• Journal of the Korean earth science society
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• v.28 no.1
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• pp.54-63
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• 2007

The sedimentary sequence of the non-marine Cretaceous Jinju Formation from Sacheon, Korea, contains a number of rod-shaped stromatolites (RSS) characterized by concentric lamination with curd-shaped, stratiform, and small columnar stromatolites. Unlike the world trend, a massive distribution of rod-shaped stomatolite was discovered in the region. The mineral composition, diagenetic alteration, and weathering process of the kind were analyzed by EPMA. The gross morphology of RSS is almost identical to broken plant twigs or stems formed by microbial activity onto which it grew. RSSs are interpreted as stromatolitic algae over plant twigs, which formed through concentric carbonate precipitation by epiphytic algal photosynthesis. The distribution of localities and horizons of the stromatolite imply that RSS is allochthonous and autochthonous. Two types of cyanobacterial filaments and one type of peen algal filament were discovered. The size frequency distribution of calcified filamentous microfossils found in stromatolite was $2.2{\mu}m\;and\;7.8{\mu}m$ in mean diameter of the former, $32.3{\mu}m$ in mean diameter of the latter. The cyanobacterial fossils played a key role in the formation of stromatolite, while the green algal filament was auxiliary stromatolite-builder stromatolites. The filamentous microfossils including trichome were found within the stromatolitic laminae.

• Journal of the Korean earth science society
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• v.36 no.7
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• pp.617-631
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• 2015

The Sesong Formation, mixed carbonate-siliciclastic deposits of late Middle Cambrian (Series 3) to Furongian in age, in the Taebaeksan Basin shows the Steptoean Positive Carbon Isotope Excursion (SPICE) with the ${\delta}^{13}C$ values ranging from 1.14 to 2.81‰ in the approximately 15-m-thick stratigraphic interval. The SPICE in the Sesong Formation occurs in the lower part of the Paibian Stage which contains trilobite biozones of the Fenghuangella laevis Zone, Prochuangia mansuyi Zone and the lower part of the Chuangia Zone. The Sesong Formation is composed of six lithofacies including laminated mudstone, nodular shale, laminated sandstone, massive sandstone, limestone conglomerate, and limestone-shale couplet facies. The Sesong Formation is known to have been deposited in the outer shelf below storm wave base. The SPICE occurs in the stratigraphic interval associated with highstand systems tract, correlative conformity and transgressive systems tract of the Sesong Formation. The peak carbon isotope value in the SPICE may coincide with the correlative conformity formed by relative sea-level fall. The occurrence of the SPICE in the Sesong Formation suggests that the SPICE can be used as a tool of global correlation for the successions of mixed carbonate-siliciclastics which lack fossils.

• The Journal of Engineering Geology
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• v.3 no.1
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• pp.21-37
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• 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 Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.1
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• pp.32-42
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• 2002

The late Quaternary deposit of Cheonsu Bay, up to 20 m in thickness above the Jurassic granite basement, consists of two sedimentary units: an upper Holocene mud and sandy mud deposit (Unit M1), and a lower late Pleistocene sand and mud deposit (Unit M2; 'Kanweoldo Deposit&apos). Unit M1 is a typical Holocene tidal-flat deposit of Cheonsu Bay, showing a coarsening upward, retrogradational facies trend. This retrograding facies trend is probably due to a relative low sedimentation rate during Holocene transgression. Overlain unconformably by Unit M1, Unit M2 deposit reaches up to 14 m in thickness and is mainly composed of muddy sediment with yellow to gray color. This unit is characterized by a variety of tide-influenced signatures such as rhythmic bedding, flaser bedding, crab burrow fossil, marine dinoflagellate assemblage and authigenic glauconite mineral, indicating very similar depositional environment to those of Unit M1 deposit. It suggests that Unit M2 was probably accumulated under the tidal-flat environment during a pre-Holocene sea-level highstand. In particular, the uppermost 3-4 m of Unit M2 appears to have undergone subaerial exposure and subsequent weathering during the sea-level lowstand after deposition. Therefore, stratigraphic unconformity between Holocene and late Pleistocene sediments is highlighted by the desiccated and weathered surface of Unit M2.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.1
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• pp.8-13
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• 1997

The Holocene mud deposits in the southeastern innershelf of the Korean Peninsula were studied using the shallow seismic reflection profiles coupled with sediment sampling. The Holocene mud deposits are developed as a belt in the innershelf area from the mouth of the Nakdong River to off Pohang along the coastline. The surficial sediments in the study area gradually become finer and well sorted from south to north. The seismic facies in the Holocene sequence change northward from parallel reflectors in the mouth of the Nakdong River and northeastward prograding reflectors in the southern part off Ulsan to transparent layer in the nearshore off Ulsan to Pohang. The regional difference of seismic facies indicates that the Holocene sediment characters are varied with localities. By combining the surficial sediments properties with seismic facies patterns, the suspended sediments mostly supplied from the Nakdong River may be transported northward along the shore by the north-flowing Tsushima warm current. The Holocene mud sequence overlying the ravinement surface which is produced by erosion of underlying sediments during a rapid transgression can be interpreted as the highstand system tracts probably formed during the highstand of sea level similar to the present-day sea level.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.323-336
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• 2011

The hydro-mechanical behavior of the Earth's crust is strongly dependent on the fractional volume and geometrical structure of effective pore spaces. This study aims to understand the characteristics of pores using electrical impedance. We measured the electric impedance of core samples (diameter, 38-50 mm; length, 70-100 mm) of three types of granite (Hwangdeung, Pocheon, and Yangsan) and two types of sandstone (Boryung and Berea) with different porosities and pore structures, after saturation with saline water of varying salinities. The results show that resistance decreases but capacitance increases with increasing salinity of the pore fluid. For a given salinity, the resistivity and formation factor are reduced with increasing porosity of the rocks, and the capacitance increases. Berea sandstone shows anisotropy in resistance, tortuosity, and cementation factor, with these factors being highest normal to bedding planes. This result indicates that the connectivity of pores is weakest normal to bedding. In conclusion, the electrical characteristics of the tested samples are related not only to their porosity but also to the pore geometry.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.165-178
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• 2013

This study is for the genetic differences of two closed asbestos mines from Jeongjeon and Ocheon areas in Boryoung, Chungnam. They are mined asbestos for past several decades. Host rocks are serpentinites for Jeongjeon mine and dolomites for Ocheon mine. Asbestos samples and their host rocks are collected from the field trips and examined with microscopes and FESEM, and analysed with XRD and EDX to confirm for the type and/or compositions of the minerals. The asbestos occur as layers, cracks and fractures assummed as a pathway of the hydrothermal water, but show different characteristics. The serpentinites from the Jeongjeon mine contain chrysotile, tremolite and actinolite asbestos. Non-asbestos minerals including tremolite and actinolite were also found. The chrysotiles occur as a cross fiber or slip fiber at veins and along cracks of several mm to cm thickness. Tremolite and actinolite asbestos occur along cracks and fractures of several cm to ten cm thickness. It suggests that the asbestos from Jeongjeon area were formed by the reactions between serpentinite and hydrothermal water. The dolomites of the Ocheon mine only contain tremolite and actinolite asbestos. The asbestos occur along layers, cracks and fractures, suggestive of asbestos from Ocheon area formed by the reactions between dolomite and hydrothermal waters influxed along layers, cracks and fractures. Overall results suggest that two asbestos mines showing different host rocks are located in a Boryoung area. They show a different type of asbestos minerals, reflecting variety of petrogeneses.

• Geophysics and Geophysical Exploration
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• v.20 no.4
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• pp.207-215
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• 2017

To develope shale play which is one of unconventional energy resources, horizontal drilling and hydraulic fracturing are necessary and those are applied to the place where the differential horizontal stress ratio (DHSR) is low. The differential horizontal stress ratio is generally calculated by the minimum and maximum horizontal stress, but it is also calculated from dynamic elastic constants and anisotropic parameters. In this study we analyzed anisotropic properties through the core samples from Danyang limestone and calculated DHSR. The three types of core samples shaped in three directions (vertical, parallel and 45 degree to bedding) were used for laboratory test. We measured P-, S-wave velocities, and density and then calculated dynamic elastic constants, compliance and DHSR. According to the results of the core sample analysis the calculated DHSR is 0.185. Thomsen parameters of the Danyang limestone used in this study are characterized by the P- and S-wave velocities varying along the bedding symmetry axis. It is observed that the DHSR value is more affected by the change in compliance value than the Poisson's ratio. It is necessary to measure SH-wave velocity for more correct petrophysical properties.

• Proceedings of the Korean Quaternary Association Conference
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• 2004.11a
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• pp.4-13
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• 2004

제주도 북제주군 한림읍 협재리에는 대부분 탄산염퇴적물로 이루어진 해안사구가 분포하고 있다. 사구를 이루는 탄산염퇴적물은 연체동물과 홍조류의 조각이 약 80% 이상을 차지하며 그 외에 저서성 유공충, 성게류와 태선동물의 조각, 그리고 화산암편으로 이루어져 있어, 제주도에 분포하는 여러 탄산염 해빈퇴적물의 입자조성과 매우 유사한 경향을 나타낸다. 이러한 탄산염 입자들은 천해에 서식하던 해양생물들에 의해 생성되며, 그 각질이 해빈으로 운반되고 바람에 의해 재동되어 사구를 형성하였다. 특히 이 연구지역의 사구가 분포하는 지점에서 북쪽으로 약 1km 떨어져 있는 협재 해수욕장에는 현재에도 천해에서 생성된 많은 양의 탄산염 해빈퇴적물이 퇴적되어 있으며, 제주도의 타 지역에 비해 매우 빠른 북동${\sim}$북서방향의 바람이 불고 있어, 퇴적물을 해빈에서부터 사구형성지점으로 운반시키는 데 효과적인 역할을 했을 것으로 판단된다. 사구를 절개하여 그 단면을 관찰한 결과, 전반적으로 희미한 수평층리와 사층리가 발달하고 있으며, 그 외의 다른 뚜렷한 퇴적구조는 관찰되지 않는다. 퇴적물의 입자들은 주로 직경이 $0.27{\sim}0.40mm$로 중립질 모래에 해당한다. 이 크기의 입자들은 가장 침식이 잘 될 수 있는 입자크기에 해당하는 것으로 알려져 있으며, 따라서 해빈으로부터 퇴적물이 운반될 때에 특히 이 크기의 입자들이 차별적으로 더 많이 운반되었을 것이라고 생각된다. 또한 퇴적물 입자의 크기와 구성성분의 함량은 각 사구의 전 층준에서 크게 변화하지 않는 것으로 나타나며, 이는 사구가 형성되는 기간 동안 탄산염퇴적물을 운반한 바람의 세기가 어느 정도 일정하였음을 지시한다. 해안사구의 형성시기를 알아보기 위하여 사구의 기반을 이루는 고토양층과 사구 최하부와 최상부의 탄산염퇴적물에 대해 방사성탄소연대측정을 실시하였다. 그 결과, 사구의 형성시기를 지시하는 고토양의 연령은 $680{\sim}720\;BP\;(1,200{\sim}1,300\;AD)$로 측정되었으며, 사구를 이루는 탄산염퇴적물의 연령은 전 층준에서 모두 약 3,500 BP로 측정되었다. 따라서 약 3,500 BP에 천해에서 생성된 탄산염퇴적물이 해빈에 분포하다가 $1,200{\sim}1,300\;AD$에 바람에 의해 재동되고 현재의 위치에 쌓여 사구를 형성한 것이라고 해석할 수 있다. 사구가 형성되기 시작하던 시기는 전세계적으로 춥고 바람이 세었던 Little Ice Age ($1,300{\sim}1,820\;AD$)에 해당하며, 따라서 해빈에 분포하던 많은 양의 탄산염퇴적물이 이 시기에 집중적으로 운반된 것으로 사료된다.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.137-150
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• 2002

Recently, plane failure mode occurred frequently along the bedding plane having low angle dip about 20 degree when cutting slopes were constructed in sedimentary rock region of the Gyeongsang Basin. Landslide of the Whangryeong Mountain which was occurred at Busan Metropolitan City in 1999 belongs to the category mentioned above. Reconstruction for cutting slope of the Whangryeong Mountain has finished in 2000 and final grade of reconstructed cutting slope is 1:2.0. To analyze slope failure mode for landslide of the Whangryeong Mountain, various analyses were performed such as in-situ investigation and test, drilling, laboratory test, aerial photograph interpretation, X-ray diffraction analysis, and slope stability analysis using Stereographic Projection and Limit Equilibrium methods. As the result, it is identified that tension cracks had been developed one year before the landslide took place. The tension crack semis to be formed by merging several joint sets. It appears that failure blocks broke down along the sliding planes of different layers. Risk of plane failure is conformed as a result of stability analysis using Stereographic Projection and Limit Equilibrium methods in case that greenish gray tuffaceous shales, regared as sliding planes, are weathered. From now on, a detailed investigation is needed for the thin layers which is sensitive to weathering, and stability analysis for this layer is performed at cut slope construction site having similar geological condition.