Permalink : http://hdl.handle.net/2115/38514

KEYWORDS : Forearc;Plate-tectonics;Cretaceous Hokkaido;Clastic supply;Unconformity

Plate-tectonic synthesis for Middle Jurassic - Late Cretaceous Hokkaido, Japan is tentatively but first presented. Middle Jurassic eastward subduction beneath the margin of Asian Continent produced accretionary body of characteristic continental clastic supply. Jump of trench to the east in the earliest Cretaceous age caused a wide forearc basin and volcanic-arc activity. During early Late Cretaceous, uplift and emergence of high-pressure type metamorphosed part of accretionary body occurred inside of the forearc, and formed local unconformity in the forearc sequence. This process shows growth and evolution of the eastern margin of Asian Continent before the Neogene opening of the Japan Sea. Geologic information given from forearc units is important for understanding the tectonics of arc-trench system.