Neogene and Quaternary Sediments

Overview

Sediments younger than Neogene produced in an island arc formed by subduction of ocean plates under the east margin of the Eurasian continent. These sediments were deposided after formation of a back-arc basin (the Japan Sea), and most of them were formed at fore-arc basins and back-arc basins. Thick Miocene sediments and volcanic rocks were deposited in a rift zone of back-arc basin formation, and especially called as "Green Tuff zone" from their characteristic color. Middle Miocene strata from Chugoku/Shikoku region to Tokai region is sometimes referred to as First Setouchi Supergroup, and Pliocene - Pleistocene strata as Second Setouchi Supergroup.

Blue: Quaternary, Red: Neogene. Neogene and Quaternary sediments overlie unconformably the basement of the Japan Island Arc such as accretionary complexes and plutonic rocks.