S. Doh

Asian dust storm particles induce a broad toxicological transcriptional program in human epidermal keratinocytes.

Exposure to airborne dust particles originated from seasonal Asian dust storms in Chinese and Mongolian deserts results in increased incidence of a range of diseases including asthma, contact dermatitis and conjunctivitis. The areas affected by Asian dust particles extend from East China to the west coast of North America. In order to study toxicological mechanisms in human skin, we evaluated the effects of dust particles collected during Asian dust storms (Asian dust particles) on gene expression in human epidermal keratinocytes (HEK). In HEK, exposure to Asian dust particles significantly increased gene expressions of cytochrome P450 1A1 (CYP1A1), CYP1A2, and CYP1B1, which is an indication of aryl hydrocarbon receptor (AHR) activation. In addition, Asian dust particles increased gene transcription of the cytokines IL-6, IL-8, and GM-CSF, which have broad pro-inflammatory and immunomodulatory properties. Asian dust particles significantly up-regulated expression of caspase 14 in HEK, suggesting that Asian dust particles directly affect keratinocyte differentiation. We also demonstrated that protein extract of pollen, a material frequently adsorbed onto Asian dust particles, potentially contributes to the increased transcription of IL-6, CYP1A1, CYP1A2, and CYP1B1. Taken together, these studies suggest that Asian dust particles can exert toxicological effects on human skin through the activation of the cellular detoxification system, the production of pro-inflammatory and immunomodulatory cytokines, and changes in the expression of proteins essential in normal epidermal differentiation.

Sedimentary fabric on deep-sea sediments from KODOS area in the eastern Pacific

Abstract An anisotropy of magnetic susceptibility (AMS) study on three sediment cores taken from the Korea Deep Ocean Study (KODOS) area in eastern Pacific was carried out to understand the relationship between magnetic fabric patterns and paleo-depositional conditions of deep-sea sediments. Most AMS measurements reveal normal sedimentary fabric patterns indicating a stable sedimentation mode. However, some intervals show deformed AMS patterns (magnetic lineation), and this anomalous fabric is mainly observed at the boundary where sediment color changes. The abrupt change of AMS parameters at this boundary provides evidence that the linear fabric was induced by input of intensified bottom currents. Based on the trend of microfossil occurrences, it is interpreted that the discontinuous color boundary was formed by hiatus between Tertiary and Quaternary age. The change of magnetic fabric at the topmost color boundary coincides with the time of prevailed antarctic bottom water (AABW) activity. In this study, the AMS properties are shown to be useful tools for making inferences concerning the paleoenvironment of abyssal basins.

Paleomagnetic and rock magnetic studies of Cretaceous rocks in the Eumsung basin, Korea

Paleomagnetic results are obtained from 41 sites from the Chopyeong Formation within the Eumsung basin, located along the northern boundary of the Ogcheon Belt, Korea. The Chopyeong Formation, deposited in early Cretaceous, yields the mean direction of D/I = 347.8°/57.3° (k = 92.8, α95 = 2.5°) before tilt correction, and D/I = 0.7°/61.7° (k = 19.6, α95 = 5.5°) after tilt correction. The parameter estimating fold test and the stepwise unfolding test of the red bed and greenish mudstone of the Chopyeong Formation yield the maximum value of k at 21.9% and at 20% untilting, respectively, indicating that the remanence whose mean direction of D/I = 350.8°/57.9° (k = 177.9, α95 = 1.8°) at 20% untilting was acquired during or after tilting of the strata. The comparison of the paleomagnetic pole from the Chopyeong Formation with those from the Youngdong basin and the Euiseong area in the Gyeongsang basin indicates that the remanence was acquired during late Cretaceous to early Tertiary. Electron microscope observations and rock magnetic experiments show that secondary hematite and magnetite grains of single domain to pseudo-single domain size were authigenically formed under the influence of fluids presumably triggered by the igneous activities, thus confirm the chemical remagnetization.It is revealed that the age of the granite in the east is Jurassic because the mean direction of the east granite (D/I = 347.0°/47.7°, k = 40.2, α95 = 3.6°) is similar to the Jurassic direction of Korea Peninsula. The age of the granite in the west, however, is left undetermined whether it is Cretaceous or Jurassic because of the weak intensity and instability of the remanence of the granite during demagnetization treatments.

Paleointensity determination of Late Cretaceous basalts in northwest South Korea: implications for low and stable paleofield strength in the Late Cretaceous

To clarify geomagnetic field behavior in the Late Cretaceous, paleointensity and rock-magnetic studies were carried out on basalts with K-Ar ages of 78.6 ± 2.5 and 73.1 ± 1.6 Ma in northwest South Korea. A total of 314 samples (262 from six lava flows and 52 from massive basalts) were subjected to Thellier-type IZZI paleointensity experiments. Through the application of seven paleointensity selection criteria that mainly verify the thermal alteration of magnetic minerals and the stability of remanence direction, fifteen paleointensity data were obtained from five of the lava flows. Based on rock-magnetic experiments and microscopic observations, it is revealed that the measured paleointensity is carried by single-domain (titano)magnetite. The site-mean paleointensities ranged 13.1−21.3 μT, which corresponds to a virtual axial dipole moment of 2.3−3.8 × 1022 Am2. The combination of this result with selected data from the IAGA paleointensity database establishes the existence of different dipole moments according to rock type. In particular, the geomagnetic field strength recorded in Late Cretaceous crystalline volcanic rock was relatively low and stable, with a mean dipole moment of 4.0 ± 1.9 × 1022 Am2 regardless of geomagnetic field reversals.

Paleomagnetism and U-Pb geochronology of the late Cretaceous Chisulryoung Volcanic Formation, Korea: tectonic evolution of the Korean Peninsula

Late Cretaceous Chisulryoung Volcanic Formation (CVF) in southeastern Korea contains four ash-flow ignimbrite units (A1, A2, A3, and A4) and three intervening volcano-sedimentary layers (S1, S2, and S3). Reliable U-Pb ages obtained for zircons from the base and top of the CVF were 72.8 ± 1.7 Ma and 67.7 ± 2.1 Ma, respectively. Paleomagnetic analysis on pyroclastic units yielded mean magnetic directions and virtual geomagnetic poles (VGPs) as D/I = 19.1°/49.2° (α95 = 4.2°, k = 76.5) and VGP = 73.1°N/232.1°E (A95 = 3.7°, N = 3) for A1, D/I = 24.9°/52.9° (α95 = 5.9°, k = 61.7) and VGP = 69.4°N/217.3°E (A95 = 5.6°, N = 11) for A3, and D/I = 10.9°/50.1° (α95 = 5.6°, k = 38.6) and VGP = 79.8°N/242.4°E (A95 = 5.0°, N = 18) for A4. Our best estimates of the paleopoles for A1, A3, and A4 are in remarkable agreement with the reference apparent polar wander path of China in late Cretaceous to early Paleogene, confirming that Korea has been rigidly attached to China (by implication to Eurasia) at least since the Cretaceous. The compiled paleomagnetic data of the Korean Peninsula suggest that the mode of clockwise rotations weakened since the mid-Jurassic. Such interesting variation of vertical rotations in the Korean Peninsula might result from the strike-slip motions of major faults developed in East Asia (the Tancheng-Lujiang fault to the northwest and the Korea-Taiwan strait fault to the southeast), near-field tectonic forcing of the subducting Pacific Plate beneath the Eurasian Plate, and far-field expressions of the India-Asia collision.

Paleomagnetism on the Quaternary marine sediment at the DH-1 long-core site in the Korean continental margin of the East Sea

A long core of 23.6 m was acquired in the Korean continental margin of the western East Sea. The core site of the DH-1 is located in the offshore of the Donghae City and the water depth is 357.8 m deep. In this area, the paleomagnetism and magnetostratigraphy were firstly reported using 420 samples collected from the long-core sediments. Based on the inclination distribution of the depositional remanent magnetization, the DH-1 core could be divided into two upper and lower units at the boundary of 1750 cm below seafloor. The upper unit is characterized by a positive polarity, whereas the lower unit by a negative polarity. The boundary of the upper and lower units was interpreted as the Brunhes-Matuyama boundary (778 ka). The chemical components of tephra layer at 2014 cm below seafloor belong to alkaline series, plotted between the tephra components of the Mount Baekdu and Ulleung Island.

Paleomagnetic records and mineral-magnetic properties of deep-sea sediments in the NW pacific: Paleoenvironmental implication

The paleomagnetic records and mineral-magnetic properties of unconsolidated core sediment from the east Mariana Basin of the western Pacific have been analyzed to trace the time-dependent variations in sedimentary environments. Progressive alternating field demagnetization effectively extracts a stable remanent magnetization showing both normal and reverse polarities. Comparison of successive polarity changes, recorded in the sediment core, with reference magnetic polarity time-scale, reveals that the recovered sediment column was deposited since the late Pliocene. From the sediment age model, calculated sedimentation rate during the late Pliocene was 9.8 times higher than that during the Pleistocene. Considering the oceanic environments and geologic setting in the study area, the anomalous high sediment flux during the late Pliocene was probably caused by enhanced current flows, such as North Equatorial Current, associated with atmospheric circulation as well as by debris flows from adjacent sea mounts. In addition, the systematic variation of mineral-magnetic properties indicates periodical fluxes of coarse and magnetically stable particles, on the fine-grained dominant sedimentary environments. Such influxes, however, would not be related to syn-volcanic activities, because the summits of seamounts were totally blanketed by biogenic Pliocene-Pleistocene sediments. It is, hence, reasonable to interpret that paleomagnetic and mineral-magnetic data probably reflect drastic paleoenvironmental changes at the boundary between the Pliocene and Pleistocene, where strong current and atmospheric circulations decreased.

Paleomagnetic evidence for local oroclinal bending in the eastern Korean Peninsula

A paleomagnetic investigation has been carried out for the Lower Triassic Donggo Formation exposed in the Danyang area on the Yeongnam Massif to constrain local and regional tectonic history of the Taebaeksan Zone, Korean Peninsula. Among a total of 201 samples from 18 sites of the Donggo Formation, the characteristic remanent magnetization (ChRM) components were obtained from 166 samples. Field tests such as tilt test and reversal test reveal that the ChRM of the Donggo Formation is of primary in origin. The Early Triassic paleomagnetic pole position calculated from the site-mean directions of the primary magnetization is at 40.7°N, 17.8°E (A95 = 5.3°). Comparison of the reliable paleomagnetic poles from the Danyang (this study), Taebaek, and Yemi areas in the Taebaeksan Zone reveals a regional division of the pole position, indicating the clockwise vertical-axis rotation of the Taebaek area by 47.2 ± 11.1° with respect to the Danyang and Yemi areas after the formation of the Pyeongan Supergroup. In addition, there is a significant relation between strike deviations and declination deviations with some flattening of the regression line in the southern Taebaeksan Zone. Thus, it is interpreted that the Pyeongan Supergroup in this region had a primary curvature at the timing of sedimentation and subsequently experienced post-Early Triassic oroclinal bending of approximately 47°.

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

The anisotropy of magnetic susceptibility (AMS) of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k3 (minimum axis of magnetic susceptibility) and shallow dispersal of k1 (maximum axis of magnetic susceptibility) and k2 (intermediate axis of magnetic susceptibility). Dominance of oblate fabrics indicates clast imbrications imposed by compaction and welding. Flow azimuth inferred from AMS data indicates the nearby intrusive welded tuff (IWT) as the source of calderas for ignimbrites. Such an inference is supported by geologic investigations, in which the IWT displays eutaxitic textures nearly parallel to its subvertical contacts. The results are compatible with a unique prolate fabric and an anomalously high inclination observed for the IWT, possibly produced by rheomorphic flows as the welded tuff is squeezed along the rough-surfaced dyke walls due to agglutination.

METEORITES: ROCKS FROM THE OUTER SPACE

According to the historical documents and paintings in many civilizations, rocks that fell from the sky fascinated humans as the message from the God or supernaturals. Scientiflc progress allows humans to recognize these exciting extraterrestrial objects as meteorites. Meteorites contain a wealth of pivotal information regarding formation of the early Solar System. Meteorites also provide broader scientiflc insights on, for example, the origin of life, interplanetary transfer of life forms, massive depletion of biosphere on Earth, and evolution of lithosphere on Earth-like planetary bodies.