Reconstruction of the Cretaceous continental arc–trench system of the Japanese Islands: A basis for Cretaceous palaeoenvironmental studies

Spatiotemporal distributions of Cretaceous rocks differs markedly between the Southwest (SW) and Northeast (NE) Japan arcs. However, four parallel zonal arrangements of rocks are recognized broadly throughout both arcs: mostly non-marine sedimentary rocks in backarc/intra-arc basins; granitic and volcanic rocks in magmatic arcs; predominantly marine and subordinately fluvial sedimentary rocks in forearc basins; and sedimentary rocks of turbiditic and mélange facies in accretionary complexes. These zones constituted a palaeo-Japan continental arc-trench system during the Cretaceous. We describe and correlate 71 Cretaceous backarc/intra-arc and forearc basinal successions from Kyushu (south) to Hokkaido (north) islands, including a southern Sakhalin and two Kuril Arc (eastern Hokkaido) successions. Stratigraphic ranges and major sedimentary facies are generally similar between the SW and NE Japan arcs, except for the pre-Aptian Lower Cretaceous in Hokkaido of NE Japan, suggesting continuity throughout the two arcs during the Cretaceous. Although Cretaceous strata are sporadically exposed in northern Honshu, NE Japan, interpretation of seismic sections suggests that Cretaceous forearc sedimentary rock measuring several tens of kilometres laterally are developed offshore beneath the present Pacific forearc. In contrast, Cretaceous forearc strata in southern SW Japan are distributed along two narrow belts that may have been deformed by post-Early Miocene tectonism.