Episodes 2023; 46(2): 269-279
Published online June 1, 2023
Copyright © International Union of Geological Sciences.
Yong-Un Chae1, Sujin Ha1, Young Ji Joo2, In Sung Paik2, Hee-Cheol Kang1,3, Hyoun Soo Lim1*
1Department of Geological Sciences, Pusan National University, Busan 46241, Republic of Korea
2Division of Earth and Environmental System Sciences, Pukyong National University, Busan 48513, Republic of Korea
3Institute of Geohazard Research, Pusan National University, Busan 46241, Republic of Korea
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Detrital zircon U-Pb dating was performed using LAMC-ICP-MS on a total of six samples to determine the depositional period of the Dadaepo Formation (DF) in the Dadaepo Basin (DB) located in the Busan area, Korea. Cretaceous zircons accounted for 81% (LD-1), 49% (LD-2), and 34% (LD-3) in the lower Dadaepo Formation (LDF), 88% (IG-1) in the ignimbrite at the boundary of the upper and lower Dadaepo formations, and 80% (UD-1) and 100% (UD-2) in the upper Dadaepo Formation (UDF). The 206Pb/238U weighted mean ages using the youngest clusters of zircons were calculated to be 98.0 ± 0.3 Ma in LD-1, 96.8 ± 0.2 Ma in LD-2, 97.1 ± 0.3 Ma in LD-3, 93.6 ± 0.2 Ma in IG-1, 93.3 ± 0.2 Ma in UD-1, and 92.8 ± 0.2 Ma in UD-2. Therefore, the DF was deposited from the early Cenomanian to the Turonian in the Late Cretaceous, and the formation is correlated with the lowermost Yucheon Group. In addition, the synthesized chronostratigraphy of the Cretaceous basins in Korea indicates that the sinistral strike-slip movement of the NE–SW-striking fault systems in the Korean Peninsula decreased starting at about 85 Ma.