• Journal of the Korean earth science society
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• v.22 no.2
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• pp.105-111
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• 2001

Seven specimens of raindrop imprints are discovered from the Late Triassic Amisan Formation of Nampo Group distributed in the Myeongam area of Boryeong-City, Chungcheongnam-do. The raindrop imprints are interpreted to had been formed in lacustrine environments under subtropical humid climate during the lowered period of the surface of the water by temporally or seasonally arid climate. The raindrop imprints are the first finding in the Lower MesozoicNampo Group, Korea.

• Journal of the Korean earth science society
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• v.34 no.5
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• pp.402-406
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• 2013

Since 1984, the author has been studying the Daedong flora and has collected a large number of fossil plants from the Amisan Formation of Nampo Group distributed in Chungnam Coal-Field. One of the fossil plants was bennettitalean male flower, which was collected in 1986. The author described it as Weltrichia sp. The occurrence of Weltrichia sp. is the first record in the Early Mesozoic Daedong flora of Korea.

• Journal of the Korean earth science society
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• v.31 no.5
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• pp.430-436
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• 2010

Some materials belonging to the Leptostrobus myeongamensis Kim were found in the Upper Triassic Amisan Formation, Nampo Group, Korea. This species is closely associated with the foliage of Czekanowskia ex gr. rigida Heer. Although none of Leptostrobus myeongamensis Kim has been found in organic connection with Czekanowskia leaves, it is considered that they belong to the same taxa based on their common occurrence. The occurrence of Leptostrobus myeongamensis Kim from the Late Triassic floras of Korea is one of the oldest records in the Mesozoic floras found in the world.

• Journal of the Korean earth science society
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• v.23 no.1
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• pp.30-37
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• 2002

Leptostrobus myeongamensis sp. nov. is newly described from the well-preserved but broken material occurring in the Upper Triassic Amisan Formation of the Nampo Group in Korea. This species is characterized by its lateral appendages of cone axis, each consisting of a rounded capsule and small scale leaf, and by its cone base covered with small scale leaves, the same size as in cone axis. This species is the first record from the Mesozoic strata in Korea.

• Journal of the Korean earth science society
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• v.25 no.1
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• pp.32-38
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• 2004

Some fine specimens of Annulariopsis bunkeiensis were collected from two fossil sites of the Amisan Formation of Nampo Group distributed in the Jogaegol, Boryeng City, Chungnam Province. According to our detailed study from our new material, the leaves of A. bunkeiensis are not mucronate, but emarginate at their apices. Accordingly, we revised the diagnostic characters given by Kimura and Kim (1988) mainly in regard to the leaf apex.

• Journal of the Korean earth science society
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• v.35 no.3
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• pp.161-167
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• 2014

Recently, a winged insect fossil the Mecoptera has been discovered for the first time in the Late Triassic Amisan Formation in the Boryeong area, Chungnam, Korea. The fossil is classified as Mesopsyche dobrokhotovae based on the characteristics of wing venation. Insect fossils which belong to this Genus show worldwide distribution in the Late Triassic, making it possible to estimate that they thrived in this period. Extant Mecoptera survive in humid environments by hanging onto tree leaves or stems and eating other small insects. Compared to the ecology of extant Mecoptera, the presence of the fossil Mecoptera indicates that the paleoenvironment in Nampo Group was very similar to the present during the Late Triassic Period. Mesopsyche dobrokhotovae is the first Mecoptera occurrence and one of the oldest insect fossil occurrences in Korea.

• The Journal of the Petrological Society of Korea
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• v.17 no.1
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• pp.1-15
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• 2008

The metasedimentary rocks of the Nampo Croup consisting of metaconglomerates, metasandstones, phyllites are exposed in the area of the Daechcon beach and Maryangri, Seocheon-gun. Their typical metamorphic assemblages of Bt-Mus-Grt-Qtz (${\pm}Pl{\pm}Chl$) and Bt-Mus-Qtz (${\pm}Pl{\pm}Chl$) indicate that they have been under intermediate P/T type metamorphism and were metamorphosed to garnet zone grade of amphibolite-facies during the Daebo Orogeny. Pressure-temperature conditions of peak metamorphism estimated from geothermobarometries are $560{\sim}595^{\circ}C$, $6.9{\sim}8.2\;kb$ respectively. The results of K-Ar biotite age determination are $143.2{\pm}3.6\;Ma$, $122.6{\pm}2.4\;Ma$ and $124.8{\pm}2.4\;Ma$ and the last two ages are considered as the results of later-stage thermal perturbation. On the bases of the formation age of Daedong Supergroup of $187{\sim}172\;Ma$ (Han et al., 2006; Jeon et al., 2007) combined with the results of this study, the hypothetical model of tectonometamorphic evolution of the study area during Daebo Orogeny is proposed. Crustal thickening resulted from folding and duplexing of thrusts in the area initiated at around 175 Ma just after sedimentation of Nampo Croup. And then rapid cooling by normal faulting due to crustal extention followed immediately after the peak metamorphism to the closure temperature of biotite.

• 한국지구과학회:학술대회논문집
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• 2003.09a
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• pp.69-70
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• 2003

• Journal of the Korean earth science society
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• v.29 no.6
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• pp.466-473
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• 2008

This study deals with the morphological characteristics and structure of organ fossils of Neocalamites carrerei such as rhizomes, aerial leafy stems, and cones collected in situ from the Amisan Formation of Nampo Group. Judging from the size of some extant Equisetum and paleoclimate of Daedong flora, it is considered that the size of Neocalamites carrerei was probably very large. The cone of Neocalamites takahashii (Kon'no) is closely associated with the leaves of Neocalamites carrerei. It indicates that two organ fossils mentioned above probably belong to the same species. Comparing with very abundant occurrence of aerial leafy stems and rhizomes in the Amisan Formation, cones are very rare. This fact implies that Neocalamites reproduce not only by spore reproduction, but also by asexual reproduction. Neocalamites largely differ in the leaf form and size from Equisetum.

• Economic and Environmental Geology
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• v.22 no.2
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• pp.129-139
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• 1989

The anthracite coalfields of Korea are confined to the areas where sedimentary rocks of Permian and Jurassic are preserved. The Chungnam coalfield lies in the sedimentary rocks of Jurassic which belongs to the Daedong Supergroup (the Nampo group). For the property analysis of each coal seam interbeded in Daedong Supergroup, Seongju area is chosen and twelve coalseams are taken. Many standard tests have been established for optical analysis (maceral analysis, coalification degree measurement), chemical analysis (proximate, ultimate analysis) and physical analysis (ignition temperature, ash fusion temperature, hardgrove grindability index and X-ray diffraction). The Jurassic anthracite mainly consist of vitrinite and macrinite and the range of the reflectance is $R_{max}$ 5.0-6.5 which means metaanthracite rank. By the chemical composition analysis, it shows low H/C and high O/C value compare with international average value. By the physical analysis, it has very high ignition temperature ($531-584^{\circ}C$) and ash fusion temperature ($1510-1700^{\circ}C$) and very low combustion velocity (0.2-1.9 mg/min). The very wide range of the hardgrove grindability index (46-132) means that the grindability controlled mainly by the structural conditions of coal bearing strata.