• Economic and Environmental Geology
• /
• v.7 no.3
• /
• pp.87-100
• /
• 1974

This paper deals with grain size analysis, heavy mineral analysis and trace element analysis of the recent sediments of Han River basin between Cheongpyong, Gyeonggi province and Seoul. For each location the samples are taken at river shoreline, river berm and river dune. The size analysis discloses that the mean values range from $-1.37{\phi}$ to $-1.60{\phi}$, sorting values range from 0.25 to 1.84, skewness values range from -0.44 to 0.51 and kurtosis values range from -0.1 to 1.75. Based on the textural parameters, the dune sand can be distinguished from the shoreline-berm sand. The content of heavy minerals of each sample ranges from 0.04 to 4.7%. The principal heavy minerals are ilmenite, magnetite, leucoxene, garnet, amphibole, pyroxene, kyanite, zircon, monazite, tourmaline, epidote, limonite, and minor minerals are apatite, sillimanite, andalusite and olivine. In general, dune sand samples contain more heavy minerals than the samples of shoreline or berm sand. This suggests that the heavy mineral concentration is affected by wind action more than by any other causes. The content of ilmenite and leucoxene decreases, whereas the content of zircon and epidote increases as it approaches the downstream region. The differences result from the variance of geological occurrences. The emission spectrochemical analysis and colorimetry analysis revealed that the content of Ni and V in the heavy minerals of the study area are higher than those of other stream sediments in Korea. On the other hand the content of Cu, Ph, Zn, Mo, W, P, Mn, Cr, Ag and Sn are lower in the study area. It has been observed also that the contents of all the elements except for Bi are higher in this area than the samples of marine sediments of Yellow Sea.

• Korean Journal of Remote Sensing
• /
• v.21 no.1
• /
• pp.73-81
• /
• 2005

We construct improved geocentric digital elevation model (DEM), estimate tidal dynamics and ice stream velocity over Sulzberger Ice Shelf, West Antarctica employing differential interferograms from 12 ERS tandem mission Synthetic Aperture Radar (SAR) images acquired in austral fall of 1996. Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry profiles acquired in the same season as the SAR scenes in 2004 are used as ground control points (GCPs) for Interferometric SAR (InSAR) DEM generation. 20 additional ICESat profiles acquired in 2003-2004 are then used to assess the accuracy of the DEM. The vertical accuracy of the OEM is estimated by comparing elevations with laser altimetry data from ICESat. The mean height difference between all ICESat data and DEM is -0.57m with a standard deviation of 5.88m. We demonstrate that ICESat elevations can be successfully used as GCPs to improve the accuracy of an InSAR derived DEM. In addition, the magnitude and the direction of tidal changes estimated from interferogram are compared with those predicted tidal differences from four ocean tide models. Tidal deformation measured in InSAR is -16.7cm and it agrees well within 3cm with predicted ones from tide models. Lastly, ice surface velocity is estimated by combining speckle matching technique and InSAR line-of-sight measurement. This study shows that the maximum speed and mean speed are 509 m/yr and 131 m/yr, respectively. Our results can be useful for the mass balance study in this area and sea level change.

• Economic and Environmental Geology
• /
• v.55 no.2
• /
• pp.183-195
• /
• 2022

Hydrothermal gold deposits are evidence of intensive fluid flow through fault zones, and the resultant vein structures and textures reflect the fluid redistribution mechanism. This review introduces the suction pump and fault valve models as fluid circulation mechanisms causing hydrothermal gold deposits in the frameworks of the concepts of fault mechanics. The suction pump and fault valve models describe faulting-driven heterogeneous fluid flow and related vein formation mechanisms, accompanied by the cycles of (1) stress accumulation and fluid pressure build-up and (2) seismic rupture and stress/fluid pressure release. The models are available under different geological environments (stress conditions), and the vein structures and textures representing the mechanisms have similarities and differences. The suction pump and fault valve models must help better to interpret the origins of hydrothermal gold deposits in Korea and improve the efficiency of further exploration.

• ALGAE
• /
• v.37 no.2
• /
• pp.123-133
• /
• 2022

Genetic diversity and distribution patterns of marine macroalgae are increasingly being documented in Southeast Asia. These studies show that there can be significant levels of genetic diversity and isolation between populations on either side of the Thai-Malay Peninsula. Bostrychia tenellla is a common filamentous red seaweed in the region and the entity is represented by at least two cryptic species. Despite being highly diverse and widespread, genetic variation and population structure of this species complex remains understudied, especially around the Thai-Malay Peninsula. We analyzed genetic diversity and inferred the phylogeographic pattern of specimens identified as B. tenella using the plastid RuBisCo spacer from samples from the Andaman Sea and the Gulf of Thailand. Our genetic analysis confirmed the occurrence of the two cryptic B. tenella species (B and C) along both coasts. Cryptic species B was more common in the area and displayed higher genetic diversity than species C. Historical demographic analyses indicated a stable population for species B, but more recent population expansion for species C. Our analyses also revealed that both cryptic species from the Andaman Sea possessed higher genetic diversity than those of the Gulf of Thailand. We also detected moderate to high levels of gene flow and weak phylogeographic structure of cryptic species B between the two coasts. In contrast, phylogeographic analysis showed genetic differences between populations of both cryptic species within the Andaman Sea. Overall, these results suggest that cryptic B. tenella species around Thai-Malay Peninsula may have undergone different demography histories, and their patterns of genetic diversity and phylogeography were likely caused by geological history and regional sea surface current circulation in the area.

• Journal of The Geomorphological Association of Korea
• /
• v.26 no.1
• /
• pp.15-26
• /
• 2019

In this study, we investigated the grain size, lithological type, and shape of coarse bed materials in the upper and middle reaches of Gongneungcheon River. For this purpose, 11 sampling points were selected along the river. For 100 samples of the coarse bed materials at each point, three axes (long, intermediate, and short) of samples were measured, and their lithological types were also identified. By measuring grain size, the sphericity and flatness of samples were calculated. Finally, every particle was classified into four shape categories: sphere, disc, blade and rod. We found that the grain size in incised meandering reach is the largest. This is mainly due to the supply of coarse materials from steep valley sides along the meandering channel. According to the lithological analysis, all samples were identified as granite, gneiss and schist, and quartz. The proportion of granite decreased, whereas the proportion of gneiss and schist increased downstream. These patterns indicate that the bedrock distribution within the study area accounts for the downstream lithological variation of coarse bed materials. With regard to the grain shape, sphericity gradually decreased while flatness gradually increased downstream. In the case of the shape classification, unlike the general downstream pattern of grain shape, the proportion of the sphere type decreased and the proportion of the blade type increased downstream. Such a reversal change in the downstream direction turns out to be determined by the lithology (such as foliation, bedding and the pattern of weathering) of coarse bed materials.

• Journal of The Geomorphological Association of Korea
• /
• v.27 no.2
• /
• pp.1-17
• /
• 2020

This study evaluated a debris landform distribution potential area map in the southwest region of the Korean peninsula. A GIS spatial integration technique and logistic regression method were used to produce a distribution potential area map. Seven topographic and environmental factors were considered for analysis and 28 different data set were combined and used to get most effective results. Moreover, in an accuracy assessment, the extracted results of the Distribution Potential area were evaluated by conducting a cross-validation module. Block stream showed the highest accuracy in the combination No. 6, and that DEM (digital elevation model) and TWI (topographic wetness index) have relatively high influences on the production of the Block stream Distribution Potential area map. Talus showed the highest accuracy in the combination No. 13. We also found that slope, TWI and geology have relatively high influences on the production of the Talus Distribution Potential area map. In addition, fieldwork confirmed the accuracy of the input data that were used in this study, and the slope and geology were also similar. It was also determined that these input data were relatively accurate. In the case of angularity, the block stream was composed of sub-rounded and sub-angular systems and Talus showed differences according to the terrain formation. Although the results of the rebound strain measurement using a Schmidt's hammer did not shown any difference in topographic conditions, it is determined that the rebound strain results reflected the underlying geological setting.

• Journal of Korean Society of Water and Wastewater
• /
• v.37 no.6
• /
• pp.363-373
• /
• 2023

Numerous studies have established a correlation between sociodemographic characteristics and water usage, identifying population as a primary independent variable in mid- to long-term demand forecasting. Recent dramatic sociodemographic changes, including urban concentration-rural depopulation, low birth rates-aging population, and the rise in single-person households, are expected to impact water demand and supply patterns. This underscores the necessity for operational and managerial changes in existing water supply systems. While sociodemographic characteristics are regularly surveyed, the conducted surveys use aggregate units that do not align with the actual system. Consequently, many water demand forecasts have been conducted at the administrative district level without adequately considering the water supply system. This study presents an upward water demand forecasting model that accurately reflects real water facilities and consumers. The model comprises three key steps. Firstly, Statistics Korea's SGIS (Statistical Geological Information System) data was reorganized at the DMA level. Secondly, DMAs were classified using the SOM (Self-Organizing Map) algorithm to consider differences in water facilities and consumer characteristics. Lastly, water demand forecasting employed the PCR (Principal Component Regression) method to address multicollinearity and overfitting issues. The performance evaluation of this model was conducted for DMAs classified as rural areas due to the insufficient number of DMAs. The estimation results indicate that the correlation coefficients exceeded 0.9, and the MAPE remained within approximately 10% for the test dataset. This method is expected to be useful for reorganization plans, such as the expansion and contraction of existing facilities.

• Geomechanics and Engineering
• /
• v.38 no.3
• /
• pp.215-229
• /
• 2024

Because of the various patterns of deep-water inrush and complicated mechanisms, accurately predicting mine water inflows is always a difficult problem for coal mine geologists. In study presented in this paper, the water inrush channels were divided into four basic water diversion structures: aquifer, rock fracture zone, fracture zone and goaf. The fluid flow characteristics in each water-conducting structure were investigated by laboratory tests, and multistructure and multisystem coupling flow analysis models of different water-conducting structures were established to describe the entire water inrush process. Based on the research of the water inrush flow paths, the analysis model of different water inrush space structures was established and applied to the prediction of mine water inrush inflow. The results prove that the conduction sequence of different water-conducting structures and the changing rule of permeability caused by stress changes before and after the peak have important influences on the characteristics of mine water-gushing. Influenced by the differences in geological structure and combined with rock mass RQD and fault conductivity characteristics and other mine exploration data, the prediction of mine water inflow can be realized accurately. Taking the water transmitting path in the multistructure as the research object of water inrush, breaking through the limitation of traditional stratigraphic structure division, the prediction of water inflow and the estimation of potentially flooded area was realized, and water bursting intensity was predicted. It is of great significance in making reasonable emergency plans.

• Korean Journal of Environmental Agriculture
• /
• v.30 no.2
• /
• pp.209-215
• /
• 2011

BACKGROUND: The paddy ecosystem is periodically disturbed with a relatively consistent cycle in short term. However, in long term aspect, the paddy as habitats of organisms has been affected by the change in farming practices. Accordingly, the composition and their densities of fauna species inhabiting the wet paddy has been changed. The geological distribution of a species is very helpful to understand the past and current status of habitats and biodiversity. METHODS AND RESULTS: We monitored 290 sites of open plain paddy or terraced valley paddy located in 138 cities or counties of South Korea and analyzed examine geological distribution of a taxon of freshwater invertebrates, diving beetles (Dytiscidae) which inhabited the paddy ecosystem. This survey was conducted from 2005 through 2007. The total species of diving beetles found in the paddy were identified to be 15 genus 26 species among the family of Dytiscidae. Among them, 24 species were found in the terraced valleys-in paddy fields, and 19 species were found in the open plain paddy fields. Eleven species of them were rarely found in the paddy. The average body size of the adult diving beetles of each species was between 2.0 and 35.0 mm. Most of the diving beetle species except for 11 species with rare frequency of occurrence were found in almost all sites of the terraced valley paddy fields but three species (Agabus browni, Agabus japnicus, and Ilybius apicalis) were not found in the open plain paddy fields. The species distributed relatively widely over some sites of the open plain paddy fields were Guignotus japonicus, and Rhantus pulverosus. Specifically, Ilybius apicalis was found in a specific region, the east-southern part of Korean peninsula, whereas Coelambus chinensis was found only in valley paddy field of the region where Ilybius apicalis was not found. Overall distribution range of diving beetles in open plain paddy fields was limited to few area than in terraced valley paddy fields. CONCLUSION(s): The differences in the range of distribution of diving beetles between terraced valley paddy fields and open plain paddy fields was thought to be the result of an complex action of physico-chemical environments such as annual water status and the degree of chemical application involving differences in the extent of disturbance of the paddy ecosystem, the connectivity of the paddy to an adjacent biotope, and interrelationships among competitors.

• Economic and Environmental Geology
• /
• v.21 no.4
• /
• pp.367-380
• /
• 1988

Most of the gold (-silver) vein deposits at Yeongdong District are mainly distributed in the precambrian metamorphic rocks. Based on the Ag/Au total production and ore grade ratios, the chemical composition of electrum and the associated sulfides, the gold(-silver) deposits at Yeongdong District may be classified into 4 classes: pyrrhotite - type gold deposits( I), pyrite - type gold deposits (IT A; massive vein), pyrite - type gold deposits (II B; nonmassive vein) and argentite - type gold - silver deposits(III). The chemical study on electrum(including native gold) revealed that Au content (2.8 to 92.4 atomic%) of electrums varies very widely for different classes of deposits. The Au content of electrum associated with pyrrhotite (Class I), ranging from 47.1 to 92.4 atomic% Au, is clearly higher than that associated with pyrite (Classes IIA, IIB and III). In contrast, classes I, II, and III deposits do not show clear differences in Au content of electrum. In general, pyrrhotite - type gold deposits(I) are characterized by features such as simply massive vein morphology, low values in the Ag/Au total production and ore grade ratios, the absence or rarity of silver - bearing minerals except electrum, and distinctively simple mineralogy. Although the geological and mineralogical features and vein morphology of pyrite - type gold deposits(IIA)are very similar to those of pyrrhotite - type gold deposits (I), Class II A deposits reveal significant differences in the associated iron sulfide (i. e. pyrite) with electrum and Au content of electrum. The Ag/Au total production and ore grade ratios from Class II A deposits are relatively slightly higher than those from Class I deposits. Pyrite - type gold deposits(II B) and argentite - type gold - silver deposits (III) have many common features; complex vein morphology, medium to high values in the Ag/Au total production and ore grade ratios and the associated iron sulfide (i. e. pyrite). In contrast to Class II B deposits, Class III deposits have significantly high Ag/Au total production and ore grade ratios. It indicates distinct difference in the abundance of silver minerals (i. e. native silver and argentite). The fluid inclusion analyses and mineralogical data of electrum tarnish method indicate that the gold mineralization of Classes I and II A deposits was deposited at temperatures between $230^{\circ}$ and $370^{\circ}C$, whereas the gold (-silver) mineralization of Classes ITB and ill formed from the temperature range of $150^{\circ}-290^{\circ}C$. Therefore, Classes I and IT A deposits have been formed at higher temperature condition and/or deeper positions than Classes IIB and III.