Neogene and Quaternary sediment accumulation in the Okinawa trough

Abstract

The Okinawa Trough (OT), one of the major receiving terminals for terrigenous materials in East Asia, has a confined tectonic environment that has kept sediments intact since the Neogene. Based on multi-channel seismic data covering the OT, this study establishes a sequence stratigraphic framework and calculates sedimentary budgets for different geological periods. The findings indicate that sedimentary budget in the OT have generally increased since the Pliocene, with the same pattern in the southern and middle segment, but a declining trend in the northern segment since the middle Pleistocene. The divergent changes from north to south are primarily associated with the back-arc rifting of the OT, and relate to the different effects of highstand of sea level on its geographical location. Due to the dominance of the East Asian Winter Monsoon during the Middle to Late Miocene, sedimentary budget of OT was low. The prevailing East Asian Summer Monsoon, the glacial-interglacial cycle climate, and the uplift of Taiwan Island are the reason for the increase in sedimentary budget since the Pliocene. The provenance changes are inferred: before the early Pleistocene, the direction of sediment source was mainly from the Yangtze River and mountainous rivers in Eastern China. After that, mountainous rivers in Eastern China, especially Taiwan, contributed significantly to the deposition.