Along-Strike Morphologic Variations of the Kyushu-Palau Ridge at 13°–17° N and Their Tectonic Implications

Abstract

Abstract The paper provides a detailed description of the topographical distribution characteristics, along-strike morphologic variations, and tectonic implications of the Kyushu-Palau Ridge (KPR) in the 13°–17° N regions. The description is based on multibeam bathymetric data that was recently collected in the mid-southern segment of KPR and its surrounding areas. The findings indicate that the KPR in the studied region comprises several discontinuous seamounts and seamount chains. Along the ridge running from east to west, there is significant variation in the topography of the seafloor. Visible on this ridge are numerous deep-sea depressions and apparent topographical discontinuities. Geological tectonic processes such as plate subduction and seafloor spreading largely determine the topography of the seafloor. During the beginning of the Parece Vela Basin (PVB) spreading, the pre-existing volcanic arcs fractured under east-west extensional stress, resulting in the development of prominent seamounts, sharp ridges, relief alternations, and rift basins in the KPR. The east-west stress was subsequently transmitted to the weak and inactive mid-ocean ridge in the West Philippine Basin (WPB), which was reactivated and resulted in an episode of magma-poor spreading during 30–26 Ma. This episode caused the KPR to move eastward, stretched, and destroyed its pre-existing structure.