Submarine canyons are of great significance to understand the transport mechanism of terrigenous clastic materials to deep sea and the deep-sea sedimentary dynamic process. In this study, the spatiotemporal framework of stratigraphic sequence in the central and southern slopes of the Okinawa Trough was established, and the geomorphological and erosional-depositional features of submarine canyons were analyzed detailedly. The submarine canyons on the continental slope of Okinawa Trough began to develop in the early Pleistocene (< 1.8 Ma), and continued to develop even today. The canyons could be divided into three parts along the axial direction: head, upstream, and downstream. The head of the canyon was mostly inherited from the ancient incised valley developed on the outer continental shelf during the last glacial maximum (LGM). The canyon channel was filled with multi-stage turbidites and mass transport deposits (MTDs). The seismogeologic characteristics, such as the MTDs associated with the bottom simulating reflectors (BSRs), the imbricated, twisty or chaotic seismic reflections, the liquefaction deformation structures, the fluid transport channels, and the gaps that indicate methane escaping on the side walls, and the truncated relationship between the BSRs and the submarine canyons all indicate that there is a complex relationship between the submarine canyons and the methane seepage associated with gas hydrate in the Okinawa Trough. Finally, a coupled model with four evolutional stages for the submarine canyons was established.

In this study, we for the first time applied a joint geodynamic-geophysical inversion (JGGI) approach to oceanic plateau subduction models, and compared the subduction style and corresponding topography and Bouguer gravity of two representative subduction scenarios with passive or active collision. We showed that the case of passive collision of the Ontong Java Plateau (OJP) crust better explains the topography, gravity, and seismic data than the active collision scenario. This implies that the OJP did not control the regional dynamics during the collisional process. We conclude that previous studies may have overestimated the role of the OJP in triggering subduction initiation, subduction polarity reversal, and even Pacific Plate rotation.

It is generally accepted that the subduction polarity reversal (SPR) results from the strong collision of two plates. Yet, the SPR of the Solomon Back-arc Basin is started in the “soft docking” stage, and the mechanism by which the “soft docking” induced subduction initiation (SI) remains elusive. We find that the mass depletion of the plateau influences the evolution of the subduction patterns during SI. And the island arc rheological strength affects the development of the shear zone between an island arc and back-arc basin which favors SI. What’s more, with the increase of the rheological strength difference, the SI is more easily to occur, and the contribution of the plateau collision to SI weakens. Hence, by combining the available geological evidence, we suggest that the Solomon Island Arc rheological strength and the Ontong-Java plateau collision jointly controlled the SI during the “soft docking” stage.