Tectonostratigraphic framework and depositional history of the South Korea Plateau, East Sea

This paper presents a tectonostratigraphic framework and depositional history of the South Korea Plateau (SKP) using multi-channel seismic reflection profile and borehore data. Total sedimentary succession of the SKP is divided into four second-order megasequences (MS1 to MS4): the syn-rift (MS1), post-rift phase 1 (MS2), post-rift phase 2 (MS3), and syn-compression (MS4) megasequences. For these four megasequences, detailed seismic stratigraphy interpretation, including geomorphology, sediment thickness, and seismic facies distribution, was performed. In addition, we analyzed geometry and distribution patterns of geological structures (i.e. faults, folds, and syntectonic growth strata) to reveal their formation mechanism, timing, and deformation patterns. Based on these stratigraphic and structural interpretation, we suggested a tectonic and depositional history model of the SKP occurred in four stages, mainly controlled by tectonic movement. In Stage-1 (syn-rift; MS1), the SKP was rifted through domino-style block faulting, resulting in formation of half-graben style rift basins. In the incipient rifting period, volcanic materials were supplied from extensional faults and eruption center of the volcanics. Afterward, the plateau was dominated by lacustrine sedimentation with fan-delta development. In Stage-2 (post-rift phase 1; MS2), turbidite and hemipelagic sedimentation prevailed throughout the plateau. In addition, submarine mass wasting was frequently generated, caused by slope failures along the steep slope of adjacent continental ridges. In Stage-3 (post-rift phase 2; MS3), hempelagic sedimentation was predominant under a tectonically stable environment. In this mud-dominant environment, polygonal fault system was developed within the MS3 due to diagenetic processes, including compaction and water explusion. In Stage-4 (syn-compression; MS4), the SKP was filled with turbidite and hemipelagic sediments with intermittent mass transport deposits. Moreover, a certain volume of sediments were provided through feeder systems such as stacked channels and channel-levee complexes connected by submarine canyon (i.e. Gangneung and Donghae canyons).