This paper attempts to examine the evolutionary relationship between the North Fossa Magna region and the Toyama Trough, which includes the Toyama Deep-sea Channel system, to constrain late Cenozoic tectono-sedimentary processes at the junction zone between the NE and SW Japan arcs. Using outcrop data, D/ D seismic surveys, exploration-well data, and published literature, we compare tectonic regimes, paleogeography, depositional systems, and sediment supply systems between the two areas, with a focus on the connectivity of submarine-fan systems. The results reveal that the North Fossa Magna region experienced a similar tectonic history to that of the NE Japan arc, including Middle Miocene rifting and Late Miocene basin inversion, whereas the tectonic history of the Toyama Trough is more similar to that of the SW Japan arc, which experienced continuous compression after the Middle Miocene rifting stage. The obtained paleogeography and depositional-system distributions indicate that submarine fans developed in the northern part of the North Fossa Magna region were connected to the Toyama Deep-sea Channel system, and the North Fossa Magna region is regarded as the major clastic provenance of the Toyama Deep-sea Channel system until at least Ma. The sediment supply system to the Toyama Trough can be characterized by multiple stepwise supply systems consisting of NE-SW-trending, parallel, terrace-like basins and interconnecting submarine fan systems, which are possibly related to the basin rifting and compression structures. The amount of clastic supply appears to have varied in response to the tectonic conditions through the late Miocene and Pliocene, causing changes in submarine-fan depositional style. When the Northern Alps of Japan were uplifted drastically, at around Ma, the major sediment supply route shifted to its present position, passing through the Toyama Plain and Bay.
