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Geological Structures of the Taean Formation in the Gomseom Area, Southwestern Gyeonggi Massif

경기육괴 남서부 곰섬 일대 태안층의 지질구조

  • Kim, Inho (Department of Geology, School of Earth System Science, Kyungpook National University) ;
  • Kim, Ae-Ji (Department of Geology, School of Earth System Science, Kyungpook National University) ;
  • Woo, Hayoung (Department of Geology, School of Earth System Science, Kyungpook National University) ;
  • Park, Seung-Ik (Department of Geology, School of Earth System Science, Kyungpook National University)
  • 김인호 (경북대학교 지구시스템과학부 지질학전공) ;
  • 김애지 (경북대학교 지구시스템과학부 지질학전공) ;
  • 우하영 (경북대학교 지구시스템과학부 지질학전공) ;
  • 박승익 (경북대학교 지구시스템과학부 지질학전공)
  • Received : 2019.04.03
  • Accepted : 2019.04.27
  • Published : 2019.04.28

Abstract

The western Gyeonggi Massif, where records evidence of Phanerozoic subduction/collision tectonics, is an important area to understand the crustal evolutionary history of the Korean Peninsula. This study presents geometric and kinematic characteristics of the geological structures of the Taean Formation in the Gomseom area, southwestern Gyeonggi Massif. We interpreted the geometric relationships between structural elements, and conducted stereographic and down-plunge projections for structural domains. As a result, at least three different deformational events ($D_1$, $D_2$ and $D_3$) are recognized in the study area. In the first deformational event ($D_1$), regional foliations being well defined by the preferred orientation of muscovite and biotite were formed. In the second deformational event ($D_2$), NNE-trending low-angle contractional faults and related crenulation lineations/cleavages were formed. The crenulation lineations shallowly plunge toward SSW~SSE or NNW~NNE. In the third deformational event ($D_3$), SE-plunging folds and NE-trending high-angle faults were formed as 'fault-related fold' and 'fold-accommodation fault', indicating that the $D_3$ folds and faults are genetically linked to each other. This contribution provides important insights into the structural evolution of the Taean Formation along western Gyeonggi Massif, where had evolved as subduction/collisional orogenic belts in the East Asia.

경기육괴 서부는 현생이언의 섭입/충돌 지구조운동을 기록하고 있어 한반도의 지각진화사를 이해하는데 매우 중요한 지역이다. 본 논문은 경기육괴 남서부 곰섬 일대에 분포하는 태안층에 대한 구조지질학적 연구 결과를 제시한다. 야외조사를 통해 획득한 구조요소들의 상관관계를 해석하고 구조구 별 하반구 투영 해석, 하향 투영 단면 작성을 수행한 결과, 연구지역 내에는 적어도 세 번의 서로 다른 변형작용($D_1$, $D_2$, $D_3$)이 인지된다. (1) 첫 번째 변형작용($D_1$)은 백운모와 흑운모의 정향배열로 뚜렷하게 정의되는 층리와 아평행한 광역엽리를 형성하였다. (2) 두 번째 변형작용($D_2$)과 관련하여 주로 북북동-남남서 방향을 가지는 저각의 수축성 단층과 이와 관련된 파랑습곡 및 벽개가 형성되었다. 파랑습곡의 힌지(파랑선구조)는 대체로 남남서~남남동 혹은 북북서~북북동 방향을 향해 저각으로 침강한다. 파랑벽개는 주로 서쪽으로 저각 경사하나 일부 구조구에서는 동쪽으로 경사하는 양상이 인지된다. (3) 세 번째 변형작용($D_3$)에서는 전반적으로 남동 방향으로 침강하는 힌지를 가지는 대규모 습곡들과 이와 관련된 북동-남서 방향의 단층들이 형성되었다. $D_3$ 변형에 의해 형성된 대규모 단층과 습곡의 경우 '단층 수반 습곡(fault-related fold)' 혹은 '습곡 수용 단층(fold-accommodation fault)'으로서 해석되며, 이는 기원적으로 상호 간 밀접한 관계를 가짐을 의미한다. 연구결과는 태안층 및 더 나아가 섭입/충돌 조산대로서 경기육괴 서부가 기록하고 있는 구조적인 진화사를 규명하는 데에 도움이 될 것으로 기대된다.

Keywords

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Fig. 1. Geological map of the Taean-Anmyeondo area (adapted from de Jong et al., 2014).

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Fig. 2. Outcrop photographs (a, b) and micrographs (c, d) of metasandstone and schist of the Taean Formation. Abbreviation - Qtz: Quartz, Bt: Biotite, Ms: Muscovite.

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Fig. 3. Structural map of the study area showing the location of following figures (satellite map from http://map.naver.com).

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Fig. 4. Equal area stereograms showing various structural components in each domain. Left stereogram: poles (contoured) to regional foliation (circle), π-axis (square), and hinges of the minor fold (triangle). Right stereogram: crenulation lineations (circle) and cleavages (great circle).

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Fig. 5. Profile constructed by down-plunge projection in each domain. The projection axes for domain 1-4 are 36.2°/120.6°, 53.2°/035.8°, 31.8°/130.7° and 53°/342.5°, respectively, that are selected from π-pole to fold (refer Figure 4). Bold black line: fault trace, Gray line: bed trace.

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Fig. 7. Outcrop photographs of D2 structures. Thrust fault (a) and related minor folds (b, c) showing top-up-to-the NW sense of shear. Low-angle contractional fault zone (d) and its cataclastic foliation (e) showing top-down-to-the SE sense of shear.

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Fig. 8. Outcrop photographs of D3 structures. NW-trending low-angle fault (a) and related minor folds (b, c) showing top-tothe NW sense of shear. (d) NE-trending high-angle fault showing anticlockwise block movement. (e) Out-of-hinge fault.

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Fig. 9. Equal area stereogram showing poles (contoured) to crenulation cleavage in all domains and π-axis (square) indicative of the overprint by a later folding event (D3).

JOHGB2_2019_v52n2_159_f0009.png 이미지

Fig. 6. (a) Outcrop photograph showing shallowly-plunging crenulation lineation. (b) Micrograph of crenulation cleavage. Abbreviation - Bt: Biotite, Ms: Muscovite.

References

  1. Berger, P. and Johnson, A.M. (1980) First order analysis of deformation of a thrust sheet moving over a ramp. Tectonophysics, v.70, p.9-24. https://doi.org/10.1016/0040-1951(80)90276-0
  2. Brandes, C. and Tanner, D.C. (2014) Fault-related folding: A review of kinematic models and their application. Earth-Sci. Rev., v.138, p.352-370. https://doi.org/10.1016/j.earscirev.2014.06.008
  3. Cho, M., Na, J. and Yi, K. (2010) SHRIMP U-Pb ages of detrital zircons in metasandstones of the Taean Formation, western Gyeonggi massif, Korea: Tectonic implications. Geosci. J., v.14, p.99-109. https://doi.org/10.1007/s12303-010-0011-7
  4. Cho, M., Lee, Y., Kim, T., Cheong, W., Kim, Y. and Lee, S.R. (2017) Tectonic evolution of Precambrian basement massifs and an adjoining fold-and-thrust belt (Gyeonggi Marginal Belt), Korea: An overview. Geosci. J., v.21, p.845-865. https://doi.org/10.1007/s12303-017-0044-2
  5. Choi, P.-Y., Rhee, C.W., Lim, S.-B. and So, Y. (2008) Subdivision of the Upper Paleozoic Taean Formation in the Anmyeondo-Boryeong area, west Korea: a preliminary approach to the sedimentary organization and structural features. Geosci. J., v.12, p.373-384. https://doi.org/10.1007/s12303-008-0037-2
  6. Choi, P.-Y., Kihm, Y.H., Chun, H.Y. and Hwang, J.H. (2015) Geological report of the Anmyeondo. Wonsando.Hwangdo.Oeyeondo.Hodo sheets. KIGAM, 80p (in Korean with English abstract).
  7. Dahlstrom, C.D.A. (1970) Structural geology in the eastern margin of the Canadian Rocky Mountains. Bull. Can. Petrol. Geol., v.18, p.332-406.
  8. de Jong, K., Han, S.Y., Ruffet, G. and Yi, K. (2014) First age constraints on the timing of metamorphism of the Taean Formation, Anmyeondo: concordant 233 Ma U-Pb titanite and 231-229 Ma $^{40}Ar/^{39}Ar$ muscovite ages. J. Geol. Soc. Korea, v.50, p.593-609 (in Korean with English abstract). https://doi.org/10.14770/jgsk.2014.50.5.593
  9. de Jong, K., Han, S. and Ruffet, G. (2015) Fast cooling following a Late Triassic metamorphic and magmatic pulse: implications for the tectonic evolution of the Korean collision belt. Tectonophysics, v.662, p.271-290. https://doi.org/10.1016/j.tecto.2015.06.016
  10. Deng, H., Zhang, C. and Li, H.L. (2009) Fold-accomodation faults and its implications (in Chinese with English abstract). Pro. Nat. Sci., v.19, p.285-296. https://doi.org/10.1016/j.pnsc.2008.07.009
  11. Deng, H., Zhang, C. and Koyi, H.A. (2013) Identifying the characteristic signatures of fold-accommodation faults. J. Struct. Geol., v.56, p.1-19. https://doi.org/10.1016/j.jsg.2013.08.006
  12. Drozdzewski, G. and Wrede, V. (1994) Faltung und Bruchtektonik-Analyse der Tektonik im Subvaricikum. Fortschritte Geologie von Rheinland und Westfalen, v.38, p.7-187.
  13. Gray D.R. (1987) Crenulation cleavages. In: Structural Geology and Tectonics. Encyclopedia of Earth Science Series. Springer, Berlin, Heidelberg, 878p.
  14. Han, S. (2014) Age constraints on sedimentation and metamorphism of the Taean Formation obtained by SHRIMP U-Pb and $^{40}Ar/^{39}Ar$ laser probe geochronology. MSc. Thesis, Seoul National University, Seoul, 75p.
  15. Han, S., de Jong, K. and Yi, K. (2017) Detrital zircon ages in Korean mid-Paleozoic meta-sandstones (Imjingang Belt and Taean Formation): Constraints on tectonic and depositional setting, source regions and possible affinity with Chinese terranes. J. Asian Earth Sci., v.143, p.191-217. https://doi.org/10.1016/j.jseaes.2017.04.028
  16. Jamison, W. (1987) Geometric analysis of fold development in overthrust terranes. J. Struct. Geol., v.9, p.207-219. https://doi.org/10.1016/0191-8141(87)90026-5
  17. Johnson, A.M. (1980) Folding and faulting of strain-hardening sedimentary rocks. Tectonophysics, v.62, p.251-278. https://doi.org/10.1016/0040-1951(80)90196-1
  18. Kim, S.W., Oh, C.W., Williams, I.S., Rubatto, D., Ryu, I.-C., Rajesh, V.J., Kim, C.-B., Guo, J. and Zhai, M. (2006) Phanerozoic high-pressure eclogite and intermediate-pressure granulite facies metamorphism in the Gyeonggi Massif, South Korea: Implications for the eastward extension of the Dabie-Sulu continental collision zone. Lithos, v.92, p.357-377. https://doi.org/10.1016/j.lithos.2006.03.050
  19. Kim, S.W., Williams, I.S., Kwon, S. and Oh, C.W. (2008) SHRIMP zircon geochronology and geochemical characteristics of metaplutonic rocks from the south-western Gyeonggi Block, Korea: implications for Paleoproterozoic to Mesozoic tectonic links between the Korean Peninsula and eastern China. Precambrian Res., v.162, p.475-497. https://doi.org/10.1016/j.precamres.2007.10.006
  20. Kim, S.W., Kwon, S., Santosh, M., Cho, D.L. and Ryu I.-C. (2014) Detrital zircon U-Pb geochronology and tectonic implications of the Paleozoic sequences in western South Korea. J. Asian Earth Sci., v.95, p.217-227. https://doi.org/10.1016/j.jseaes.2014.05.022
  21. Kim, S.W., Kwon, S., Park, S.-I., Yi, K., Santosh, M. and Kim, H.S. (2017) Early to Middle Paleozoic tectono-metamorphic evolution of the Hongseong area, central western Korean Peninsula: Tectonic implications. Gondwana Res., v.47, p.308-322. https://doi.org/10.1016/j.gr.2016.05.016
  22. Kim, S.W., Cho, D.-L., Lee, S.-B., Kwon S., Park, S.-I., Santosh, M. and Kee, W.-S. (2018) Mesoproterozoic magmatic suites from the central-western Korean Peninsula: Imprints of Columbia disruption in East Asia. Precambrian Res., v.306, p.155-173. https://doi.org/10.1016/j.precamres.2017.12.038
  23. Kwon, S., Sajeev, K., Mitra, G., Park, Y., Kim, S.W. and Ryu, I.-C. (2009) Evidence for Permo-Triassic collision in Far East Asia: The Korean collisional orogen. Earth Planet. Sci. Lett., v.279, p.340-349. https://doi.org/10.1016/j.epsl.2009.01.016
  24. Lim, S.B., Choi, H.I., Kim, B.C. and Kim, J.C. (1999) Depositional systems of the sedimentary basin (I): Depositional systems and their evolution of the Proterozoic Paegryeong Group and Taean Formation. MOST/KIGAM, 116p.
  25. Marrett, R. and Bentham, P.A. (1997) Geometric analysis of hybrid fault-propagation/detachment folds. J. Struct. Geol, v.19, p.243-248. https://doi.org/10.1016/S0191-8141(96)00092-2
  26. Marshak, S. and Mitra, G. (1988) Basic Methods of Structural Geology. Prentice Hall, New Jersey, 464p.
  27. Mitra, S. (1990) Fault-propagation folds: geometry, kinematic evolution, and hydrocarbon traps. AAPG Bull., v.74, p.921-945.
  28. Mitra, S. (2002) Fold-accommodation faults. AAPG Bull., v.86, p.671-693.
  29. Na, J., Kim, Y., Cho, M. and Yi, K. (2012) SHRIMP U-Pb Ages of Detrital Zircons from Metasedimentary Rocks in the Yeongheung-Seonjae-Daebu Islands, Northwestern Gyeonggi Massif. J. Petrol. Soc. Korea, v.21, p.31-45 (in Korean with English abstract). https://doi.org/10.7854/JPSK.2012.21.1.031
  30. Oh, C.W., Kim, S.W., Choi, S.G., Zhai, M., Guo, J. and Sajeev, K. (2005) First finding of eclogite facies metamorphic event in South Korea and its correlation with the Dabie-Sulu collision belt in China. J. Geol., v.113, p.226-232. https://doi.org/10.1086/427671
  31. Oh, C.W., Imayama, T., Yi, S.-B., Kim, T., Ryu, I.-C., Jeon, J. and Yi, K. (2014) Middle Paleozoic metamorphism in the Hongseong area, South Korea, and tectonic significance for Paleozoic orogeny in northeast Asia. J. Asian Earth Sci., v.95, p.203-216. https://doi.org/10.1016/j.jseaes.2014.08.011
  32. Oh, C.W., Imayama, T., Jeon, J. and Yi, K. (2017) Regional Middle Paleozoic metamorphism in the southwestern Gyeonggi Massif, South Korea: Its implications for tectonics in Northeast Asia. J. Asian Earth Sci., v.145, p.542-564. https://doi.org/10.1016/j.jseaes.2017.06.030
  33. Park, S.-I., Kim, S.W., Kwon, S., Thanh, N.X., Yi, K. and Santosh, M. (2014a) Paleozoic tectonics of the southwestern Gyeonggi massif, South Korea: Insights from geochemistry, chromian-spinel chemistry and SHRIMP U-Pb geochemistry. Gondwana Res., v.26, p.684-698. https://doi.org/10.1016/j.gr.2013.07.015
  34. Park, S.-I., Kwon, S., Kim, S.W., Yi, K. and Santosh, M. (2014b) Continental origin of the Bibong eclogite, southwestern Gyeonggi massif, South Korea. J. Asian Earth Sci., v.95, p.192-202. https://doi.org/10.1016/j.jseaes.2014.08.024
  35. Park, S.-I., Kim, S.W., Kwon, S., Santosh, M., Ko, K. and Kee, W.-S. (2017) Nature of Late Mesoproterozoic to Early Neoproterozoic magmatism in the western Gyeonggi massif, Korean Peninsula and its tectonic significance. Gondwana Res., v.47, p.291-307. https://doi.org/10.1016/j.gr.2016.11.006
  36. So, Y.S., Rhee, C.W., Choi, P.-Y., Kee, W.-S., Seo, J.Y. and Lee, E.-J. (2013) Distal turbidite fan/lobe succession of the Late Paleozoic Taean Formation, western Korea. Geosci. J., v.17, p.9-25. https://doi.org/10.1007/s12303-013-0016-0
  37. Suppe, J. (1983) Geometry and kinematics of fault-bend folding. Am. J. Sci, v.283, p.684-721. https://doi.org/10.2475/ajs.283.7.684
  38. Wrede, V. (2005) Thrusting in a folded regime: fold accommodation faults in the Ruhr basin, Germany. J. Struct. Geol, v.27, p.789-803. https://doi.org/10.1016/j.jsg.2005.01.008