Abstract
As a premise for reconstructing the Paleo-Japan Cretaceous continental arc-trench system, its constituent geologic units such as Cretaceous plutonic, volcanic and sedimentary rocks are briefly reviewed, referring to recently updated geologic papers, books and maps concerned with regional geology, chronostratigraphy and lithofacies. The Cretaceous plutonic and volcanic rocks are widely distributed along the Inner Zone (the northern continental-side region) of Southwest (SW) Japan and the whole Northeast (NE) Japan, though volcanic rocks are dominated along the Pacific coast in NE Japan. These distributions indicate the intensive magmatism and volcanism had occurred within the Cretaceous volcanic arc. The southeastern margin of andesitic rock distributions drawn on the reconstructed map of the Paleo-Japan Cretaceous continental arc suggests the generally straight volcanic front throughout SW and NE Japan. Mainly non-marine Lower Cretaceous strata are sporadically distributed in separated intra- and back-arc small basins around the volcanic arc in Southewest Japan. On the other hand, mainly marine and subordinately fluvial Cretaceous strata are distributed sporadically but continuously along the Pacific coastal area and the offshore Pacific subsurface in NE Japan, and the southern end of the Inner Zone and the Chichibu Belt of the Outer Zone in SW Japan. Their stratigraphy and sedimentary environments are broadly correlated as forearc basin fills throughout two arcs of SW and NE Japan. The stratigraphic ranges of the strata entirely cover all Cretaceous stages, though the range and geographic distribution is not so wide in each distribution area of the strata. Based on the reconstructed configuration of the Paleo- Japan Cretaceous continental arc-trench system, the present land area of Northeast Japan is equivalent to the Inner Zone of Southwest Japan. On the other hand, the Outer Zone of Southwest Japan will be traced into the subsurface area of the offshore Pacific in Northeast Japan.
