilled from 23 sites, covering virtually all the formations of the Cretaceous $Ky\check{o}ngsang$ Supergroup. Alternating field and thermal demagnetization experiments were conducted to reveal the primary magnetization. Due to the homoclinal nature of the strata in the area, it was not possible to make use of the conventional fold test It is, however, believed that the primary remanent components have been obtained from the majority of the formations, considering the similarity of the palaeomagnetic pole positions with those of contemporary strata of other blocks and the existence of antiparallel reversed remanence. It was found neither any significant difference in magnetic declination on each side of the strike-slip faults nor systematic change of magnetic declination with distance from the fault-line. This does not support such a block rotation hypothesis associated with the strike-slip faulting in the area as alleged by some authors. The samples from the outcrops on or near the fault-lines were severely overprinted by the recent magnetic fields regardless of age and lithology. Epithermal Au-Ag-Cu-Pb-Zn mineralizations are known along some fault lines in the area. It is interpreted that these two facts are closely related with fluid circulations along the fracture zones caused by fault activities. In regard to the age of the strata as deduced from the magnetostratigraphic consideration, the $Ch\check{o}mgok$ formation and the lower strata should be older than Barremian or 124 Ma. The age of volcanics of the $Yuch^{\prime}\check{o}n$ Group sampled in this study should be younger than Campanian or 83 Ma.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.231-238
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• 2005

Incompetent sediments and competent volcanics are consisted of the Cenozoic geology in Korea. Although the Cenozoic area is small, it is necessary to special interesting for ground of these geological material. The Cenozoic geology shows heterogeneous characteristics. We can look at the weak Cenozoic sedimentary rocks under the hard Cenozoic basalt in the area. Some Cenozoic un(or half)-consolidated soft sediments have large, heavy and hard boulders. Some volcanics and tuffaceous sediments have swelling clays. These characteristics give very difficult problems to engineering geologists and civil engineers.