• The Korean Journal of Malacology
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• v.10 no.2
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• pp.10-23
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• 1994

패류화석은 지구를 이루는 퇴적암 중 석회암을 이루고 있는 주요 구성원 중의 하나이다. 지난 20년간 지질학자 및 해양학자들은 주로 심해에 쌓여 있는 퇴적물 중의 미화석(microfossil)을 이용하여 과거의 기후 및 해양의조건을 규명하기 위하여 많은 노력을 하여왔다. 그 결과로서 지질학적 시대 중 중생대 이후로부터 신생대에 이르기까지 지구 전반에 영향을 주었던 고기후에 대한 많은 정보가 얻어졌다. 또한 일부 학자들에 의하여 천해에 서식하였던 여러 화석들의 생태와 지화학적 분석(geochemical analysis)을 통하여 지엽적인 고기후(paleoclimate) 및 고해양학적(paleoceanographic)이해도 증진되어 온 것이 사실이다. 천해에 서식하고 있는 석회질 골격(calcareous skeleton)을 만드는 생물종들은 주로 생화확적인 작용을 통하여 아라고나이트와 방해석이라는 탄산염 광물을 침전시킨다. 특히 이 중에서 아라고나이트라는 광물은 불안정하여 속성작용 (퇴적물이 쌓인 후 거치는 물리, 화학적 작용)동안에 방해석으로 변하게 된다. 따라서 특이한 속성환경의 조건에 의해 아라고나이트로 보존되어 있는 패류를 제외하고는 주로 방해석으로 이루어진 화석의 분석을 통하여 고환경 복원을 위한 여러 정보를 얻을 수 있다. 이를 근거로 하여 분석 대상이 주로 된 것은 완족류나 방해석으로 이루어진 이매패류(e.g., 굴등)이었다.우리나라에서는 최근에 이르러서야 패류 화석의 지화학적 분석을 통하여 고해양학적 연구가 수행되기 시작하였다. 신생대 제 3기 마이오세에 해당하는 포항 부근에서 발견되는 연체동물 화석들은 변질이 안된 상태로서 우리에게 매우 귀중한 고해양학적 정보를 제공한다. 과거에 생물이 자랐던 성장 온도는 산소 동위원소의 비를 측정하여 구할 수 있는데 그결과에 의하면 해수의 온도가 현재보다 약간 높았음을 지시한다. 제주도 내의 서귀포 부근에서는 현재 천연기념물로 지정되어 있는 서귀포층내에서 많은 화석들이 산출되고 있다. 이 시대는 빙하기와 간빙기가 교호하던 시대로서, 분석 결과에 의하면 서귀포층이 쌓일 당시에 우리 나라는 빙하기의 영향을 받았던 것으로 생각된다.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.281-291
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• 1996

Samples of Badwater greenstones from the Crystal Falls terrane in northeastern Wisconsin have been analyzed for major, trace and rare earth elements. Geochemical characteristics of the rocks provide clues to the petrologic character and paleotectonic environment of basaltic magma generation. They have chemical composition typical of continental tholeiites. The low Mg values and abundances of Ni and Cr indicate that the lavas were extensively fractionated prior to extrusion. The variations of incompatible elements suggest that the rocks were affected by interaction with crustal rocks. The samples least affected by contamination have trace element compositions similar to those of T-type mid-ocean ridge basalts. The parent was modified by crustal contamination process and this process shifted the rock compositions to that of continental tholeiites as the rock evolved. Interpretations of the chemical characteristics of the rocks, based on modem analogs, favor their emplacement in an extensional tectonic regime.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.187-206
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• 1994

Through a computer model study, optimum system configuration and field parameters were determined for high-resolution marine reflection surveys. Characteristics of far-field signatures were analysed in both time and frequency domains for the six individual R/V Onnuri. The analysis shows that the cluster fired at the depth of 2m below the sea surface generates the most ideal far-field signatures among the above seismic sources. Compared with the 96-channel streamer on the R/V Onnuri, the 12-channel streamer is suitable for shallow reflection profiling due to its high resolution both in the vertical and horizontal directions despite its lower signal-to-noise ratio. Considering factors including target depth, frequency range, airgun volume, number of recording channels, and capacity of compressors, optimum values for record length, sample period, and shot interval are believed to be is, 1ms, and 3.125m or 6.25m, respectively.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.571-577
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• 1994

It has been controversial whether the United States Atlantic margin, which developed during Mesozoic separation of Africa and North America, is a volcanic or non-volcanic rifted margin. To understand its nature, the basement images of multi-channel seismic profiles off the southeastern United States continental margin have been examined. One of prominent results is the presence of seaward-dipping reflector (SDR) wedges, the most diagnostic feature of volcanic rifted margins. Two sets of SDR wedges appear to exist here; one along the basement hinge zone ('the hinge SDR wedge') and another seaward of the East Coast magnetic anomaly ('the outer SDR wedge'). Seaward of the basement hinge zone, the lower crustal high-velocity body previously known as the 7.2 km/s layer and the underlying smooth Moho configuration are also observed. Based on the comparison of these basement images with the crustal structures of the well-known volcanic rifted margin, the southeastern United States Atlantic margin can now be characterized as a typical volcanic rifted margin.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.3
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• pp.171-180
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• 2005

Related to the tsunami impact caused by the 2004 Sumatra earthquake, field excursion of the title 'Tsunami impact on the coastal zone of Thailand' was carried out along the damaged coasts of Thailand fur three days. The damaged coastal zones along the Andaman Sea coasts of Thailand are classified into the severely damaged, the moderately damaged, and the slightly damaged coastal zone by the degree of damage. Channels of the river- mouths were widen, and the beach sands were eroded, transported, and then redeposited in the near shore or in the back beach area. Field excursion stops were 12 in the representative areas like Phang Nga province, the severely damaged coastal zone and Phuket Island, the slightly damaged coastal zone. In this report, the geo-logical effects on the coastal zone of Thailand by tsunami will be mainly illustrated by the satellite data before and after tsunami and the photographs taken during the field excursion.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.271-280
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• 2022

Landfast sea ice forms near coastlines in polar regions. Continuous monitoring of this sea ice is important, as it plays a key role in the marine ecosystem and affects the operation of nearby research stations. This study detected landfast sea ice around Jang Bogo research station in East Antarctica by stacking interferometric coherence images of Sentinel-1 synthetic aperture radar (SAR) data with 6-, 12- and 18-day temporal baselines. A total of 50 landfast sea ice maps were generated covering July 2017 to June 2018. The time series revealed regional differences in the timing of the maximum extent as well as growth rate of landfast sea ice. Overall, detecting landfast sea ice using interferometric SAR coherence seems promisingly feasible; however, limitations remain owing to low backscattering coefficients from new and smooth sea ice surfaces and subtle movements of sea ice in contact with the Campbell Glacier Tongue.

• Economic and Environmental Geology
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• v.35 no.5
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• pp.455-463
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• 2002

There have been few geophysical studies on the crustal structure of the continent-ocean zone around the middle eastern part of Korean peninsula, because of the lack of database in both land and ocean. The area for the study on the internal crustal structure using gravity data is bounded by the latitude of 37$^{\circ}$-38"N and longitude of 128$^{\circ}$-132$^{\circ}$E. WCA correction is applied to shipborne gravity data to integrate with gravity anomalies obtained on land. The high frequency components of the shipborne gravity data which are considered as the noise on survey track are effectively removed by means of correlating with satellite gravity data. The corrected shipborne free-air gravity anomaly is integrated with the Bouguer gravity anomaly on land under the same condition. The integrated gravity anomaly is divided into four areas for power spectrum analysis. The depths of Moho discontinuity increases gradually from inland to Ulleung basin. As the result of modeling based on power spectrum analysis, Moho discontinuity depth is about 33-35 km in the continental zone of Korea and 18-28 km at the continental margin. Such structural character is well elucidated in changing gravity data around Ulleung basin. The depths of Moho discontinuity in the southern ocean of Ulleung-island is 16--17 km, which is much lower than in the land. The result of crustal structure modeling in this study is similar to that computed by prior seismic exploration around this area.

• Economic and Environmental Geology
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• v.41 no.4
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• pp.383-392
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• 2008

This study aims to evaluate the mechanical-chemical stability of used coal ash blocks, for improving fishing grounds. The surface of weathered ash blocks in seawater showed a decrease in the Ca and an increase in the Mg contents, compared to that of fresh blocks. This result reflects the substitution of Ca by Mg in seawater. The compressive strengths of ash blocks submerged into seawater during 12 months ranged from 235.23 to $447.43\;kgf/cm^2$; this is higher than the standard strength of wave-absorbing blocks($180\;kgf/cm^2)$ that are used for harbor construction. In addition, the compressive strength of ash blocks tends to increase with increasing installation time in seawater. The result of leaching experiments on coal ash blocks by Korean Standard Leaching Test(KSLT) method showed that leached concentrations of most metals except Cr(that leached up to 50 ppb, approaching standard concentration) do not exceed the seawater quality standards. A long-term(112 days) heavy metal leaching test to analyze seawater without mixing-dilution also showed that the concentrations of leached heavy metals, except for Cu, under anaerobic conditions do not exceed the seawater quality standards. Accordingly, the use of coal ash blocks in marine environments appears to be safe from chemical and mechanical factors that decrease the efficiency of concrete. Also, leaching concentration of Cu seems to be stable by decrease of leaching concentration due to dilution of seawater.

• Geophysics and Geophysical Exploration
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• v.27 no.2
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• pp.119-128
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• 2024

Marine magnetic surveys provide a rapid and cost-effective method for pioneer geophysical survey for many purposes. Sea-surface magnetometers offer high accuracy but are limited to measuring the scalar total magnetic field and require dedicated cruise missions. Shipboard three-component magnetometers, on the other hand, can collect vector three components and applicable to any cruise missions. However, correcting for the ship's magnetic field, particularly viscous magnetization, still remains a challenge. This study proposes a new additional correction method for ship's viscous magnetization effect in vector data acquired by shipboard three-component magnetometer. This method utilizes magnetic data collected simultaneously with a sea-surface magnetometer providing total magnetic field measurements. Our method significantly reduces deviations between the two datasets, resulting in corrected vector anomalies with errors as low as 7-25 nT. These tiny errors are possibly caused by the vector magnetic anomaly and its related viscous magnetization. This method is expected to significantly improve the accuracy of shipborne magnetic surveys by providing corrected vector components. This will enhance magnetic interpretations and might be useful for understanding plate tectonics, geological structures, hydrothermal deposits, and more.

• Journal of Korea Spatial Information System Society
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• v.9 no.2
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• pp.55-66
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• 2007

There has been increasing concerns regarding marine mineral resources as the land energy resources has been depleting from worldwide energy crisis. Also, all the coastal countries around the world are getting into the high competition as EEZ implemented to widen each country's marine autonomy. Especially, the adoption of EEZ in UN's marine regulation agreement at the January of 1996 has aggravated conflicts among coastal countries and eventually resulted in critical agenda to determine the boundaries of EEZ among such countries. It is imperative for us to have negotiation with neighboring countries to determine the boundaries of EEZ. For the preparation of such negotiation, it is essential to have data such as mineral distribution, deep-sea geology, related agreement and marine laws, etc. Therefore, this study mainly concentrates on analyzing existing data of resources exploration and establishing standards for each type of data and manipulating data based on such standards, thereby building a database for more efficient management of EEZ data from marine resources survey. MRIS has also been developed to diversely analyze and visualize graphic and attribute data considering data usage and inter-relationship in the database. This system can provide various spatial analysis and spatial searching techniques to enable easier comparison of cost-benefit analysis and data provision of any area in EEZ thereby facilitating major policy making. In addition, the system can support sustainable management of marine resources of EEZ regions and data supply for systematic management of national marine resources. Furthermore, this will be very useful for negotiating with neighboring countries to determine EEZ boundaries to lead more favorable results.