Seismic stratigraphy of the western South Korea Plateau,East Sea: implications for tectonic history and sequence development during back-arc evolution |
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| Authors: | Y K Kwon S H Yoon S K Chough |
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| Institution: | (1) Petroleum and Marine Resources Division, Korea Institute of Geoscience and Mineral Resources, Daejeon, 305-350, Korea;(2) Department of Earth and Marine Sciences/Marine and Environmental Research Institute, Cheju National University, Jeju, 690-756, Korea;(3) School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-747, Korea |
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| Abstract: | The western South Korea Plateau in the East Sea (Sea of Japan) is occupied by rifted continental fragments formed in association
with the early phase of back-arc opening. The present study focuses on the seismic stratigraphy of the sedimentary succession
and the underlying acoustic basement in this region, based on closely spaced multichannel seismic reflection profiles. The
sedimentary succession occurs mainly within a series of subparallel basement troughs (grabens or half grabens) bounded by
faulted continental blocks (horsts) or volcanic ridges, and commonly floored by extrusive volcanic rocks showing hyperbolic
reflectors. These features are strongly suggestive of continental rifting accompanied by normal faulting, volcanic activity
and high rates of basin subsidence. The sedimentary succession can be subdivided into four seismic units. Unit 1 is characterized
by short and irregular high-amplitude reflectors and interpreted as a syn-rift deposit consisting of a non-marine volcanics/sediment
complex in topographic lows. Units 2 and 3 formed in an open marine environment during the Middle Miocene to Early Pliocene,
characterized by an onlap-fill and later draping marine sedimentary succession dominantly composed of hemipelagic sediments
and turbidites with frequent intercalation of mass-flow deposits. Along the western margin of the plateau, these units were
deformed under a compressional regime in the Early Pliocene, associated with the back-arc closing phase. Unit 4 (deposited
since the Early Pliocene) comprises hemipelagic sediments and turbidites with evidence of sporadic slides/slumps. |
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