Journal of the Geological Society of Korea (지질학회지)

The Geological Society of Korea (대한지질학회)
권호 표지

Upper Ordovician and Silurian deposits in the Pyeongnam Basin: Songrim Conglomerate and its paleogeographic implication

평남분지의 하부와 중부 고생대층: 송림역암의 고지리적 의의

  • Lee, Dong-Jin (Department of Earth & Environmental Sciences, Andong National University) ;
  • Choi, Yong-Mi (Department of Earth & Environmental Sciences, Andong National University) ;
  • Lee, Dong-Chan (Department of Heritage Studies, Daejeon Health Sciences College) ;
  • Lee, Jeong-Gu (Exhibition Planning and Coordination Division, Gwacheon National Science Museum) ;
  • Kwon, Yi-Kyun (Department of Geoenvironmental Sciences, Kongju National University) ;
  • Cao, Lin (College of Earth Science, Jilin University) ;
  • Choh, Suk-Joo (Department of Earth and Environmental Sciences, Korea University)
  • 이동진 (안동대학교 지구환경과학과) ;
  • 최용미 (안동대학교 지구환경과학과) ;
  • 이동찬 (대전보건대학교 문화재과) ;
  • 이정구 (국립과천과학관) ;
  • 권이균 (공주대학교 지질환경과학과) ;
  • 조림 (중국길림대학 지구과학학원) ;
  • 조석주 (고려대학교 지구환경과학과)
  • Published : 2013.02.28
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Abstract

In 1934, Silurian corals were discovered in the base of the Early Jurassic Daedong Supergroup exposed at Gyeomeepo of Hwangju-Gun, Hwanghae Province. The discovery hinted the possibility of the presence of Middle Paleozoic strata in the Korean Peninsula. Subsequent works revealed that only clasts in the "Gyeomeepo calcareous conglomerate" (later renamed as the "Songrim Conglomerate") yield Silurian or Late Ordovician to Carboniferous fossils. The Songrim Conglomerate constitutes the base of the Songrimsan Series of the Daedong Supergroup exposed along the Daedong River valley and is estimated to be 300 m in maximum thickness. The lower part mainly consists of lime breccias containing middle Paleozoic fossils, whereas the upper part consists of well-rounded slate and quartzite clasts, and lime breccias with Lower Cambrian to Ordovician fossils. Tabulate corals are a dominant fossil group of the Songrim Conglomerate and are mostly of Silurian in age. These tabulate corals are comparable to those occurring in Koksan Series exposed in Suan-Koksan-Singye-Poptong areas of Hwanghaebuk Province and constitute the "Koksan-Songrim Bioprovince". Tabulate corals discovered in the southern Pyeongnam Basin have not been known in the Sino-Korean Platform, but show an affinity to the South China fauna. North Korean geologists maintained that the Koksan Series from which corals in the Songrim Conglomerate were derived was deposited in a narrow "Koksan-Songrim Sea" which extended through North Korea and South China. On the other hand, South Korean geologists do not rule out the possibility that these strata are remnants of a overthrusted nappe of South China affinity overlying the Sino-Korean platform due to thrust faulting during the accretion of Sino-Korean and South China blocks. Establishment of refined Paleozoic stratigraphic framework of North and South Korea is urgently needed to elaborate Paleozoic paleogeography of East Asia and to understand detailed collision sequence of the Sino-Korean and South China blocks.

1934년 황해도 황주군 겸이포(현재 황해북도 송림시에 편입)에서 전기 주라기 대동누층군의 기저부에 역으로 포함된 사일루리아기의 산호화석이 보고되면서 이전에는 한반도에 존재하지 않는다고 생각되어온 중기 고생대층의 분포 가능성이 처음으로 제기되었다. 후속 연구에서 "겸이포석회질역암"(현재 송림역암으로 개칭)의 역들만 사일루리아기 또는 후기 오르도비스기에서 석탄기를 지시하는 화석을 포함한다는 사실이 알려졌다. 송림역암은 대동강 유역의 대동누층군에 해당하는 송림산통의 기저부에 포함되며 층후는 최대 300 m 정도로 추정된다. 하부는 중기 고생대의 화석을 포함하는 석회각력 위주로 구성되고 상부는 캄브리아기 하부-오르도비스기의 화석을 포함하며 원마도가 양호한 점판암, 규암 및 석회암력으로 이루어져 있다. 송림역암의 역에서 산출된 화석으로는 사일루리아기의 상판산호류가 가장 우세한데, 그 조성에서 황해북도 수안-곡산-신계-법동 지역에 분포하는 곡산통(사일루리아기)에서 산출된 상판산호류와 유사하며 함께 "곡산-송림동물구"를 구성한다. 이러한 "곡산-송림동물구"의 산호류 화석은 지금까지 한중대지 지역에서 보고된 바 없으며, 대부분의 분류군에서 남중국동물군의 특징적 요소를 가지는 것으로 평가되었다. 송림역암의 산호화석을 포함하는 역의 주 공급지인 사일루리아기층의 기원에 대하여 북측 연구자들은 당시 한반도 북부와 남중국이 "곡산-송림해"라는 좁고 긴 바다로 이어져 있었다고 상정하고 있는데 반해, 남측 연구자들은 이 지층들이 고생대말-중생대초 한중대지와 남중국의 충돌, 접합시 충상단층에 의하여 한중대지 위에 얹힌 추복체(nappe)의 잔류물일 가능성을 배제하지 않는다. 한반도 남북 지역 간 고생대층의 정밀대비와 층서의 이해는 거시적으로 동아시아 지역의 고생대 고지리 및 한중대지와 남중국대지의 봉합과정을 심층 이해하기 위해서 반드시 필요하며, 따라서 향후 평남분지의 층서 및 고생물 자료의 면밀한 재검토가 요구된다.

Keywords

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