• Economic and Environmental Geology
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• v.45 no.4
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• pp.465-476
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• 2012

The Anatolia peninsula consists of several continental fragments that include the Pontide Block in north and the Anatolide-Touride Block in south as well as the Arabian Platform in southeast. These continental blocks were joined together into a single landmass in the late Tertiary. During most of the Phanerozoic these continental blocks were separated by paleo-oceans, such as Paleo-Tethys and Neo-Tethys. The Pontide Block in north show Laurasian affinities, and was only slightly affected by the Alpide orogeny; they preserve evidence for the Variscan and Cimmeride orogenies. The Pontic Block is composed of the Strandja, Istanbul and Sakarya zones that were amalgamated into a single terrane by the mid Cretaceous times. The Anatolide-Tauride Block in south shows Gondwana affinities but was separated from Gondwana in the Triassic and formed an extensive carbonate platform during the Mesozoic. The Anatolide-Tauride Block was intensely deformed and partly metamorphosed during the Alpide orogeny; this leads to the subdivision of the Anatolide-Tauride Block into several zones on the basis of the type and age of metamorphism and deformation. The Arabian Platform in southeast forms the northernmost extension of the Arabian Plate that shows a stratigraphy similar to the Anatolide-Tauride Block with a clastic-carbonate dominated Palaeozoic and a carbonate dominated Mesozoic succession. A new tectonic era started in Anatolia Peninsula in the Oligocene-Miocene after the final amalgamation of these continental blocks and plate. This neotectonic phase is characterized by extension, and strike-slip faulting, continental sedimentation, and widespread calcalkaline magmatism, which played a very important role in producing beautiful landscapes of the Anatolia Peninsula today.

• 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.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.13-26
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• 2022

Calcite twins were analyzed in six oriented samples of the Pungchon limestone, Joseon Supergroup, to reconstruct the paleostress field. The orientations of c-axis of calcite and e twin plane were measured along with the average thickness and numbers of twins, and the widths of calcite grains. Twin strain, mean width, and intensity of twinning, and the relative magnitude and orientations of principal stresses were calculated using Calcite Strain Gauge program. Twin strain, mean width, and intensity of twinning showed ranges of 1.09-15.36%, 0.53-3.72 ㎛ and 21.0-53.1 twim/mm, respectively. Metamorphic temperatures calculated from the twins were 170-200℃, indicating that the twins developed after the Pungchon limestone was uplifted to at least half of the maximum burial depth. Results for five of the samples indicate that the calcite twins formed during two events with principal stress axes of different orientations, while the remaining sample recorded only one event that produced calcite twins. The axis of maximum compressive stress was oriented mainly WNW-ESE to ENE-WSW, and to a lesser degree NW-SE and NE-SW. Comparison of paleostress orientations measured here and in other studies indicates that most twins were produced during the Songrim orogeny. However, the Daebo orogeny and the Bulguksa orogeny also produced calcite twins in the Punchon limestone.

• Journal of the Korea Construction Safety Engineering Association
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• s.51
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• pp.30-43
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• 2010

Yehliu is located at Wanli of Taipei Country with a long cape. Because the rock layer of nearby seashore contains limestone subject to sea erosion, weathering and earth movements, Yehliu is full of seawater-eroded holes as well as numerous rocks in the shape of mushroom, candle, ginger, and chessboard. All these make this 1,700-meter-long cape a geology park with rich ecological resources and a prosperous fishing village. It indicates how the geological features formed by the foundation orogeny and collapsed due to the marine erosion over thousands of years.

• The Journal of Engineering Geology
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• v.24 no.3
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• pp.311-322
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• 2014

Limestone bodies under the tectonic environment have experienced various tectonic processes, and also changed the stress state. In this study, calcite twins found in limestones of the Joseon Supergroup and Pyeongan Supergroup in the northeastern part of the Ogcheon Belt, South Korea were measured, then the paleostress (i.e., the maximum shortening axis) was reconstructed using the new calcite strain gauge (NCSG) technique. The average twin thickness and average twin intensity increase as the total twin strain increases. We utilize the appearance of twins, the average twin thickness and average twin intensity, and the total twin strain to estimate that the observed calcite twins were produced at temperatures of < $200^{\circ}C$ in the Joseon Supergroup and $170^{\circ}C$ in the Pyeongan Supergroup. In the Joseon Supergroup, the dominant direction of the maximum shortening axis WNW-ESE to NW-SE; NE-SW shortening is also observed. The maximum shortening axes in the Pyeongan Supergroup are oriented NW-SE and NE-SW. The NE-SW direction of maximum shortening is associated with the occurrence of the Songrim orogeny of the Paleozoic to Early Jurassic, and the NW-SE direction of maximum shortening correlates to the Daebo orogeny of the Early Jurassic to Late Jurassic. It is thus concluded that the paleostress across the study area changed from NE-SW to NW-SE during the Mesozoic.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.121-137
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• 2002

Metamorphic evolution of the Ogcheon metamorphic belt has been studied by many investigators for the past few decades. P-T conditions of the Ogcheon metamorphic belt were estimated as 4.2-9.4 kbar and $490-630^{\circ}C$, corresponding to the medium-pressure type. In addition, the clockwise P-T-t path suggests a crustal-thickening event in association with the formation of thrust nappes. However, some details on deformation and orogeny of the Ogcheon metamorphic belt have been ambiguous yet. Although the metamorphic age has been also equivocal, recent isotopic studies strongly suggest that the peak metamorphism in the Ogcheon metamorphic belt has occurred at ca. 300-280 Ma between Late Carboniferous and Early Permian. It is thus inferred that the Ogcheon metamorphic belt and the Taebaegsan basin have evolved as separate terranes and that both were sutured at ca. 250-220 Ma. These results are partly in contrast with those of previous workers and require a revised framework for tectonic evolution of the Ogcheon belt. In addition, it is likely that the Ogcheon belt is correlative with the Hida marginal belt and the Hida metamorphic belt.

• Economic and Environmental Geology
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• v.1 no.1
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• pp.35-46
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• 1968

Some of geologists in Korea recently postlated that Okchon system previously known to be precambrian age was the metamorphosed sediments of post-Chosen (Ordovician and pre-Kyeongsang (late Jurassic to Cretaceous) periods, or even definitely of Triassic period simply on the basis of the fact that Okcheon system overlies the Great Limestone series of Chosen system of Camber-ordovician age, and of other few assumptions of minor importance. As a result of such correlation, thick series of metasediments and Okcheon system of unknown age were established in this particular region and vaguely correlated to Paleozoic and Mesozoic sediments. Recent study done by the author reveled that: 1) only the upper Okcheon bed of S. Nakamura was true Okcheon system, and the middle and lower Okcheon beds were excluded, because they were correlated to Cambrian and Permian sediments resfectively, 2) Sangnaeri, Seochangri, and rengam formations of unknown age, and Baekhwasan, Jobong, and Ihwaryeong formations of Okcheon system of also unknown age were the metamorphosed Yangdeok system of Cambrian age, all of these formations were differentiated by the previous workers and were equivalent to the middle Okcheon system of S. Nakamure, and. 3) These metamorphosed Yangdeok system overlaid apparently the Great Limestone series in forms of overthrust and klippe which were produced by the orogeny took place during post-Daedong and pre-Kyeongsang period (probably middle to the Jurassic). The Sobaeksan Range, folded mountain Chains was also formed by this orogeny. Thus, Okcheon system newly defined by the author is precambrain age and consists in ascending order of Kemyenogsan, Hyangsan dolomite, and Daehangsan quartzite formation which were previously classified into metasediments of unknown age, and Munjuri, and Hwangkanri, formations which were differentiated into Okcheon system unknown age by the previous workers, but are of reversed sequence. Myeongori and Bukrori formations of Okcheon System are regard by the author as part of Hwangkanri formation. Few other assumption of minor important taken by the previous workers as their positive evidences are carefully explained that they were misinterpreted.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2002.05a
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• pp.1-3
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• 2002

The eastward extension of the suture zone between the Sino-Korea and Yangtze cratons in the Korean Peninsula and Japanese islands remains debatable (Hiroi, 1981; Cluzel et al., 1991; Yin and Nie, 1993; Sohma and Kunugiza, 1993; Isozaki, 1997; Arakawa et at., 2000), and is related to our understanding of the continent-continent collision orogeny. The collision orogeny varies in tectono-metamorphic processes and the timing differs from place to place, as exemplified by the absence of coesite and micro-diamond in the Korean Peninsula and Japanese islands, because it is a long-lived process of more than several tens of million years from subduction to exhumation in the Wilson cycle, and because the suture zone extends more than several thousand kilometers with a curved shape from the Qinling area of China to the Hida highland area of Japan. Hiroi (1981) is the first paper to correlate the Unazuki metamorphic rocks of the Hida metamorphic belt in Japan with the Ogcheon belt in the Korean Peninsula based on the presence of 240 Ma medium P/T metamorphic rocks in both belts, but there is a lack of recent studies on this correlation. To resolve the correlationship, there are two approaches: 1) petrological studies characterizing the origin and P-T history of rocks and 2) in-situ micro-dating of fine-grained, zoned minerals of zircon, monazite, uraninite and thorite using the EPMA (U-Th-Pb chemical dating or CHIME depending on calibration method) and the SHRIMP (Sensitive High-resolution ion Microprobe) to decipher the timing of geological events. As a first step of these approaches, micro-dating was undertaken to rocks of the Hida metamorphic belt and its Mesozoic cover (Tetori Group) in the Hida highland area, central Japan.

• Economic and Environmental Geology
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• v.2 no.4
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• pp.73-90
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• 1969

The area studied is a southwestern part of Okcheon geosynclinal zone which streches diagonally across the Korean peninsula in the mid-central parts of South Korea, and is bounded by Charyeong mountain chains in the north and by Sobaek mountain chains in the south. The general trend of the zone is of NE-SW direction known as Sinian direction. Okcheon system of pre-Cambrian age occupies southwestern portion of Okcheon geosynclinal zone, and Choseon and Pyeongan systems of Cambrian to Triassic age in northeastern portion of the zone. It was defined by the writer that the former was called "Okcheon Paleogeosynclinal zone" and the latter "Okcheon Neogeosynclinal zone," although T. Kobayashi named them "Metamorphosed Okcheon zone" and "Non-metamorphosed Okcheon zone" respectively and thought that sedimentary formations in both zones were same in origin and of Paleozonic age, and C.M. Son also described that Okchon system was of post-Choseon (Ordovician) and pre-Kyeongsang (Cretaceous) in age. According to the present study two zones are separated by great fault so that the geology in both zones is not only entirely different in origin and age, but also their geolosical structures are discontinuous. Stratigraphy and structure of Okcheon system are clearly established and defined by the writer and its age is definitely pre-Cambrian. It is clarified by present study that the meta-sediments in and at vicinity of Charyeong mountain chains are correlated to Weonnam series of pre-Cambrian age which occupies and continues from northeast to southwest in and at south of Sobaek mountain chains, and both metasediments constitute basement of Okcheon system. Pyeongan, Daedong and Kyeongsang systems were deposited in few narrow intermontain basins in Okcheon paleogeosynclinal zone after it was emerged at the end of Carboniferous period. Granites of Jurassic and Cretaceous ages and volcanics of Cretaceous age are cropped out in the zone. Jurassic granite is aligned generally with the trend of Okcheon geosynclinal zone, whereas Cretaceous granite lacks of trend in distribution. Many isoclinal folds and thrust faults caused by Taebo orogeny at the end of Jurassic period are also parallel with Sinian directieon and dip steeply to northwest. Charyeong, Noryeong, Sobaek, and Deogyu mountain chains are located in areas of anticlinorium, and Kyongsang system in narrow synclinal zones. Folds in Okcheon neogeosynclinal zone are generally of N 70-80W direction but deviate to Sinian direction at the western parts of the zone. This phenomena is interpreted by the fact that the folds were originated by Songrim disturbance at the end of Triassic period and later partly modified by Taebo orogeny. Thrust faults of Taebo orogeny coentinue from Okcheon paleogeosynclinal zone into neogeosynclinal zone, forming imbricated structure as previously described. Strike-slip faults perpendicular to Sinian direction and shear faults diagonally across it by 55 degrees also prevail in neogeosynclinal zone. It is concluded from viewpoints on geology and geological structure that l)Okchon geosyncline had changed its location and affected by numerous disturbances through geologic time, and 2)mountain chains in the area such as Charyeong, Noryeong, Sobaek, and Deogyu were originated as folded mountains. Differing from others, however, Sobaek range was probably formed at the time of Songrim disturbance and modified later by Taebo orogeny. It is cut by Danyang-Jeomchon fault at the vicinity of Joryeong near Munkyeong village and does not continue to southwest beyond the fault, whereas southwestern portion of erstwhile Sobaek range continues to Taebaek rangd northeastward from Deogyusan passing through Sangju, Yecheon, and Andong. From these evidences, the writer has newly defined the erstwhile Sobaek range in such a way that Sobaek range is restricted only to northeastern portion and Deogyu range is named for the southwestern portion of previous Bobaek range.

• Economic and Environmental Geology
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• v.21 no.1
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• pp.69-83
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• 1988

Orthogneiss of the study area is meta-igneous complex that composed of granite gneiss, porphyroblastic gneiss and migmatitic gneiss. Migmatitic gneiss produced from granite gneiss and porphyroblastic gneiss by strong ductile shearing. These rocks show mostly gneissic and partly mortar textures by strong regional metamorphism and ductile shearing during several orogenies. $^{40}Ar-^{39}Ar$ incremental-release ages of these rocks have been determined for 1 hornblende. 1 biotite and 3 muscovite concentrates separated from orthogneisses in this area. Ages of regional metamorphism and ductile shearing of these rocks are more than 5 stages(1500 Ma, 260 Ma, 190 Ma, 180-170 Ma and 160 Ma) under $300^{\circ}C$ to $500^{\circ}C$. These rocks had not been nearly effected by Daebo orogeny, because this area is far from Daebo granite bodies. The general trend of major chemical composition and mineral composition of these orthogneisses suggest that these rocks are some series of differentiated products from magma.