• Journal of the Korean earth science society
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• v.24 no.8
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• pp.657-667
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• 2003

Deep-drilled core sampling and high-resolution seismic survey were carried out to identify a Holocene-late Pleistocene boundary in Gyeonggi Bay, western coast of Korea. Analysis of core sections revealed the existence of an oxidized and semi-consolidated sediment layer, Iying immediately below a Holocene horizon (Unit I) and being developed at the top of a late Pleistocene deposit (Unit II). The oxidized sedimentary layer (uppermost part of Unit II) is characterized by semi-consolidated, yellowish sediments showing signs of desiccation and alteration such as high N value, low water content, periglacial cryogenic structure, depletion of smectite, and high geochemical weathering index (Ba/Sr ratio). This feature, together with radiocarbon ages, suggests that the layer has formed as a result of prolonged subaerial exposure of Unit II sediments during the late Wisconsin sea-level lowstand, producing a regional unconformity. Such unconformitic-bounding surface corresponds to a prominent near-surface reflector (R), which is observed in seismic profiles obtained across the drilled-core sections in the study area. Consequently, the buried oxidized-sedimentary layer associated with the seismic reflector possibly plays a key horizon for the understanding of late Quaternary environmental changes as well as evidence of the emergence of the Yellow Sea shelf during the late Wisconsin sea-level lowstand.

• Journal of the Korean earth science society
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• v.35 no.4
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• pp.290-294
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• 2014

In this study, we investigated the characteristics of rodent (mainly ground squirrel) burrows found near the Lake Hovsgol, Mongolia. Those burrows are straight to slightly curved and gently inclined in lateral view. Cross-sectional shapes are either circular or elliptical with diameters ranging from mostly 8-10 cm. Most abandoned burrows are passively filled with soils and/or pebbles. The size and architecture of these Mongolian burrows are remarkably similar to those of the previously reported Late Pleistocene burrows from Korea. Therefore, the rodent burrows found at Korean Palaeolithic sites are thought to have been formed by ground squirrels. However, the difference in burrow-fills suggests that the mean annual precipitation of the Korean Peninsula during the Late Pleistocene is much higher than that of Mongolia.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.368-368
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• 2001

• Proceedings of the Korean Quaternary Association Conference
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• 2003.05a
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• pp.36-38
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• 2003

• Proceedings of the Korean Quaternary Association Conference
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• 2002.12a
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• pp.82-84
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• 2002

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.1 no.1
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• pp.1-12
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• 1996

A paleomagnetic study was carried out on three gravity cores recovered from the KODOS-90 area in the North Pacific to obtain a magnetostratigraphic information and to correlate the magnetic records between cores. The sediments bear a stable remanent magnetization and the polarity sequence of the three cores can be correlated with the gomagnetic polarity time scale for the Plio-Pleistocene. The abrupt change in the magnetic susceptibility profile at 285 cm depth of the gravity core 26 indicates the presence of a major hiatus. The average sedimentation rates of the gravity cores 08 and 26 are about 2.7 and 1.4 times higher than that of the gravity core 20 (0.09 cm/100yr), respectively.

• Journal of the korean society of oceanography
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• v.33 no.3
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• pp.71-79
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• 1998

Silty tidal rhythmites were found from the upper Pleistocene sequence unconformably overlain by the Holocene tidal deposits within the macrotidal coastal zone of Youngjong Island, western coast of Korea. The rhythmites occur as vertically accreted, parallel and planar laminae that are 0.1-2.5 mm in thickness. Each lamina grades from coarse silt (mean grain size: 5-6.5 ${\phi}$) at the lower part into fine silt to mud (mean grain size: 6-7.5 ${\phi}$) at the upper part. The rhythmites can be classified into two types based on the patterns in laminar thickness variation. Type I is a bundle of 12-20 laminae in which laminar thickness varies sinusoidally. Type ll is an alternation of thick and thin laminae as a couplet. Type I is inferred as a product of varying tidal energy during a semimonthly (neap-spring) tidal cycle, in which thicker laminae were deposited during spring tides and thinner laminae were formed during neap tides. Type ll is interpreted to have been formed by asymmetric semidiurnal tidal currents in association with diurnal inequality, whereby thick lamina of each couplet represents dominant tidal current and the thin lamina reflects subordinate tidal current.

• The Korean Journal of Quaternary Research
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• v.4 no.1
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• pp.27-40
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• 1990

$^{14}C$ age dating by AMS (accelerator mass spectrometry) technique was performed on twenty five small sized fossil shells and one peat taken from the sixteen piston cores in the southern and southeastern Korean Sea. AMS technique is available to date only a few milligram of amorphous carbons compare than conventional dating technique. It is described in detail of sample pre-treatment and experimental, and applied to the reconstruction of the sea level changes since the late Pleistocene in the Korean Sea. Dated age ranges from 520$\pm$100 to older than 33,500 years. Sedimentary facies in the study area represents a different environmental set which is affected by sea level fluctuation since the late Pleistocene.

• The Korean Journal of Quaternary Research
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• v.11 no.1
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• pp.25-38
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• 1997

한국서남해안에 위치한 해남만의 조수 퇴적층(체)에 관한 층서 설정이 제4기후기 (late Quaternary)의 시간범위로 가능하였다. 즉 현재의 해남만에 분포하고 있는 조간대층은 지난 중기와 후기 현세(middle to late Holocene)동안에 형성된 퇴적지층단위(depositional sequence unit)이며 이 지층단위는 선현세(late Pleistocene)조간대 퇴적지층단위 disconformity 의 부정합 관계로 피복하고 있다 본연구에서는 전자를 Unit I(8-10m 내외의 두께)이라 칭하고 후자를 Unit II(10m 내외의 두께)라고 구분 명명하였다, 그런데 Unit II는 암상(lithofacies)의 특징에 근거하여 상부(upper part)와 하부(lower part)로 나누어진다. 상 부는 약 3-4m 의 두께를 가지고 있으며 황갈색을 분명히 나타내며 게 구멍 화석과 동토구 조(cryogenic structure)그리고 매우 높은 값의 전단응력을 나타낸다, 그러나 하부는 회색을 띄며 낮은 전단응력 값을 나타내 상부와 뚜렷이 구분된다 이러한 Unit II의 상부가 나타내 는 암상적 특징은 지난 간빙하기(Eemian interglacial time)에 형성된 오늘과 같은 조간대층 이 18,000년 전후의 최대 빙하기(last glacial maximum : LGM) 동안의 지배하에 노출되었 고 오랜동안 토양형성 과정이 풍화작용을 받은 증거를 나타내고 있다, 따라서 이지층의 층 서학적 단위 설정과 부정합 (disconformity) 적인 경계의미는 우리나라 제4기 층서(late Quaternary stratigraphy)를 규정하는데 매우 중요하다고 제안하는 바이다.

• Economic and Environmental Geology
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• v.17 no.3
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• pp.215-230
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• 1984

Petrological, paleomagnetic, geomorphological and structural studies on the southern part of, so called, Chugaryeong rift valley, have been carried out in order to clarify the nature of the rift valley. Three stages of volcanic activities characterized by Jijangbong acidic volcanic rocks and tholeiitic and andesitic basalt of Cretaceous age(?), and Jongok Quaternary olivine basalt occurred along the Dongducheon fault line. Jijangbong acidic volcanic rocks distributed in the central part of the studied area consist of rhyodacite, acidic tuff and tuff breccia, which are bounded by Dongsong fault on the east and Daegwangri fault on the west. The Jongok basalt differs from those of Ulrung and Jeju islands in mineralogy, chemical composition and differentiation. Jongok basalt distributed along the Hantan river dilineates the vesicles curved toward downstream direction and increment of numbers and thickness of lava flow toward upstream direction. These facts suggest that lava flowed from upstream side of the river. Rectangular drainage patterns also support the presence of the Dongducheon, Pocheon, Wangsukcheon and Kyonggang faults which were previously known. LANDSAT image, however, does not show any lineaments which could be counted as a graben or rift valley. Displacement of Precambrian quartzite and Jurassic Daedong supergroup along the southwestern extension of the Dongducheon fault shows the right lateral movement. The Paleomagnetic study of the tholeiitic and andesitic basalts from Baegeuri, Jangtanri and Tonghyeonri located at 2. 3km east, 0km east, and 1.5km west of Dongducheon fault respectively shows that their VGP(Virtual Geomagnetic Pole) being to intermediate geomagnetic field of short duration which suggests that they formed in almost same period. Mean VGP of Jongok basalt is located 82.4N and 80.6E. This is in good coincidence with worldwide VGP of Plio-Pleistocene indicating that Jongok basalt was extruded during Plio-Pleistocene epoch, and suggesting that the studied area has been tectonically stable since then. From the present study, the tectonic episode of the region is concluded as following three stages. 1. The 1st period is worked by the Daebo orogeny of Jurassic during which granodiorite was intruded in Precambrian basement. 2. The 2nd period is the time when right lateral strike-slip fault of NNE-SSW direction was formed probably during late Cretaceous to Paleogene and the Jijangbong acidic volcanic rocks and the older basalts were extruded. 3. The 3rd period is the time when the fault was rejuvenated during Pliocene or Pleistocene accompanied by the eruption of Jongok basalt. As a conclusion, geologic structure of the studied area is rather fault line valley than graben or rift valley, which is formed by differential erosion along the Dongducheon fault suggesting a continuation of the Sikhote-Alin fault. The volcanic rocks including the Jijangbong acidic rocks, tholeiitic-andesitic basalt and olivine basalt are associated with this fault line.