The Journal of the Petrological Society of Korea (암석학회지)

The Petrological Society of Korea (한국암석학회)
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Flow Directions and Source of the Dongmakgol Tuff in the Cheolwon Basin, Korea

철원분지 동막골응회암의 유향과 공급지

  • Hwang, Sang-Koo (Department of Earth and Environmental Sciences, Andong National University) ;
  • Kim, Jae-Ho (Department of Earth and Environmental Sciences, Andong National University)
  • 황상구 (안동대학교 자연과학대학 지구환경과학과) ;
  • 김재호 (안동대학교 자연과학대학 지구환경과학과)
  • Received : 2010.01.25
  • Accepted : 2010.03.02
  • Published : 2010.03.31
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Abstract

The Dongmakgol Tuff is a stratigraphic unit which is composed of voluminous ignimbrites in the Cheolwon basin. The ignimbrites belong to pumice-rich vitric tuffs that show eutaxitic to parataxitic fabrics from fiamme or pumice clasts. They are almost densely welded and strongly flattened, but often parallel aligned and stretched. Also they exhibit flow indicators such as flow lineations, imbrications, tensional cracks and boudins from their alignment and/or elongation, and lithic and pumice clasts show lateral grading in their average maximum diameter. Flow direction map from the lineations, asymmetric structures and lateral grading diagram indicate that the Dongmakgol Tuff has a source from its southwestern part near a boundary between southern Dongmakri and northern Gomunri, and is considered that the ignimbrites took emplacement processes of laminar flows during the final stage of flowage and the flow lineations are from the result of shear stress during that times.

동막골응회암은 철원분지에서 큰 용적의 화쇄류암으로 구성되는 하나의 층서단위이다. 이 화쇄류암은 부석풍부 파리질응회암에 속하며, 부석편 혹은 피아메가 대부분 심하게 편평화되고 치밀 용결되어 있지만 평행 배열되고 신장되어 있다. 이들은 배열과/혹은 신장에 의한 유상선구조, 와상배열, 인장틈과 부딘구조 등과 같은 흐름지시자를 보여주고 평균최대 암편과 부석편들은 측방으로 입도변화를 나타낸다. 동막골응회암에서 유상선구조에 의한 유향도, 암편과 부석의 여러 비대칭 구조, 평균최대 암편과 부석 입경의 측방점이도 등에 따르면, 이 응회암을 집적시킨 화쇄류는 동막리 남부와 고문리 북부의 경계부 근처에서 공급되었다. 이 응회암을 집적시킨 화쇄류는 흐름의 마지막 단계에 층류로 이동하였으며, 유상선구조는 이때 화쇄류의 일차성 흐름으로 전단력에 의한 정치과정을 겪은 것으로 판단된다.

Keywords

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