Seismic stratigraphy and structural evolution of the South Korea Plateau, East Sea (Sea of Japan)

Abstract

The South Korea Plateau (SKP), a typical submarine plateau, preserves an important tectono‐sedimentary evolutionary record and represents a major frontier area for petroleum exploration in the East Sea (Sea of Japan). However, its tectonic mechanisms and their controls on sedimentary fill are underexplored. Here, we present the first integrated tectonostratigraphic framework of the SKP using reprocessed, two‐dimensional, seismic‐reflection profiles and borehole data. Four regional megasequence boundaries are interpreted, delineating four tectonostratigraphic packages: the syn‐rift (MS1), post‐rift phase 1 (MS2), post‐rift phase 2 (MS3) and syn‐compression (MS4) megasequences. We propose a four‐stage structural and sedimentary evolution model for the SKP based on the megasequences and structural development. Stage‐1 (latest Late Oligocene−Early Miocene): the SKP was rifted and extended through block faulting, resulting in the formation of rift basins dominated by fan‐delta and shallow‐lacustrine depositional systems. Stage‐2 (late Early Miocene−Middle Miocene): hemipelagic sedimentation prevailed with gravity‐controlled slope failures under a tectonically stable environment associated with slow thermal subsidence. Stage‐3 (late Middle Miocene−Late Miocene): continued thermal subsidence allowed the predominance of hemipelagic biogenic deposits accompanied by intermittent mass‐wasting‐induced turbidites and resulted in the development of a polygonal fault system. Stage‐4 (Early Pliocene−present): the SKP was influenced by E−W compression caused by an eastward movement of the Eurasian plate. Turbiditic and hemipelagic sedimentation was predominant with turbidity‐flow‐leveed channels derived from direct riverine input or through slope failures. Based on this tectonostratigraphic analysis, we reveal the variation in depositional systems and sand‐dispersal patterns for the SKP, highlighting potential targets for sandstone reservoirs: MS1, fan‐deltas and lacustrine‐fan turbidites; MS3, deepwater fan turbidites; and MS4, deepwater fan turbidites, channel‐levee complexes and turbidite frontal‐splay deposits. This study proposes a structural and sedimentary evolution model for the SKP that could enhance our understanding of reservoir potential for petroleum‐exploration in the future.