• Economic and Environmental Geology
• /
• v.16 no.3
• /
• pp.223-243
• /
• 1983

palaeomagnetism is a major implement to define tectonic provinces and to estimate their past relative position quantitatively. In this sort of investigation it is tacitly assumed that the magnetization of the rocks under study was acquired at the time of their formation. However, because of the possibility of secondary alteration and/or replacement of magnetic minerals, this assumption is not always legitimate. To secure reliable palaeomagnetic data it is therefore fundamental to identify the carrier mineral of magnetization. This paper reviews magnetic mineralogy relevant to palaeomagnetism of terrestrial rocks. Under the heading of each mineral its genesis, crystal structure, magnetic properties, criteria for ore microscopic determination and secondary alteration are summerized. This paper should also be helpful in application of magnetic mineralogy to geothermometry and oxygen barometry in igneous petrology, diagenesis and provenance study in sedimentary petrology, metamorphic temperature determination and genesis study of ore deposits.

• Economic and Environmental Geology
• /
• v.24 no.1
• /
• pp.27-41
• /
• 1991

Taebaeg-Hajang area, in the northern part of Taebaeg city, comprises of Paleozoic sedimentary sequences and Cretaceous intrusive and volcanoclastic rocks. The rocks in the area are affected by folding and thrusting during the Bulgugsa Orogeny. In Taebaeg area, geologic structures related with thrust movement are dominant. These structures are small scale of klippe and window, back thrust, and asymmetric folds related with blind thrust. Tear fault or compartment fault due to differential movement of thrust sheets have "en echelon" arrays. Small scale transpression effects occurred along these faults and produced the flower structure. According to strain measurement using by ooids from limestone and quartz grains from quartzite, strain ratios are very low and strain ellipsoids are apparent oblate type.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2005.05a
• /
• pp.203-208
• /
• 2005

We have performed magnetotelluric (MT) surveys to investigate the deep crustal structure of Gyeongsang basin. The MT data were collected in the frequency range from 0.00042 to 320Hz along a profile across the Gyeongsang basin, and 2-D inversion was carried out to interpret the geoelectrical structure. We also extracted gravity data around the MT profile from KIGAM database and calculated the density inversion to compare with the geoelectrical structure. The results obtained are good agreement with geological distribution and indicate contrasts of physical properties of sedimentary rock, igneous rock and metamorphic rock.

• Geophysics and Geophysical Exploration
• /
• v.11 no.3
• /
• pp.197-203
• /
• 2008

A shallow high-resolution seismic reflection survey was carried out at the Mineopo tidal flat on the western coast of Korea. The purpose of the survey was to investigate shallow sedimentary structure of the tidal flat associated with the recent sea level change. A total of 795 shots were generated at 1 m interval from a 5-kg hammer source and recorded on 48 channels of 100 Hz geophones along two mutually perpendicular profiles. The water-saturated ground condition resulted in suppressed ground rolls by significantly decreasing rigidity. In addition, seismic velocities over 1500 m/s provided easy segregation of reflected arrivals from lower velocity noise. As a consequence, seismic sections from the study area show significantly higher resolution and signal to noise ratio than conventional land seismic sections. The tidal flat consists of 5 sedimentary sequences above acoustic basement. The seismic sections reveal the continuous structure of the tidal flat formed in association with sea level rise during the Holocene.

• The Journal of Engineering Geology
• /
• v.3 no.1
• /
• pp.21-37
• /
• 1993

In order to investigate the correlation of sedimentary rock properties. specific gravity, porosity, water content, sonic wave velodty, and point4oad strength index of core samples of limestones, sandstones and shales were measured. The relationships between density and velocity show $V_p=16300d-38719.3,{\;}V_s1896.4d-29225.1$ of regression equation for sandstones and $Vp=4085d-10264.8,{\;}V_s=3519d-7841.3$ for shales and <$Vp=4085d^2-20747d+303,{\;}V_s=3899d^2-21442d+318$ for limestones. Seismic wave velocity of shales which have high density is lower than that of sandstones, and this seems to be an effect of bedding in shale. P-wave velocity and S-wave velocity of limestones, sandstones and shales show the linear relationships as a whole. The regression equations are respectively calculated V_s=0.26V_p+1041.6m/sec,{\;}V_s=0.43V_p+424.2m/sec,{\;}and{\;}Vs=0.51V_p+261.9m/sec$ and the correlation coefficients of the velocity show r= 0.86 in sandstones, r= 0.75 in limestones and r=0.86 in shales. According to the point4oad strength test for limestones, point4ord strength anisotropy was not so dear even though the specimens show generally the banded structure. Variations of dip angle of bedding whihin the range $30^{\circ}-60^{\circ}$ does not have much influence upon the diametral strength index and axial strength index. From the result of point load test, P-wave velocity increases with point4ord strength index but the regression equations are $V_p=98.5lI{s_d}+4082.1m/sec,{\;}V_p=106.41{s_a}+3954m/sec$ and their correlation coefficient is low.

• The Journal of the Convergence on Culture Technology
• /
• v.10 no.5
• /
• pp.693-698
• /
• 2024

As there are various types of discontinuities developing along with various rock types, the orientation and density of each type of discontinuities were measured to analyze the behavior of groundwater within the rock mass. Among the orientations of discontinuities, the strike was measured in azimuth and expressed as a discontinuity trajectory, and the density of discontinuities was quantified as the sum of the lengths of discontinuities developed per unit area. The overall discontinuity trajectory in the study area is predominantly in the northeast direction, the north-south and east-west directions are dominant in the igneous rock distribution area, and the east-west and northeast directions are dominant in the sedimentary rock distribution area. Among the types of discontinuities, they show discontinuity trajectories similar to the northeast direction, which is the dominant orientation of stratum boundaries, stratification, and foliation. The discontinuity density ranges from 0.1 m^-1 to 1,000 m^-1. The density distribution of discontinuities was expressed in the form of discontinuity contour diagrams. As a result, the crushed rock near Demiseam in the southern and southwestern part of the study area, the igneous rock area around Maryeong-myeon, the igneous rock area near Yongdam Dam in the northeast, and the igneous rock area near Unilam and Banilam in the northwest showed the highest density of discontinuities at over 100m^-1., the sedimentary rock area near Maisan Mountain showed relatively low values. It suggests that the results of geophysical exploration and drilling survey data in the existing study area, as well as the geological structure and density and trajectory of discontinuities, may be important factors in the behavior of groundwater in rock mass in the future.

• Journal of Korean Society on Water Environment
• /
• v.31 no.3
• /
• pp.304-312
• /
• 2015

In this study, we tried to determine the vertical variation of sediment structure and geochemical characteristics, core sediment was collected in the Nakdong River midstream on August, 2014. Core sediment mainly composed of sand (51.48%) and silt (46.21%) and coarsing upward changed from sM to mS facies. IL and TOC were decreased from lower to upper layer. C/N ratio was lower than 10 so the organic matters were originated from underwater creatures and C/S ratio was decreased from lower to upper layer. Heavy metal (Al, Fe, Zn, Cr, Pb, Ni, Cu, Cd) content were decreased from lower to upper layer and seriously polluted condition is not. These results are thought to be due to the effect of natural and anthropogenic in the fluctuation of flow.

• The Korean Journal of Petroleum Geology
• /
• v.1 no.1 s.1
• /
• pp.53-62
• /
• 1993

The geologic structure of the Yongil Bay was studied in detail based on high resolution seismic profiles. The seafloor trends NE to SW with a deeper part off the Kuryong Peninsula. The seafloor is rather smooth due to the Quaternary fluvial deposits in the lower part and muddy sediments in the upper part. The seafloor off Umockri is very irregular due to erosion where Tertiary sedimentary rocks crop out. The underlying basement rocks were strongly deformed with faults and folds. High-angled reverse faults mostly trend N-S and NNW-SSE and are indicative of westward thrusting. Normal faults in NW-SE and WNW-ESE directions occur locally. Large folding structures trend NE-SW nearshore area of Umockri. The geologic structure suggests that the bay was subject to compressional stress regimes trending E-W and/or NW-SE prior to the early Late Miocene.

• Geomechanics and Engineering
• /
• v.10 no.3
• /
• pp.335-355
• /
• 2016

Most laboratory test research has focused on grouting efficiency in homogeneous reconstituted soft clay. However, the natural sedimentary soils generally behave differently from reconstituted soils due to the effect of soil structure. A series of laboratory grouting tests were conducted to research the effect of soil structure on the performance of compensation grouting. The effects of grouting volume, overlying load and grouting location on the performance of compensation grouting under different soil structures were also studied. Reconstituted soil was altered with added cement to simulate artificial structured soil. The results showed that the final grouting efficiency was positive and significantly increased with the increase of stress ratio within a certain range when grouting in normally consolidated structured clay. However, in the same low yield stress situation, the artificial structured soil had a lower final grouting efficiency than the overconsolidated reconstituted soil. The larger of normalized grouting volume could increase the final grouting efficiency for both reconstituted and artificial structured soils. Whereas, the effect of the overlying load on final grouting efficiencies was unfavourable, and was independent of the stress ratio. As for the layered soil specimens, grouting in the artificial structured soil layer was the most efficient. In addition, the peak grouting pressure was affected by the stress ratio and the overlying load, and it could be predicted with an empirical equation when the overlying load was less than the yield stress. The end time of primary consolidation and the proportion of secondary consolidation settlement varied with the different soil structures, grouting volumes, overlying loads and grouting locations.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.267-272
• /
• 2007

Uiseong subbasin belonging to Kyungsang basin resulted from volcanic activity in the late Cretaceous. In this study, we carry out MT and gravity survey at the Hwasan caldera, which was formed of volcanic and abyssal rocks complex, then analyze and identify geological substructure. Potential survey such as gravity and magnetic survey has been mainly carried out in former studies, so depth information for understanding substructure was not enough. To complement a potential survey, we use MT method, which has high vertical resolution. Moreover we make a simple 2D model comparing with former study. The result of MT and gravity 2D modeling shows that this area is roughly composed of 3 layers; The bottom layer is a basement. In the second layer, intrusive rocks having high resistivity is placed along the ring faults and the sedimentary layer of low resistivity is inside caldera. The highest layer is alluvium. To comprehend the 3D structure of the Hwasan caldera, we perform 3D gravity inversion, and construct the 3D model from the result of 3D gravity inversion. MT responses are calculated by using the constructed 3D model and the 3D model of the Hwasan caldera's structure is suggested after comparing the calculated values with the observed values at MT line.