전남 고흥지역에 분포하는 두원층과 고흥응회암의 저어콘 U-Pb 연대 = Zircon U-Pb ages of Duwon Formation and Goheung Tuff in Goheung area, southern Korea

다국어 초록 (Multilingual Abstract)

The zircon U-Pb dating was performed to determine the maximum depositional age of the Cretaceous Duwon Formation and the eruption age of the Goheung Tuff, which are located in the Goheung area, the southern part of the Korean peninsula. The Duwon sandstone yields a youngest 206Pb / 238U weighted mean age of 123.1 ± 1.1 Ma(n=12), and the 206Pb/238U weighted mean ages of the lowermost and uppermost parts of the Goheung Tuff are 85.6 ± 0.23 Ma and 86.4 ± 0.71 Ma, respectively. Considering our age-dating results together with previous workers, the Duwon Formation is interpreted to have been deposited at ca. 123 Ma (Aptian), and can be correlated with the Nakdong Formation of the Sindong Group in the Gyeongsang Basin. The eruption age of the Goheung Tuff is considered to be ca. 86 Ma, the boundary between the Coniacian and Santonian. Unlike other regions of the Milyang Subbasin, there is a long time gap of ca. 37 Myr between the Duwon Formation and Goheung Tuff, suggesting that the basin history of the Goheung area was different from the Milyang Subbasin.

국문 초록 (Abstract)

한반도 남부에 위치한 고흥지역에 분포하는 백악기 두원층과 고흥응회암의 지질연대를 구하기 위해LA-MC-ICP-MS 및 SHRIMP 저어콘 U-Pb 연대를 측정했다. 분석결과 두원층 사암에서 약 123.1±1.1 Ma (n=12)인 가장 젊은 백악기 저어콘의 206Pb/238U 가중평균연대를 구했고, 고흥응회암의 최하부와 최상부에서는각각 85.6 ± 0.23 Ma와 86.4 ± 0.71 Ma의 206Pb/238U 가중평균연대를 얻었다. 연대측정 결과와 기존 연구결과를 함께 고려하면 두원층은 하부 백악기 앱티안 시기인 약 123 Ma에 퇴적되었으며, 경상누층군 신동층군의 낙동층의 퇴적시기와 대비된다. 고흥응회암은 후기 백악기 코니아시안과 산토니안의 경계 시기인 약 86 Ma에 분출된 것으로 판단된다. 밀양소분지의 다른 지역과는 달리 고흥지역의 두원층과 고흥응회암 사이에는 약 37 Myr의 긴 시간적 공백이 존재하며, 이는 고흥지역의 분지 진화사가 달랐다는 것을 지시한다.

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