Evolution of the Late Cretaceous Dadaepo Basin,SE Korea,in response to oblique subduction of the proto-Pacific (Izanagi/Kula) or Pacific plate |
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| Institution: | 1. Department of Geological Sciences, Pusan National University, Busan 609-735, Republic of Korea;2. Department of Geology, Gyeongsang National University, Jinju 660-701, Republic of Korea;3. Department of Earth and Environmental Sciences, Pukyong National University, Busan 608-737, Republic of Korea;1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. Department of Earth Sciences, Durham University, Durham DH1 3LE, UK;3. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;4. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;5. Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences, ul. B. Khmel''nitskogo 2, Blagoveshchensk 675000, Russia;6. Far East Geological Institute, 159 Pr 100-let Vladivostoku, Vladivostok, Russia;7. Engineering School, Far Eastern Federal University, 8 Sukhanova Str, Vladivostok, Russia |
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| Abstract: | The Dadaepo Basin is a small Late Cretaceous sedimentary basin in SE Korea, located on the eastern margin of Asia. The basin is an isolated extensional basin situated between the NNE-striking Yangsan and Dongnae faults. The basin-fill sediments, named the Dadaepo Formation, consist of channelized conglomerates and sandstones intercalated with dominantly purple mudstones in the lower part. The upper part is dominated by fine- to coarse-grained tuffaceous sandstones and olive to dark gray mudstones with abundant volcanic interbeds. The formation unconformably overlies dacitic rocks dated at ca. 94 Ma and is overlain by basaltic andesite dated at ca. 69 Ma (Ar–Ar ages). The overall configuration of the strata of the Dadaepo Formation indicates syndepositional tilting of the basin floor to the north-northeast. A number of outcrop-scale faults are observed in the basin-fill sediments, of which the majority are NW-striking normal faults, including syndepositional growth faults. The orientations of mafic (magmatic) and clastic dikes, interpreted as being approximately contemporaneous with the deposition of the Dadaepo Formation, are also nearly parallel to the strikes of outcrop-scale normal faults. All these extensional structures consistently indicate NE–SW extension of the basin and obliquely intersect the basin-bounding Yangsan and Dongnae faults at angles of 40°–60°. It is thus concluded that the Dadaepo Formation was deposited in a pull-apart basin that subsided as a result of NNE-striking sinistral strike–slip faulting in the southeastern part of the Korean Peninsula during the Campanian (Late Cretaceous). This strike–slip faulting was related to north-northwestward oblique subduction of the proto-Pacific (Izanagi/Kula) or Pacific plate under the eastern margin of the Eurasian plate. |
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