Reconstructing Jurassic?Cretaceous Intra?Oceanic Subduction Evolution in the Northwestern Panthalassa Ocean Using Ocean Plate Stratigraphy From Hokkaido, Japan

Plate reconstructions of the Panthalassa Ocean typically portray a simple system diverging plates surrounded by active margins, yet geological and seismic tomographic records demonstrate that intra-oceanic subduction existed. Here, we reconstruct plate tectonic evolution pre-Cretaceous Oku-Niikappu island arc, remnants which are exposed on Hokkaido, Japan. This arc formed at Jurassic zone separating two oceanic plates: Izanagi here proposed ‘Izanami’ Plate. The was previously shown to have gone extinct in an setting, subsequently (hyper)extended, overlain Berriasian cherts. remained ocean floor for ?45 Myr until its ?100 Ma accretion revealing original position far from continental margin likely above identified Telkhinia slabs. We show extinction coincided with northwestern reorganization recorded ?30° change spreading direction, subsequent extension is straightforwardly explained Izanami-Pacific ridge followed continued divergence between Pacific plates. From our reconstruction, it follows outer Japan, accretionary complex Complex resides belongs, separated inner back-arc basin during Early mid-Cretaceous. study illustrates value orogens development lost ancient particularly when combined marine geophysical data sets.